Eagar 133 Supplement

8/12/2019 Eagar 133 Supplement

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Proceedings of High Energy Electron Beam W elding and M aterials ProcessingCambridge MA Sept. 21-23 1992 American Welding Society M iami FL 1993 p. 262-290.

SURFACE MODIFICATIONIHEAT TREATMENT WOR KSHOPChairmen: Dr. Thomas W. Eagar, R. P Simmons Professor of Metallurgy, MassachusettsInstitute of Technology MIT) and Dr Vernon L. Bailey, Senior Staff Scientist, Pulse Sciences,Inc. (PSI)RICHARD HUBBARDINAVAL RESEARCH LABORATORY NRL)I d like to amplify a little bit on the point that I raised in the meeting. There are several existingfacilities for this particular application of heat treatment and shock hardening applications. Ithink it s worthwhile looking at the types of machines that might be available for quick experi-ments that would be the kind of experiments that might involve somebody from the material sci-ences side of things collaborating in a very small effort on one of these accelerators. This isequipment that you wouldn t have had access to a few years ago because they were heavily sub-scribed in charged particle beam research. But the times have changed and I was told by onerepresentative from Livermore that the ATA (Advanced Test Accelerator) injector now is beingoperated on an experiment full time for a million dollars a year. These are machines that get youinto a parameter regime that is different from that currently available from the SRL (ScienceResearch Laboratory) machines. One of the important things that Joe Mangano mentioned thefirst day is that they re going down a path for technology that gives you a device that s in wattsper dollar.THOMAS W. EAGAWSSACHUSETTS INSTITUTE OF TECHNOLOGY (MIT)What are the parameters that are going to be different?RICHARD HUBBARD NRL)As an example, ATA, with the existing machine, operated at one pulse per second, but it couldoperate in a burst mode that produced five to ten pulses separated by roughly a millisecond ortwo. ATA could do that for hour after hour. As an example of the parameter regime, the lastmajor experiment that was done on ATA had beam currents of about six kiloamps and an energyof ten MeV. So the advantage that I see is to be able to determine if there is an advantage to get-ting into the 5 MeV range and above. There are a handful of machines that get us into thatregime and I think they re available now.The last day that we ran the ATA machine we operated at ten pulse bursts and the feeling wasthat we could have achieved 15or 20 pulses in a burst. Twenty seconds later you d be able to doanother burst. Another advantage, by the way, is that some of the institutions which use thesemachines are used to handling the radiation problem. Therefore you don t have to pay for all theshielding because it s already there.THOMAS W. EAGAR MIT)Has ATA already got a window or a foil to extract the beam?RICHARD HUBBARD NRL)That s right. Now, ATA is not probably suitable for the welding applications because I don tbelieve the brightness is good enough. However, for demonstrations that involve larger beams,


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it can get us into a regime that we would not otherwise be able to achieve in the near future. Dowe have anybody from Sandia here on theRHEPBOB N. TURMANISANDIA NATIONAL LABS (SNL)Yes, but before I say anything about the RHEP though, I have to rain on your parade on ATA.Once a facility is shut down or has stopped or go away from the routine facility operations, it isvery difficult and expensive to return it to full operation.RICHARD HUBBARD (NRL)ATA is being operated now. It s actually being operated more or less full time performing someexperiments with a crew of one physicist and a hand full of technicians that are doingmicrowave experiments,.SAMG LAMBRAKOS NRL)I want to continue on the point of what I m about to do with large scale simulation and the con-tribution that large simulation can make at this point. About the big error of investments in sim-ulation, that point is well taken. But I feel that the time has passed, and nobody talks about opti-mizing this code or structuring it for this machine. That era is over and there s a lot of basicallymature numerical technology currently available. The point that I want to make is that we tookan existing code that was developed for conventional deep penetration welding in 304 stainlesssteel and applied it to the HEEB problem. Richard Hubbard and I discussed the size of the heataffected zone which was not a result I was looking for when I ran these simulations. I probablyalready have that data in my data files. I think that adopting the same attitude, there s a lot ofexisting numerical technology that can be used to support this work.The code that we have developed for conventional deep penetration welding is a 3-D code. Heatis deposited on the surface boundary of the material according to a deposition model of yourchoice. As the system heats up, the vapor-liquid interface isotherm becomes the boundary of thesystem. In the model, you don t really see a gas phase, the vapor-liquid zone acts as a movingboundary to which is applied a no slip fluid boundary condition. This allows you to actually seethe evolution of the keyhole.VERNON L. BAILEY (PSI)So you re talking about calculating realistic MPR instabilities and things like that with this code?SAM LAMBRAKOS (NRL)Yes, with enhanced resolution as you approach the keyhole.VERNON L. BAILEY (PSI)Does this mean you can heat into the whole sample?SAM LAMBRAKOS NRL)Well, no. While the whole problem can be done in principle, you would have a very large com-puter cost. The numerical technology does exist, not only in this problem, but for a lot of otherrelated problems. It was developed during those past ten years.


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OLE SANDVEN (MIT)I d like to make some comments about transformation hardening. I see the advantage of HEEBin that we have so much power available, we can expose in a wide track. In other words, wedon t have to make several parallel runs. That s very important because with laser technology,that I m most familiar with, you have to limit yourself to narrow tracks because of power consid-erations. With several parallel tracks, you get all sorts of complication in the overlaps like tem-pering, hardening, whatever. So by using ther power available with the HEEB you spread itover a wide area?THOMAS W. EAGAR (MIT)Expanding the beam is not a problem for the HEEB technology.OLE SANDVEN MIT)Then you have a wonderful heat source particularly for things like large gears. Now if you cantake your beam and program its power density such that the leading edge of the beam track cre-ated a hotter surface, then there is a big advantage in creating transformation. This is reallygood for the transformation department. By bringing the temperature up quickly and then allow-ing it to cool slowly, you have an opportunity for the kinetics of the hardening process to takeplace. This should allow the carbon to go into solution and form austenite and transform tomartensite on cooling.JAY BOUDREAUBALLENA SYSTEMS CORPORATION (BSC)I d like to introduce the idea of using high energy electron beams to anneal radiation damage inpressurized water reactors. We ve done a little bit of work on this so we can get into some of thenumbers later on, but basically there is a 35 billion dollar a year industry whose plants areaging. The NR Nuclear Regulatory Commission) has a guideline out for reissuing licenses tothese plants and it is tied most strongly to this particular issue. The pressure vessels tend toembrittle due to the fast neutron radiation damage. Now this arises, evidently, from impuritiesintroduced into the welds of the vessels at the time when copper in filler rod was used. The cop-per impurities do something to lower the temperature for embrittlement. The reason this is anissue is that in reactors it s relatively probable that the reactor will go through flow transients. Itis very possible for very cold coolant water to come into contact with hot surfaces creating ther-mal shock that could literally cause failure of the entire reactor vessel. This is really a bad thing.It could lead to total loss of coolant control resulting in a probable melt down with the highestradiation releases. An industry position on this is not formed at this point. I think their worriesare primarily in the area of costs to anneal.They arc cognizant of some work that has been done on common weldments which use resis-tance heating to anneal the damage. This is a relatively grotesque process. It involves removingall of the internals of the reactor, saturating the reactor vessel for some many hundreds of hoursat 65 degrees centigrade after which there is no way to determine the extent to which theembrittlement has been annealed out. The standard approach is to use coupon samples from theinside surface of the vessel to evaluate the level of annealing achieved. It s very difficult to doany in-depth sampling of the vessel without destroying the vessel wall. So I d say that it s anarea ripe for some innovative science because the physics and phenomenology, either of the


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embrittlement process or the annealing process, are not well understood. What do high energyelectron beams bring to this problem? Basically, the possibility of introdu cing a very steep tem-perature profile, which is volumetrically centered in the material. That in conjunction with thepossibility of introducing micro shocks, may have some material science benefit to annea ling.We have performed caluculations for beam energies as high as 300 MeV. Obviously you don'tworry about induced radiation. We have limited the current to around 200 amps. Th e reason forthat, without knowing a lot of material science, was to just keep the internal pressures below20,000 psi, somewhat below the yield stress of the material. That may or m ay not be a goodidea.BOB N. TURMAN (SNL)What thickness of w all material were you considering there?JAY BOUDREAU (BSC)About 9 inches.BOB N. TURM AN (SNL)And that's what drive's the larger beam energies?JAY BOUDREAU (BSC)Yes, there are very thick sections.RICHARD HUBBARD (NRL)Just a quick comment. There is a class of accelerators that haven't been discussed here that maybe better to go to high energy and modest current. They're basically R devices and that may bea better solution for your problem. We'll talk about that.PAUL FARRELL/BROOKHAVEN TECHN OLOGY GR OU P (BTG)I've been involved with commercial applications of accelerators for about 25 years. I'm interest-ed in sterilization applications, medical applications. I guess you could call them materials, butthese are plastics and medical devices. It seems to me from my experience working with DCmachines, the likely uses of this technology are for high volume applications kilowatts alwaystranslates into volume. Whether it's running 24 hours or 8 hours a day, it needs to be either athigh volume or a very value added kind of a process. In any case, in commercial applications,unlike in government applications, you have to always look ahead at what the cost of the p rocessis going to be. It's the economics that is going to drive us. So far I haven't heard too much aboutthe economics. I'm also interested in how it went from the discussion Monday morning of thecost per kilowatt of a machine from 10 down to 2 a watt by the afternoon. No one has ques-tioned these big cost discrepancies. What's the SRL machine benefit factor over the RHE Pmachine at San dia? That is a point I would like addressed.JOHN NUNES, ARMY MATERIALS TECHNOLOG Y LABORATORY (AMTL)I'm involved with materials. It appears this is a technology that's looking for a home. Fromwhat I've heard there are probably several types of this class of acce lerators where materials


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research could be done. It s seems that it s a matter of identifying some of these surveys and per-form some of the cost effectiveness studies suggested. Because of the existing equipment, youwouldn t need to get involved in constructing some rather expensive user facility.The problem right now is to take one step at a time and identify those programs where you cando some of this materials science and not get involved in a whole new system that requires largeexpenditures. I can see where some of the benefits could accrue in terms of things like shockhardening, transformation inducement, type of effects on materials that you could seal, and pro-cessing. But, I don t see a specific application where you could identify it. I see this more as aresearch tool and I d like to see us put people in charge to take advantage of what s already avail-able, or that will be available in the near future.RICHARD ADLERINORTH STAR RESEARCH, INC. (NSRI)I have some familiarity with induction accelerator technology and I m trying to understandwhere legitimate applications for very short beam pulses exist as opposed to applications whichare purely heat pulse applications or applications which re really more amenable to continuousprocesses. In general, I ve found that for these very low heat cycles there are few applications.In the end you ll find that a W rocess is more effective.SPEAKER UNIDENTIFIEDGenerically, I d be interested in thin range applications, as I ve learned to call them, which Iwould like to study and try to take advantage of the localization of energy deposition. First, I dlike to see how small a region we could deposit the energy in, and what beam parameters areassociated with that application, such as lithography in mind. Secondly, would be to take advan-tage of the displacement damage introduced by these beams to cause enhanced diffusionprocesses and interface reactions such as enhancing adhesion. Thirdly, with the surface meltingapplications, maybe we ll decide to call it reaction forming, where the liquid state is actuallyreacting with either end. Finally, I have an interest in the ablation yield of these beams, how thatrelates to the beam parameters, and how we could take advantage of that either as a source fordeposition or as a means of producing small particles.THOMASW EAGAR (MIT)But looking at shock hardening and radiation damage, you ve already got the localization, or doyou? Are you using it as a source of localized energy?RONALD GILGENBACH/UNIVERSITY OF MICHIGAN (UM)As you know, automobiles re the main industry in Michigan, so I ll talk about the automotiveindustry a little bit. I ve been working with General Motors research labs for about the last eightyears, mostly on laser processing. One thing I ve discovered is that there s very little metal on acar that s much thicker than one inch, especially nowadays. But there s lots of sheet metal incars, and so a lot of the applications that they re interested in re fairly mundane things like cut-ting exhaust pipes. It sounds like a waste, but it turns out that it s very labor intensive to cutexhaust pipes and the kinds of surfaces they have after cutting by conventional means are sharpand risk injury to the workers. Lasers leave a nice smoothed edge. There are lots of other appli-cations, and I would emphasize that because of the thickness of the metal in cars, that the lower


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energy beams should not be ignored. We have a one megavolt 1 kiloamp multi-microsecondelectron beam generator and we ve observed many interesting surface effects over the years onall the materials that we have exposed to the beam. We ve never really looked at them under amicroscope, but if you adjust the current density, you can avoid surface blow-off effects. We cancontrol blow off by changing the current density. On a machine like ours, you ve got about 1 to2 kilojoules per pulse, and so it s possible to expose fairly large areas.THOMAS W. EAGAR (MIT)When you say interesting surface effects, do you have any non-proprietary ones you can tell usabout?RONALD GILGENBACH (UM)Well, we ve seen a lot of this exfoliation, we ve seen a lot of texture effects, and then we ve alsoseen more or less pitting effects where surface melting has occurred. We ve used all kinds of targets such as tungsten and aluminum plates. We ve used lots of different things as collectors, andabout the only thing that completely survives without some kind of surface damage is graphite.I think these phenomena need to be looked at in more detail. It may be possible to produce someinteresting phase transformations with these beams on or close to the surface.THOMAS W. EAGAR MIT)Now, can I ask a little bit more about why Ford s been looking at MeV beams hitting materi-als? You say they ve been doing this for 1 years?RONALD GILGENBACH (UM)No, they ve been looking at lasers. I ve been working with them mostly on lasers. What I minterested in doing now is to find out whether the electron beams have some applications tothings that they currently do with lasers.THOMAS W EAGAR (MIT)I thought you said Ford had a 1 MeV beam?RONALD GILGENBACH (UM)No, we do at my lab. Our lab has a 1 MeV beam. GM has lasers too. I think they had a fifteenkilowatt C02 laser, but they weren t able to use it for welding because they couldn t get a goodenough focal spot with it.THOMAS W. EAGAR (MIT)Perhaps they couldn t get it to work?RONALD GILGENBACH (UM)One of the things that you d have to pay attention to here would be to determine if you can pro-duce these kinds of electron beams with a good enough focal spot so they could use it for weld-ing gas tanks together.


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RONALD GILGENBACH (UM)The reason I'm here is to see whether there are some things that they could do with electronbeams, but more lower energy ones. One point I should emphasize on the laser system for cut-ting exhaust pipes, for instance, is that they use a lot of robotics to handle the materials. Whenyou start getting up to these higher MeV energies, you're going to probably wipe out a lot ofelectronics on the robotics if you're not careful. That's another reason for proceeding prudentlyat the lower energies and working your way up rather than going right to several MeV.RICHARD HUBBARD (NRL)I have a related question. You said that a large fraction of the lasers are directly used in cutting.It seems to me cutting is something an electron beam should be able to do very well. In generalelectron beam generators are substantially more efficient than lasers why aren't we doing that?OLE SANDVEN (MIT)Well, for one thing the laser can cut an open area and you can do it very, very quickly. Also, youcan cut much thicker than you can weld.THOMAS W. EAGAR MIT)Well, that's because you ignite the metal. They actually blow oxygen into the cutting region andactually ignite the metal and bum through. It is possible to cut half inch thick material with aone kilowatt laser.OLE SANDVEN (MIT)You could do so but you won't get a very good edge that way. I don't think cutting is a good ideabecause there are so many cutting processes to compete with. In fact, with the laser cut you getabout 318 of an inch maximum. There are other processes that are much cheaper. I think itwould be a waste of time.THOMASW. EAGAR (MIT)The largest application of high power lasers, high power being above 5 watts, is actually not formetals. It actually happens to be cutting cloth, 2001250 watt lasers. I could take you to any littlemachine shop of a dozen people and they will have a 500 to 1000 watt laser hooked up to apunch press. Instead of using mechanical punch pressing in a small little job shop, it pays tohave a 100,000 laser that has flexibility. So it's just not clear to me when you go to cuttingarmor why you would not do it with oxyacetylene or plasma cutting or something. There arethings that are a lot less expensive than HEEB systems and I believe the x-ray problem is goingto wipe you out here. I mean, with these other things, you can have someone working right nextto it.RICHARD HUBBARD NRL)I think along the lines of you've got a regime where the x-ray problem is relatively benign. But Ithink you're right. Efficiency is not the issue.RONALD GILGENBACH (UM)It's hard to compete with lasers. You'll have to find some applications that lasers can't do better.


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Treating large areas might be one of them because, of course, the laser has a fairly small spot.If you wanted to treat a large area with electron beams, you might be able to do that.OLE SANDVEN (MIT)Also, I had the impression that you could probably manipulate your beam a little easier than thelaser.BOB N. TURMAN (SNL)I ve got several comments. The RHEP accelerator will be on line next month. Then we ll have abeam for doing some experiments at MeV that will deliver about one kilojoule of energy perpulse and 120 pulses per second. Over the course of a year we will increase the energy to 2 5MeV.THOMAS W. EAGAR MIT)The primary application for RHEP right now is for simulation effects?BOB TURMAN (SNL)No. The primary purpose for RHEP is to move into general processing areas. The first order ofbusiness has been to check out the pulse of power. That s what we ve been doing the last yearand we ll be checking out pulse of power with a MeV diode and performing some materialsprocessing of various types; e.g., polymers.THOMAS W. EAGAR MIT)So DOE is funding this for processing?BOB N TURMAN (SNL)For technology applications, for general processing applications, polymers, metals, some com-posites. We ll be conducting a variety of tests at this facility. Earlier there was a question aboutcost and the cost differentials. When we got into a discussion about cost, I spoke prematurely.There s probably not much difference in the cost per watt if you think of the way these machinesare really handling energy. They are usually scaled and sized for the energy of a single pulse,and when operated repetitively you gain average power. Recall SR s operating up to a kilo-hertz; and we re operating at greater than a hundred pulses per second. We both have to designand build about the same kind of hardware to handle each individual pulse, and therefore yougain pretty quickly by going up in operating frequency. That really is the best thing to do interms of getting that power.We arrived at 120 Hz operating rate for our experiment somewhat accidentally. We got a nice120 Hz alternator for SDIO. For this application, the accelerator was originally required to pro-duce huge single pulses. To do this we spent a lot of money with Westinghouse redesigning thisalternator so that you could dump the energy at a much lower frequency than the 120Hz forwhich it was originally built. Through the course of the years, there has been less emphasis onrail gun beams and other large pulse applications. Since then we have been using the alternatorat its natural frequency. Through the SDF (Strategic Defense Facility), we will eventually bringon line a solid state modulator that will allow us to go to a higher frequency than the alternator.


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The RHEP ccelerator will produce about 400 kilowa tts of beam energy at 2 5 MeV.THOMAS W. EAGAR (MIT)What will be your beam spot size?BOB N. TURMA N (SNL)Spot size is planned to be large. RHEP is intended for beam processing rather than high currentdensity applications. The beam spot size will be on the order of ten centimeters.OLE SANDVEN (MIT)Circular?BOB N. TURMAN (SNL)Yes. Now w e can also make rectangular beams and we ve been looking at some designs forthat. We have looked at one design that would have a beam that s about 3 feet by about 10cen-timeters to make a really long narrow width beam. That may be getting a little bit marginal forhandling all the current flow, but on paper it looks pretty good. So it looks like we can m ake awide beam if we w anted to process something like a roll of newspaper or plastic film.In terms of single shot machines, we have sev eral of them at Sandia, the Hermes you had put upthere. It operates at 15 to 20 megavolts in a single shot. It is a very high current machine(800KA s). We just let that beam spread out to do non-destructive testing.Then w e also have the Sap per single shot accelerator which operates at 5 to 10megavolts. Oneof the things about the RHEP is that this next year we w ill be doing some ion beam processing,ion beam treatment. Reagan S tinett is doing an experiment there that will look at surface hard-ening and surface corrosion treatments.THOMA S W. EAGAR (M IT)RHE P s also an ion source?BOB N. TURMAN (SNL)If you reverse the voltage, yes.RICHARD HUBBARD NRL)Now, Bob, will that be the really first high rep-rate ion beam source in that parameter regime?BOB N. TURMAN (SNL)Cornell is doing some low rep rate ion-diode development at one to few pu lses per second. Ibelieve this will e the first accelerator to really go to high rep-rate. Cornell is working withReagan Stinett. Cornell has been working with SN L for several years on ion sources.RICHA RD I-IUBBARD NRL)Now, what about the smaller machines that you g uys used to have aroun d?


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BOB N TURMAN (SNL)We try to keep them available. We've got the old Troll accelerator which is equivalent to Thor atNSWC, same blueprints. The PI 112, a 1 MeV machine, for the low end and then we have the 4MeV RLA injector accelerator that DARPA funded. We have tried to keep those machines in astate where they can be brought back up, and so we exercise them routinely.PAUL FARRELL (BTG)I'm still interested in the cost. Does that mean that at 400 kilowatts that the RHEP will be about2 a watt also or does that mean that the SRL machine will come up to lo?BOB N. TURMAN (SNL)No, at 400 kilowatts the RHEP is going to cost about 5/watt.PAUL FARRELL (BTG)That's 2million to build it.BOB N. TURMAN (SNL)Yes, now we put a lot more R&D into that, but if you don't count the R&D, if you look at thecost of the next generation of machine or the hardware, it's going to be like 2 million.KEN STRUVE/MISSION RESEARCH CORPORATION (MRC)I attended a meeting at NSWC about a year and a half ago and the original focus was electronbeam welding. It became clear throughout that workshop that there were a lot of other applica-tions that made as much or more sense than welding. I became interested in the materials hard-ening end of the process and I have since written several proposals on that subject. In particular,there's one feature of the high energy electron beam welding which makes a lot of sense. That'sthe fact that you can quickly heat say along a strip or, a weld joint that you may want to annealor harden. If the beam quickly moves along the joint, the self quenching rate is still sufficientlyfast so that you get cooling rates high enough to achieve hardening. The cooling rates can belo4maybe even 105 degrees C per second. Based on that, I've been very interested in exposingsome demonstration samples for heating with some of the existing machines to look at some ofthese features with the low beam energies we have. For this application, we don't need to have a10 megavolt machine that has a high rep-rate. We could do this work with a single shot or somelow level pulse shots with the SRL machine and demonstrate some of these effects. That is thegist of the things that I've been interested in.I wrote a paper for this application for the Beams Conference in May and presented that justbecause I thought it was such a good idea. I got quite a bit of interest from the Japanese and theRussians. There is a Russian group doing the same kind of things and are very interested in thistopic. In fact, they're interested in collaborating. I'd be glad to talk to Nikita Wells and give himthe names of the people I have; maybe it's worth looking them up. There will be some opportu-nities there. But back to this doing experiment, I really think that we can do some decent experi-ments with existing machines like all the experiments described by Joe Danko and Carl Lundin.


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I think those are excellent experiments. I believe some of that kind of work needs to continue.Now, I also believe we can do those experiments without blowing up the material. We can be alittle more subtle about how we put the beam energy into the materials. We need to be carefulabout how we measure the beam fluence and how we characterize the materials afterwards. So Ithink it makes a lot of sense to do those kinds of things and doing that, we can get some direc-tion as to what kind of facility is needed, what kind of accelerators make the most sense, andeven if a user facility makes sense. But I strongly suggest that we continue that kind of activity.RICHARD HUBBARD NRL)Maybe to amplify just a little on Ken Struve's comments. It would be very useful for us to knowwhat applications require a single pulse with a relatively large area, and relatively high totalenergy, because there are several machines that can do that.DAN GOODMAN, SCIENCE RESEARCH LABORATORY, INC. (SRL)I just wanted to show a few things to answer some of the questions that were brought up. Theissue of what experiments to do has a lot to do with cost, and with expected payoff. We'vealready identified a few applications. It clearly is either going to e high end value experimentsor it's going to be high through-put experiments. I mean those are the things I think we shouldattack first, and the high through put experiments would be surface hardening. Now, I'm veryinterested in your comment about quickly bringing up the temperature followed by fast cooling.It's very easy for us to change the repetition rate on a machine in order to change the energydeposition time; that's controlled by how many pulses you give it in the first 10 milliseconds andhow many you give it the next second. Although we need a better way of diagnosing what thetemperature is on the surface; we have used thermocouples to measure the temperature, but I'mnot sure that's necessarily the best.OLE SANDVEN MIT)In the past we did some work using infrared measurements, but it's a little difficult with a laserbecause you need an energy absorbing layer, otherwise, you do not get any energy into the tar-get.DAN GOODMAN SRL)You could easily do that. At SRL we learned now that you have to make measurementsbetween beam pulses. There's a tremendous amount of noise associated with the operation ofthe accelerator. After a pulse, you have a millisecond or a fraction of a millisecond to measurethe sample temperature. This is sufficient time to make the measurements; it's a question ofprocess control. If you do need to maintain a specific time temperature history, then we willneed to develop a feedback control system of some sort.On the issue of cost, it keeps coming up, so at least I should address it here. When we talk aboutcost, it is only the hardware and fabrication costs. It does not include any mark up you take tosell the devices. Our estimates do include operating costs such as power, maintenance costs, butdo not include the facility cost with its associated labor. But if you do these numbers and for a10 MeV system, which may not be the right basis to use, but is required for deepest penetration,then the modules cost about 0.5M each. That makes a total of five million dollars. To arrive at


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this figure, we made the assumption of a couple thousand hours a year of operating time. Thesecosts end up being factors of 10 times less than lasers. These are the num bers that we've beenquoting recently, the 2 per beam watt com es from operating at 500 0 Hz. True we haven'tdemonstrated this frequency yet; the best I've done is about 14 00 H z recently and there may besom e cooling issues, but we are approach ing this operational level.KEN STRUVE (MRC)Aren't these costs pretty irrelevant at this point? I mean, this is a research machine.DAN GOO DMAN (SRL)And it may co me down you're saying?KEN STRUVE (MRC)Yes. I'm say ing that, it's really premature t o put cost on things because we're building researchmachines at this point.DAN GOODMAN (SRL)Well, you w ere asking for the numbers, and these are the numbers.BERTRAM HU I (DARPA)I agree. You have to address the cost issue up front and find out where the ceilin g is. Right nowif this is cheaper, then all it can d o is go up and this project is finished.KEN STRUVE (MRC)No, I'm saying it will go down.THO MAS W. EAGAR (M IT)Well, it may g o down, but the point is, at 1.75 per square meter, you're talking processing quar-ter inch thick steel which is ten pounds a square foot, whether it's a surface hardening or someform of phase transformation process. I could imagine cycling quarte r inch thick steel around itscritical phase transition fo r grain refinement, for example. Som ething that you can't do rightnow, because you can put the energy in very quickly here. Well, if that means that it's going tocost me 30 a ton if I get 10% better properties, I can afford 30 a ton. I can't afford 2000 a tonfor carbon steel. This basically says the machine could be used in an aluminum rolling mill or asteel rolling mill o r something like that. It's got enough power t o do it. If the costs go down, somuch the better, but certainly if I can improve the properties of my steel for 10 or 20 or 30 aton and can sell it for 300 a ton, then the economics are favorable.. S o I don't have to get toobig an improvement in properties whether it's toughness, or strength, or whatever, to be a ble tojustify incorporating the technology. I think that's the only purpose for estimating the cost, andthat's why I don't want t o sit here and debate cost. You talk about it being related to pulse fre-quency and I think you're right but a lot of this is utilization. My experience in high power elec-tron beam units right now is, if you want to assume that I have 100% utilization on my equip-ment, I can get my cost down to seem very realistic But the problem is right now you go out toBabcock Wilcox or someone who's got a 2 million electron beam welder and they're notusing it 100% of the time; in fact, they're not using it 5%of the time because they don't have that


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much work to go through.P UL F RRELL (BTG)Well, in the plastics industry they do. In other industries they don't.OLE S NDVEN (MIT)Is the reason lasers are being used for cutting is because they're going to use them 24 hours a dayand that's what they do.THOM S W. E G R (MIT)Right. n fact, that little shop I was talking about has 12 employees and a 100,000 laser. Theydon't just run that hours a day, they have a second shift where people come in and use it.SPE KER UNIDENTIFIED

technical question: at constant energy density per unit volume, how does the cooling ratechange as you increase the beam energy? I'm just wondering whether we stay in the sameprocess regime.THOM S W. E G R (MIT)By going to higher energies you heat a greater volume. I don't know exactly how cooling ratechanges because I think rep rate probably affects cooling rate more than anything else in thiscase. I mean, how much of what your total energy per unit time is going in there. But as you goup in voltage, your heating a large volume so the maximum energy delievered per unit mass ofmaterial is going down per pulse (for a fixed pulsed energy). But you're heating more materialthrough the thickness. Does that answer you question?SPE KER UNIDENTIFIEDNo.THOM S W. E G R (MIT)If you assume a constant temperature and you put more energy in, I'll guarantee you you're cool-ing rate will go down.SPE KER UNIDENTIFIEDI'm just wondering whether we're moving out of the surface hardening range?THOM S W. E G R (MIT)It has to do with your interaction time. In your surface hardening procedure, you're using themetal underneath to quench the layer that you're heating, and what happens in surface hardeningis you use a flame source or induction source, or whatever, and you're using anywhere between20 and 80%of your heat just to heat up the base material underneath you. If you can put all thisenergy directly into the material at depth while maintaining a fairly sharp interface, it will coolmore rapidly, and require less energy from these heat sources.


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KEN STRUVE (MRC)If you could heat along a line, then you would have an axial energy distribution which wouldprovid e a very fast heat flow.THOM AS W. EAGAR (MIT)Yes, but right now peop le aren t even doing that. It s just kind of a one dimensional problem.I m just thinking in the simple one dimension, but you re right if I go to two dimensional heatsources, I could double my cooling rate.KEN STRUVE (MRC)I m doing the calculation. It gets fast.OLE SAND VEN (MIT)It s very fast. But again it depends on the material.SPEAKER UNIDENTIFIEDBut the laser would be faster since it doesn tOLE SANDVEN MIT)Well, the laser delivers its energy on the surface and then conducts into the bulk of the materialthere, but you have a limited amount of depth you re going to get to because if you go faster, youmelt. Furthermore, the delievered power must be limited to prevent surface melting.BOB N. TURMAN (SNL)I think that s one of the reasons we re looking at ion deposition for the surface too. The ionrange i s very short so that energy is put right o n the surface more rapidly.VERNON L BAILEY (PSI)But you re sort of stuck. I mean , you don t want to bring the surface above melt.OLE SANDVEN (MIT)Exactly.VERNON L. BAILEY (PSI)You can t even stick it in melt; you have to wait until thermal diffusion takes your wave in and atthat point, you can guaran tee that the slope is quite small.OLE SANDVEN MIT)No, the coo ling is very high but it depends on how deep you want to go. You can t go too deepbecause if you go too deep, you melt the surface.THOMAS W. EAGAR (MIT)Well now that you ve given your inputs, it s my turn to give mine, and then w e ll go aroun dagain. There are two kinds of high volume areas that I d like to think of for processing. One iswhat I ll call the primary metal mill processing, whether we re talking about a steel mill that is


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trying to thermally cycle to get a phase transformation for the improvement of the microstructureor whether we re performing what I d proposed in the past for silicon iron transformer steelwhere you might improve its magnetic properties at 2000 a ton. With this technology, we havethe power to do the things that no one has had access to; it should be possible to process materialat the same rate that it comes through the mill. As an example, you end up trying to do texturingby melting through a grid or whatever. As yet, I haven t decided what the most promising thingsare, but I think we should look at steel mill processing, steel mill, or aluminum mill. For exam-ple, the aluminum alloys tend to be hardened with fairly high Z (atomic number) alloys, such ascopper, and some of the newer ones that contain iron inclusions. With the HEEB, you couldpreferentially heat your precipitates. Now what that would do in terms of creating residual stresszones in your aluminum I m not sure. It might be beneficial, or it might be detrimental. Butcertainly you could essentially tailor some of your metals right now to make them effectively, Ithink, composite light materials. You d process them as if they were homogeneous, and you dheat them preferentially because you have the ability to put heat locally into the high Z precipi-tates very rapidly, and so you can essentially heat one part of your material in a cool matrix.This would cause some mechanical expansion as the whole thing cools down you ll get certainresidual stress zones. So there s high volume processing like that to improve the value added ofsomething that s produced in terms of millions of tons a year. The other thing that I see as Imentioned in my presentation, is casting. A melting technology where you could make netshape. So those are my two processing applications.BERTRAM HUI (DARPA)This project has been tried many times with lasers and there has been some successes, but therehave been problems as well such as teh laser treatment of camshaft surface metal.THOMAS W. EAGAR MIT)Well, originally Siaky built a machine for Ford with laser hardening of camshafts and it didn twork because the laser put the maximum temperature right on the surface. When it cooleddown, you ended up with tensile residual stresses on the surface and they had to rebuild a com-pletely new machine with electron beam with enough penetrating capability so you heatedbeneath the surface for your maximum temperature, so that you got compressive residual stress-es on the surface. So, there are cases where you can do tailoring of residual stresses, becauseHEEB deposition profiles how the maximum temperature is beneath the surface.We re here to really talk about how can we justify this as a materials processing tool, not somuch on which machine we should use. From the things I ve heard there are single shotmachines and there are rep rated machines which may be available for research. Unless wecome up with some specific high interest products, I don t think anyone s going to pay for thedevelopment of the technology. We need to have an improved end product that comes out of theprocessing. I m not going to prevent you from saying anything, but I encourage you to think interms of where are the big payoffs for this technology. People are not going to continue to payto have this process developed unless you ve got a product in sight that you re going to be able tosell it. I don t think selling the process is the goal. Everyone feel sufficiently chastised now?


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KEN STRUVE (MRC)Let me ask you a qu estion. Is the automotive industry really interested in impro ving the life ofthe vehicles?THO MAS W. EAG AR (MIT)Well, if you re goin g to make a 50 year vehicle, no. Th e automotive industry w ants a car to wearout in 10 years, and they certainly want them t o last beyond the 6 year warranty period.RONALD G ILGENBACH (UM)There s motivation to make the American cars better than the Japanese cars right now. There isstrong motivation for that. Let s p ut it that way.THOMAS W. EAGAR (MIT)Right now, the managem ent hasn t really thought it out. I mean, if you cam e up with som ethingand you could make a car that would look like new after 20 years, somewhere down the linesome manager might figure out that that might not be good for business 20 years from now oreven 10 years from now. Right now, they re pushing s o hard on quality and improving thingsand trying to conv ince the American people that they re just a s good, or better than the Japanese.If you have anything that improves quality for them right now, they ll talk to you. Th ere is also amarket for cosmetic improvements even if the process is mo re expensive as long a s the changesare noticeable and sellable to the consumer. Today the industry is willing to pay m ore for quali-ty; and that was not true 10 years ago. They won t pay a fortune for quality and it s g ot to besomething that the consum er values. Recently they ve been able to sell a little bit of safety fea-tures. However, the Edsel w as a great safe car but it failed because it was unappealing and peo-ple wouldn t buy safety back in the 1950 s. Well, today you can sell an air bag, you can sell anti-lock brakes, but then what people really want is to never have to take the car back to the shop.In fact, I know of o ne automotive comp any in their luxury car line that has a goal of design ing acar which will never need any m aintenance except an oil chang e at 100,000miles.RICHARD HUBBARD (NRL)Richard A dler mad e the point that generally C W (continuous wave) o r D C (direct current)mach ines are cheap er electron beam sources than the pulse induction machines. U p until recent-ly that had been my bias and then I ve heard it at this meeting that that may not be the case. Isthis the technology that w e should really be focusing on , aside from th e fact that virtually every-body here has a background in pulse induction accelerators?DAN GOODMAN SRL)I think that if you need the absolute highest peak and average powers, th e induction acceleratortechnology is the only way you can really go. S o you have tw o questions, you have a questionof dollars per watt and you ve also got a question of how much power d o we need. Because ifyou need a quarter of a megawatt, you don t hav e any other choice.JOSEPH MANGANO (SRL)There s another point. A 5 to 10 MeV, W machine is very large. Th e 5 MeV CW is the highestpower CW accelerator built. To my knowledge, the MeV, a CW system that was built by


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Dynamitron is operated at 200 kW. That system represents the limit of that technology in termsof average power. I believe that the 200 kW Dynamitron cost 3M, or about 15 per beam watt.What I'm saying to conclude is that if you want high power, very high power, for a machine tosatisfy very high through-put applications, the pulse machines are optimum . I think if you'retalking about a 2 kilovolt or so machine, then I think that the W ources become m ore eco-nomical.THOMAS W. EAGAR (M IT)From a processing point of view, if I have the ability to pulse at reasonably high-rep rates, one to3 pulses per secon d, then I h ave the ability to put heat in very rapidly and ge t the types ofpressures for induced shock hardening, whereas in a continuous machine I can't do that. Rightnow I can get a 200 kilowatt beam. There have been plenty of 200 kilovolt, 200 kilowatt elec-tron beam welders built or 120 kilowatt electron beam we lders built. Now they don't have thepenetrating capability, and they don't have the shock hardening capability. It seem s to me thatthe pulsing g ives me something that's new. I don't know what you've go t that's new, if you g o toa CW machine. If you're at 5 MeV and at 4 milliamps, it works out to 200 kilowatts. You'vegot plenty of penetrating capability, but you don't have the shock harden ing capability. From amaterials processing point of view, if I have the pulsing capability at a couple of thousand hertz,I can either pulse it or I can make the m aterial think it's seeing a continuous beam depending onhow I adjust my pulse rate.PAUL FARRELL (BTG)I'd like to make one last point on this. When w e quote the Dynam itron technology, not discoun t-ed or anything, that's the selling price for a commercial machine and manufacturing price isabout half of that.JAY BOUDREAU (BSC)There's one other m achine which is available because it's being mothballed at L ivermore w hichhas somewhat similar parameters to ATA except it has lower current and much higher repetitionrate. So, I guess my only point is that if an yone is interested in demo nstrating where the pene-tration rate is critical, there exists an o perational 5 MeV machine. Unfortunately, they're mostlyout of the business.OLE SANDVEN (MIT)High speed tube welding might be som ething that we didn't think of.THOMAS W. EAGAR (MIT)That's true. That technology is currently limited by the welding speed. We're talking aboutthings like the Alaskan pipeline here folks; about 314 thick steel that you want to weld at metersper minute, or tens of meters per minute.OLE SAND VEN (MIT)There's also tube mills for even thinner titanium tubes. Current mills run at, maybe, six to seveninches per minute; they would like to run about three or four hundred inches per minute.


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THOMASW. EAGAR MIT)Plus, you should recognize that the welding machine that's currently used on that costs on theorder of one or two million dollars. It's just an arc welding machine. A lot of the cost is just fix-turing. You've got to have some big things to move, twenty ton pieces of pipe, but it's millionsof dollars for a machine. In the steel industry, millions of dollars is not a big deal for equipment,if it provides a good product.JAY BOUDREAU (BSC)I'm going to try to make the argument a little clearer as to why high energy electron beams mightbe suited for this reactor vessel annealing issue. This is a picture of the cross section through thewall of a reactor vessel. The damage is probably due to the fast neutron component. You cansee damage decreases a couple of orders of magnitude from the inside wall to the outside wall.Most of the damage is perceived to be on the inside wall. Look at the way that the problem hasbeen done in the CIS (Commonwealth of Independent States). I have a report here, if anybodyis interested, on the annealing of Navolvo Rock Ranez Unit Three. What the CIS has done is tobuild an electrical heating rig, about half the size of this front area, which they drop down insidethe reactor vessel. It is used to heat the entire inside of the vessel. This takes about a thousandhours. That's fine for the Soviet vessel because their vessels are joined with one circumferentialweld in the middle. U.S. vessels tend to have a lot of longitudinal welds in addition to many cir-cumferential welds, and this leads to concerns about increased stresses that may occur in theU.S. vessels. Furthermore, the U.S. regulations require that the vessels be maintained at a tem-perature well below that of the annealing processes. So you're right on the ragged edge withannealing of hitting some limits. The argument I make for high energy electron beams is againvolumetric heating and what it basically does to allow you to deposit in depth, with a relativelysmall spot size, pulses of well controlled energy, so that you can tailor the thermal stresses andprobably stress relieve both in the welds and through the wall in reducing radiation damage.This is shown for a single 3 MeV pulse. It was deliberately designed to keep the instanta-neous temperature rise down low enough that we didn't induce shocks that would exceed theyield stress. The resulting temperature profile through the wall after 17pulses would look some-thing like this. You can see from the curve it is possible to raise the temperature to that used bythe Soviets to anneal their vessels except now there is a very steep temperature profile. Thequestion that I have for the material scientists is, does that steep temperature profile assist in theannealing process, hurt what's going on with the copper interstitials that get deposited throughthe matrix? Or could you tailor a different set of pulse traces to both stay below the U.S. toler-ance limits on stresses and at the same time affect the annealing? The report that I have heretried to draw conclusions between what would be needed for U.S. annealing jobs compared tothe Soviets and I'll just summarize briefly. As I mentioned earlier, Soviet apparatus has a muchshorter annealing zone. In the U.S. we must cover very long longitudinal type welds. By usingan articulating system, in principle it should be possible to heat the U.S. vessels in a more rea-sonable manner rather than heat soak the entire structure. The U.S. vessels welds are a lot lessaccessible from both inside and outside; the idea of introducing a giant apparatus in there to heatthe whole structure is problematic. At the same time it's not very easy to drain U.S. reactors andthat introduces a whole other layer of complexity in how the annealing job might be done. So Iguess I've raised as many questions as I've addressed, but it seems like the flexibility of e-beamsmight have some virtue. It would take a fair amount of R D to nail that down.


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RONALD GILGENBACH (UM)Is that primarily annealing of the metal itself?JAY BOUDREAU (BSC)The weld is the weakest element, and the one of most concern as it tends to demonstrate crack-ing first. But you basically have embrittlement over a very large portion of the vessel itselfaround the central plane.THOMASW EAGAR (MIT)Any of the material scientists want to respond? I guess I would have a couple of points; f i r t ofall, that the rate of rise on the annealing curve is not that important to the annealing processbecause everything that happens takes place at the higher temperature. It s a thermally activatedprocess, basically it s diffusion that you re dealing with. If you integrate the diffusion rate on therise, you know what s happening. The rate does not matter because it is dominated by the diffu-sion rate at the final temperature achieved.JAY BOUDREAU (BSC)But the diffusion would still go as the slope of the temperature, right?THOMAS W. EAGAR (MIT)Yes, but it turns out that if you integrate over time to your maximum temperature, the amount ofdiffusion time is the same to within a factor of two. It doesn t really matter too much how fastthat rise goes, you tend to get about half of what s going to happen on the rise irrespective of thetemperature rise rate because half of what happens, occurs at the maximum temperature if youdon t maintain the maximum temperture very long, but that s mostly to get uniform temperature.However, there are several things that concern me. One is with the HEEB process you heat toolocalized an area while the rest of the structure is cold and rigid. This can cause the material togo through a thermal cycle that will introduce residual stresses. Now, you have to stress relievethese vessels. Anything over an inch and a quarter according to pressure vessel code has to bestress relieved. Which means you can either do a local stress relief where you put these big ther-mal blankets on, where you re heating an area of about two inches or two feet on either side ofthe weld in which case the thermal stresses aren t too bad because their internal gradients arelow, or you have to heat the entire vessel. People build thermal stress relief buildings, furnacesessentially the size of a three or four story building and 30 feet in diameter to stress relieve avessel. If the heating is too localized, it will create residual stresses that are just as bad as thewelding residual stresses.JAY BOUDREAU (BSC)So we re going in the wrong direction?THOMAS W. EAGAR (MIT)Yes. I think so. I mean you have to look at the residual stress. I mean you might want to gothrough and estimate what your temperature gradients are and what your residual stresses aregoing to be If you find that the residual stresses are significant, then it would be necessary toheat treat the whole vessel after the be m heating.


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JAY BOUDR EAU (BSC)Can I interject some questions for the beam people? How m uch can you move the beam andwhat kind of sweep rate can you make ove r a big region in order to tailor the energy deposition?THOM AS W. EAGAR (M IT)That s right. I mean, don t localize it so much that you might have to spread it out. I think youhave to think abou t heating of a two foot wide region, not a two inch wide region, O.K.?JAY BOUDREAU (BSC)So, you cou ld spread the beam, but you are going to need to be able to articulate the transportsystem to move the beam around. The other associated question is how much can you robotical-ly inject a beam in a com plicated geometry?VERNON L. BAILEY (PSI)Well that depends on the energy and several things about the beam, but using light beam pipesallows you to articulate that beam and move it around in some complex geom etry; so in princi-ple, you can move it around. In terms of moving the beam, I haven t tried to look at how quickyou can scan, but when we have a beam going unstable in the atm osph ere it will go this far...JAY BOUDREAU (BSC)All by itself?VERNON L. BAILEY (PSI)back and forth like that in 10or 20 nanoseconds. It s possible for beams to move fast.RICHARD HUBBARD NRL)And in that parameter regime, you were talking about 200 amps as I recall?JAY BOUDREAU (BSC)That s the calculation.RICHARD HUBBARD NRL)s a representative number. That beam a t that very high energy rate of current would be verystable over distances of many m eters. We could essentially back off a ways and do the sweepingby just m agnetically aiming it where we wanted it. That part is relatively easy.THOMAS W. EAGAR (MIT)O.K. My second concern happens to be radiation; how are you going to sh ield this thing?JAY BOUDREAU (BSC)Of course reactors are already radioactively hot.THOMAS W. EAGAR MIT)No, I mean all the neighbors that are a half a m ile down the road.


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VERNON L BAILEY (PSI)Because they a re half a mile dow n the road, the shielding problem i s easier.JAY BOUDREAU (BSC)They re already shielded.BOB N. TURMA N (SNL)They re already shielded by the reactor facility itself.JAY BOUDREAU (BSC)You w ould not h ave an ope rator right adjacent to the reactor.THOMASW EAGAR (MIT)If I didn t know you have 300 MeV gamma rays com ing out of the reactor.DAN GOODM AN (SRL)You d have to loo at the numbers because this is really very energeticKEN STRUVE (MRC)No, the attenuation values level off at about 5 or 10 megavolts.THO MA S W. EAGAR (MIT)Is it? O.K. Tha t s fine.VERNON L BAILEY (PSI)So that as the energy is increased above 10 MeV, the shielding requirements do not increasemuch.SPEAKER UNIDENTIFIEDWhat kind of accelerator do you use to get 300 MEV at 200 amps?RONALD GILGENBAC H (UM)Micro trons go up to 50 MeV.BOB N. TUR MA N (SNL)Several organizations have looked a t high energy beam accelerators as part of the charged parti-cle beam program.THOMASW EAGAR (MIT)But again we re getting off the main topic, and worrying about who s going to buy what acceler-ator, and w e should be focusing on the processing.NIKITA WELLSISCIENCE APPLICATIONS INTERNATIONAL CORPORATION (SAIC)Relative to the hardening of steel, I ve heard this thing about the train rails hardening and I am afan of railroading. Is this still in the running, of going along the railroad tracks and hardening


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the steel?DAN GOODMAN (SRL)Well, yes, we want to demonstrate this, and the numbers look like we could do this economicallyas long as you can isolate the populace from the HEEB radiation as it moves along the track. Idon t know if it will be possible to get anyone to pay for it even though we could probably justi-fy it economically. If you just figure out how much rail steel there is out there, and how often itwears out, yes it makes sense.NIKITA WELLS (SAI)How often does it wear out? Do you really need to do this?THOMAS W. EAGAR (MIT)Typically, they talk about ton miles. How many tons go over the rail before repairs are needed.I can t remember the exact numbers, but it s like 10 million tons before the rail has to bereplaced. This translates to about 30 years before replacement. Now, one of the problems is ifyou go out and make a rail that will last for 90 years on some railroad line, you ll liable not tohave a steel producer that will produce rails for you when you need to replace them. They re notgoing to keep that mill running for you to come in every 3 years and give them a years worth ofwork.SPEAKER INIDENTDFIEDAren t you going to have magnetic levitated trains in 30 years.THOMAS W. EAGAR (MIT)There is a glut right now of rail capacity in this country partly because other countries are dump-ing rail steel into this country. So, it s problematic economically whether the railroads can justi-fy replacement of their capital equipment. You probably will have the steel companies up inrms because they re not going to be selling all that steel, and they may shut down. Then whatare you going to do when you need steel?

BOB N. TURMAN (SNL)I ll bet shifting road bed problems are a bigger problem that rails; shifting of the road bed andspikes working loose, and having to do realignment.OLE SANDVEN (MIT)I also noticed that there are a lot of railroad tracks around that are not being used.THOMAS W. EAGAR (MIT)It turns out that on premium lines they re now using concrete ties and other quality materialsbecause they can t afford the down time to go in and replace the ties 20, or 30 years later. Theypay the extra cost to put in concrete ties. If you go look at the Japanese bullet trains, they all runon concrete ties. So, anyway, I think it could be done technically, but I think there are all kindsof political hurdles to actually doing it. If you could convince the world that we only neededthree rail mills rather than twenty, then you could probably justify it. But which of the seventeen


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are going to close down, an d which countries are going to own the rail business?KEN STRUVE (MRC)The other thing is these austenitic stainless steels can t be hardened by quenching. I don t knowwhat effect the electron beam would have on perhaps hardening or modifying the microstruc-ture.THO MA S W. EAG AR (MIT)They ca n be cold worked to g et the right hardness in many cases.KEN STRUVE (MRC)Suppose you took a cold worked material; e.g. tw o sheets welded together. This would hav ereduced the strength properties along the weld. Th e question is, can these propertie s be restoredwith an electron beam, and if so, could these structures then be m ade with thinner piec es of steelto obtain a cost savings?THOMAS W. EAGAR (MIT)Shock hardening. Tha t is essentially shock hardening over large areas think.KEN STRUVE (MRC)Shock hardening should improve strength along the weld. In particular, for the austenitic stain-less steels shock harden ing will increase their hardness.THO MA S W. EAGAR (MIT)Can we now talk about shock hardening of the piece rather than just the welds? Th e reason peo-ple only shock harden welds is because all they had was a Q switch laser which costs so muchand could do s o little in terms of its power and energy output. Now we hav e a tool that can letus conside r hardening whole sheets of material, or plates, o r whatever.BO B N. TURM N (SNL)I ve got a coup le of things. don t think we ve mentioned anything about cross-link bonding ofpolymer surfaces. I think that could be important. You had mentioned also silicon evaporationprocess and that is not done now because it required too high an energy density. Is that some-thing that might be an important area? What about evaporational deposition?SPEAKER UNIDENTIFIEDYes, but think there are limits to that technology. We need to solve the through-put problem.The high energy densities also give rise to what s called spitting, where liquid droplets com e ou tof the melt.THOMASW EAGAR (MIT)With volumetric heating, spitting will be cut down a great deal because the other sources heatthe surface which cau ses them t o vaporize.


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SPEAKER UNIDENTIFIEDDo you mean con trolled evaporation?THOMAS W. EAGAR (MIT)We could call it controlled evaporation. There s one idea that Joe Mangano had a while back,regarding whether you could use HEEB in the controlled vapor deposition (CVD ) of diamond.It turns out that defects supposedly stabilize the diamond crystal structure over graphite. Thebeam would be introducing defects into the substrate. But in addition, current CVD of diamon dis done at a reduced pressure. At high pressure the VD discharge tends to arc. f it were possi-ble to use the beam, then the C VD a t high pressures could be pursued.BOB N. TURMAN (SNL)In most of our discussions, we ve been thinking of the beam as just a heat source. It is also asource of electrons that might be used for driving chemistry, as well as thermodynamics. Thiscame to mind as you w ere talking about some of the nanograins formation. I think we sho uldn tforget that we might be able to control certain types of chemistry with the beam.THOM AS W. EAGAR (MIT)Tailoring of interfaces and com posites, polymer based co mposites, where you ve got some fiberin there and you want to have the right type of interface adhesion. Or in other cases you mightput tw o polymers together and produce some cross linking across there where ordinarily thosetwo polymers don t link. Interface control in polymers, I guess we can call it.BOB N. TURMAN (SNL)One of the problems that DO E faces is large amounts of hazardous waste. Som e of this materialis both radioactive and toxic. DOE is looking at ways of breaking the bonds to change the mate-rial to a pure radioactive waste.DAN GOOD MAN. (SRL)I m just feeling a little bit overwhelmed here and confused because we ve now thrown ou t a lotof ideas over the last day and a half, and I still can t tell what experiments we can or should do.THOM AS W. EAGAR (MIT)Well that s what we got for the last 20 minutes. I ll give everyone three votes. You ve got threevotes out of 25 topic areas for what you think are the three most important areas to work on. I dlike to restrict it to these 25 things, which re materials processing things for your top threevotes. Are people willing to do that? I ll give you two minutes to read and pick and then wewill go through and we will write numbers and take a show of hands on what we have. Doesthat make sense, Dan? Is that going to get to where you want?DAN GOODM AN (SRL)Well, then som ebody has to dec ide what s possible and what s difficult.THOMAS W. EAGAR (MIT)Have you voted? Take your seats, I m going to tell you how I m going to resolve this .


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Everybody take your seats. We have three winners. I would say, we got consolidation of pow-ders with three over there, we ve got 15votes for bonding of dissimilar materials. I would sug-gest that we should list bonding and consolidation of materials which includes powder com-paction which is one of the major processes. It also includes making dissimilar metal joints andwe can make that as a big heading, and then we could have the sub-headings underneath them.VERNON L. BAILEY (PSI)It also includes shock hardening. All of them require reasonable high pressures I would say.THOMAS W. EAGAR (MIT)O.K., but I think most people were thinking shock hardening as introducing dislocations, where-as this is a bonding process and consolidation in an interfacial; to me they are just bondingprocesses, one s powders, one s solids. Shock hardening, I think, is introducing mechanical dam-age within the material. Agreed it s all interrelated somehow, but surface or volumetric harden-ing, treating large areas, seems to me that s very similar and it s the same thing. We see high vol-ume opportunity for surface treatment here. I think we re talking of mill processing or largeparts, things that require large area thermal treatment where we could take advantage of the vol-umetric heating capability of this process; does that sound about right?OLE SANDVEN MIT)Yes.THOMAS W. EAGAR (MIT)Now, are there any others that got lots and lots of votes? Well, we got point defects that comesin third, after we combine everything else. Actually high volume steel processing or aluminumis really part of 11and 3 in a sense, the aluminum. So we got two things. We tried for three andwe got two.DAN GOODMAN (SRL)Could you say them one more time?THOMAS W. EAGAR MIT)O.K., the first one is, well not necessarily the first one, but the easiest one to state is bonding andconsolidation of materials, which includes joining of dissimilar materials and consolidation ofpowders, and we re really using the mechanical energy to create the mechanical pressure; in thiscase to create bonds.DAN GOODMAN (SRL)Is it really mechanical or is there also melting?THOMAS W. EAGAR (MIT)Well, there is heating. It s heating and mechanical. It s a forging together of everything, if youwill. But in any case, it depends on how much energy you put in. Basically, we re consolidatingmaterials whether it s two large pieces of material to make a dissimilar material joint, or whetherit s consolidation of powders or formation of composites; I mean, if you m x different powders


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you ve got a composite material, right?DAN GOODMAN (SRL)So does this require a focused or an unfocused beam?THOMAS W. EAGAR (MIT)Well, you re really using shock energy, you may have an additional layer on the top that you takeoff at the end. f you re going to do powders you ll probably do them in a can. You hit the canand squeeze it all together and then remove the can by machining.BOB N. TURMAN (SNL)Sounds like a moderately focused beam.THOMAS W. EAGAR (MIT)Yes, it s not a very high brightness beam. It s not high brightness, but it is short pulse introduc-ing shock pressure into the material.DAN GOODMAN (SRL)Well, the thing about the powders and the cans is that, while it s true the electron beam provideshigh shocks, they re very localized sorts of things, in general.THOMAS W. EAGAR (MIT)Depending on how localized the beam is, because in this case we might want ten nanosecondpulses over a large area.DAN GOODMAN (SRL)There is only 10 to 50 joules in a pulse burst from the SRL machine, that you re not going to beable, in 5 or 10 nanoseconds, to provide that much pressure impulse on a base plate. You can geta very high instantaneous pressure if you focus the beam down to maybe a few millimeters, butyou re not going to be able to over large areas. It will be necessary to go to higher current accel-erators to do that.THOMAS W. EAGAR (MIT)But, it s very important now in explosive bonding, to actually end up having to have a coverplate and pulse it in different locations. You re pulsing it fast enough and scanning the beam atthe same time, that you are essentially controlling the explosive front along that sacrificial coverplate.DAN GOODMAN (SRL)So you can do it little by little, you don t have to do it all at once?SPEAKER UNIDENTIFIEDI d have to take a look at the old data, but you want to do it fast enough that the driver platedoesn t decelerate. It is necessary to provide uniform acceleration of the bonding plate. And itmay mean that the rep rate may have to be higher than you re currently considering.


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DAN GOODMAN SRL)Yes, I just can t believe that our parameters would be high enough to do that.SPEAKER UNIDENTIFIEDThey may not be. I think we re probably talking about a different machine.THOMAS W. EAGAR (MIT)O.K., so that s the first one, bonding and consolidation of dissimilar materials or advanced mate-rials, and I ll break it down a little bit underneath that. The other area is surface and subsurfacethermal treatment of materials over large areas. That can include a number of things, but essen-tially in the first one we re taking advantage of the high power capability and the mechanicalenergy that we can generate with these beams, and in the second one we re taking advantage ofis the high power and the thermal energy deposited subsurface. Now, we come back and tell theconference that these combinations of localized mechanical shock and energy should be able todo unique things that can t be done with with explosive bonding or other means in terms of pro-ducing new materials that are difficult to produce otherwise, or thermal treatment over largeareas, where we might talk high volume type of industries where we can do thermal processingslightly sub-surface, within a few millimeters of the surface, sub-surface; that s something thatwe cannot do with any technology. While you could consider lasers, it would take too many tobe practical.If I look at these two, they actually do pick up combinations. If I put them together there are noother processing tools that can do those things, or the combination of those things: large areathermal treatment or controlled high pressure mechanical deformation and consolidation. So Iactually can bond things together, large, solid objects together, that I might not be able to dowith explosion. In the explosion process you also have all this loss at the ends. You havedefects you have to cut away, whereas in principle we might be able to spin around somethingand consolidate different shapes and stuff that people apparently do. Does that make sense? Isit specific enough but also general enough that it hasn t left out lots of things?VERNONL.BAILEY (PSI)I think it would be good to keep the integrity of that entire list as well as the emphasis on thosetwo general areas, but that s a good list of ideas that we came up with.

WORKSHOP SUMM RYTHOMAS W. EAGARfMASSACHUSETTS INSTITUTE OF TECHNOLOGYOur group went around several times and we listed 25 different issues which I will not gothrough in detail; in fact, I won t even put them all up. But then we went through and gaveeveryone three votes and it came out very obvious that there were several main areas. We endedup combining those and then came up with two final comparable areas. The first area for oppor-tunities in high energy electron be m materials processing was essentially using the high powercapability and the volumetric surface heating capability to process large volumes of material.There were a number of ideas that f i t into that, such as heat treatment of steels, surface harden-


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ing of steels, and phase cycling (steel or titanium going through a phase transition at certain tem-peratures and by cycling around that temperature you can do grain refinement or general struc-ture modification of different types of steels.) We talked about carbon steels, high nitrogen andother stainless steels, and preferential heating of second phases for driving chemical reactionsFor example, in aluminum x-alloys where x has a higher atomic number, lower specific heat, oris a higher density, the beam will tend to preferentially heat that material. The second phase par-ticles or fibers are rapidly heated locally in a cold matrix which would produce, on cooling,residual stresses in that matrix. This could be very beneficial, and you might be able to produceproperties that you could achieve no other way. Polymer cross-linking we thought that therewas certainly some opportunity here to combine polymers, either sheets of polymers in control-ling the interface or doing cross-linking within a bulk polymer. Tearing of composite interfacesand producing residual stresses could be beneficial to the properties of that composite. Becauseyou can heat beneath the surface you can get compressive residual stresses on the surface ofmaterials. You can put heat into these materials more rapidly than if you have to wait for it todiffuse into the material. You have large powers, large wattage available with these machines.Again, as I presented in my talk, you need to think of combinations, and the combination here isa large total power capability as well as the ability to do volumetric heating. There is no otherprocess that combines those two in this way that we can think of.The other topic area is bonding in consolidation of composites into similar materials throughmechanical shock treatment. Essentially, in this application we are combining the mechanicalenergy with the large total power. So, again, you could do large volumes of material andalthough you could do explosive bonding of these similar materials, we think there s going to bea lot more flexibility here than with just using charged explosives in terms of controlling thevelocity of the interface, the ability to consolidate advanced powder materials, whether these areamorphous metals, or advanced interrnetallics, or consolidation of composites where you havemixtures of powders, whether it be ceramics and metals mixed together. The preferential heat-ing of the interface that you can get with this mechanical energy should allow us to consolidatematerials that we have no other way to consolidate to make bulk materials. Also bonding of dis-similar materials for cladding applications, whether it be aluminum and iron or iron and titani-um, etc. Just to give you a reminder of that, Vern Bailey had presented this one before where heshowed the explosive technique. There are a number of problems with this technology, and infact the radiation problem is not a barrier because here you can t really be very close to it eitherbecause of the noise. Essentially this is only done in a couple of places in the world. It s donein some valley in Pennsylvania because it s close to Dupont. It s also done by explosive fabrica-tors out in some mountain valley near Denver. It is done in small volumes sometimes in vacuumchambers within a laboratory, but there are lots of problems. As Vern said, they can t lower thevelocity of the detonation front as slow as they would like. With the HEE technology, wethink we d be able to consolidate more complex geometries.So, those were the two general topic areas and I think both of them combined at least two of theproperties. In one case, the volumetric heating and the high power. In the other case, themechanical energy that you can generate through shock waves and the high power. Both ofthem allow you to process high volume materials and in some cases also high value added mate-rials. We consolidated all this into two fairly general areas.


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You notice welding was not one of the primary areas that people came up with in our group.One other thing that our group mentioned is that there are a number of machines out there. Infact, I didn t realize the machine in Sandia for example, is actually being built to do large areaprocessing. They don t have a very high brightness beam like the SRL (Science ResearchLaboratory) machine. They have a much larger be m on the order of centimeters, tens of cen-timeters, I guess, in size. But it actually is being built to do some materials processing and sur-face hardening and things like that. There are a number of single shot machines and a number ofthem came up that people felt could be used for this type of work.

Eagar 133 Supplement

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