Tungsten Heavy Alloys

8/20/2019 Tungsten Heavy Alloys

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TUNGSTEN HEAVY ALLOY

Design Manual

S. G. Caldwell, Ph.D.

1!" C#un$% Line adMadis#n, AL '("()***+""*+!"!***+*+!1! -awww.$ungs$en/0#d.#2


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Table of Contents

1. The Metallurgy of Tungsten Heavy Alloys ……………………..…………………. 3

2. Alloy Selection Criteria …………………………………………..…………..…… 5

Why use WHAs?

ensityMechanical !ro"erties

Ther#al an$ %lectrical !ro"erties

&Mag& 'ersus &(on)Mag& Alloys

3. esign Consi$erations ……………………..…………………………………….... *

The (ature an$ A$vantages of !+M

Monolithic or Multi)!art?

&,a$iation -oints&!reserving Mai#u# Mechanical Strength

/. Machining 0ui$elines …………………..………………………………………….

11

Saing

0rin$ingMilling

Turning acing an$ 4oring

rillingTa""ing

%MTher#al Contouring

5. -oining ………………………………….………..………………………………. 1/

Mechanical

4raingWel$ing

Sinter 4on$ing

6. inishing …………………………………………………………………………. 15

Corrosion 4ehavior

Coatings

7. Ty"ical A""lications ……………………………………………………….…….. 16

,a$iation Shiel$ingAircraft Counter8alances

Well 9ogging

,acing Weights

4oring 4ars:r$nance A""lications

2


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Conclu$ing ,e#ar;s

1. The Metallurgy of Tungsten Heavy Alloys

The na#e &tungsten& is $erive$ fro# the Se$ish ter# #eaning &heavy stone&.Tungsten has 8een assigne$ the che#ical sy#8ol W after its 0er#an na#e wolfram.

While so#eti#es regar$e$ as a scarce or eotic #etal its a8un$ance in nature is actually

a8out the sa#e as that of co""er. The largest ;non tungsten reserves are in #ainlan$China though "lentiful reserves also eist in (orth A#erica.

Tungsten has the highest #elting "oint of all #etals. The

etre#ely high #elting "oint of "ure tungsten #a;es all the co##on #anufacturingtechniues use$ for #etals such as iron i#"ractical. S"ecialie$ #etho$s #a;e "ossi8le

the "rocessing of "ure tungsten into ro$ sheet an$ ire for a i$e variety of high

te#"erature a""lications inclu$ing incan$escent la#" ire T@0 el$ing electro$es an$

high te#"erature heat shiel$ing.

Another i#"ortant in$ustrial "ro"erty of tungsten is its high $ensity of 1.3 g+cc. @n a$$ition to high gravi#etric $ensity its high ra$iogra"hic $ensity #a;es

it an i$eal #aterial for shiel$ing or colli#ating energetic ) an$ γ )ra$iation. or such

a""lications tungsten is co##only alloye$ in or$er to circu#vent the etre#ely high

"rocessing te#"eratures that oul$ otherise 8e reuire$ to #elt an$ cast the "ure #etal.

Tungsten heavy alloys are i$eally suite$ to a i$e range of $ensity

a""lications offering a $ensity a""roaching that of "ure tungsten 8ut ithout the very

costly "rocessing an$ inherent sie an$ sha"e li#itations of the for#er. WHAs are

"ro$uce$ 8y a "o$er #etallurgy techniue ;non as liui$ "hase sintering in hich co#"letely $ense fully alloye$ "arts are for#e$ fro# "resse$ #etal "o$ers at a

te#"erature less than half the #elting "oint of "ure tungsten. While sintere$ steel an$co""er alloy "arts co##only contain significant resi$ual "orosity that #ay reuire

"oly#eric infiltrants to seal sintere$ WHAs have a non"orous surface.

WHA "arts are #anufacture$ fro# very fine high "urity #etal "o$ers B ty"ically

tungsten nic;el an$ iron. The 8len$e$ #etal "o$er is co#"acte$ un$er high "ressure


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structure of a co##on co##ercial WHA is to)"hase consisting of a lin;e$ netor; of

tungsten s"heroi$s containe$ in the $uctile #atri "hase.

The s"heroi$ie$ #icrostructure shon 8elo is ty"ical for #ost co##ercial WHA

"ro$ucts. The roun$e$ "hase is essentially "ure tungsten hich

is surroun$e$ 8y a #etallic nic;el)iron 8in$er "hase containing so#e $issolve$ tungsten.

This structure "rovi$es the #ai#u# #echanical "ro"erties for a given alloy co#"osition.Through the "rocess of "ressing an$ 9!S #etal "o$ers are transfor#e$ into fully $ense

sha"es that are very close to the $i#ensions of the finishe$ "arts.

WHAs can su8seuently 8e su8ecte$ to "ost sinter heat treat#ent an$ #echanical

$efor#ation to increase tensile "ro"erties an$ create $irectional #icrostructures. While

such o"erations are co##only reuire$ for #ilitary a""lications co##ercial WHAsgenerally $o not reuire this a$$itional "rocessing an$ are su""lie$ in the as)sintere$ state

for #ai#u# econo#y.

WHAs are a s"ecial class of #aterials $iffering fro# "ure tungsten. They share

al#ost no co##on characteristics ith &tungsten steels&


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2. Alloy Selection Criteria

Why Use WHAs?

WHAs "rovi$e a uniue co#8ination of $ensity #echanical strength #achina8ility

corrosion resistance an$ econo#y. Conseuently WHAs are i$ely use$ for

countereights inertial #asses ra$iation shiel$ing s"orting goo$s an$ or$nance "ro$ucts. These versatile #aterials "rovi$e $istinct a$vantages hen co#"are$ to

alternate high $ensity #aterials as seen in the ta8le 8elo.

Material ensity!g"cc#

TensileStrength

Stiffness Machin-ability

To$icity %adio-acti&ity

'ost

W() *+,-*., moderate high e$cellent lo/ none moderate

Lead **,0 ma$, &ery lo/ &ery lo/ &ery lo/ high none lo/1ranium *2,+-*2,. moderate medium special high present high

As can 8e seen fro# these $ata WHA overco#es the toicity $efor#a8ility an$ inferior

$ensity of lea$ an$ its alloys. 9i;eise it can "rovi$e euivalent $ensity to $e"lete$uraniu# 8ut ithout the s"ecial #achining consi$erations an$ licensing reuire#ents for a ra$ioactive su8stance. WHA is truly the

#aterial of choice for high $ensity a""lications. These uniue alloys "rovi$e the $esigner

ith #any ne free$o#s.

There is one s"ecial category of $ensity a""lications in hich WHAs shoul$ not 8e

use$. or a""lications in hich the service te#"erature ill ecee$ E3==°C slight surfaceoi$ation ill occur in air. @t is i#"ortant to note that at service te#"eratures ecee$ing

E5==°C WHA strength ill fall off ra"i$ly even in a "rotective at#os"here. or these

s"ecial cases "ure tungsten #ay "rovi$e a 8etter o"tion. @f reactive at#os"heres are

"resent in co#8ination ith elevate$ te#"erature the 8est choice for very $ense #aterialsill 8e the "latinu# grou" #etals B 8ut at etre#ely high cost.

Density

ensity is the single #ost i#"ortant "ro"erty that #a;es a WHA the #aterial of

choice for a given a""lication. The selection of a s"ecific co#"osition for a given $ensity

a""lication #ay ulti#ately 8e #a$e on the 8asis of concurrent #echanical "ro"ertyreuire#ents or sintering consi$erations unless a s"ecific value of $ensity is critical.

WHAs can a""roach the $ensity of "ure tungsten an$ G ithout the high cost of the

for#er or the licensing an$ s"ecial han$ling reuire#ents of the latter.

As is true ith #ost #echanical $esigns the o"ti#u# $esign is the one that

a$euately a$$resses all critical "ara#eters an$ offers the 8est co#"ro#ise of there#aining o"tions. As the $ensity of a WHA is increase$ the availa8le $uctility $ecreases.

5


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Alloy $ensity varies accor$ing to tungsten content as can 8e seen in the folloing ta8le of

Tungsten !ro$ucts stan$ar$ alloys.

TP)lloy3

'omposition!Wt, 4#

M5L-T-6**0'lassification

Typical ensity!g"cc# !lbs"in6#

Magnetic

Permeability !µ#

S*+ .W-!7Ni"Fe# 'lass * *+,*0 ,8*. >8,ens6* .W-!+Ni"Fe# 'lass * *+,6 ,866 *,6-*,9

S*+9 .6,9W-!7Ni"Fe# 'lass 6 *+,86 ,87+ 0,9-9,

ens67 .6,9W-!+Ni"Fe# 'lass 6 *+,88 ,872 *,6-*,9

S*2 .9W-!7Ni"Fe# 'lass 7 *2,*7 ,899 0,-0,9

ens69 .9W-!+Ni"Fe# 'lass 7 *2,*8 ,898 *,*-*,6

S*29 .+W-!7Ni"Fe# 'lass 0 *2,9+ ,8+* 6,9-7,

@n a$$ition to these stan$ar$ co#"ositions Tungsten !ro$ucts can also #anufacturecusto# alloys. !lease inuire ith any s"ecial a""lications you #ay have.

Mechanical ro!erties

Mechanical "ro"erties of #o$ern WHAs far sur"ass those availa8le fro# WHAs

even a fe $eca$es ago. Three factors "ri#arily contri8ute to this a$vanceF higher

"urity ra #aterials cleaner an$ #ore "recisely controlle$ "rocess environ#ents an$ the use of #o$ern tungsten)nic;el)iron co#"ositions rather than the ol$er

alloys containing co""er.

@t is also i#"ortant to note as a general consi$eration that #ai#u# attaina8le

"ro"erties for these alloys varies ith the sie of the 8lan;. This is a $irect conseuence of

the nature of the sintering o"eration use$ to #a;e the "arts. A nu#8er of gra$ients B

ther#al che#ical an$ gravitational B eist $uring sintering. As the #ai#u# sectionthic;ness of a given "art is increase$ ther#oche#ical re#oval of i#"urities fro# the

center of the "resse$ "art "rior to surface "ore closure 8eco#es #ore $ifficult. Therefores#all "arts ill alays ten$ to have higher #echanical "ro"erties than larger ones.

Tungsten !ro$ucts offers a stan$ar$ set of co##ercial alloys that confor# to M@9)T)

21=1/ ASTM 4777)*7 an$ AMS)77254 reuire#ents for #echanical "ro"erties. Asseen in the ta8le 8elo the no#inal "ro"erties liste$ #eet or ecee$ these s"ecification

reuire#ents. All values shon are for #aterial in the as)sintere$ state as this is the #ost

co##only su""lie$ con$ition of the #aterial for co##ercial a""lications.

TP )lloy3 Wt,4 W 1TS !:si# ,64 ;S !:si#


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S*29 .+ ** +9 7 96 62

All WHAs are susce"ti8le to hy$rogen e#8rittle#ent hich loers the $uctility of

the alloy. Tungsten !ro$ucts can "rovi$e alloys in a hy$rogen outgasse$ con$ition hich in so#e cases #ay $ou8le the tensile elongation. urther

"ro"erty enhance#ents are "ossi8le through a$$itional "ost)sinter "rocessing. or structural a""lications it is reco##en$e$ that #aterial 8e use$ in the #ost$uctile con$ition feasi8le for the given "art.

Ther"al an# $lectrical ro!erties

The "ro"erties of WHA are governe$ 8y the "ro"erties of its "rinci"al constituent

tungsten. While "ro"erties ill vary slightly ith tungsten content 8in$er co#"osition

an$ #icrostructure several "ro"erties ill 8e cite$ for a ty"ical alloy such as S175. This

#aterial ill have a ther#al con$uctivity of E12= W+#)° an$ a corres"on$ing electrical

con$uctivity of E13D @ACS. The ther#al e"ansion is very lo ith a CT% of

E5.=%)6+°C at 2=°C. The s"ecific heat of S175 is E=.36 cal+g+°C. While the #elting "oint of "ure tungsten is etre#ely high WHAs ill 8egin to for# a liui$ "hase hen

heate$ in ecess of E1/5=°C . WHAs are not suita8le for high te#"erature

a""lications.

%Mag% versus %&on'Mag%

@t is unfortunate that in$ustry literature has $escri8e$ fa#ilies of agnetic& an$

&non)#agnetic& WHAs thus i#"lying significant #agnetiation of the for#er. &Magnetic&$enotes a reasona8le attraction to a #agnet B not that the WHA itself 8ehaves as a

"er#anent #agnet in the con$ition su""lie$. The #agnetic res"onse of WHAs is #ost

co##only #easure$ ith an instru#ent such as the Low Mu Permeability Indicator


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(. Design Consi#erations

!o$er #etallurgy offers to o"tions for WHA #anufacturing B near netsha"e 8lan;s or net sha"e "arts. These consi$erations a""ly as ell to !+M "arts of

#aterials such as co""er an$ steel as ell. urther the s"ecific nature of WHA "resents

a$$itional consi$erations that #ust ta;en into account in the $esign "rocess.

The &ature an# A#vantages of )M

!+M is a very useful #o$ern #anufacturing "rocess that "rovi$es a #eans of

"ro$ucing "arts fro# 8len$e$ #etal "o$ers that circu#vents the nee$ to start ith larger

than nee$e$ #ill sha"es an$ then s"en$ #oney an$ ti#e re#oving ecess stoc;. Through

!+M in$ivi$ual "arts can so#eti#es 8e #a$e


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area. Higher DW alloys shoul$ 8e use$ for greater slu#" resistance. or #any

a""lications $ue to these !+M consi$erations a 2.5DW alloy ill 8e a goo$ choice.

Single iece or Multi'art?

While conventional is$o# hol$s that there is econo#y in sie this "hiloso"hy has a

li#it hen a""lie$ to !+M. As "art sie increases attaina8le #echanical "ro"erties

$ecrease slightly. 9arge "arts also invite the for#ation of a front to 8ac; $ensity gra$ientes"ecially in loer DW alloys. Also as "art sie increases #achining alloances #ust

also 8e increase$ to guarantee clean u" of the 8lan; to the finishe$ geo#etry. 'ery tall

"arts oul$ "rove i#"ractical to #a;e as a single "iece 8ecause of furnace height

li#itations an$ ten$ency for gravitation colla"se $uring 9!S.

The solution for large or s"ecial geo#etry "arts is to fa8ricate the# as s#aller

&8uil$ing 8loc;s& hich can either 8e #echanically fastene$ to su""orting structures or

furnace 8rae$ into a large #onolithic co#"onent an$ then #achine$. The 8uil$ing 8loc; a""roach also #a;es "ossi8le the creation of functionally gra$ient #aterials hen utilie$

in furnace 8rae$ or sinter 8on$e$ asse#8lies.

:riginal reuire#ent 4etter o"tion

Ma;ing a large eight co#"onent as a series of s#aller #echanically attache$ ones

overco#es #anufacturing sie li#itations an$ can result in 8etter #echanical "ro"ertiesan$ #ore econo#ical "arts that if $a#age$ in service can 8e re"lace$ 8y section as nee$e$

rather than as a hole.

Tungsten !ro$ucts currently offers 7 stan$ar$ gra$es of WHA in a variety of 8loc;

flat an$ roun$ sha"es B or custo# #achine$ to final for#. Sies can range fro# gra#

eight to #any hun$re$s of ;ilogra#s. Sheet is availa8le in thic;nesses $on to =.=25&.

%*a#iation +oints%

esire$ "art too

large+tall for

$e"en$a8le 9!S

!art asse#8le$

fro# 3&8uil$ing 8loc;s&

for #achining


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Many cylin$rical sha"e$ ra$ioisoto"e containers having noncircular ra$ial in$os

oul$ 8e virtually i#"ossi8le to #anufacture as a single "iece as it oul$ 8e etre#ely$ifficult to $evise a #etho$ to %M the a"erture an$ "reserve any shar" angular $efinition.

The solution is to e#"loy Tungsten !ro$ucts &ra$iation oint& construction hich "revents

any "ossi8ility of straight line of sight ra$iation lea;age 8y #eans of geo#etric offsets inthe #ating halves. As seen in the transverse cross sectional $iagra#s 8elo even very

carefully #achine$ flat oints can allo so#e ra$iation "enetration. 4y use of a si#"le

ste" the ris; of $irect line lea;age fro# the containe$ source is eli#inate$. A #oreela8orate oint ith larger offsets that further re$uces ra$ial features #ay 8e ustifie$ in

so#e a""lications. Securing har$are such as 8olts can 8e also #a$e of WHA to "reserve

"rotection level.

!oor 0oo$ 4etter

reserving Ma,i"u" Mechanical Strength

0oo$ #echanical $esigns avoi$ unnecessary stress concentration. This is es"ecially

i#"ortant consi$ering the notch sensitivity of all WHAs. Attention to $etails such as the

shar"ness of internal corners root ra$ii of notches grooves an$ threa$s an$ the "roi#ityof holes or other cutouts to "art e$ges hel" "reserve the #ai#u# attaina8le strength fro#

a WHA "art. Concave ra$ii shoul$ 8e li#ite$ to =.=2=& or greater henever "ossi8le.

Holes shoul$ not 8e locate$ closer than 1.5 ti#es hole $ia#eter fro# the e$ge of a "art.While #ost eights are reuire$ to su""ort only lo acceleration centrifugal or inertial

loa$s these strength of #aterials consi$erations 8eco#e even #ore i#"ortant in "arts that

also serve a structural function or are utilie$ in high s"ee$ a""lications.

!oor "ractice

0oo$ "ractice

1=

source


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-. Machining ui#elines

A "rinci"al a$vantage of WHAs over "ure tungsten for $ensity a""lications is their

a8ility to 8e rea$ily #achine$ into co#"le geo#etries using co##on #etalcutting toolsan$ techniues. While it is generally sai$ that WHAs #achine si#ilar to gray cast iron

this $escri"tion can 8e #islea$ing. 9oer DW alloys ith high $uctility ten$ to #achine

#ore li;e a stainless steel of co#"ara8le har$ness. ue to the high elastic stiffness of

WHAs cutting forces ill 8e higher than for #ost #etals. ,igi$ tooling an$ a$euates"in$le torue are #an$atory for goo$ results. Coolant+lu8ricants if e#"loye$ shoul$ 8e

the non)al;aline ater solu8le ty"e.

Sa/ing

4lan;s of WHA #ay 8e rea$ily cut using a heavy $uty sho" 8an$sa eui""e$ ith either a 8i)#etal 8la$e ith hoo; "rofile teeth or a seg#ente$ e$ge car8i$e 8la$e at lo s"ee$

. Coolant is not reuire$ for 8an$sa sectioning. WHAs #ay also 8e cut on

an a8rasive sa using alu#ina or silicon car8i$e 8la$es ith coolant.

rin#ing

WHAs are ca"a8le of ecellent surface finishes hen centerless or surface groun$.'itrifie$ 8on$ alu#ina or silicon car8i$e heels of #e$iu# har$ness are reco##en$e$. A

ater solu8le coolant shoul$ 8e use$. ia#on$ heels shoul$ not 8e use$ $ue to ra"i$loa$ing. Surface grin$ing of very thin stoc; shoul$ 8e "erfor#e$ carefully so as to avoi$ 8oing fro# intro$uce$ resi$ual stress.

Milling

'irtually all co##ercial WHAs easily for# short chi"s hen #achine$. The

ece"tion to this rule is lo DW alloys su""lie$ in a very $uctile state in hich case

chi"8rea;ing #ust 8e a$$resse$ in tooling selection. Milling of WHAs is 8est "erfor#e$using #ulti)insert cutter hea$s. The use of coolant+lu8ricant is o"tional.

Roughing5S= 'arbide>rade

%a:e

!°#

'learance

!°#

rade

%a:e

!°#

'learance

!°#


12/18

?*9 or ?6 ° to @+° ° to -**° > ,7-,* ,9-,7 7-9

So#e #o$ern cutter+insert co#8inations ill "er#it $e"ths of cut on roughing to ecee$

=.25& on #achines of sufficient "oer. 4est final surface finish is "ro#ote$ 8y the use of large nose ra$ius inserts high s"in$le s"ee$s light fee$ rates an$ "ositive ra;e inserts.

While coate$ inserts offer i#"rove$ life hen #achining #ost #etals this a$vantage isso#eti#es offset hen #achining WHAs $ue to the higher cutting forces create$ 8y theroun$e$ e$ges necessary for coating of the insert.

Turning)0acing)oring

While HSS cutting tools can 8e use$ o"ti#u# "erfor#ance ill 8e realie$ through

the use of shar" e$ge$ car8i$e inserts. @f chatter occurs ith longer etensions toolhol$ers

fa8ricate$ fro# WHA "rovi$e the 8est solution to the "ro8le#.

Roughing

5S= 'arbide>rade

%a:e!°#

'learance!°#

rade

%a:e

!°#

'learance

!°#


13/18

8e successfully ta""e$. @t is generally 8est to ta" large holes ith a single "oint tool. or

other $ifficult to ta" situations the use of a slightly larger "ilot hole #ay solve the "ro8le#

8ut ith re$uce$ threa$ engage#ent area.

$DM Sha!ing

%M 8oth ire an$ sin;er ty"es are routinely use$ to sha"e WHA 8lan;s. %M

shoul$ hoever 8e a &last resort& techniue for several reasons. irst it is inefficient

co#"are$ to #etalcutting alternatives. WHAs have high arc erosion resistance an$ areoccasionally use$ as %M tools. %M sha"ing is therefore very slo. Also even at loer

s"ar; energy settings %M can still intro$uce surface layer $a#age that can in so#e

a""lications "rove $etri#ental. Gsing %M to sha"e highly $uctile WHAs can so#eti#es

e#8rittle the# through reintro$uction of hy$rogen into the #etal. Still %M re#ains theonly "ractical sha"ing techniue in so#e s"ecific a""lications. An ea#"le is the

#achining of 8lin$ non)circular holes ith relatively shar" corners an$ ta"er.

Ther"al Contouring

Techniues such as oyfuel "las#a et an$ laser cutting are not reco##en$e$ for WHAs. These #etho$s ty"ically "ro$uce unacce"ta8le levels of oi$ation an$ ty"ically

"ro$uce localie$ ther#al crac;ing.

13


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. +oining

WHA can rea$ily 8e oine$ to itself or other #aterials. Whenever feasi8le

#echanical #etho$s of attach#ent are "referre$ as they avoi$ "ossi8le ther#oche#ical

alteration an$ its effect on local #echanical "ro"erties.

Mechanical

-oining is #ost co##only "erfor#e$ using stan$ar$ fasteners such as 8olts an$ "ins.WHA "arts can 8e li;eise 8e threa$e$ to "erfor# as fasteners . @n choosing a #echanical oining #etho$ it is i#"ortant to ;ee" in

#in$ the notch sensitivity i#"act sensitivity an$ lo CT% of WHAs. Threa$s shoul$

have as generous a root ra$ius as "ossi8le for #ai#u# strength. @#"act fasteningtechniues such as riveting are not reco##en$e$. Shrin; fitting is "ossi8le "rovi$e$ the

WHA "art is the inner #e#8er. or shrin; fitting an interference fit of E=.==5& "er si$e is "re"are$ an$ the WHA "art coole$ in $ry ice or 9( 2 hile the outer #e#8er is heate$ to

several hun$re$ $egrees 8efore fit u".

ra3ing

4raing is 8est "erfor#e$ in a hy$rogen furnace to "rotect the WHA "art fro#

oi$ation. A variety of filler #etals such as "ure co""er #onel an$ stan$ar$ 8raingalloys 8ase$ on co""er silver an$+or nic;el can 8e use$. 4raing te#"erature constraints

an$ the en$ a""lication generally $eter#ine the filler #etal choice. 9arge co#"onents can 8e asse#8le$ fro# a nu#8er of s#aller "ieces using this a""roach. As ith any 8raingo"eration goo$ oint "re"aration is essential for "ro$ucing fully 8on$e$ interfaces.

Clearances of E=.==2& or less are ty"ical. 4raing can alter the che#istry ithin the

i##e$iate vicinity of the oint. !oints of attach#ent shoul$ not 8e locate$ along such

ones. Manual torch 8raing using a flu is also "ossi8le 8ut ill result in oi$ation an$ isli#ite$ to oining s#aller co#"onents. 9o te#"erature sol$ers ill not et WHAs.

Wel#ing

Wel$ing is generally not "erfor#e$ on WHAs $ue to the vast $ifference in #elting

"oint 8eteen the W "hase an$ 8in$er "hase. A T@0 torch can hoever 8e use$ asa very intense heat source to flo fillers such as #onel "ure nic;el or nic;el)8ase$

su"eralloys into a oint for a &uasi)el$&. This techniue reuires #uch e"erience for

goo$ results.

Sinter on#ing

1/


15/18

This is a techniue that is ty"ically li#ite$ to oining "arts at the ti#e of #anufacture

to for# larger asse#8lies. !erfor#e$ in a hy$rogen furnace at the 9!S te#"erature sinter

8on$ing results in an invisi8le interface ith no local $egra$ation in #echanical "ro"erties.

4. 0inishing

WHAs are reasona8ly resistant to corrosion an$ are not susce"ti8le to stress

corrosion crac;ing as is a co#"etitive high $ensity #aterial G. or so#e $ensitya""lications such as aircraft counter8alance eights long ter# corrosion resistance

8eco#es a concern $ue to "ersistent e"osure to harsh environ#ents. @n such cases a

variety of "rotective finishes can 8e a""lie$. While relatively resistant to corrosion un$er

a#8ient con$itions etre#e hu#i$ity salt s"ray an$ the "resence of strong electrolytescan "ro#"t surface corrosion. This is $ue to the electroche#ical $ifference 8eteen the

#atri an$ the tungsten "hases hich sets u" #icro)scale galvanic cells on the e"ose$

surface. The #atri "hase is #ost rea$ily attac;e$ 8y aci$ic solutions hereas the

tungsten "hase is #ost ra"i$ly $issolve$ 8y al;aline solutions. WHAs are not generallyuse$ in #arine a""lications 8ut shoul$ have a "rotective coating for any such use.

@t is i#"ortant to note that certain conversion coatings though in i$es"rea$ in$ustrial use are not suita8le for WHAs. As an

ea#"le the che#istry of 8lac; oi$e "rocesses for steels is 8ase$ on the "resence of an

iron)rich surface hich is $efinitely not the case for any co##ercial WHA. Therefore if such a techniue is utilie$ the e"ecte$ a""earance an$ $ura8ility of oi$e coating on

WHA ill not 8e achieve$. Si#ilarly ano$iing "rocesses hich are i$ely use$ for

alu#inu# an$ reactive #etals are not a""ro"riate for WHAs hich 8y nature $o not for#the sa#e ty"e of coherent surface oi$e layer.

Conversely hen a unifor# che#ical attac; is $esira8le the sa#e electroche#ical $ifferences 8eteen

the to "hases co#"rising WHA "revents consistency of $issolution res"onse. While

8asic #ar;ing can 8e $one che#ically it ill not 8e unifor# on a #icrosco"ic scale. @f

high $efinition solvent resistant "atterns or @ #ar;ings are reuire$ on WHA "arts it isreco##en$e$ that either vi8ratory scri8e or laser #ar;ing syste#s 8e e#"loye$.

Metallic

Ca$#iu# "lating ith a chro#ate overcoat is co##only use$ for aircraft eights.

This ty"e of "lating is i$eal shoul$ the coating nee$ to 8e "erio$ically stri""e$. or #ore$ura8le an$ less toic "rotective coatings nic;el is an ecellent choice. Al;aline "lating

solutions shoul$ 8e use$ to avoi$ hy$rogen intro$uction into highly $uctile "arts.

5rganic

A variety of "oly#eric finishes inclu$ing e"oy an$ acrylic 8ase$ #ay 8e

effectively use$. :rganic coatings are "ro8a8ly the 8est choice in #ost a""lications.!aints a$$itionally allo convenient color co$ing an$ @ #ar;ing of co#"onents hen

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reuire$. :rganic coatings also "rovi$e a $ielectric layer useful in "reventing the

for#ation of a galvanic cou"le hen WHA eights are fastene$ to $issi#ilar #etals such

as alu#inu# alloys. or o"ti#u# $ura8ility organic coatings shoul$ 8e $rie$ 8y 8a;ing atthe reco##en$e$ te#"erature to ensure the full set of curing reactions occur.

6. Ty!ical A!!lications

*a#iation Shiel#ing

Mo$ern in$ustrial ra$iogra"hy an$ oncology syste#s currently utilie 8ea# energies

that can ecee$ 2 Me' fro# isoto"ic sources an$ ell over 2= Me' fro# s#all

accelerators. The a8sor"tion 8ehavior of WHAs for high energy electro#agnetic ra$iationis $erive$ fro# the high linear a8sor"tion coefficient of the "rinci"al tungsten "hase.

These alloys are ecellent #aterials for the shiel$ing an$ colli#ation of )an$ γ )ra$iation

$ue to their co#8ination of ra$iogra"hic $ensity #achina8ility strength an$ lo toicity.

WHAs offer a su"erior "rotection level to lea$ in an euivalent thic;ness. 4ut unli;e lea$WHAs resist $efor#ation an$ can 8e accurately fastene$ B i#"ortant factors in the

construction of #ulti)leaf ra$iation colli#ators. WHA can 8e su""lie$ in the for# of thinrolle$ an$ #achine$ sheet for such a""lications. or 8ul; shiel$ing a""lications Tungsten

!ro$ucts has #anufacture$ #any shiel$ing co#"onents in the 1==)1=== ;g sie range.

9arge isoto"e containers can 8e fa8ricate$ ith co#"le geo#etry ra$ial 8ea# "orts using

&ra$iation oint& construction. Class 2 3 or / WHAs are ty"ically use$ for shiel$ing.

Aircraft Counterbalances

Counter8alance eights for fie$ an$ rotary ing aircraft have 8een use$ for #any

years. WHA eights unli;e lea$ hich cree"s un$er its on eight at roo# te#"eraturecan 8e securely fastene$ to aerostructures. @n contrast to G eights WHA eights arefree fro# SCC concerns s"ecial licensing reuire#ents environ#ental issues an$ the

negative "u8lic res"onse to having #any "oun$s of ra$ioactive #aterial routinely flying

overhea$. WHA eights are ty"ically #achine$ fro# near net sha"e 8lan;s to "recise

tolerances an$ "rovi$e$ ith a "rotective coating to the custo#erJs s"ecification. This isan a""lication here a coating is highly reco##en$e$ to resist corrosion fro# te#"erature

an$ #oisture cycling $e)icing flui$s aggressive aircraft cleaning flui$s an$ galvanic

contact ith fasteners an$ the airfra#e. Class 1 or 2 WHAs are #ost co##only use$.

Well 7ogging

WHA is an ecellent casing #aterial for $on hole logging of oil ells. Casings

#ust 8e sufficiently heavy to rea$ily sin; through #aterials such as 8arite #u$ an$ strong

enough to ithstan$ the hy$rostatic "ressure of this harsh environ#ent. Most $esigns arehighly #achine$ for sensor an$ in$o "ositioning. Mechanical "ro"erties are very

significant to the surviva8ility of these rather large co#"onents. Tungsten !ro$ucts has

years of e"erience in "ro$ucing high "ro"erties in large 8ars of class 1 2 or 3 #aterial.

*acing Weights

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rivers consistently re"ort they can sense $ifferences in ho a car han$les on the

trac; if the eight on a given heel varies only 8y a cou"le of "oun$s. ine tuning a car to a given trac; is a very cu#8erso#e an$ ti#e consu#ing or$eal ith conventional lea$

"late eights. WHA eight 8loc;s offer u" to 5=D #ore eight in a given volu#e ith

the a$$e$ a$vantages of $irect attach#ent via threa$e$ holes or thru)8olting an$ thefree$o# fro# $efor#ation that is a constant "ro8le# ith lea$. Class 1 or 2 WHAs are

#ost co##only use$. The high $ensity of WHAs "er#it eights to 8e "lace$ in the loer

half of (ASCA, eight a$ust#ent tu8es effectively loering the overall center of gravity for i#"rove$ han$ling. Tungsten !ro$ucts has a s"ecialie$ line of racing eights

for these a""lications.

oring ars

The high $ensity high elastic #o$ulus an$ co#"osite #icrostructure of

WHAs #a;e the# i$eal #aterials for lo chatter 8oring 8ars an$ long etension

toolhol$ers of various ty"es. WHAs are very stiff an$ resistant to $eflection. Their high$ensity cou"le$ ith the to "hase #icrostructure of the alloy "rovi$e effective vi8ration

attenuation. Class 1 or 2 WHAs are #ost co##only use$.

5r#nance A!!lications

WHAs have 8een routinely use$ in high $ensity frag#enting $evices an$ ar#or

"iercing a##unition ranging fro# s#all cali8er 5.56 ## roun$s u" to 12= ## anti)

tan; "roectiles an$ 8eyon$. Material for ;inetic energy "enetrators is ty"ically vacuu#

anneale$ an$ resolutionie$+uenche$ for #ai#u# $uctility


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Tungsten Heavy Alloys

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