Modern Methods of Surface Engineering - iiw.kuleuven.be · from 250-300 Hv for soft metal or spray...

Modern Methods of Surface Engineering

Institute of Engineering Mechanics and Transport

Department of Applied Materials Science and Materials Engineering

Asssistant professor, PhD.Tepla Tetiana

LVIV POLYTECHNICNATIONAL UNIVERSITY

LVIV POLYTECHNIC NATIONAL UNIVERSITY

INTRODUCTION

Surface engineering - is the sub-discipline of materials

science which deals with the surface of solid matter. It has

applications to chemistry, mechanical engineering, and

electrical engineering.

It is an

enabling

technology and

can impact a wide

range of industrial

sectors.


INTRODUCTIONCombining chemistry, physics, and

mechanical engineering with

metallurgy and materials science, it

contributes to virtually all

engineering disciplines.

- It can be done on a given surface

by metallurgical, mechanical,

physical, and chemical means, or by

producing a thick layer or a thin

coating.

- Both metallic and non-metallic

surfaces can be engineered to

provide improved property or

performance.

Texture

d

Multilayer Coatings


What are the benefits and there are they used?

The surface engineering is to develop and implement procedures

which a particular part or component the desired properties by

controlling the characteristics of its surface.

This type of treatment is used to:

- Cutting

- Forming

- Decoration

- Bio-medical

- Automotive



Specific properties rely on surfaces

- Wear, friction, corrosion, fatigue,

reflectivity, emissivity, color,

thermal/electrical conductivity, bio-

compatibility, etc.

By improving durability, it reduces waste

of natural resources and energy.



Benefits

- Extend product life (durability)

- Improve resistance to wear, oxidation and

corrosion (performance)

- Satisfy the consumer's need for better and

lower cost components

- Reduce maintenance (reliability and cost)

- Reduce emissions and environmental waste

- Improve the appearance; visually attractivity

- Improve electrical conductivity

- Improve solderability

- Metallize plastic component surfaces

- Provide shielding for electromagnetic and radio

frequency radiation.


Scales of Surface Engineering

Surface engineering technologies

span:

- Five orders of magnitude in thickness

- It can vary from several mm for weld

overlays to a few atomic layers or

nanometers for physical vapor deposition

(PVD) and chemical vapor deposition

(CVD) coatings or ion implantation.

Atomic-layer deposition is also possible.

- Three orders of magnitude in hardness

Superlattice

Coatings

Thermal Spray

Coating

Superhard

CVD-Diamond

Films


Scales of Surface Engineering

Surface engineering technologies

span:

- Example of coating hardness range

from 250-300 Hv for soft metal or spray

coatings, 3500 Hv for Titanium Nitride

PVD coatings and up to 10,000 Hv for

diamond coatings

- Almost infinite possibilities in the range

of compositions and/or microstructure

- Nano-composite, nano-layered,

amorphous, crystalline, quasicrystalline,

Etc

Superlattice

Coatings

Thermal Spray

Coating

Superhard

CVD-Diamond

Films


Evolution and Significance of Surface Engineering

Evolution of

Coating

ArchitecturesNanostructured,

Superlattice,

Gradient

Single componen

Multicomponent, Multilayer

Adaptative (smart)


Evolution and Significance of Surface Engineering

It is an enabling technology

- It can combine various surface treatments with thin film and

coating deposition.

- It can improve wear and corrosion resistance of structural

components.

- It increases component lifetime and resistance to

aggressive environments.

- It can produce functional coatings that modify

biocompatibility and optical and electrical properties of

critical components


Classification of Surface Engineering Processes

The traditional, well

established processes:

- Painting

- Electroplating

- Galvanizing

- Thermal spraying

- Plasma spraying

- Nitriding

- Carburizing

- Boriding



The more technologically advanced coating

technologies:

-Physical vapor deposition (PVD)

-Chemical vapor deposition (CVD)

- Ion implantation

- Ion-assisted deposition

- Ion-beam mixing

- Laser treatment

- Femtosecond laser processing



Nowadays, a multitude of options are available to select

and specify a treatment or a combination of treatments to

engineer the surfaces of components or structures.

Plasma Spray Plasma-source Ion Implantation Plasma Nitriding



- Ion implantation

- Laser treatment

- Femtosecond laser treatment


Ion implantation


Ion implantation

In ion implantation,

ionized impurity

atoms are

accelerated through

an electrostatic field

and strike the

surface of the

target


Ion implantation


Ion implantation

• depth distribution of defects

can be determined by Monte-

Carlo-methods

• TRIM: Transport of Ions in

Matter

• Stopping and Range of Ions in

Matter

• does not take into account

defect annealing, diffusion, dose

rate effects and channeling

• defect concentration too large,

but distribution can sufficiently

be calculated

• maximum of defect density

before maximum of implanted

ions

Depth distribution of atomic displacements


Ion implantation


Ion implantation

• when transferred energy >

displacement energy (10 - 40

eV): • Frenkel pairs are

generated as result of a

displacement cascade •

vacancy only stable, when it is

located outside of

recombination volume of

interstitial atom (size of this

volume is temperature

dependent)

• primary ion generates many

vacancies, but only a few

survive

Implantation-induced defect generation


Ion implantation

Microstructure of V-alloy after ion implantation by Nitrogen


Ion implantation.

Advantages

- fast, homogenous on large wafers, reproducible result

- exact control of implanted amount of dopant

(measurement of current);

especially important for small dopant levels

- excellent cleaning of dopants during implantation by mass

separation

- simple mask techniques with thick oxide-, nitride- und

photo lacquer layers

- doping through thin passivation layers

- doping profile easily adjustable by multiple implantation

not possible by diffusion techniques)

- very small device structures possible


Ion implantation.

Disadvantages

- irradiation damage up to amorphisation

- additional annealing steps necessary (defect annealing)

- doping atoms often not at regular lattice sites after

implantation (interstitial position); electrical activation

necessary by additional annealing (diffusion of dopants,

danger of impurities)

- implantation only possible for near-surface region

- channeling leads to larger penetration depth of a fraction of

dopant atoms


Ion implantation

Change of material properties by ion implantation

• decrease of minority carrier lifetime: 1012 cm-2 B in Si t = 10-9 s

• free charge carriers are compensated; r = 106 ... 109 Wcm obtainable

• carrier mobility decreases too; may become smaller than 1 cm2 /Vs

(normal >103 )

• optical transmission becomes smaller by additional energy levels in

the band gap

• refraction index changes (thus also reflection index): light propagates

in an inner layer (integrated light pipe)

• SIMOX: hidden SiO2 isolation layer can be done by oxygen

implantation and annealing

• for high doses: density- and volume change

• change of elastic and plastic properties (embrittlement of reaction

pressure vessel steel in nuclear power plants)


Laser treatment

Laser treatment


Laser treatment

Basics of Implementation

• select a property improvement (i,e. wear, corrosion, erosion, lubricity,

etc.)

• select a base alloy

• design an alloy surface that provides the improvement

• form a master alloy powder blend and apply it to the surface of the

base alloy as a paint or thin film

• master alloy layer ~ 100-200 microns

• apply thermal energy via laser optics to melt the master alloy addition

• into the top layer of the base material

-laser optics optimized to achieve uniform heating

-laser optics dwell time very short, permitting rapid cooling and

formation of refined grain, non-equilibrium structures

-new alloy depth into base metal variable from 25-1000 microns

-fiber-optic laser beam delivery permits precise control of

location


Laser treatment

Laser Induced Surface

Improvement (LISI)

• Refined laser surface alloying

• Improved optics for flat beam profile

• Additive metallurgy process

• Uniform surface with low HAZ

• Full metallurgical bond with substrate


Laser treatment

How does LISI compare to other processes?

1. Current limit due to laser spot size; anticipated change over next few year up to

several hundred sq.ft./h.

2.Cost based on part complexity, quantity and current processing speed limitations.


Laser treatment


Laser treatment

Technical Advances

• Permits precise selection of area to be modified

• Requires a very small amount of modifier alloy

• Results in extremely rapid heating and cooling of the surface

• Produces wide variety of chemical and microstructural states

outside of typical phase diagrams

• Produces no distinct bondline; will not delaminate

• Requires little or no surface preparation for certain applications

• Produces minimal hazardous waste stream

• Performed remotely with robotics and fiber-optics

• Performed at rates between 20-50 sq.ft./h


Laser treatment

LISI layer/base alloy

transition

In A356 Al


Laser treatment

Steel Corrosion Protection

Comparison of LISI Processed Plain

Steel and 304 Stainless Under

Accelerated Corrosion Conditions

A - Carbon Steel 24 Hrs

B - LISI Surface on Carbon Steel

232 Hrs

C - 304 Stainless 232 Hrs


Laser treatment

General Applications

Corrosion Protection

• superior alloy, refined grain size

• current NAVAIR SBIR Cadmium replacement

Environmental Substitution

• EPA funding as hard-chrome replacement process

• pumps, cylinders, rollers and die-casting dies

Wear Resistance

• surface metal matrix composites using SiC, WC, TiC, TiB2, Al2O3,

etc.

Fracture Toughness Enhancement

• tough, softer layer on low toughness substrate


Laser treatment

General Applications

Surface Compatibility

• surface modification of dissimilar materials

• spark resistant surfaces for oxygen valves

Durable Non-skid Surfaces

Protection from hydrogen embrittlement

• current NASA program for SME

Soft-Phase Surfaces

• current NASA program on cryogenic couplings


Femtosecond laser treatment




Femtosecond (FS) laser is an

infrared laser with a wavelength

of 1053nm.

The first FS laser system was

designed at the University of

Michigan in the early 1990s



A schematic of femtosecond laser system



• peak power

laser pulse ~ 1014 W

• pulse duration

in the nanosecond

range (10-9 second)



In the materials under the influence of femtosecond

pulses of moderate intensity phenomena:

• nonequilibrium heating and cooling

• relaxation of electrons and ions

• Conduction electrons during the absorption of laser

irradiation are heated up to a temperature of 10000 K,

while the crystalline lattice temperature remains below

the melting point.

• The "hot" electrons emit light, i.e. there is a heat

irradiation by "cold" metal.

Generally, under the action of ultra-short pulses,

formation of surface structures is accompanied by a set

of non-stationary processes



Schematic diagram of the laser beam

profile focused on the entrance surface

of a transparent dielectric material.

The laser pulses are coming from the

top of the diagram. The intensity

distribution of each laser pulse is also

indicated with reference to the surface

damage threshold indicated by the

dashed, horizontal line. a) high fluence

used to produce high aspect ratio

channels (b) intermediate fluence for

pockets and surface patterning (c) low

fluence, below surface damage

threshold, for bulk modifications and

exit surface structuring utilising non-

linear selffocusing (Kerr effect).



Changing the scanning speed of the beam, we can change

the width, structure, and morphology of the surface

Microstructure of the surface layers of 04Х13AG20 steel after

femtosecond laser treatment: a – power 750 MW, Scanning speed of the

laser beam 5 mm/s ; b – power 750 MW, Scanning speed of the laser beam

10 mm/s



Microtopography and the histogram of surface distribution of

parameters of 04Х13AG20 steel structures after processing by the

femtosecond laser



Advantages

• Much less energy input is required to produce the same

amount of material removal

• Thermal damage around the irradiated area is

considerably reduced

• Multi-photon excitation can be exploited to achieve

smaller structures

• There is no laser interaction with the ablated particles

• Non-linear optical processes in the dielectric material

can be utilised to produce novel material processing

possibilities



Disadvantages

• Size restriction

• Not enough research data

• Expensive equipment


Conclusions

Depending on your needs, we can choose the surface

treatment methods.


Thank you

Modern Methods of Surface Engineering - iiw.kuleuven.be · from 250-300 Hv for soft metal or spray...

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Transcript of Modern Methods of Surface Engineering - iiw.kuleuven.be · from 250-300 Hv for soft metal or spray...