MFS CSO 90714

Dr. Mark F. SmithCold Spray Workshop

Albuquerque, NMJuly 14-15, 1999

Overview of Cold Spray

ParticleVelocity (m/s)

> 325

> 350

> 375

> 400

> 450

> 475

> 500

> 425

2000 100 300 400 500

Gas

Pre

ssu

re (

psi

g)

200

250

300

350

400

Gas Temperature (ˆC)

Air, 22 µm Copper

100 µm

MFS CSO 90714

250 m/s Cu

A “Cold” Process Technologyfrom Siberia

900 m/s Cu

Deposition Efficiency

CopperCoating Material

Iron Nickel Aluminum

After Alkimov, et al , 1990

400 500 600 700 800 900 1,000

0.80.70.60.50.40.30.20.1

0

Particle Velocity m/s

MFS CSO 90714

Sandia Cold Spray System

HEATED GASGasInlets

Heater

TC

Gas Heater

PowderFeed

RobotManipulator

MFS CSO 90714

Spray Ductile Metals, Cermets, Polymers

Active Braze Alloy AluminumAluminum BronzeCopper304 Stainless Steel420 Stainless Steel

Fe3Pt MolybdenumMonel80Ni/20CrNiCrAlYNiCr-Cr3C2

Polymer StelCarTantalumTinTitaniumWC-Co (nanophase)

Examples of Materials Successfully Deposited at Sandia

MFS CSO 90714

Cold Spray vs. Air Plasma Spray

Plasma Sprayed Copper

Cold Sprayed Copper

100 µm

100 µm

• Superior Density• Less Oxide

MFS CSO 90714

Some Exciting New Possibilities

• Avoid melting & solidification- Avoid thermally induced stress- Avoid undesirable phases- Avoid oxidation (deposit metals in ambient air!)- Preserve desired phases & chemistry- Preserve original grain size (nanocrystalline mat’ls)

• Low Porosity (>99% dense, as deposited)• High thermal / electrical conductivity (>80% OFHC Cu)

• High Deposition Efficiencies (>98%)

• Recycle feedstock & process gas• Work with highly dissimilar materials combinations

MFS CSO 90714

New Possibilities, cont’d.

• Highly wrought material (high hardness / strength)

• Potential for high deposition rates• Relatively insensitive to standoff, work up close (

MFS CSO 90714

Cold Spray Direct Fabrication

• Additively build net / near-net shapes directly from a computer

• Key technical challenge is focussing the spray stream

~ 1 mm FocusedStream for

Subsonic Flow

Do you want a print or a part?Print Build OK

OK

Do you want a Print or a Part?PrintBuild

MFS CSO 90714

Example Applications

• Anti-corrosion (superior density, less oxide)

• Wear resistance (superior hardness & density)

• Metals on ceramics / glass

• High-alloy / specialty metals (preserve composition & phases)

• Plastic coatings without volatile organics

• Defect repair (minimal masking / heating, machinable)

• Direct fabrication

• Satellite structures (high conductivity, low residual stress)

MFS CSO 90714

Reclaiming Parts & $$$

Unusable $150k GPSsatellite part reclaimed

with Cold Spray

• Low heat input• Low stress• Dense, machinable• High conductivity,

MFS CSO 90714

State of the Art

• Technology ~ 10 years old• Success with many metals, some cermets & polymers• New materials / processing / manufacturing possibilities • Considerable industrial interest• Patented, but licenses available• No commercial use yet

MFS CSO 90714

Barriers to Commercial Use

Technical Issues:

• Process fundamentals poorly understood• Cannot predict materials / parameters• Reduce / eliminate expensive helium• Nozzle fouling / optimization

Build-up in nozzle

MFS CSO 90714

Barriers to Commercial Use

Manufacturing Issues:

• No commercial equipment / coating suppliers• Need articulated robot compatible spray gun• Lack of property data / field experience• Need better fine powder feeders

Uneven deposition dueto uneven powder feed

MFS CSO 90714

Understanding Critical Velocity

Raw Particle Velocity Distributions

0

20

40

60

80

100

200 400 600 800 1000 1200

0 %53 %95 %

No

rmal

ized

Co

un

ts

Particle Velocity (m/s)

DepositionEfficiency

1 2 3

19 µm Copper powder onto Aluminum

0

20

40

60

80

100

450 500 550 600 650 700 750 800

Dep

osi

tio

n E

ffic

ien

cy (

%)

Mean Particle Velocity (m/s)

3

2

11

2

3ExperimentPrediction

MFS CSO 90714

Process Maps Guide Optimization

ParticleVelocity (m/s)

> 325

> 350

> 375

> 400

> 450

> 475

> 500

> 425

2000 100 300 400 500

Gas

Pre

ssu

re (

psi

g)

200

250

300

350

400

*DV�7HPSHUDWXUH��Û&�

Air, 22 µm Copper

MFS CSO 90714

Models Guide Nozzle Design

dDdP

= CD ApM 2

2− 1

dVpdt

= Dm

Vp = particle VelocityD = Drag forcem = particle MassP = Pr essure

CD = Drag coefficientAp = Area of particleM = Mach number

max @ M = 2 = 1.4

(air)

(helium)

A*/A = Choke Point/Nozzle Exit Area Ratio(Axial Position measured from choke point)

MFS CSO 90714

“Estimator” ver. 1.0 for Spray Parameters

Air Helium

MFS CSO 90714

Understanding Particle Impact

1 km Asteroid Impacting Ocean 300 Gigatons TNT Equivalent (10x Peak of All Cold War Nuke’s)

Sandia Teraflops computer running CTH code100 million computational cells18 hr @ 91% capacity (8,192 of 9,000 processors)

MFS CSO 90714

Computational Impact Model& Experimental Comparison

Predicted peak temp.of 1280 K is below the

melting point of Cu(1357 k)

Cu

Stainless Steel25 µm

4

3

2

1

0

- 1

- 2

- 3

- 4

Cu

StainlessSteel

t = 70 nst = 70 ns

X (microns)- 4 - 2 0 2 4

Y (

mic

ron

s)

Copper

Steel

Void

Temperature K

980

900

810

720

630

540

450

380

25 µm Cu Sphere into 304 Stainless at 600 m/s

MFS CSO 90714

Summary

• New materials / processing / manufacturing possibilities • Opportunity to be first to exploit market advantage• Several pre-competitive barriers need to be solved• Faster / cheaper / better to work together on pre-comp.• Partners will gain access to best technology & new IP