October 7‐10, 2012 • Atlanta, Georgia, USA
1Ames Laboratory-USDOE, Division of Materials Sciences and Engineering, Ames, IA
2Iowa Powder Atomization Technologies, Inc., Ames, IA
Support for this work was provided by the Grow Iowa Values Fund (GIVF) and the US Army (ARDEC) and performed at Ames Lab under
contract no. DE-AC02-07CH11358
October 7‐10, 2012 • Atlanta, Georgia, USA
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Melt Stock Powder MetalInjectionMolding
Laser ElectronBeam
Oxy
gen
(ppm
wt%
)
Net Shape Titanium Powder RequirementsNet Shape Titanium Processing
Titanium Alloy
Powder
Morphology: SphericalTi-6Al-4V ELI
spherical powder of <45 m is ideal for all net-shape processing
High yield <45µm powder
High throughput and simple process
ELI O2content
Chemistry: Low Oxygen
ASTM F‐2885
2.5 nm native oxide (RT) on 20µm powder
Net shape consolidation
October 7‐10, 2012 • Atlanta, Georgia, USA
High Energy Transfer
Free Fall vs. Close-Coupled Gas Atomization
Does NOT currently exist in industry!
LowEnergy Transfer
Ti-6Al-4V results
D50 = 200µm%< 45µm (<5%)
D50 = 29µm%< 45µm (>70%)
Representative Fe‐alloy run
100-150°C superheat
[1] Heidloff et al. JOM, 2010
[1]
October 7‐10, 2012 • Atlanta, Georgia, USA
400-1000 rpm
Composite Pour Tube Fabrication
YSZTungstenSub-Oxide Yttria
Yttria Final Part
Tung.
YSZ
Yttria
Sintering of Y2O3 allows for sub-oxidation and sintering of plasma spray splat boundaries (patent pending)
Induction andconduction heating of flowing metal to increase melt superheat for close-coupled atomization
USPTO#’s: 6,358,466; 6,425,504
October 7‐10, 2012 • Atlanta, Georgia, USA
Element (wt%) 250°C Superheat ASTM F1472
Ti 89.1 88.75‐91.0
Al 6.26 5.5‐6.75
V 4.2 3.5‐4.5
Y 70ppm 50ppm (max)
O 1573ppm 2000ppm (max)
N 204ppm 500ppm (max)
C 187ppm 1000ppm (max)
Wear (μm) 30±31
Ti-6Al-4V Pour Tube Trials: Univ. Birmingham
superheat
[1] Heidloff et al. JOM, 2010
[1]
[1]
TEM BFI TEM HAADF[1] [1]
October 7‐10, 2012 • Atlanta, Georgia, USA
Ames Laboratory Titanium Close-Coupled Atomizer
5” copper crucible with 20 lb. Ti capacity
Inductively-heated pour tube
Downstream passivation 15’ free-fall distance
PAM for 4” custom alloy ingot production (MPC)
October 7‐10, 2012 • Atlanta, Georgia, USA
Composite Pour Tube Operation Without Metal
Tungsten acts as heat-generating and superheating layer
Induction field allows for pre-heating of pour tube to 2000°C prior to metal flow
Optical Pyrometer For proper
performance, manipulation of:
• Induction field• Material properties• Heat transfer
October 7‐10, 2012 • Atlanta, Georgia, USA
Composite Pour Tube Performance
• Composite pour tube hotter than Tm of metal allows tube to run completely dry
• May allow for semi-continuous use if molten metal is available
October 7‐10, 2012 • Atlanta, Georgia, USA
Initial Atomization: Ti-48Al-2Cr-2Nb
Melt stream flow initiation is highly
predictable
Spray cone from supersonic atomization
gas is highly stable
Crown formation from limited superheat
Real time: 50 ms
October 7‐10, 2012 • Atlanta, Georgia, USA
Gas Atomized Ti Powder Morphology
Spherical morphology
Very few satellites
Very low gas entrapment
Dia. <45µm Dia. <45µm
Dia. <45µm
October 7‐10, 2012 • Atlanta, Georgia, USA
Element ATI Specification
Ingot (ATI)
Run #1<45 m
Run #2Cast
Run #3<45m
Ti REM 59.7 58.9 60.3 58.9
Al 32.5-33.5 32.8 33.7 32.3 33.4
Cr 2.4-2.7 2.58 2.5 2.6 2.7
Nb 4.5-5.1 4.8 4.6 4.8 4.7
O (ppm) 400-1300 700 1300 1100 1300
N (ppm) 200 30 47 27 34
C (ppm) 150 30 250* 170* 400*
Y (ppm) 50 <5 60* 50 50Metal Flow Rate (lb/min) -- -- 10 12.5 17
Pour Tube Liner -- -- Y2O3 Sub-Y2O3 Sub-Y2O3
Powder Chemistry Analysis
October 7‐10, 2012 • Atlanta, Georgia, USA
Downstream Passivation and In-situ AlloyingAmes Lab mantra: Free-fall chamber is a REACTION chamber
• containerless• very clean metallic surfaces• in-situ processing• wide variety of capabilities (O2, N2, NF3, SF6)
Heat transfer modeling of droplet cooling profile
Demonstrated F-containing coating on -TiAlpowder (190 ppmw F), should improve oxidation
resistance of consolidated parts
Stand-off Distance?
Atomization
PassivationUSPTO#’s: 5,372,629; 5,589,199
20-25m powder
4.5nm
~4.5nm in-situcoated surface
oxide
Opened to air with no special handling
October 7‐10, 2012 • Atlanta, Georgia, USA
Crucible Temperature
Atomization Temperature
Target Temperature
ΔT ~ 150°C
Composite Pour Tube Optimization: Fe-Cr Alloy
Fe-Cr alloy in ceramic crucible with accurate melt temperature (1800°C)
2-color optical pyrometer of outlet temperature (1950°C)
[2] Rieken et al. MPIF, 2012
[2]
October 7‐10, 2012 • Atlanta, Georgia, USA
Technology Summary and Future Work
Optimize close-coupled atomization parameters for titanium
Testing of pour tube lifetime (large batch capacity)
Modification of current system to enable larger batch production
Induction melting for molten metal supply to composite pour tube
Composite pour tube allows for superheating of molten metal andhot inner wall allows for complete emptying of the pour tube
Close-coupled gas atomization provides higher yields of <45µmspherical powder
In-situ surface alloying allows for simplified powder passivationand/or improved consolidated part properties
October 7‐10, 2012 • Atlanta, Georgia, USA
Acknowledgements
From Ames Laboratory:
• Jim Anderegg for Auger Electron Spectroscopy
• Tyler Slinger• Eduard Zahariev• Stephanie Choquette
Thank You
Support for this work was provided by the Grow Iowa Values Fund (GIVF) and the US Army (ARDEC) and performed at
Ames Lab under contract no. DE-AC02-07CH11358
