corrosion resistance of p/m s.st
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Corrosion Resistance of P/M S.St.
Richard R. Phillips,
Engineered Pressed Materials
Dennis Hammond
Apex Advanced Technologies, LLC
Objective
• Using 316L, 17-4ph, 409LCb & 434L
• Achieve higher densities
• Higher densities at lower sintering temperatures
• Obtain good corrosion resistance
History
• Historically difficult to get high density
• Compressibility limiting factor
• Work hardening during pressing
• High surface oxides on powder
• Limited oxide reduction in sintering and densification
• Lower densities interferes with corrosion resistance
Water atomized 316L3200 ppm O2
5200X
Gas atomized 316L150 ppm O2
5200X
Powder Preparation
• 100 mesh standard powders of 316L, 17-4ph, 409LCb & 434L
• A group with 0.75 % Lithium Stearate
• A group with an Activation Technology
• TRS bars pressed at 690 Mpa (50TSI)
Activation Technology
• Blend Additive/Lubricant Master Batch • Hydrostatic distribution of additives &
lubricant during compaction• Particles are aligned in a best fit
arrangement• Density gradients eliminated • Activation is initiated in the delubing
stage and finalized in the early stage of sintering
EPM 8
Density Gradient – Shape Retention
Lithium stearate Activation Technology
Compressibilityg/cm3 at 690 Mpa (50TSI)
Material Li Str. Activation
• 316L 6.83 6.76
• 17-4ph 6.28 6.23
• 409LCb 6.63 6.58
• 434L 6.51 6.47
Processing• TRS bars delubed at 400OC (750OF) in Air
• Sintering in a H2 box furnace with a slow cool > 1 hr.
• Sintering in a continuous vacuum furnace with a 2 bar fast N2 quench < 10 min.
• Sintered at: 1120 (2050), 1177 (2150), 1232 (2250), 1288 (2350), 1343 (2450) & 1388OC (2530OF)
• Time at temperature 45 min.
Atmosphere Box Furnace
Continuous Vacuum N2 quench
Sintering size change and densification
ASTM B895 Standard for Test Method 2
For alloy screening and process optimization
316L
C (F)
1120 (2050)
1177 (2150)
1232 (2250)
1288 (2350)
1343 (2450)
1388 (2530)
Li Str ATMO D X C B B XActiv. ATMO D X C B A X
Li Str VAC C B A A A A
Activ. VAC B A A A A A
744 hrs. immersion in 5% NaCl
0%A, <1%B, 1-25%C, >25%D
0%A, <1%B, 1-25%C, >25%D
17-4PH C
(F)1120 (2050)
1177 (2150)
1232 (2250)
1288 (2350)
1343 (2450)
1388 (2530)
Li Str ATMO C X B B B XActiv. ATMO C X B A A X
Li Str VAC D C C B B A
Activ. VAC D D D C A A
744 hrs. immersion in 5% NaCl
409CbC
(F)1120 (2050)
1177 (2150)
1232 (2250)
1288 (2350)
1343 (2450)
1388 (2530)
Li Str ATMO D X D D C XActiv. ATMO D X C A A X
Li Str VAC D D C B B A
Activ. VAC D C B A A A
744 hrs. immersion in 5% NaCl
0%A, <1%B, 1-25%C, >25%D
434L OC (F)
1120 (2050)
1177 (2150)
1232 (2250)
1288 (2350)
1343 (2450)
1388 (2530)
Li Str ATMO D X D C C X
Activ. ATMO D X D C B X
Li Str VAC D D D D D C
Activ. VAC D D D D C B
744 hrs. immersion in 5% NaCl
0%A, <1%B, 1-25%C, >25%D
0%A, <1%B, 1-25%C, >25%D
744 hrs. immersion in 5% NaCl
0%A, <1%B, 1-25%C, >25%D
744 hrs. immersion in 5% NaCl
0%A, <1%B, 1-25%C, >25%D
744 hrs. immersion in 5% NaCl
0%A, <1%B, 1-25%C, >25%D
744 hrs. immersion in 5% NaCl
Conclusion
BETTER CORROSION RESISTENCE
• Higher density
• Faster cooling rate
• Activation Technology
Higher density at a lower temperature
` Better response with continuous Vacuum
Best corrosion resistance
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