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