A low Density Lubricant System with Significantly Improved Green Strength

and Ejection forces

Dennis Hammond

Apex Advanced Technologies

Cleveland, OH

Green Strength Problems• Cracks from ejection

• Chipping

• Handling system damage

• Defects post sintering

• Powders that do not hold together during compaction

• Inverse relationship with green density

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Mechanism of Green Strength

• Powder variables-geometric, intrinsic and surface related

• Inter-particle locking

• Weakest link-lubricant ,oxides

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New Lubricant SystemEnhancer ST

• Modified polymer, surface treated with a lubricant

• Lubricant portion allows for slippage- metal particle to metal particle

• Polymer portion deforms with shear

• Polymer simulates metal particle interlock

• Energy needed to deform 120 F( 49C ) to180 F (82 C) ideal part temperature

4

Stainless Steel • Stainless powder is inherently on the low

side of ideal for green strength

• Stainless re-mill difficult to press

• Stainless gas atomized powder not considered press able due to low green strength

• Low density applications are not readily pressable due to low green strength

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Non-Press able Stainless Applications

• 316L, 5.5g/cc, special particle size, 1330 PSI, 1% Enhancer ST, in production

• 316L 100% re-mill, non-pressable 1% Enhancer ST, in production

• 316L gas atomized powder D-50, 40Micron, 50 TSI, 859 PSI green strength, 6.68g/cc, 2% Enhancer ST

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Iron Parts

• Low density- low green strength, cracks, chips, handling defects etc

• Rising cost of sponge verses water atomized

• Re-mill low green strength

• Off grade powder –inherently low green strength

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Non traditional Metals

• Product acts as binder

• Titanium CP, Titanium 6-4, Titanium Carbide, Zinc, Tungsten /Iron

Conclusions

• Stainless Steel P/M parts made with this product can be made having significantly higher green strength with better ejection

• Non typical Stainless applications can be pressed into parts-low density, gas atomized,100% re-mill

• Low density water atomized iron parts can be made with green strength adequate for processing

Conclusion cont.

• Water atomized can be substituted for sponge in some applications and can have adequate green strength, with better ejection and lower compressibility than sponge

• Copper base metal powder can have excellent green strength and lower ejection

• Non traditional powders can be processed

Conclusion cont.

• Zinc Stearate can be eliminated by using this product with better compressibility, lower ejection, and higher green strength without environmental issues

• A.D is not as good with this product as Zinc Stearate, more comparable to Acrawax. Flow is typically as good or better than either product

Conclusions Cont.

• A.D. can be improved with the co-addition of Zinc Stearate or Lithium Stearate 75-90% Enhancer ST 25-10% Zinc or Lithium Stearate

• Some loss of green strength with these additions, proportional to use E.G 10% ZnSt, 6 % decrease in G.S