Development of a PM nickel-base superalloy

An optimal powder metallurgy (PM) approach to produce a nickel-base superalloy similar in composition to Inconel 600(+) was developed utilizing simple uniaxial pressing. The efficiencies of lubricant and binder additions, sintering times, and temperatures were monitored in terms of green and sintered densities, and microstructural changes that occurred during processing. It was observed that increasing the polyvinyl alcohol (PVA) content resulted in a decrease in compact density. With 0.75 w/o lubricant (Microwax), green densities >70% of the pore-free level were obtained. Samples were subsequently sintered in air at 1,270 degrees C for times ranging from 0.5 h to 5 h, and in vacuum with temperatures ranging from. 1,260 degrees C to 1,400 degrees C. On sintering for 5 h in air, chromium enrichment occurred at grain boundaries with subsequent depletion of 1 nickel and iron, but was not I observed after sintering for 2 h in air, or after sintering I in vacuum. After vacuum 11 sintering under optimal conditions (2 h, 1,300 degrees C, <7.8 < 10(-6) bar) the sintered compacts were successfully cold rolled to 40% of their original thickness without cracking. Alloy strength was measured in terms of hardness and was observed to compare favorably with that of the wrought form of the alloy.