Structure/property evaluation and comparison between shock-wave consolidated and hot-isostatically pressed compacts of RSP pyromet 718 alloy powders

Abstract

Shock-wave processing of a nickel-based superalloy (Pyromet 718) powder is explored and compared to conventional hot-isostatic processing. The shock consolidated powder has extensively deformed particle interiors, A fine microcrystalline phase was observed at interparticle regions, and is attributed to rapid solidification of melt formed during the consolidation process. The shock consolidated material has a yield strength of 1 GPa prior to heat treatment, which is at least 10% higher than that of the hot isostatically pressed alloy. A high density of very fine disk-shaped γ″ precipitates nucleate in the shock consolidated material after solution treatment and upon aging at 620°C for 8–40 h. A lower density of coarser precipitates nucleate in the hot-isostatically pressed alloy subjected to similar thermal aging conditions. The shocked and heat treated alloy exhibits a 20% higher yield strength and a 40% higher UTS than the hot isostatically pressed and heat treated alloy, with comparable ductility. The improvement is attributed to a finer intraparticle grain size, very fine grained interparticle material, and a higher density of very fine and uniformly dispersed y″ precipitates resulting from faster nucleation kinetics in the shock consolidated material.