Effect of trace elements on forgeability of superalloys

Abstract

Trace elements in superalloys can he grouped under three major headings, those which are detrimental to forgeability hut can he removed hy volatilization under vacuum, those which are detrimental and are not removed hy vacuum treatment hut can he comhined with neutralizers, and those elements which are generally regarded as being beneficial to forgeahility. It can he argued that all of the trace elements considered in this paper are detrimental to forgeahility and examples are given which illustrate that even the so-called beneficial elements can he detrimental given the appropriate circumstances. In this context the henefits to he gained by eliminating trace elements with neutralizers are compared and contrasted with the dangers which can occur from their inappropriate use. To put trace elements into context in today's alloys the various factors which affect forgeability are discussed in terms of forging environment and metallurgical factors. The methods of assessing forgeahility are briefly descrihed as are the effects of specffic trace elements on the forgeahility test. Finally, some of the prohlems associated with forgeability in superalloy powders are discussed in the context of trace element effects.