The Effect of High Temperature Air Exposure on the Stress Rupture Life of Nickel and Cobalt Base Superalloys

Abstract

The effect of prior air exposure on rupture life of superalloys is reported.Oxygen is identified as a damaging species leading to severe losses in both rupture life and ductility.Similar embrittlement is observed in pure nickel and a mechanism is proposed in terms of reduced grain boundary mobility.Two cobalt base alloys and an oxide dispersion strengthened nickel base alloy do not embrittle in air.It is suggested that the cobalt alloys are immune to oxygen damage and the ODS alloy is intrinsically embrittled as processed.