Effect of inclusions on LCF life of HIP plus heat treated powder metal rené 95

Abstract

Effects of inclusions on 538 °C (1000 °F) strain control low cycle fatigue life of hot isostatically pressed and heat treated powder metal René* 95 compacts were evaluated. Size and location (surface or internal for the test bar) effects along with inclusion types and sources are categorized. Five types of inclusions were identified based on fracture initiation site appearance, although only two major types commonly contribute to significant life low cycle fatigue life degradation. Prior particle boundary decoration reactive type inclusions typically cause the most severe low cycle fatigue life degradation, and those are followed by the discrete ceramic type inclusions. Known potential contaminant seeding study evaluations were used to confirm sources for specific inclusion types. Attempts to minimize the sources for introduction of these contaminants in the argon gas atomization process facilities were only partially successful. An advanced processing approach for the manufacture of René 95 to achieve superior low cycle fatigue life has been proposed based on the improved understanding of the inclusion problem.