Monotonic tension and creep behavior of single crystal CMSX-486 under combustion environment

Abstract

The monotonic tension and creep loading behavior of single crystal nickel-base superalloy, CMSX-486 was investigated at 1093°C under ambient laboratory and simulated combustion environments. There was degradation in tension and creep performance under combustion environment. A reduction of about 30% in yield strength and ultimate tensile strength and 75% reduction in strain-to-failure were observed in combustion environment relative to laboratory environment. The creep rupture life reduced in combustion environment in comparison to laboratory environment. The creep rupture occurred at a lower strain level in the combustion environment when compared to laboratory environment. The laboratory environment tested specimens experienced higher % neck area reduction, exhibiting more ductility relative to the combustion tested specimens. The mass loss in combustion environment was about 3 times larger than in laboratory environment. The microstructure showed different distribution patterns of γ/γ′ phases. The combustion environment resulted in relatively more contiguous regions of γ phase which presented favorable condition for faster propagation of defects resulting in creep rupture over shorter time span. The subcritical crack growth regions on the fracture surface of the laboratory environment tested specimens were relatively much rougher with more number of craters/voids resulting in longer creep rupture life.