EVALUATION OF HIGH-TEMPERATURE BEHAVIOR OF CMSX4-CRYSTAL NICKEL-BASE SUPERALLOY(YTTRIUM SINGLE)

CMSX4 + Y, a highly strengthened rhenium-containing second-generation single-crystal nickel-base superalloy, has been studied by creep, low- cycle, and thermomechanical fatigue in the temperature range 500 to 11 00-degrees-C. The alloy exhibits good high-temperature mechanical prop erties that are superior or comparable to other single-crystal superal loys. Thermomechanical fatigue resistance is equivalent to low-cycle f atigue and is cycle-shape dependent. High-temperature mechanical prope rties have been studied using life prediction relationships that are f requently used for creep and low-cycle fatigue data evaluation. Examin ation of fracture surfaces revealed that fracture induced by creep dam age is internal and starts from pore-initiated cracks; however, fatigu e damage starts on the external surface and propagates inward in stage II mode.