Effect of the Prior Microstructure Degradation on the High Temperature/Low Stress Non-Isothermal Creep Behavior of CMSX-4? Ni-Based Single Crystal Superalloy

摘要

The effect of thermal cycling on the creep behavior and life of the second generation Ni-based single crystal superalloy CMSX-4? has been investigated in the very high temperature/low stress domain. Repeated overheatings at 1100°C and/or at 1150°C were introduced in the course of the creep life of the alloy at 1050°C/120 MPa. The detrimental effect of the thermal cycling compared to the isothermal creep behavior of the alloy is shown: thermal cycling leads to an increased average creep strain rate and a reduced creep life. This is always the case even when compared to the isothermal creep behavior at the highest temperature of the cycle (i.e. 1150°C/120 MPa). Moreover, the detrimental effect of the thermal cycling frequency is observed: the greater frequency the larger the creep properties decay. Compared to the first generation MC2 alloy under the same thermal cycling conditions, CMSX-4~ exhibits superior non-isothermal creep properties in the very high temperature domain (T l 1100°C) due to its rhenium and γ' contents.