Determination of creep damage in the ODS superalloy MA6000

Ni-based superalloys are widely accepted as being suitable candidates for use in the blade sections of gas turbine engines where improvements in high temperature creep resistance properties are possible as a result of a designed microstructure. The intrinsic changes in microstructure and mechanical properties resulting from the process of creep may become a life-limiting factor. The oxide dispersion strengthened (ODS) superalloy MA6000 was subjected to a high temperature creep environment at stresses ranging from 150-550 MPa and temperatures of 750, 950 and 1050 °C. The potential of certain destructive and non-destructive techniques in detecting the resultant creep damage was explored. The microstructural damage was examined by (1) qualitative and quantitative metallography, (2) ultrasonic wave velocity measurements and (3) microhardness indentations. The responses from the different techniques were compared to each other and to results obtained from austenitic and ferritic steels in order to serve as a basis for assessing residual life.