Mechanical properties and fracture modes of an advanced Ni–Co-base disk superalloy at elevated temperatures

The successful development of an advanced cast and wrought disk alloy, TMW-4M3, was initiated in the NEDO program supported by the Japanese government in cooperation with Mitsubishi Materials Corporation. This paper reports the mechanical properties and fracture modes of TMW-4M3 disk alloy, in order to support its high temperature uses and to understand prospective failure scenarios. The mechanical properties and fracture modes of tensile, creep, low cycle fatigue, and fatigue crack growth were evaluated up to 760 °C on specimens machined from the full-scale pancake-shaped disk. The excellent overall mechanical properties of TMW-4M3 alloy were demonstrated. Fracture modes were compared with different testing conditions and fractographic examinations indicated that the fracture modes shifted with changing test conditions. Surface crack initiation was the main failure mode at elevated temperatures. Crack propagation rate was accelerated above 650 °C due primarily to oxidation and degradation of mechanical strength. The results indicated that the TMW-4M3 alloy has at least 650 °C general capabilities and is promising for 700 °C or more applications.