Effect of Heat Treatment on High Temperature Crack Growth under Static Load in Alloy 718.

摘要

Alloy 718 in its conventional heat treated form possesses very poor resistance to crack growth under static load in the temperature range of 425 to 760 C. Since this crack growth is found to be sensitive to the microstructure, a detailed investigation of the effect of heat treatment on the crack growth behavior has been made and various heat treatments have been evaluated with respect to their resistance to this crack growth. Among the heat treatments evaluated it is shown that solution at 926 C for 10 hours and age at 734 C for 48 hours would significantly improve the crack growth resistance without sacrificing its tensile properties. This improved resistance is attributed to the formation of Ni3Cb precipitates which effectively strengthen the grain boundaries. (Author)