Relationship between the microstructure and the heat treatment and creep behavior of Fe-33Ni-19Cr alloy

In the present study, the relationship between heat treatment, grain size, and the creep rupture properties of Fe-33Ni-19Cr alloy was investigated. The microstructure analysis showed that Fe-33Ni-19Cr alloy consists of the austenite phase matrix and a small number of precipitates such as titanium nitride and titanium carbides. Fe-33Ni-19Cr alloy shows an increase in steady-state creep rate with increased grain size from 94 to 381 mu m, due to the grain boundary sliding mechanism. The result also exhibited that the alloy that was subjected to creep test failed in ductile mode and cavitation at the grain boundaries. The fracture surface shows a transgranular fracture but an intergranular fracture at the recrystallized grains at the fracture area. Taken together, the result exhibited that the Fe-33Ni-19Cr alloy subjected lower heat treatment temperature possess a smaller grain size, which led to better creep property along with more excellent service life during operation.