Influence of simulated heat-affected zone thermal cycle treatment on mechanical performances and microstructural stability of Ni-17Mo-7Cr based superalloy

In the work, a Ni-17Mo-7Cr (wt.%) based superalloy was prepared, and its high-temperature (800 °C) mechanical properties and microstructural stability was evaluated when subjecting to the treatment of simulated heat-affected zone (HAZ) thermal cycle. The results reveal that a lamellar-like structure, which occurs in the alloy, is actually the mixture of Ni matrix and carbides (mainly MoC). When the peak temperature is elevated up to 1350 °C during the HAZ simulation, an equivalent excellent mechanical property is obtained relative to that of the alloy without treatment, due to formation of the typical structures in the alloy. After tensile tests, the hybrid fracture behavior appears on the fracture surfaces, in which the inter-granular fracture with torturous fracture surfaces in company with the ductile fracture are concurrently found. At last, the simulated microstructure can maintain its stability during the tests of isothermal stress relaxation. Based on the results of tensile tests and stress relaxation, we can infer that the simulated microstructure can preserve its excellent mechanical properties and stability at high temperatures.