Effect of high-temperature aging on microstructure and mechanical properties of Ni–Mo–Cr based superalloy subjected to simulated heat-affected zone thermal cycle

Abstract

In the work, the effect of high-temperature (800–1100 °C) aging treatment on microstructural evolution and mechanical properties of the Ni–17Mo–7Cr based superalloy subjected to heat-affected zone (HAZ) thermal cycle. When the aging temperature is in excess of 800 °C, massive tiny MoC particles and a few chromium carbides are precipitated in the alloy. The lamellar-like structures grow in the alloy and tiny MoC are precipitated around them. In addition, some nano-sized chromium carbides with needle-like morphology are formed in the MoC. With increasing the aging temperature, the tensile and yielding strength decrease slightly due to increased precipitates in the alloy. In comparison with the alloy that does not go through the HAZ simulation, both of their mechanical properties share the close value at each temperature. The retention interval above 1300 °C during the HAZ simulation also influences the alloy's microstructure and mechanical properties. More lamellar-like structures are produced when elevating the retention interval over 5 s. Due to the increase of solidification defect and stress concentration, the tensile and yielding strength decrease sharply when the interval is increased from 5 s to 10 s. Further improving the interval has a limited influence on the alloy's mechanical properties.