Characterization of the Ni–Mo–Cr superalloy subjected to simulated heat-affected zone thermal cycle treatment

•The constitution of Ni–17Mo–7Cr alloy was convincingly ascertained by TEM analysis.•The Ni–17Mo–7Cr alloy was thermally cycled with a peak temperature up to 1350 °C.•The lamellar-like phases in the alloy were firstly determined by TEM and HRTEM.•The formation mechanism for the lamellar-like phases was unveiled rigorously.•Effect of lamellar-like phases on the alloy’s performances was evaluated in depth.

A representative Ni–Mo–Cr superalloy with basic composition of Ni–17Mo–7Cr (wt.%) was fabricated in the work and the relationship between the microstructure and mechanical properties while it went through simulated heat-affected zone (HAZ) thermal cycle treatment was investigated. The results reveal that the Ni–Mo–Cr alloy mainly consisted of Ni matrix and MoC carbides. The critical peak temperature that a lamellar-like structure occurred in the alloy was found to be 1300 °C. These products were firstly characterized by transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) analysis, and they were essentially Ni matrix and carbides (MoC and chromium carbides) generated through local melting. The equivalent mechanical properties of the alloy relative to that of un-treated alloy were received owing to its unique architecture even the peak temperature during thermal cycle was up to 1350 °C. The results obtained suggests these lamellar-like products dispersed near the fusion line in a Ni–Mo–Cr welded joint will not influence the joint’s mechanical strength and stability while the peak temperature in the HAZ was adjusted below 1350 °C, providing valuable guideline in designing and applying the Ni–Mo–Cr system superalloys.