The welding heat-affected zone (HAZ) of C-HRA-2 nickel-based alloy under various primary peak temperatures (T_p1=1150, 1250, and 1350 °C) and the secondary peak temperatures (T_p2=850, 950, 1050, 1150, 1250, 1350, and 1450 °C) was obtained by welding thermal simulation. The effect of peak temperature (T_p) and thermal cycling times on the evolution of simulated HAZ microstructure of C-HRA-2 alloy was investigated. The microhardness of simulated HAZs was measured. The HAZ microstructure and carbide were characterized by the optical microscope, scanning electron microscope, and transmission electron microscope. Results show that the fine M₂₃C₆ carbides appear along the grain boundaries in the simulated HAZ with T_p1=1150 °C. For HAZs with T_p1>1250 °C, the γ matrix bonded with M₂₃C₆ carbides appears near the grain boundaries due to component liquefaction. When T_p2 is 1050–1250 °C, the carbides similar to those in HAZ with T_p1=1150 °C can be observed near the grain boundaries due to the difference in the solid solubility of Cr in the matrix obtained at T_p1 and T_p2. In HAZ with T_p2>1250 °C, the melted microstructure similar to that with T_p1=1250 °C can be observed near the grain boundaries. The microhardness fluctuates significantly with increasing the T_p2. The microhardness of specimen with T_p2=1250 °C is slightly higher than that of the base material, because of the grain boundary strengthening effect of the carbides near the grain boundaries.