Effect of Temperatures on Mechanical Properties and Microstructure Evolution of Laser-Welded Ni-Base Superalloy

Ni-base superalloys are widely used for thin-wall components that need to resist high-temperature environments in aero-engines and high-speed aircraft. Hence, their mechanical properties and microstructures after laser welding at high temperatures are essential to be investigated and evaluated. In this study, the evolution of main mechanical properties (including the yield strength, and tensile strength) and microstructures of laser-welded Ni-based superalloy and base metals (BM) under tensile deformation at different temperatures (20 ℃, 300 ℃, 500 ℃) are investigated and compared. The tensile strength results indicate that the strength of the welded part is slightly higher than that of the BM at room temperature, while the results turn to the opposite trend with increasing temperatures. The microstructural results suggest that evolutions of carbide precipitates and grain sizes in the welded joint under different temperatures concurrently affect the strength. At 20 ℃, the strengthening effect from carbide precipitates after welding is more apparent, leading to a slightly higher stress level in the welded alloy; while at 300 ℃ and 500 ℃, the softening effect caused by the increasing grain sizes in the welded alloy plays the dominant role, leading to the reduction of strength after welding.