Effects of Long-Term Aging and Sensitization Heat Treatments on the Microstructure of Ni-Base Alloy 600 Surface-Melted by a CO_2 Laser Beam

摘要

Heat treatment effects on the microstructure of Ni-base Alloy 600 with surface melted by a CO_2 laser were investigated using microscopic equipments. The long-term aging treatment of laser surface melted (LSM) Alloy 600 at 400 deg C for 235 days caused no considerable effects on the microstructure, including grain boundary related properties. On the other side, sensitization heat treatment of that alloy at 600 deg C for 24 hours induced Cr-rich M_(23)c_6 and Cr_7C_3 carbide precipitated on some high angle grain boundaries, and the minimum Cr concentration along the grain boundary was measured to be about 12 wt