Effect of heat treatment on the microstructure of Co-Cr-W alloy fabricated by laser additive manufacturing

Stellite 6 cobalt-based alloy powder was used to produce Co-Cr-W alloy using laser additive manufacturing technology, and then different heat treatment strategies were carried out on the deposited sample. The characteristics of microstructure under different heat treatment conditions were investigated using scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscope, and x-ray diffraction. The results show that the as-deposited sample has few cracks or pores, and the microstructure is typical dendritic structure, and lamellar eutectic carbides are rich in Cr in interdendritic. The matrix mainly consists of gamma phases and a few epsilon phases. Some gamma phases transform into epsilon phases after 900 degrees C/6 h aging treatment and lamellar eutectic carbides transform into blocky carbides presenting as a network, most of the carbides are rich in Cr and a few are rich in W. When heat treated at 1200 degrees C/1 h followed by water cooling and then treated at 900 degrees C/6 h followed by furnace cooling, it can be found that some gamma phases transform into epsilon phases. The carbides transform into elliptical M23C6 carbides that are rich in Cr with the size of 1 to 3 mu m and a part of W-rich carbides. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)