Effect of Cooling Rate on Microstructure of K4169 Superalloy Coating Prepared by Laser Cladding

K4169 superalloy coating was fabricated using a diode laser. Solution and aging treatment were applied on the coating. During the solidification of the coating, the liquid nitrogen was used to cool the substrate to increase the cooling rate for studying the influence of the cooling rate on the microstructure of the coating. The microstructure and the precipitation phase in the coating were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy. The precipitation temperatures of the phases were measured by differential thermal analysis (DTA). Results show that high cooling rate inhibited the segregation of Nb and precipitation of harmful Laves phase in superalloy K4169 coating. The microhardness of the coating was improved by the heat treatment, and the high cooling rate facilitated the improvement of the micro-hardness of the coating.