激光熔覆原位制备ZrC颗粒增强涂层的行为特征

Mixed powders of zirconium dioxide and graphite were added into Ni-based alloy powder, and then the ZrC particles reinforced NiCrBSi composite coating was prepared on mild steel by laser cladding. Microstructure, phase and composition of the NiCrBSi+Zr composite coating were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD), respectively. The morphology, formation and growth mechanism and distribution of ZrC reinforcements were studied, and the hardness of the coating was investigated as well. The results show that ZrC reinforcements are uniformly distributed in the upper part and the middle part of the coating. The morphologies of ZrC are mainly triangle, quadrilateral similar to rhombus and long-bar shaped, which is attributed to obstruction from the interdendritic growth, collision and sintering caused by high convection and repulsion between solid-liquid interface in the molten pool. The hardness of the composite coating is improved by ZrC reinforcements and carbide such as M₂₃C₆. Therefore, the hardness (HV_0.2) of the composite coating can reach 7200 MPa.