Evaluation of the mechanical properties of WC-Ni composite coating on an AISI 321 steel substrate

In this study, The WC-Ni composite powders were fabricated by the electroless plating of nickel-phosphorus, followed by the appliance of the obtained particles as a coating on an AISI 321 steel by laser cladding method. Effects of main laser parameters, including power, scanning speed, and powder feed rate on the geometric properties were reviewed. The optimum single-pass specimen was chosen after considering the geometrical shape, dilution, and crack and porosity amount of the single-pass specimens. It was found that the increase in laser power and powder feed rate results in the rise of the height and the width of the coatings. In contrast, coatings with lower height and width were achieved by employing lower laser power and powder feed rates. The procedure was followed by the laser cladding of the WC-Ni powders on 321 steel substrate under the optimum coating parameters with a variety of overlap amounts; 30, 50, and 70 percent. By investigating the formed phases and microstructure of the overlap specimens, the 70 percent overlap coating was chosen as the optimal one. Mechanical and wear tests were conducted on the optimal overlap specimen. Experiments indicated that the hardness, elasticity modulus, and fracture toughness of the coating were, respectively, 1457 Vickers, 6.24 Mpa.m(1/2), and 250 GPa. The micro-hardness of the WC-Ni coating was 1.2-1.6 times higher than the WC-Ni, WC-Co and WC-Co-Ni coatings, made by thermal spray coating. Also, the toughness of the coating was 1.5 times higher than the WC-Co thermal sprayed coat. The elasticity modulus of the WC-Ni coating (250 GPa) was 1.1 times more than the WC-Co coating manufactured with the laser cladding method.