In Situ Growth Of WB-CrB Particles Reinforced Ni Matrix Composite Coatings By Laser Cladding

In situ synthesised ceramic coating by laser irradiation through in situ reaction among the elements and compounds has one or several high elastic modulus, high strength ceramic reinforcement, thus to strengthen the matrix and greatly improve the surface properties of materials by combining the high toughness of metal with the ceramics properties such as high corrosion resistance, high wear resistance, high hardness.In situ laser cladding ceramic coating is characterized by in situ nucleation, small and dispersed enhancing particulates and structure refinement, which has a good compatibility with matrix, strong bonding, surface pollution, and whose hardness, wear resistance and so on are significantly increased.Boride ceramics has high melting point and hardness, whose boron atoms combine with each other firm characteristics, making it at a high temperature and corrosive environment has high chemical stability and unique wear resistance. Due to its excellent performance, boride ceramics has already applied to most of the surface engineering of metallic materials, such as cutting tools, wear resistant heat engine components, widely used in construction machinery, and has also been widely used in the pharmaceutical, chemical, light industry, textile, fire, building materials, agricultural, military and national defense sector.In this paper, laser cladding boride was prepared in situ ceramic particle reinforced nickel based coatings, and its preparation, structure, hardness and wear resistance were systematically studied. Results and main conclusions are as follows:(1) In situ WB-CrB particle reinforced nickel matrix composite coatings with good morphology and improving performance were firstly successfully prepared on 45 steel by employing a proper amount of Ni60+(WO3+B2O3+C) doping using laser cladding. The optimum preparation techniques are 16wt.% content of (WO3+ B2O3+C)-doping,50mm defocusing length,1.8 kW laser power and 2 mm/s scanning velocity.(2) The microstructure of the Ni60+16wt.%(WO3+B2O3+C) coating is mainly composed of in-situ synthesized WB-CrB particulate phases and the Cr3C2 stripe phase uniformly dispersed in the y(NiFe) dendrite matrix.(3) The average hardness of the WB-CrB particulate reinforced composite coating was enhanced to HV0.31350, which is 68.7 percent higher than that of pure Ni60 coatings (HV0.3800). Friction tests showed that its excellent wear resistance is 7 times as high as that of pure Ni60 coatings. The improvement in hardness and wear resistance is due to the presence of a great deal of in-situ synthesized WB-CrB particles and their well distribution in the composite coatings.