Research On Microstructure And Properties Of Ni-65WC Laser Cladding Coating

Wear and corrosion are the main forms of surface failure of carbon steel mechanical parts.With the development of laser cladding technology,WC reinforced Ni based cladding layer has a broad application in the field of surface engineering because of its excellent friction-wear properties and corrosion resistance.In this paper,micron,submicron and micro-nano scale WC reinforced Ni matrix cladding layers were prepared on the surface of carbon steel by laser cladding technology.The microstructure and composition of the Ni-based cladding layer reinforced by WC at different scales were analyzed,the friction and wear properties of the cladding layer under different working conditions were studied,and the influence mechanism of the scale effect of WC on the microstructure and properties of the Ni-based cladding layer was clarified.The main conclusions of this paper are as follows:(1)Both laser cladding and heat treatment micron scale WC reinforced Ni base cladding layers are mainly composed of ?-Ni,WC and W2C.The interdiffusion layer of Ni/WC interface is thickened after high temperature heat treatment.which improves the bonding strength of Ni/WC.And the average grain size of the Ni matrix in the cladding layer increases with the increase of heat treatment temperature,leading to the decrease of the hardness and corrosion properties of the cladding layer.(2)The friction coefficient and wear rate of micron-scale WC reinforced Ni based cladding layer in atmosphere and 3.5wt%NaCl environment decrease first and then increase with increasing temperature,the wear mechanism is mainly abrasive wear.The wear rate of the cladding layer decreases gradually with the increase of heat treatment temperature under the erosion wear condition,and the erosion wear rate of the cladding layer at 900? is reduced by about 47%compared the unheat treated cladding layer.(3)Under the conditions of 20wt%binder and 20000 r/min atomizer speed,WC reinforced Ni matrix composite powders with particle size of 50?200 ?m were obtained.The submicron scale WC-reinforced Ni base cladding layer is prepared under the conditions of a laser power of 3000W and a scanning speed of 2mm/s,and the microstructure from top to bottom of the submicron scale WC-reinforced Ni base cladding layer is layered,needle-like and massive,the hardness decreases first and then increases,and the corrosion resistance is worse than micron scale WC-reinforced Ni substrate cladding layer.(4)Under atmosphere and 3.5wt%NaCl environment,the friction coefficient of the sub-micron WC-reinforced Ni-based cladding layer increases and decreases with the increase of the load,and the wear rate gradually increases with the increase of the load,the wear mechanism is mainly abrasive wear and fatigue wear.Under erosion wear condition,the erosion wear rate of the cladding layer is about 72%higher than micron cladding layer,because the submicron scale WC has a higher ability of brittle spalling resistance.(5)By controlling the scanning speed of laser cladding,the melting and precipitation process of WC with submicron scale was controlled,and the micro-nano composite scale WC reinforced Ni-based cladding layer was prepared.The structure of the cladding layer is dense,the interface between the cladding layer and the substrate is well combined;The WC particles in the cladding layer prepared at high laser scanning speed(6mm/s)are fine and uniform,and the self-corrosion potential is 0.19V to the right of the submicron-scale WC-reinforced Ni-based cladding layer.(6)Under atmosphere and 3.5wt%NaCl environment,the wear rate of Ni-based cladding layer enhanced by micro-nano scale WC decreases with the increase of scanning speed.The wear mechanism in atmospheric environment is brittle fracture wear,abrasive wear,adhesive wear and oxidation wear,while the wear mechanism under 3.5%NaCl environment is abrasive wear.The wear rate of micro-nano scale WC reinforced Ni base cladding layer decreases with the increase of scanning speed under erosion wear condition.The erosion wear rate under high scanning speed(6mm/s)is 1/24 and 1/6 of the micron and sub-micron WC reinforced Ni-based cladding layer,respectively.