Microstructure And Wear Resistance Of WC/Ni60 Composite Coatings Prepared By Supersonic Laser Deposition

45 steel,combined quality structural and functional performaces,economical,has been widely used in shaft parts and machinery manufacturing industries.However,the wear and failure often occurs due to its low strength.The application of surface engineering technology can improve and optimize its surface wear and fatigue resistances,and can make it possible to prolong service life of parts and remanufacture failure parts.In the study,the supersonic laser deposition?SLD?was emploied to synthesize Ni60 composite coatings by adding different WC contents on the surface of 45 steel.The microstructure,phases,compositions and interface structure of the kind of alloy powder and its coatings were analyzed by metallographic microscope,scanning electron microscope?SEM?,X-ray diffraction?XRD?and energy dispersive spectroscopy?EDS?,etc.And effects of WC on the microstructure and interface bonding mechanism of the composite coating were also studied.In addition,the influence of WC on wear properties of the coatings and the wear mechanism were also investigated by microhardness and friction and wear experiences.The results showed as:?1?All Ni60 and WC/Ni60 composite coatings prepared by SLD had a good compactness despite a few holes and pits distributed.With increase of WC content,voids and pits in the coastings had an increasing trend,and the porosity also increased.The best WC loading ratio is 20%.?2?The main phases of WC/Ni60 composite coating were Cr₇C₃,Cr₂₃C₆,FeNi and WC.The added WC,presenting dendritic crystals,was distributed uniformly throughout the matrix.The deposition process of SLD mainly involves the physical accumulation of the sprayed particles without obvious heating effect on the coating.The WC/Ni60 composite coating basically maintained the original composition of the sprayed particles,the interface was wavy,and the interface bonding mechanism is combination of mechanical bonding and metallurgy.?3?The microhardness of the WC/Ni60 composite coating was significantly higher than that of the matrix,and it tended to increase from the inside of the matrix to the surface layer of the coating,and gradually increased with WC content.When the content of WC was 30%,the hardness of the composite coating was the highest,reaching at 845 HV_0.2?the average microhardness was 809.1 HV_0.2.?4?The friction coefficients of SLD coatings varied from 0.275 to 0.375 and decreased with the increase of WC content.When the content of WC was 30%,the friction coefficient was the lowest,and the wear loss of the coating after 30 minutes'friction is 0.69 mg,showing the coating being a good wear resistance.?5?Slight furrows,plastic deformations such as bulging and depression,and peeling of oxide films occurred on the wear surface of Ni60 coating without WC,showing the wear mechanism is abrasive wear.The wear morphology of 10%WC/Ni60coating is similar to Ni60 coating,while the surface oxide films were severely peeled off owing to the increased wear,which shows the wear mechanism are mainly abrasive wear and oxidation wear.The surface furrows of 20%WC/Ni60 coating were thin and shallow,with oxide film on its surface only suffered localized damage but without serious oxide film peeling,showing the wear mechanism of oxidation wear.By contrast,30%WC/Ni60 coating,endowned with more fine furrows and massive oxide film exfoliation pits and some abrasive bonding materials,marking the wear mechanism is responsible for conbination of the three of abrasive,adhesive and oxidation wears.