超音速激光沉积Cu-Al2O3-石墨复合涂层微观结构及耐磨损性能OA北大核心CSTPCD

In this paper,the Cu-Al2O3-graphite composite coatings with different mass fraction of graphite prepared by supersonic laser deposition technology were used for studying the effects of graphite content on the microscopic morphology,microhardness and wear resistance of the composite coatings.A scanning electron microscope,an energy chromatograph,a Vickers hardness tester,a laser confocal scanning microscopy system,an X-ray diffractometer,and a friction and wear tester were used to analyze the microscopic morphology,microhardness and wear resistance of the composite coatings.The deposition efficiency of the Cu-Al2O3-graphite composite coating decreased with the increase of the proportion of copper-plated graphite in the original powder.The hard ceramic phase Al2O3 particles in the composite coating had the effect of in-situ shot peening on the deposited particles,which could tamp the coating and enhance the bonding between the coating and the substrate.In addition,the synchronous heating of the spray powder and the substrate by laser could soften the surface of the spray particles and the substrate,improve the plastic deformation ability of both,and promote the interface bonding between the Cu-Al2O3-graphite composite coating and the Cu substrate.Although laser irradiation was introduced in coating preparation,the diffraction peak of Cu oxide was not detected in the XRD pattern,and the graphite was not burned by laser irradiation during the deposition.This showed that the laser had little effect on the original composition and microstructure of the coating material in this process.Single addition of Al2O3 particles could increase the hardness of the Cu coating from 108.19HV0.2 to 121.82HV0.2.However,with the addition of graphite,the microhardness of the coating gradually decreased.When the content of copper-plated graphite in the original powder increased from 5%to 15%,the hardness of the composite coating decreased from 116.09HV0.2 to 94.17HV0.2.The wear rate of SLD-Cu coating was 14.1×10-4 mm3/(N·m),the wear rate of the coating with Al2O3 particles(CuAlGr0)decreased to 4.4×10-4 mm3/(N·m),indicating that adding Al2O3 particles in the Cu coating could effectively reduce the wear rate of the coating.With the addition of graphite in the original powder,the wear rate of the composite coating further decreased.The composite coating(CuAlGr10)with 10%graphite had the best wear resistance,and the wear rate was only 0.7×10-4 mm3/(N·m).In the process of friction and wear,graphite with low shear strength was likely to form a solid lubricating layer on the wear surface of the coating,which could effectively separate and prevent the direct contact of the friction pair,thus reducing the friction coefficient and wear rate.At the same time,Al2O3 particles embedded in the lubricating layer could also effectively reduce the wear rate of the coating as a load support and wear-resistant phase.It is worth emphasizing that the simultaneous introduction of laser irradiation in the cold spraying process can improve the interface bonding between the reinforcing phase particles(graphite and Al2O3)and the bonding phase(Cu)in the composite coating,thus avoiding the damage of the graphite lubrication coating caused by the falling off of the hard Al2O3 ceramic particles.