| Wear is the main reason of the failure of machinery parts and ancients.As an effective method to reduce friction and wear,atmospheric plasma spraying(APS)technology can deposit wear-resistant coatings on the surface of mechanical parts,which can greatly meet the urgent needs of modern industry for energy saving and life extending.?-SiAlON ceramic is the material with high hardness and excellent wear resistance.However,it can't be applied to plasma spray since its decomposition under high temperature conditions.In this study,TiO2 and SiAlON were compounded and deposited as a coating on the 316-stainless steel substrate successfully.Studies have been conducted from the aspects of structural characterization,formation mechanism of composite coatings,coating properties and wear resistance.The main research results are as follows(1)XRD,SEM,EDS and other technologies were used to observe the microstructure of the composite coating to analyze the formation process and mechanism of the composite coating.The phases of the coating included rutile and anatase TiO2,retained SiAlON ceramics and SiO2 formed by deposition of SiAlON ceramics.The thickness of the coating was about 200 ?m,and the surface was a typical sputtering pattern of plasma spraying.The cross-section structure is dense.The coating formation process:the composite powder reached two states of full melting and partial melting in the high temperature plasma arc.The full molten powder contained SiO2 and rutile TiO2.The coating structure formed in this state was dense but with a low content SiAlON ceramic;the partial molten powder was rutile TiO2 droplets in the outer layer that surround the anatase TiO2 and SiAlON ceramic particles in the inner layer.The coating formed in this state had larger porosity with a high content of SiAlON ceramic(2)Image-J,Vickers hardness tester and universal testing machine were used to measure the porosity,hardness and bonding strength of the coating,and explore the inherent relationship between them and wear resistance of the coating.The porosity of the coating was about 9%,which was in the standard range of porosity for thermal spray coatings.For wear-resistant coatings,these pores could be used as a temporary place to store lubricant and abrasive debris during friction and wear to improve friction and wear behavior;the micro-hardness of the composite coating first increased and then decreased with the interface distribution,which was related to the pore distribution of the composite coating.Its average micro-hardness was 501.3 HV,which was about 128%higher than that of the substrate.The bonding between the layer and the substrate was good with the average value about 24.3MPa(3)The friction and wear behavior of the coating and the substrate were compared and analyzed under the conditions of dry friction and oil starved lubrication,and the mechanism of friction and lubrication of the composite coating were discussed.The composite coating had the lowest friction coefficient under starved oil-lubricated conditions and had been stable at about 0.1,showing the best friction performance;the wear rate of the TiO2-SiAlON composite coating was only 1/3 of the substrate under the conditions of dry friction and oil starved lubrication.And the wear rate of the composite coating under starved oil lubrication was 68%under dry friction,which illustrated effect of the pores to storage the oil on the surface of the composite coating;the wear mechanism of the substrate was mainly a combination of severe abrasive wear and adhesive wear with accompanied by plastic deformation,the surface of the composite coating showed brittle fracture and slight abrasive wear. |
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