Microstructure And Properties Of Ceramic Coating Prepared By Laser/Sol-Gel Composite Method On Stainless Steel Surface

3Cr13 stainless steel has high strength,hardness and wear resistance,and is often used as a cutting tool,medical instrument,measuring tool,etc.in industrial production.Due to the harsh working environment,it is prone to wear,corrosion and hardness reduced caused by temperature increase after a period of service.This will not only cause safety hazards,but frequent replacement of workpieces will also increase production costs and waste resources.By preparing a ceramic reinforced coating on the surface,the life of the workpiece can be effectively extended.The ceramic coating is prepared by sol-gel composite laser cladding,the ceramic reinforcing phase is generated in-situ during melting of the gel composite powder,which enhances the wettability with the matrix and avoids cracking,significantly improving the hardness,wear resistance and corrosion resistance of the coating.In this paper,TiO₂/carbon uniformly mixed precursor powder was prepared by sol-gel method,and the carbon source was carbon nanotubes?CNTs?and micro-graphite.The composite coatings of titanium carbide and chromium carbide ceramics were prepared on the surface of 3Cr13 stainless steel by laser cladding,which can provide reference for the application of ceramic reinforced coatings in improving hardness,wear resistance and corrosion resistance of parts in industrial and agricultural production.In this paper,the microstructrure,elemental composition and phase composition of the coating prepared by sol-gel composite laser cladding were analyzed by scanning electron microscopy,energy spectrum analyzer and X-ray diffractometer respectively.The effect of carbon source and carbon content on the properties of ceramic coatings prepared by sol-gel laser cladding was investigated.The microhardness,normal temperature/high temperature friction and wear properties,and the corrosion resistance of the coatings were studied.The process of preparing precursor powder from sol-gel was optimized and the mechanism was analyzed.The formation mechanism of strengthening particles in the optimal coating was explored,and the mechanism of in situ reaction producing different carbide particles in the coating was analyzed.The results show that when the carbon source is the same,increase of the carbon content in the precursor can promote the in-situ reaction to form more ceramic strengthening phase,and the formation of the ceramic strengthening phase will cause lattice distortion inside the coating,thereby achieving the effect of fine grain strengthening.When the carbon content in the precursor powder is the same,it can in-situ produce more TiC and Cr₇C₃ strengthening phases in the coating with CNTs added,and the TiC size is smaller than that of the micro-graphite coating.The hardness,wear resistance and corrosion resistance of the micro-graphite coating increased with increase of the carbon content.As the carbon content increases,the hardness and wear resistance of the 20%CNTs coating increase,and the corrosion resistance changes little.When the carbon content is the same and the carbon source addition type is changed,the particle size of the strengthening phase in the coating prepared by adding CNTs is smaller than that of the micro-graphite coating.The hardness and wear resistance of the coating are larger than that of the micro-graphite coating,and the corrosion resistance has little differentce.When n?TiO₂?:n?C?is 1:8,the coating with 20%CNTs as the carbon source has the best performance.The average microhardness reaches 750 HV_0.2,up to 795 HV_0.2,which is about 1 time higher than that of the micron graphite coating.The wear resistance at room temperature is 4.5 times higher than that of the substrate,which is 1 times that of the micro-graphite coating.The high-temperature wear resistance is 6.8 times higher than that of the substrate.The corrosion resistance is 5.5 times higher than that of the substrate.The preparation of precursor powder by sol-gel method is a heterogeneous nucleation process,and TiO₂ can be uniformly coated on the surface of CNTs and micron-graphite for nucleation and growth.During the in-situ reaction,TiC strengthening phase will preferentially form and Cr₇C₃ will grow with TiC as the heterogeneous nucleation point.TiC can improve the nucleation rate of Cr₇C₃ and play a fine-grained strengthening effect on the coating.The reaction mechanism in the molten pool is the reaction-diffusion mechanism.In summary,the process,microstructure and properties of ceramic coating prepared by sol-gel/laser composite method were studied.The effects of carbon source and carbon content on microstructure and properties of the coating were analyzed.The strengthening mechanism of the coating was explored.This study will provide a new method for the application of ceramic reinforced coatings in industrial and agricultural production.