Microstructure And Properties Of Ni35+SiC Coatings Prepared By Laser Cladding

As one of the most advanced technologies emerging in the 21st century,laser cladding technology has been widely used in industrial production to enhance the surface modification and remanufacturing of wear-prone parts.Marine plunger parts are generally made of modulated 45 steel.The working environment of these parts is complex,and they often fail in the form of wear,corrosion or wear and corrosion coupling.In this paper,Ni35,SiC,Ni/Mo S₂,CeO₂ and other cladding materials were used to prepare nickel-based ceramic laser cladding layer on the surface of 45 steel by preset laser cladding technology,which provides experimental reference and theoretical support for rapid laser repair of Marine jacking cylinder plunger and hydraulic cylinder plunger.The optimal process parameters were determined by single factor optimization method.The influence of process parameters on the quality of the cladding layer was deeply studied.The microstructure and properties of the coating were studied by means of metallographic microscope,and the influence of Ni/Mo S₂ and CeO₂ on the microstructure and properties of the coating was analyzed.The main research work is as follows:1)In order to explore the influence of process parameters on the morphology and microhardness of Ni35+20%SiC coating,single-channel laser cladding experiment was carried out by single-factor experimental method to study the influence of laser power and scanning speed on the forming size and microhardness of the coating.The relationship between laser power and fusion width is positive,and the relationship between scanning speed and fusion width is negative.The laser power and scanning speed have little effect on the melting height.The microhardness increases first and then decreases with the increase of laser power and scanning speed.The optimal process parameters are as follows:laser power P=1000W,scanning speed V=8mm/s.2)Ni35+20%SiC coating was prepared by a better process.The microstructure and properties of the coating were studied.The microstructure of Ni35+20%SiC coating is compact,mainly composed of SiC,Ni₂Si,Fe Siand other compounds,and the microhardness is up to 880.62HV_0.2.Compared with45 steel,the self-corrosion potential of the coating is increased by 0.462V,which makes the corrosion more difficult.The wear loss weight of 45 steel is only 1/4 of that of 45 steel.The wear type is mainly abrasive wear and adhesive wear.3)In order to improve the friction and wear properties of Ni35+20%SiC coating,Ni35+20%SiC coating added 20%Ni/Mo S₂ was prepared by using better process parameters.The microstructure and properties of the coating were studied.The coating mainly contains solid solutions such as Ni-Cr-Fe and metal sulfides such as Mo S₂,Nis and Cr₂S₃,and the hardness of the coating is 701.52HV_0.2.The corrosion tendency and speed of Ni35+20%SiC coating are decreased with the introduction of Ni/Mo S₂.The metal sulfide exhibits obvious anti-wear and anti-friction effect during the friction process,further reduces the weight loss,and the friction coefficient decreases from 0.81 to 0.62.4)In order to study the influence of rare earth oxide CeO₂ on the forming quality and properties of Ni35+20%SiC coating,Ni35+20%SiC coating added 1%CeO₂ was prepared,and the microstructure and properties of the coating were studied.The microhardness of the coating is as high as 910.43HV_0.2.The addition of CeO₂ increases the nucleation rate of the cladding layer and refines the grain of the cladding layer.Adding CeO₂ reduces the corrosion speed and improves the corrosion resistance of the coating.Under the action of CeO₂ dispersion strengthening and fine grain strengthening,the weight loss of the coating under 40N loading force for 20min is only 2.5mg,the friction coefficient is 0.68,and the wear mechanism is abrasive wear.