Wear Resistance And Residual Stress Of IN718/WC Composite Coating Prepared By Ultrasonic Vibration Assisted Laser Cladding

Laser cladding has been widely used in aerospace,marine and other nickel-based additive and repair fields due to its advantages of high energy density,small heat affected area and good metallurgical combination.Laser cladding is prone to crack,uneven distribution of microstructure and element segregation.Besides,the distribution of WC is uneven due to density difference.In this paper,ultrasonic vibration is introduced into the laser cladding process,and cavitation and acoustic flow effects generated by ultrasonic are used to improve WC particle distribution,coating structure and properties,optimize the hardness and wear resistance of IN718/WC coating,and achieve the goal of reducing coating residual stress and preventing crack initiation.The main contents are as follows:(1)Combined with fluid dynamics and ultrasonic vibration theory,the model of WC movement was established to analyze the distribution mechanism of WC in the molten pool under the action of ultrasonic vibration.Based on the theory of solidification and grain growth of liquid metal,combined with cavitation and acoustic flow effect caused by ultrasonic vibration in molten pool,the influence mechanism of ultrasonic on microstructure and element distribution was investigated.(2)The laser cladding orthogonal experiment was designed to optimize the cladding process parameters,and the forming coefficient was taken as the main criterion to obtain the influence relationship of laser power,powder feeding rate and scanning speed on the coating under the condition of ensuring the dilution rate.To construct a system of ultrasonic assisted laser cladding,the ultrasonic vibration aided cladding IN718/WC coating experiment,by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),and other equipment,analysis of ultrasonic vibration on the WC particle spatial distribution,phase composition,microstructure and element distribution of influence law.Semi-automatic hardness tester and annular friction and wear testing machine were used to test the material properties of the ultrasonic assisted coating.The effects of ultrasonic vibration on the microhardness and wear resistance of the coating was discussed and the transformation of the coating wear mechanism were analyzed.(3)The ultrasonic vibration-assisted laser cladding model was established by ANSYS software to simulate the evolution of temperature and stress fields of the coating,and the influence of ultrasonic vibration on the residual stress of the coating and the re-adjustment mechanism were explored.The experimental verification was carried out by using X-ray residual stress tester.The crack distribution of cladding layer with or without ultrasonic was compared,and the control mechanism of ultrasonic vibration on coating crack was analyzed.