Microstructure And Property Of WC/IN718 Composite Coating Prepared By Ultrasonic Field Assisted Laser Cladding

Laser cladding has been widely used in the field of mechanical parts repair due to its advantages of low heat input,fast cooling speed,small deformation of substrate and good metallurgical interface.However,in the preparation of WC / IN718 composite coating,the thermal properties of WC Ceramic Particles and IN718 nickel base alloy powder are quite different,which leads to a sharp increase in the number of pores,cracks and other defects in the laser cladding composite coating,and the increase in the crack sensitivity of the cladding layer.In this paper,in order to improve the microhardness and wear resistance of WC / IN718 composite coating,the cavitation effect,acoustic flow strengthening effect and thermal effect induced by ultrasonic energy field were used to control the solidification process and microstructure defects of laser cladding.The main contents and achievements of this paper are as follows:(1)According to ultrasonic theory,rapid solidification theory of metal and laser cladding theory,the cavitation effect,acoustic flow strengthening effect and heat effect of ultrasonic on the solidification process of molten pool are analyzed.The mechanism of grain refinement in the solidification process of the molten pool under ultrasonic vibration is discussed,and the effects of ultrasonic cavitation nucleation and proliferation theory and ultrasonic dendrite fracture theory on grain refinement are studied,and the movement mechanism of WC Ceramic Particles in the molten pool under the action of ultrasonic is explored.(2)Based on the multi-objective comprehensive scoring method,the optimization of laser cladding process parameters is carried out.The laser power,scanning speed and powder feeding rate are taken as factors,and the dilution rate and forming coefficient of cladding layer are taken as evaluation indexes.The orthogonal experiment of laser cladding is designed to obtain the optimal combination of process parameters.The finite element analysis model of laser cladding was established by ANSYS software,and the temperature field was simulated to verify the consistency between the simulation results and the experimental results.At the same time,the numerical analysis model of ultrasonic assisted laser cladding coating under different ultrasonic amplitudes is established to reveal the influence of ultrasonic amplitudes on the temperature field and temperature gradient of the molten pool.(3)The ultrasonic assisted laser cladding device was built independently and the experimental research was carried out.The microstructure and phase composition of laser cladding composite coating before and after ultrasonic assisted were analyzed by means of three-dimensional microscope,optical microscope(OM),scanning electron microscope(SEM)and X-ray diffractometer.The microhardness of the top,middle and bottom of the composite coating under different ultrasonic amplitudes was studied by microhardness tester.The influence of ultrasonic vibration on the high temperature friction and wear properties of laser cladding composite coating was analyzed by high temperature friction and wear tester,and the mechanism of ultrasonic energy field improving the structure and properties of laser cladding composite coating was revealed.