Study On Ultrasonic Assisted Laser Cladding Of Ni60 Coating

H13 hot work die steel is the most widely used hot work die material,and its repair and surface strengthening after failure determine the service life of die steel.In this thesis,a laser cladding process is used to prepare a Ni-based coating on the surface of H13 steel,and ultrasonic vibration is used to improve the performance of the cladding coating.The parameters of the ultrasonic-assisted laser cladding experiment are explored for the cladding coating The mechanism of action and influence of performance,a group of cladding layers with fewer pores and cracks,finer microstructure,higher microhardness and good friction and wear properties are obtained.The main research contents are as follows:The finite element method was used to simulate the experimental process of Ni-based alloy powder laser cladding and ultrasonic-assisted laser cladding of Ni-based coating,which narrowed the parameter selection range for the choice of cladding experiment parameters,thereby reducing the number of experiments.The simulation results show that when the laser power is 1400 W,the dilution rate of the cladding layer is moderate,and it can form a good metallurgical bond with the substrate;the maximum temperature,temperature gradient and thermal stress value of the cladding layer after ultrasonic vibration are all reduced Trend,can effectively reduce the incidence of pores and cracks in the cladding layer.The simulation results were used as the basis for the selection of experimental parameters,combined with nine groups of orthogonal experiment methods with three factors and three levels and a controlled single variable method to carry out the Ni-based alloy powder laser cladding experiment,and the laser power,scanning speed and powder feeding voltage were obtained.The relationship between the dilution rate,microstructure and microhardness of the cladding layer.The analysis shows that when the power is 1400 W,the scanning speed is 3 mm/s,and the powder feeding voltage is 14 V,the number of cracks in the cladding layer is less,the microstructure is refined and the microhardness is higher.The Ni-based coating was prepared by the ultrasonic vibration-assisted laser cladding process.The microstructure and energy spectrum analysis of the cladding layer were carried out using metallographic microscope and scanning electron microscope(SEM).The analysis results showed that when the ultrasonic frequency is A cladding layer with fewer pores and no cracks can be obtained at 40 k Hz;the grain size of the cladding layer is refined under the action of ultrasonic cavitation after ultrasonic vibration is applied;composition segregation occurs in the cladding layer at 30 k Hz With the increase of frequency,the phenomenon of component segregation at 40 k Hz has been better resolved.Friction and wear experiments were performed on the cladding layers with different cladding processes.The experimental results show that the Ni coating after laser cladding has higher wear resistance than the H13 steel substrate,while the Ni-based coating with ultrasonic vibration The layer has a smaller wear coefficient and its wear resistance is better than that of ordinary Ni-based coatings.After 30 min and 60 min friction and wear experiments,there is no obvious surface peeling phenomenon on the surface of the ultrasonic vibration Ni-based coating,and the wear type is mainly lighter plough wear.