Numerical Simulation Of Ultrasonic-assisted Laser Cladding Repair Layer On Worn Surface Of Mold

H13 die steel is used in forging,extrusion,hot forming,etc.During continuous use,there will be hot and cold cycles and metal flow,which will cause thermal fatigue cracks and thermal wear.In the laser cladding process,due to the rapid heating and cooling that cause greater thermal stress,adding ultrasonic vibration to the laser cladding can improve the quality of the mold.For this reason,this paper uses finite element simulation to study the thermal-stress coupling of the ultrasonic-assisted laser cladding process of Ni-based powder.Combined with the actual establishment of a numerical model,the APDL command stream is used to complete the Gaussian heat source instruction to realize the loading and movement of the Gaussian heat source.The analysis of the temperature field of laser cladding Ni-based powder shows that the temperature of the cladding can be increased to an extremely high temperature in a short time.With the increase of the cladding time,the maximum temperature of the coating gradually increases,reaching 1551°C.Experiments have been conducted to verify that the maximum temperature difference is 69°C,and the gap between the width and depth is within 0.02mm.The effects of different coating thicknesses and process parameters on temperature are analyzed,and it is pointed out that factors such as laser current and defocusing amount have obvious effects on temperature,and the effect of scanning speed is very small.The stress field simulation of laser cladding has been carried out.The highest residual stress on the cladding surface is 1517.4Mpa.Numerical simulation and experimental research show that the maximum difference of transverse welding residual stress is 76MPa,and the maximum difference of longitudinal welding residual stress is 86MPa,stress trend Unanimous.The residual stress change s under different coating thicknesses and different process parameters are analyzed.The results show that the thermal stress changes continuously as the scanning process progresses.When the laser heat source is irradiated,the coating and the heat-affected zone are both compressive stresses.The laser heat source moves,the compressive stress of the coating changes to tensile stress.The residual stress increases with the increase of the coating thickness,and the stress state does not change.The laser current and scanning speed have a small effect on the stress,while the defocus has a large effect.On the basis of thermal stress coupling,APDL was used to compile the command stream of ultrasonic vibration.Through finite element analysis and experimental verification,ultrasonic vibration increased the peak temperature of the cladding by 78°C.As the ultrasonic amplitude increased,the maximum temperature rose.The existence of ultrasonic vibration reduces the residual stress of cladding by 537Mpa.As the ultrasonic amplitude increases,the residual stress of the cladding decreases first and then increases.When the ultrasonic amplitude is 20?m,the minimum residual stress is 980.13MPa.