Process Analysis And Optimization Of Multi Pass Laser Cladding 42CrMo Steel For Less Allowance Maching

Aiming at the processing of 42 Cr Mo steel cladding layer,this paper proposes a multitrack laser cladding process and method for less machining allowance.The proposed process is analyzed and verified by theoretical analysis,finite element simulation and experiment.The temperature change trend of cladding layer is obtained by establishing the theoretical model of cladding temperature change in single track laser cladding.The temperature of cladding layer in multi track laser cladding process is calculated by using finite element simulation software,and the residual stress distribution of cladding layer is calculated by thermal mechanical coupling The macro morphology,micro morphology,element distribution,microhardness and friction and wear of the cladding layer were studied,and the effect of lap ratio on the performance of the cladding layer was discussed.The cladding layer was processed by layer-by-layer method to explore the minimum processing quantity of cladding layer under different lap ratio,and the residual stress of cladding layer was measured by hole-drilling technique.In this paper,the heat source model of single track laser cladding and the analytical model of temperature rise of cladding layer are established Through the finite element software ANSYS,the cladding layer with different lap ratio was simulated,and the temperature variation law of the cladding layer with different lap ratio was discussed.The thermal mechanical coupling of the calculated temperature results was carried out to obtain the residual stress distribution of the cladding layer with different lap ratio,and then the position of the minimum residual stress in the cladding layer was discussed.The simulation results show that the temperature of cladding layer increases with the increase of lap ratio.The residual stress in the cladding layer is mainly distributed on both sides of the joint between the substrate and the cladding layer.The residual stress in the cladding layer is the minimum at 50% overlap ratio,and the minimum value is0.2mm away from the cladding layer surface.The Fe based powder and 42 Cr Mo steel were chosen as the powder and substrate respectively.Under the laser power of 1500 w,spot diameter of 5mm and scanning speed of 5mm / s,the cladding experiments with 30%,40%,50%,60% and 70% overlap rate were carried out respectively.The macro morphology,micro morphology,microhardness,friction and wear,and element distribution of the cladding layer with different lap ratio were measured to study the effect of lap ratio on the microstructure and properties of the cladding layer.The experimental results show that with the increase of lap ratio,the area of cladding layer decreases gradually,the grain is refined gradually,and the distribution of elements tends to be uniform.At the same time,with the increase of lap ratio,the microhardness increases and the friction coefficient decreases.When the lap ratio is more than 50%,the friction coefficient increases again,and some defects such as pores appear in the cladding layer.Considering that the performance of the cladding layer is better under 50% lap ratio,it has higher microhardness and wear resistance.The geometric model is used to calculate the theoretical processing quantity of cladding layer,and then the layer-by-layer method is used to grind the cladding layer to obtain the actual processing quantity.The reason of the deviation between the actual processing quantity and the theoretical processing quantity is analyzed,and the residual stress in the cladding layer is measured by the hole-drilling technique.The results show that the surface morphology of the cladding layer is wavy and uneven due to the influence of temperature,spot diameter and surface tension.The actual removal amount is less than the theoretical removal amount,and the residual stress measurement results are in good agreement with the simulation results.The most suitable lap ratio for processing is calculated by method of weighting,and it is found that the cladding layer with 50% lapping rate is most suitable for subsequent processing.