Study On The Effect Of Laser Energy Density On The Mechanical Properties And Cutting Performance Of 3540Fe Based Alloy Cladding Layer

Laser cladding technology,with its high efficiency and green features,has received a lot of attention in the field of remanufacturing and has been successfully used for the repair of damaged surfaces of parts.The laser cladding coating on the surface of damaged parts has significantly improved the surface mechanical properties,but the cutting performance of the cladding layer compared with the base material has also changed.The influence law and mechanism of laser process parameters on the cutting performance of the cladding layer are yet to be studied.This paper selects 42Cr Mo steel as the base material and 3540Fe+1.2%Ce O₂as the cladding powder material to optimize the mechanical properties and cutting performance of the clad layer,to investigate the cutting behavior of multi-lap 3540Fe based alloy clad layer under different milling speeds,and to reveal the influence law and mechanism of laser energy density on the mechanical properties and cutting performance of the clad layer.Firstly,laser cladding experiments with different process parameters were designed and carried out using the BBD experimental scheme,and the prediction model of laser process parameters and cladding layer properties was established based on the response surface method.The results showed that the errors of the prediction models were 7.14%and 2.74%for the microhardness and aspect ratio of the melted layer,respectively,indicating that the prediction models were accurate.The response surface analysis shows that the laser power has the greatest effect on the melt width and microhardness,the scanning speed has the greatest effect on the melt height and aspect ratio,and the spot diameter has the greatest effect on the melt pool depth and dilution rate.Secondly,the experiments were carried out to investigate the influence of laser energy density on the morphology and mechanical properties of the molten layer by testing the macroscopic morphology,cross-sectional morphology and mechanical properties of the molten layer under different laser energy densities.It is found that the laser energy density has a low influence on the overall macroscopic morphology of the clad layer,but has a certain influence on the surface flatness of the clad layer,and a larger laser energy density can obtain a relatively flat clad layer.The increase of laser energy density will lead to coarse grain organization inside the clad layer,but it will not affect the grain type and has no effect on the phase composition.Due to the increase in grain structure,the hardness of the clad layer tends to decrease with the increase in laser energy density and the wear resistance also decreases.Then,different milling speeds were used to test the cutting force,tool wear,machined surface roughness and microhardness of the molten clad layer at different laser energy densities to study the effect of milling speed on the cutting and machining performance of the molten clad layer.The results showed that the cutting force of the molten cladding layer with different laser energy densities increased with the milling speed,and the cutting tool wear gradually increased,mainly in the form of scratches and pits,and the main wear mechanism was abrasive wear and bonded wear,and the machined surface roughness first decreased and then increased.For coatings prepared with smaller laser energy densities,the increase in milling speed decreases the microhardness values of the machined surfaces,while for coatings prepared with larger laser energy densities,the trend of the microhardness values of the machined surfaces is exactly the opposite.Finally,in view of the different cutting performance trends of different cladding layers with the change of milling speed,milling experiments were conducted on the cladding layers prepared with different laser energy densities to test the cutting force,tool wear,machined surface roughness and microhardness during the milling process to study the influence of laser energy density on the cutting performance of the cladding layers.It was found that the milling force fluctuated with the increase of laser energy density when the lower milling speed was used,while the milling force remained stable with the increase of laser energy density when the higher milling speed was used.It was found that the increase in laser energy density effectively slowed down the tool wear,and the main wear mechanism of the tool was abrasive wear.Measurements of the roughness and microhardness of the machined surfaces of the different cladding layers showed that the increase in laser energy density decreased the microhardness and roughness of the machined surfaces at low milling speeds,and the effect of laser energy density on the microhardness and roughness of the machined surfaces diminished when the milling speed increased.