Study On Technology And Microstructure And Properties Of 431 Stainless Steel Laser Cladding Layer Based On 316L Transition Layer

45 steel is widely used in the production of hydraulic piston rods due to its excellent comprehensive mechanical properties and low price,but in some special working environments,its lack of wear resistance and corrosion resistance limits its application.Existing research shows that by laser cladding 431 stainless steel(martensitic stainless steel)on the surface of 45 steel,the wear resistance and corrosion resistance of hydraulic piston rods can be greatly improved.However,the431 stainless steel coating is directly cladding on the surface of 45 steel.Due to the large hardness gradient and internal stress of the cladding layer and the substrate,crack defects often occur in the cladding layer,which seriously affects the quality of the product.In this paper,the idea of first laser cladding 316L stainless steel coating on the surface of 45steel substrate as the transition layer,and then laser cladding 431 stainless steel coating on the surface of the 316L transition layer as the surface coating,studied the 316L transition under different process parameters The forming rule of the cladding layer on the surface and 431 surface,through OM,SEM,EDS and XRD to observe and analyze the microstructure,element distribution and phase composition of the cladding layer,and use a micro hardness tester,electrochemical workstation and friction The performance of the cladding layer was tested by the wear tester.The test results show that when the 316L transition layer is cladding on 45 steel,when other parameters remain unchanged,the laser power increases from 1900W to 2500W,the cladding layer height decreases and the width increases,and the dilution rate increases from 5.38%to 16.37%;when other The parameters remain unchanged.When the scanning speed increases from 2mm/s to 5mm/s,the height and width of the cladding layer decrease,and the dilution rate decreases first and then increases.When the scanning speed is 4mm/s,the dilution rate is the lowest,7.52%When other process parameters are fixed,when the powder feeding voltage is increased from 15V to 27V,the height and width of the cladding layer increase,the penetration depth decreases,and the dilution rate is greatly reduced from 28.28%to 6.59%.The optimized process of combining the surface forming and dilution rate of the cladding layer to obtain the 316L transition layer is laser power2300W,scanning speed 4mm/s,powder feeding voltage 23V.When the 431 stainless steel coating was cladding on the surface of the transition layer,the effects of laser power,scanning speed and powder feeding voltage on the cladding layer forming and dilution rate were studied.The research results show that:the results of the comprehensive cladding layer forming and dilution rate can be The optimized process for obtaining the surface coating is that the laser power is 2300W,the scanning speed is 4mm/s,and the powder feeding voltage is 23V.At this time,the surface of the cladding layer is well formed without any defects,and the dilution rate is 6.37%.The structure of the cladding layer is plane crystal,cell crystal,columnar crystal and equiaxed crystal in order from the bonding area to the top of the cladding layer.When the laser power increases from 1900W to 2500W,the grain structure becomes coarse,and the average hardness of the cladding layer surface also decreases from 543HV to 513HV.When the scanning speed increases from 2mm/s to 5mm/s,the crystals in the cladding layer The grain structure is refined and the average hardness of the cladding layer surface increases from 518HV to536HV.When the powder feeding voltage is increased from 15V to 27V,the cladding layer structure is refined and the average hardness of the cladding layer surface increases from 514HV to 542HV.The Cr and Ni elements are abruptly changed in the interface transition area with a width of10μm.The diffusion area of the elements does not exceed the range of the transition layer.The transition layer is all austenite.The surface cladding layer is mainly martensite and a small amount.Residual austenite structure.The hardness of the entire cladding layer shows a tendency to decrease from the top down.The hardness of the surface cladding layer is 537HV,which is 3 times higher than that of the substrate.The average hardness of the transition layer is 300HV.The average friction coefficient of the cladding layer is 0.3127,and the amount of wear is 2.43mg,which greatly improves the wear resistance of the substrate.The corrosion current of the cladding layer is 0.956910-~6A,and the corrosion voltage is-0.16644V.The corrosion resistance of the cladding layer is better than that of the substrate.