| 45 # steel has good comprehensive mechanical properties,not only high strength but also excellent plasticity and toughness.Its price is also very low,so it is widely used in various parts and engineering components.But it also has the insurmountable shortcomings of poor resistance to abrasion and corrosion.In general,heat treatment such as quenching and tempering,surface quenching,carburizing or nitriding can significantly improve the surface wear resistance.However,the issue of poor resistance to corrosion has not been effectively solved.The AISI 431 coating by laser cladding on the surface of 45 # steel not only improves the wear resistance of the 45# steel surface but also significantly improves its corrosion resistance.In this paper,coating of AISI431 was laid on the surface of 45# steel,the effect of processing parameters on geometry and grain morphology was studied through control variate method,the effect of processing parameters on the microstructure and properties of coating was make clear too.The effect of processing parameters on geometry,dilution,grain morphology,and average micro-hardness of coating was studied by experiments.The results show that: when the laser power was gradually increased from 1800 W to 2600 W,the width of the cladding layer was increased by 21%,the height of the cladding layer was increased by 30%,the dilution rate was increased from 5.50% to 14.64%,the plane crystal on the cross-section of the coating was mostly around 3% with little change,the proportion of cell crystal and columnar dendrite gradually decreased from the maximum value of 43% to 22%,and the proportion of equiaxed dendrite increased from the minimum value of 54% to the maximum value 75%,the average hardness of the cross-section of the cladding layer was reduced from561 HV to 518 HV.When the scanning speed is gradually increased from 1mm/s to 4mm/s,the width of the coating decreased by 16%,the height of the coating decreased by 58%,the dilution rate was reduced from 10.02% to 7.89%,and the average micro-hardness of the coating gradually increased from 495 HV to 541 HV.When the scanning speed was increased from 1mm/s to 3mm/s,the proportion of plane crystals on the coating didn't change much,the proportion of cell crystals and columnar dendrites decreased by about 30%,and the proportion of equiaxed dendrites increased about 28%.When the powder-feeding voltage was gradually increased from 18 V to 33 V,the width of the coating fluctuated around 6000?m without obvious changes,and the height of the coating was gradually increased by 43%,the dilution rate was gradually decreased from 10.71% to 4.71%,the average micro-hardness of coating gradually increased from 497 HV to 553 HV.When the powder feeding voltage was increased from 18 V to 33 V,the proportion of planar crystals of the coatings did not change much,cellular and columnar dendrites increased by about 48%,and equiaxed dendrites decreased by about 26%.In order to obtain a perfect coating with a width of 6mm and a height of 1mm,orthogonal experiments had been taken.The results show that when the laser power is 2300 W,the scanning speed is 3mm/s,and the powder-feed voltage is 23 V,the width of the cladding layer is 6009.94?m,the height is 1107.37?m,and the appearance is beautiful and free of defects.The X-ray diffraction was used to analyze the phase of the cladding layer cladding with the best process parameters.The results show that the cladding layer was mainly composed of martensite,ferrite and a small amount of austenite.The electrochemical workstation and the universal friction and wear testing machine were used to characterize the corrosion resistance and wear resistance of the coating with the best process parameters.The results show that the corrosion resistance of the cladding layer was significantly higher than that of the 45 # steel substrate,and the wear resistance of the cladding layer was significantly better than that of the substrate. |
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