Process And Methods For Mechanical Properties Enhancement Of Metallic Components Based On Selective Laser Melting

The rapid development of science and technology puts forward higher requirements on the mechanical properties of metal materials.From the two aspects of process optimization and material design,the mechanical performance improvement method of Ti6Al4V alloy and Fe-based alloy are studied by selective laser melting?SLM?technology.The effect of the island size of SLM manufactured Ti6Al4V alloy on surface morphology,densification,microstructure and mechanical properties has been investigated.The influence of hot isostatic pressing?HIP?on the phase,microstructure,hardness,tensile and low cycle fatigue properties of Ti6Al4V by SLM has been compared.The evolution of microstructure before and after HIP has been analyzed.The WC/Fe composites have been prepared.The effects of laser processing parameters on the densification have been studied.The influence mechanism of scanning speed on microstructure,hardness and wear resistance has been analyzed.Ti6Al4V samples with different island sizes have been prepared by SLM.When the island size is 5 mm,the surface quality is the best,achieving a maximum densification of 99.7%.The hardness and tensile strength under this condition also reached maximum of 452.7 HV_0.2 and 1202 MPa,respectively.When the island size is smaller or bigger than 5 mm,the densification is lower and the mechanical properties are poor.The microstructures of the samples with different island sizes were not significantly different,and all showed fine needle-shaped martensite.After HIP,the densification increased from 99.8%to 99.94%.The needle-shaped martensite has been transformed into a?+?dual-phase structure.The microhardness of the as-built sample reached 459.6 HV_0.2,the tensile strength was 1233.5 MPa.After HIP,they decreased to 388.15 HV_0.2and 1048 MPa,respectively,but the elongation increased from 4.7%to 8.8%.The cycle number of as-built sample can reach more than 1000 cycles at the strain level of 1.0%.The fatigue life is significantly enhanced after HIP,and the lower the strain level,the greater the increase in fatigue life.WC reinforced Fe-based composites have been successfully manufactured by SLM.The densification increases with increasing laser power and decreasing scanning speed.When v=200mm/s and P=100 W,the highest densification reaches 98.5%.An in-situ gradient interface forms between the WC particles and the matrix,and the eutectic phase with network structure distributes homogeneously in the matrix.At the processing parameter with a v of 300 mm/s and a P of 78 W.The microhardness reaches 511.6 HV_0.2,and the lowest coefficient of friction of 0.30 and the lowest wear rate of 3.1×10^-5 mm³/?Nm?are obtained.