Process And Performance Control Of Laser Additive Manufacturing Of Ni-based Composites Based On Thermal-Mechanical Coupled Method

Based on the close combination of ANSYS finite element numerical simulation and experimental investigation,quantitative thermal behavior and stress behavior during Selective Laser Melting(SLM)of WC/Inconel 718 composites was performed,and the effects of the behavior on the internal microstructural evolution and mechanical performance was further discussed in this paper.The results showed the existence of heat accumulation effect in SLM process and,the tailored set of cooling time of 8 ms during the powder delivery alleviated that effectively.The maximum temperature gradient in the molten pool increased from 1.31 × 104 °C/mm to 2.57 × 104 °C/mm as the laser power was increased from 75 W to 150 W.However,it was negligibly sensitive to the variation of the laser scan speed.The microstructure of SLM-processed WC/Inconel 718 composites could be significantly influenced by the addition of WC particles.Fine dendrites which were almost vertical to the edge of the particle could be observed when small WC particles(5.25 ?m)were used in the composites,increasing the contact area between the particle and the matrix and thus improving the interfacial bonding strength between them.In this case,the distribution of the Coefficients of Frication tended to be uniform with a lower average value of 0.21 in wear properties.Based on the thermal-mechanical coupled numerical simulation of stress behavior during SLM process,the author further discovered that the stress mainly generated during the solidification process of SLM and tensile stress showed the dominance on the top surface of the powder bed.The distribution of the stress on the top surface of the powder bed under different scan speeds was similar with that under different laser powers.When the laser power or the scan speed was increased,the stress level was improved significantly and,the stress around the center of the powder bed was higher than that at the periphery of the powder bed.The maximal value of the stress located at the local interface between the metal substrate and the powder bed and,the average value of ?x was higher than that of ?y in this case.The optimized processing parameters(v = 100 mm/s,P = 125 W)contributed to achieve a sound metallurgical bonding between neighbor tracks,adjacent layers and between the particle and the matrix with a relatively smooth surface due to the proper molten pool size(length: 119 ?m;width: 108 ?m;depth: 66.7 ?m).The maximum residual stress was lower than the yield strength of Inconel 718,showing the low possibility of deformation and crack within the SLM-processed material in this case.