Study On Microstructure And Properties Of TiC/316L Stainless Steel Composites Fabricated By Selective Laser Melting

316L stainless steel?316Lss?is widely used in chemical industry,shipping,automobile and other fields because of its good corrosion resistance,high temperature resistance,creep resistance,high toughness and non magnetism.However,with the improvement of our comprehensive strength in aerospace,military industry,automobile,national defense and other fields,higher and higher requirements are put forward for the strength,toughness,wear resistance and corrosion resistance of 316L stainless steel,and the traditional forming methods are difficult to meet the complex requirements for the preparation of the 316L stainless steel.Selective laser melting SLM?selective laser melting,SLM?forming technology is a research focust in the field of additive manufacturing technology at present.This technology uses high-energy laser beam as the energy source,through the layer by layer accumulation forming of materials,it can realize the high-performance precise forming of complex shape metal components,and is suitable for the manufacturing of multiple varieties and small batches of complex components.In this paper,based on the 316L stainless steel,aiming at the fact that the 316L stainless steel fabricated by SLM are difficult to meet the requirements of high strength and high wear resistance in the fields of national defense science and technology,nuclear power and other related fields.Ceramic particle reinforced phase is introduced to prepare TiC/316L stainless steel composite.The influence of TiC ceramic particle reinforced on the microstructure and properties of TiC/316L stainless steel composite is systematically studied.After the experiments of sliding friction and wear under different conditions,the differences of friction coefficient,wear amount and wear morphology of the formed samples were analyzed.The main research contents and results are as follows:?1?The distribution of temperature field and the change of weld pool size during SLM forming of 316L stainless steel were studied.The results show that,when the laser power increases from 160 W to 240 W,the width of molten pool increases from 102.9?m to 126.3?m,increased by 18.53%,and the depth of molten pool increases from 36.89?m to 53.37?m,increased by 30.88%.When the laser power is fixed,the point spacing increases from 40?m to 120?m,the width of the molten pool decreases from 126.9?m to 101.2?m,20.25%reduction,and the depth of the molten pool decreases from 52.86?m to 38.06?m,27.98%reduction.In the process of SLM,with the increasing of laser power and the decrease of point spacing,the laser energy density increases,which makes the laser absorption of powder increase continuously,and then forms a large pool.The proper size of the pool is the premise of forming a good lap.Considering the influence of laser power and point spacing on the temperature field of the SLM forming process,the simulation results show that,when the laser power is 200 W and the point spacing is 80?m,the width?114.5?m?and depth?44.46?m?of the molten pool are appropriate,which can ensure the good combination between adjacent layers and is conducive to the smooth progress of SLM process.?2?The effects of process parameters on the microstructure,mechanical properties and corrosion resistance of 316L stainless steel parts formed by SLM were studied.The results show that,when the laser power is 200 W,the surface of the formed part is relatively smooth,without cracks and holes,and the forming performance is the best;the average microhardness of 316L stainless steel formed by SLM is significantly improved,reaching 262 HV_0.1;the corrosion speed of 316L stainless steel formed by SLM is slow,and the corrosion current density is also smaller than that of traditional rolled 316L stainless steel.The microstructure of 316L stainless steel formed by SLM is more compact,the component segregation is less,and the distribution of Cr and Ni elements is even,which makes the corrosion resistance improved.?3?The influence of the ball milling parameters on the powder morphology of TiC/316L stainless steel composite and the effect of TiC particles on the microstructure and mechanical properties of TiC/316L stainless steel composite formed by SLM were studied.The results show that,when the ball material ratio is 8:1 and milling time is 8h,the TiC particles of the mixed powder are evenly distributed and have good sphericity.After adding 2 wt%and 4 wt%TiC respectively,TiC/316L stainless steel composite powder was formed by SLM,and the best form ability was obtained by adding 2 wt%TiC particles.In addition,with the increasing of TiC content,the microhardness of TiC/316L stainless steel composite increases first and then decreases;the corrosion rate of TiC/316L stainless steel composite formed by SLM decreases first and then increases.?4?The effect of different load and sliding speed on the tribological behavior of TiC/316L stainless steel composite formed by SLM was studied.The results show that the wear rate of the composite decreased with the increasing of the sliding speed.When the sliding speed is 60 mm/min,the wear rate of the sample is 40 mg/2×10³m,and the wear mechanism is separating layer wear and slight oxidation wear;when the sliding speed is 100mm/min,the wear rate of the sample is 35 mg/2×10³m,and the wear mechanism is dominated by oxidation wear.With the increasing of the load,the surface roughness increases from Ra=2.03?m to Ra=2.41?m,and the wear rate of the composites increases,the fluctuation of friction coefficient increases and the stability decreases.Under different loads,the main wear mechanisms of SLM composites are abrasive wear and oxidation wear.The friction and wear properties of TiC/316L stainless steel composite can be effectively improved by TiC ceramic particle reinforced phase.