Cr3C2对激光选区熔化316L合金组织及力学性能的影响OA北大核心CSTPCD

The application of 316L alloy is limited due to its low strength and low wear resistance.The addition of Cr3C2 particles is beneficial to the improvement of strength,hardness,and wear resistance of 316L alloy.As an advanced metal additive manufacturing technology,selective laser melting(SLM)has the characteristics of an extremely high cooling rate and micro-molten pool solidification,which makes the forming samples have a fine microstructure and good mechanical properties.The work aims to study the phase composition,microstructure,hardness,strength and wear resistance of 316L alloy and Cr3C2/316L alloy fabricated by SLM and discuss the effect of Cr3C2 particles on the microstructure and properties of 316L alloy. In this study,10wt.% Cr3C2 powder was mechanically mixed with 316L powder,and the samples were fabricated by the SLM machine(Hanbang HBD-150D).The preparation process was carried out under the protection of argon.The process parameters were as follows:laser power of 350 W,layer thickness of 30 μm,scanning speed of 2 000 mm/s,hatching space of 60 μm,checkerboard scanning strategy,and rotation angle of 67° between each layer.Pure 316L alloy was prepared under the same process parameters.The phase of the two alloys was analyzed by X-ray diffraction(KYOWAGLAS H-12).The microstructure was observed by optical microscopy(Leica DM4000),scanning electron microscopy(Nova NanoSEM 430),and transmission electron microscopy(Tecnai G2 F20).The hardness was tested by Vickers hardness tester(HMV-2T),and the tensile property at room temperature was tested by Instron 5565 double-column electronic universal testing machine,and the tensile fracture was observed.The dry sliding wear tests were performed on friction and wear tester(UMT TriboLab).The wear morphology was observed and the wear rate was calculated. The results showed that the 316L alloy was mainly composed of the γ-Fe phase.In addition to the γ-Fe phase,the Cr3C2/316L alloy also contained Cr23C6 and Cr3C2 phases.The microstructures of both the 316L and the Cr3C2/316L alloys were composed of columnar grains and equiaxed grains.With the addition of Cr3C2 particles,the coarse columnar grains in the Cr3C2/316L alloy were reduced,the equiaxed grains were increased,and the microstructure of the Cr3C2/316L alloy was refined obviously.The addition of Cr3C2 particles increased the microhardness of the Cr3C2/316L alloy.The hardness of the Cr3C2/316L alloy was 327HV0.1,and that of the 316L alloy was 265HV0.1.The hardness of the Cr3C2/316L alloy was 23% higher than that of the 316L alloy.The yield strength and tensile strength of the Cr3C2/316L alloy were 687 MPa and 1 029 MPa,which are about 50% higher than those of the 316L alloy.The Cr3C2/316L alloy also improved wear resistance compared to the 316L alloy,with a 50% reduction in wear rate. The addition of Cr3C2 particles in the rapidly solidified SLM process leads to the non-spontaneous nucleation and the increase of overcooling degree which leads to the obvious refinement of the microstructure.The increase in hardness,strength and wear resistance of the Cr3C2/316L alloy is the result of the combined effect of fine grain strengthening,solid solution strengthening,and precipitation strengthening produced by the addition of Cr3C2 particles.