利用激光选区熔化(SLM)工艺成形TiB₂/S136复合材料,研究了激光体能量密度η对SLM成形试样致密度、微观组织及力学性能的影响。采用X射线衍射仪、场发射扫描电镜、透射电镜等研究成形试样物相成分、表面形貌及微观组织。结果表明:当η过低时,粉末熔化不完全,形成大量残余孔隙;而当η过高时,受热应力影响,成形试样存在微裂纹。当η=66.7 J/mm ³时,成形试样表面缺陷少,致密度高达97.3%,存在细化的、分布均匀的等轴晶,其平均显微硬度高达742.4 HV0.1,平均摩擦系数和磨损率分别为0.5593和0.272×10 ^-4 mm ³·N ^-1·m ^-1,耐磨性能优异,抗拉强度达到1051.3 MPa,延伸率为5.84%,塑性较好。因此,SLM成形TiB₂/S136复合材料的最佳η为66.7 J/mm ³,η过高或过低,均会严重影响TiB₂/S136复合材料的致密度及力学性能,该研究为SLM成形高性能模具钢材料提供了有益的理论和工艺借鉴。

The selective laser melting (SLM) technology is used to process the TiB2/S136 composites and the effect of laser energy density η on the densities, microstructures and mechanical properties of SLM-processed specimens is investigated. X-ray diffraction instrument, field emission scanning electron microscopy and transmission electron microscopy are used to study the phase compositions, surface morphologies and microstructures of specimens. The results show that, when η is low, the powders are not fully molten and thus a large amount of residual pores are formed. However, when η is too high, the micro-cracks are formed in the specimens because of thermal stress. When η is 66.7 J/mm 3, the specimens have less surface defects, their densities are up to 97.3%, and there exist fine and uniformly-distributed equiaxed grains. As for these specimens, the average micro-hardness is up to 742.4 HV0.1, and the average friction coefficient and wear rate are 0.5593 and 0.272×10 -4 mm 3·N -1·m -1, respectively, indicating an excellent abrasion resistance performance. The tensile strength is 1051.3 MPa and the elongation is 5.84%, indicating a relatively good plasticity. Above all, the optimal η for the SLM-processed TiB2/S136 composites is 66.7 J/mm 3, and if η is too high or too low, the densities and mechanical properties of TiB2/S136 composites would be seriously affected. This study provides a useful theoretical basis and a process guidance for SLM-processed high-performance die steels.