采用选区激光熔化(SLM)技术制备4Cr5MoSiV1模具钢试样, 研究激光线能量密度η对显微组织、碳元素损耗及显微硬度的影响。研究表明：SLM成型4Cr5MoSiV1模具钢试样的显微组织主要为马氏体和少量残余奥氏体。脱碳反应、飞溅行为和元素烧蚀共同造成碳元素的损耗, 当η=950 J·m-1时, 碳元素损耗率高达17.7%。随着η的增加, 试样的晶粒尺寸增大、碳元素损耗率升高、马氏体含量降低; 在同一η下, 试样过渡区的晶粒尺寸最小、碳元素损耗率最低, 而热影响区的晶粒尺寸最大、碳元素损耗率最高。随着η的减小, 孔隙缺陷增多; 当η过大时, 试样将出现冷裂纹缺陷。当η=905 J·m-1时, 试样显微组织均匀, 致密度高, 具有较高的显微硬度(熔池中心区域为710.3 HV, 过渡区为732.4 HV)。

The 4Cr5MoSiV1 die steel samples are fabricated by the selective laser melting (SLM) technique. The influence of laser linear energy density η on microstructures, carbon loss and micro-hardness of samples is investigated. The results show that the microstructures of SLM-formed 4Cr5MoSiV1 die steel samples are mainly martensite and a little amount of residual austenite. The decarburization reaction, splashing behavior and elemental ablation together cause carbon loss, and the carbon loss rate is as high as 17.7% at η=950 J·m-1. With the increase of η, the grain sizes of samples increase, the carbon loss rate increases and the martensite content decreases. Under the same η, the grain size and the carbon loss rate in the transition zones of samples are the smallest, while those in the heat affected zones are the highest. With the decrease of η, the pore defects become more. When η is too large, the cold cracks appear. When η is 905 J·m-1, the samples possess uniform microstructures, high densities, and relatively high micro-hardness (that in central zone of molten pool is 710.3 HV and that in transition zone is 732.4 HV).