选区激光熔化成形24CrNiMo合金钢的组织结构与力学性能

Microstructure and Mechanical Properties of 24CrNiMo Alloy Steel Formed by Selective Laser Melting

采用选区激光熔化(SLM)技术制备了24CrNiMo合金钢件,研究了SLM工艺参数对成形合金钢件显微组织、致密度、硬度及拉伸性能的影响。结果表明:成形合金钢的显微组织由回火马氏体和少量残余奥氏体组成;随着激光功率增大和扫描速度降低,熔池体积增大,冷却速度降低,回火马氏体板条粗化,热影响区变宽,合金钢的硬度降低;同时,成形合金钢内未熔合孔洞减少,致密度增加;当激光功率为320 W、扫描速度为750 mm/s时,合金钢的致密度最高,为99.93%;当激光功率为320 W、扫描速度为950 mm/s时,成形合金钢的拉伸性能最佳,其抗拉强度和屈服强度分别为1362 MPa和1252 MPa,延伸率为16.2%。在合适的激光成形参数下,SLM成形24CrNiMo合金钢的综合力学性能明显优于铸态合金钢。

The selective laser melting(SLM)technology is used to obtain the 24CrNiMo alloy steel for studying the influence of the laser scanning process parameters on its microstructure,relative density,hardness,and tensile properties.The results demonstrate that the microstructure of the SLM-formed alloy steel comprises tempered martensite and a small amount of retained austenite.The molten pool volume increases,whereas the cooling rate decreases with increasing laser power and decreasing laser scanning speed,resulting in the coarsening of the tempered martensite lath and the widening of the heat affected zone;further,the microhardness of the steel is observed to decrease.Meanwhile,the pores induced by the non-melted particle decrease,improving the relative density.The highest relative density of 99.93%can be obtained when the laser power and scanning speed are 320W and 750mm/s,respectively.When the laser power is 320 W and scanning speed is 950 mm/s,the SLM-formed alloy steel exhibits optimal tensile properties,its tensile strength and yield strength are 1362 MPa and 1252 MPa,respectively,and its elongation is 16.2%.Under reasonable SLM parameters,the comprehensive mechanical properties of the 24CrNiMo alloy steel formed via SLM are significantly better than those of the as-cast steel.