激光快速熔疑40Cr钢表面硬度与残余应力研究

研究40Cr在激光单道熔凝和叠道熔凝下材料表面显微组织分布特征,表面硬度分布规律和残余应力状态,结果显示单道激光熔凝的强化层组织由表层熔化区、亚表层相变硬化区及与基体相连的高温回火区组成,最大残余应力为拉应力,出现在熔凝带中心,在熔化带边缘为压应力,在热影响区为拉应力:叠道激光熔凝试件表面显微组织和硬度分布的差异在回火软化区和二次淬硬区。。叠道扫描的残余应力要比单道激光熔凝的小,新的熔凝带对前道熔凝带施加了应力并产生了韧化作用。

Study on Surface Hardness and Residual Stress of 40Cr Steel Modified by Laser Rapid Solidification

The microstructure distribution, surface hardness and residual stress of the 40Cr, which is modified by single-line solidification and folded-line solidification, are studied in this article. It is indicated that the surface microstructure of the material treated by single-line laser solidification, is comprised of surface melting zone, sub - surface phase hardened zone and high temperature annealed zone connected with substrate. The difference betwenn the folded -line laser solidification and the single - line solidification are the surface hardness and microstructure of the annealing region and secondary - hardened region. And the test of residual stress indicates that : in single-line laser rapid solidification, the maximal residual stress, which is pulling stress, emerges on the central line of the solidification zone, On the margin of melting zone, there exists compressive stress and in the heat affected zone there is pulling stress again. The residual stress of the folded - line solidification has new characteristics, that is the range values are smaller than those of single - line solidification, and the later solidification zones bring stress on the former solidification zones and furthermore tempered the former ones.