氮氩流量比对MZ刀具激光渗氮层组织演变的影响  

Effect of Nitrogen/argon Flow Ratio on Microstructure Evolution of Laser Nitriding Layer on MZ Tool

作　　者：雷瑛[1] 李达[2] 罗森怡 李刚 Lei Ying;Li Da;Luo Senyi;Li Gang(School of Mechanical Engineering,Xi'an Jiaotong Engineering University,Xi'an,Shaanxi 710300,China;School of Materials Science and Engineering,Southwest Jiaotong University,Chengdu,Sichuan 610031 China;Xi'an Stark Material Technology Co.,Ltd.,Xi'an,Shaanci 710300,China)

机构地区：[1]西安交通工程学院机械工程学院,陕西西安710300 [2]西南交通大学材料科学与工程学院,四川成都610031 [3]西安斯塔克材料科技有限公司,陕西西安710300

出　　处：《应用激光》2022年第12期83-88,共6页Applied Laser

基　　金：四川省国际交流合作项目(2019YFH0048)。

摘　　要：为了提高W6Mo5Cr4VZ(MZ)高速钢刀具表面的综合性能,通过高功率半导体激光对W6Mo5Cr4VZ高速钢实施表面渗氮,对比了纯氮气与氮氩混合气体引起半导体激光渗氮熔池与表面组织形态的差异性,分析不同渗氮工艺下渗氮层物相成分、组织形态与硬度变化。研究结果表明,提高氩气比例后,在渗氮层内形成了更少的AlN树枝晶,原先大尺寸枝晶逐渐转变成了更加短小的等轴晶结构。在150~300μm深度处形成了AlN与Al两种组织相,深度介于450~600μm范围内的组织相主要由Al构成。氮氩比介于3∶1~1∶3时,表层硬度达到900~1000 HV。提高氩气比例后,熔池内的氮含量减小,过冷度增大,形成了更长的一次与二次晶轴,枝晶端部曲率半径降低。该研究有助于改善MZ刀具激光渗氮层的组织结构,可以拓宽到其他对表面有高要求的材料上。To improve its comprehensive properties,the W6 Mo5 Cr4 VZ(MZ)high speed steel tool surface was nitrided by high power semiconductor laser.The differences of nitriding pool and surface microstructure undergone pure nitrogen and nitrogen-argon mixture gas were compared.The changes of the phase composition,microstructure and hardness of nitriding layer under different nitriding processes were analyzed.Results show that dendrites become fewer in the AlN nitride layer by increasing the ratio of argon,and the original large dendrites are gradually transformed into shorter equiaaxial crystal structures.AlN and Al are formed at the depth of 150~300μm,and Al is the main phase at the depth of 450~600μm.When the ratio of nitrogen and argon is between 3∶1 and 1∶3,the surface hardness reaches 900~1000 HV,and the hardness of nitriding layer decreases slowly.As the proportion of argon increases gradually,the proportion of nitrogen decreases and less AlN dendrites are formed.With the ratio of argon rising,the nitrogen content in the molten pool decreases and the degree of undercooling increases,which makes the primary and secondary crystal axes longer,and reduces the radius of curvature at the dendrite tip.This study is helpful to improve the microstructure of laser nitriding layer of MZ tool,which can be extended to other materials with high surface requirements.

关 键 词：激光渗氮 气体流量 裂纹 微观组织 

分 类 号：TG113[金属学及工艺—物理冶金]