扫描速度对40Cr表面等离子束硬化层组织和性能的影响

Influence of Scanning Speed on Microstructure and Property of Plasma Beam Hardening Layer on 40Cr Surface

采用等离子束热源对40Cr表面进行硬化处理。利用扫描电镜和金相显微镜分析了硬化层的显微组织结构,并对硬化层进行显微硬度和耐磨性测试。结果表明:硬化区整体形貌呈月牙形,熔凝区组织形态为隐针马氏体+网状索氏体+残余奥氏体,相变淬火区组织为隐针马氏体+网状屈氏体+残余奥氏体+铁素体;其他工艺参数不变,随扫描速度的增大,硬化层深度和宽度减小,而最高硬度增加;沿硬化层层深的硬度分布规律是,从硬化层由表及里显微硬度先升高后降低,最高硬度在次表层;沿硬化层层宽的硬度分布规律是,硬化层中心部位硬度略有降低,向两侧硬度先升高后降低,直至40Cr基体硬度。硬化处理后试样耐磨性显著提高。

The 40Cr surface was hardened by plasma-beam.The microstructure of the hardened layer was analyzed by SEM and OM.The hardness and wear resistance of hardened layer were tested.The results show that the overall morphology of hardened zone shows a crescent-shaped.In remelt-solidified region,the microstructure is martensite,sorbite and austenite.In the transformation hardening region,the microstructure is martensite,troostite,austenite and ferrite.With the scanning speed increasing,the width and depth of the hardened layer diminishes,and maximum hardness increases.From the surface to inner,the microhardness firstly goes up then goes down and the highest hardness point is in second-surface layer.With the hardening layer upon layer width,the hardness of the hardened layer center decreases slightly,the hardness firstly goes up then goes down to two sides,until the 40Cr substrate achieves the minimum value.The wear resistance of the hardened layer significantly improves.