球墨铸铁表面等离子束熔凝硬化区组织和性能分析

Analysis on Microstructure and Performance of Plasma Beam Remelt-solidified Layer on Nodular Cast Iron Surface

研究了球墨铸铁表面等离子束熔凝硬化区的组织和性能。结果表明:工作电流达50 A时可实现球墨铸铁表面的微熔硬化处理;工作电流增大,熔凝层和硬化层的深度、宽度增加,硬度值降低;熔凝硬化后,熔凝区石墨相消失,组织为细小的变态莱氏体+残余奥氏体,相变硬化区的组织为隐针马氏体+残余奥氏体+球状石墨+铁素体;过渡区出现包围石墨球的双壳组织,对提高耐磨性有利;沿硬化层深度方向显微硬度先降后升,达到最高值后又缓慢下降。

The microstructure and performance of plasma beam remelt-solidified layer on nodular cast iron surface were analyzed.The results show that the micromelted-solidified hardening of nodular cast iron surface can be realized when working current is 50 A.With the working current increasing,the width and depth of remelt-solidified layer and hardened layer increase,hardness goes down.The graphite phase in remelt-solidified region vanishes after remelt-solidified hardening.The microstructure of remelt-solidified is tiny ledeburite and remaining austenite;and the microstructure in transformation hardening region is acicular martensite,remaining austenite,spheroid graphite and ferrite.The microstructure of double shell around the graphite nodular is advantageous to enhance wear resistance.From the surface to inner,the microhardness shows a tendency of firstly goes down and then goes up,after achieving the top,the value slowly drops.