大气等离子喷涂Fe基涂层及其氩弧重熔层的组织与力学性能

Microstructure and Mechanical Properties of Atmospheric-plasma-sprayed and TIG-remelted Fe-based Coating

采用氩弧重熔技术对大气等离子喷涂Fe基涂层进行了重熔处理,分析了重熔前后涂层的显微组织和力学性能。结果表明,重熔后Fe基喷涂层的层状结构以及气孔、未熔颗粒、夹杂物基本被消除,孔隙率由4%降低到0. 4%,重熔层组织致密。喷涂层主要由微晶区、纳米晶区和过渡区组成,结晶度较差,原子排列较混乱,而重熔层由单晶区和(Fe,Cr)23C6相构成,析出相与基体界面处无显微裂纹,结晶度较好,原子排列较规则;喷涂层与基体结合处有明显缝隙,结合方式为机械结合,而重熔层与基体界面产生"白亮带",结合方式为冶金结合;相对于喷涂层,重熔层的平均显微硬度和弹性模量分别提高了33. 4%和53. 2%,表面粗糙度降低了43. 2%。氩弧重熔处理显著地改善了Fe基涂层的显微组织及力学性能。

In the present work,we applied tungsten inert gas arc (TIG) process to remelt a Fe-based coating which had been deposited by atmospheric plasma spraying technique,and characterized and determined the remelted coating’s microstructure and mechanical properties.The results showed that after TIG remelting,the lamellar structure,pores,unmelted particles and inclusions of the as-sprayed coating are eliminated,the porosity significantly decreases from 4% to 0.4% and the microstructure becomes quite compact.The as-sprayed coating consists mainly of microcrystalline region,nanocrystalline region and transition region,and has a low crystallinity and disordered atomic arrangement.The remelted coa-ting,on the contrary,contains single crystal region and (Fe,Cr) 23 C 6 phase,displays no microcrack at the pricipitates/matrix interfaces,and has better crystallization and atomic arrangement.A clear gap could be observed between the as-sprayed coating and the substrate,thus,the bon-ding formed between the as-sprayed coating and substrate is ascribed to mechanical bonding.However,the “white light belt” emerged at the interface between the remelted coating and substrate,the remelted coating was bonded with the substrate metallurgically.Compared with the as-sprayed coating,the average microhardness and elastic modulus of the remelted coating increased by 33.4% and 53.2% respectively,and the surface roughness of the remelted coating decreased by 43.2%.Therefore,TIG remelting process has considerable effect for improving the microstructure and mechanical properties of Fe-based coating.