激光熔覆Co-Cr-Ni-Mo涂层的粘塑性摩擦及组织演变行为

摘要

The viscoplastic friction and nanostructure formation mechanism of laser-clad Co-based coating were studied by rotary friction between laser-clad Co-Cr-Ni-Mo coating and WC-Co rod.The friction coefficient,friction interface temperature and axial displacement-time curves during rotary friction process were measured.The results showed that all the curves firstly experienced rising stage and then steady stage.The rising stage corresponded to sliding friction while the steady stage corresponded to viscoplastic friction.After viscoplastic friction processing,three typical zones of viscoplastic deformation zone,thermo-mechanically affected zone,and original laser-clad zone can be observed successively from the friction surface to the interior.The viscoplastic deformation significantly crushed the network M23C7 phase in original laser-clad zone and made it dispersively distributed with equiaxial shape and in nano-scale.The viscoplastic zone,in width of 37-131 μm,is mainly characterized by refined M23C7 and α-Co phase with grain size bellow 50 nm,and even a small quantity of amorphous.Thus,the hardness of viscoplastic zone about HV997 was improved compared with the hardness of original laser-clad zone about HV600.%通过激光熔覆Co-Cr-Ni-Mo合金与WC-Co硬质合金之间的旋转摩擦变形实验,研究钴基合金的粘塑性摩擦及纳米组织形成机制.考察粘塑性摩擦过程的摩擦系数、界面温度及轴向缩短量随时间的变化关系.结果表明以上物理量首先进入快速上升阶段,然后进入稳态阶段,其中第一个阶段属于滑动摩擦,第二阶段属于粘塑性摩擦.粘塑性摩擦后,激光熔覆涂层从表面至内部可分为粘塑性变形区、热力影响区、激光原始组织3个典型区域.粘塑性变形可将原始组织中的网状M23C7相破碎为弥散分布的等轴形状纳米晶粒.粘塑性区的宽度为37～131 μm,其典型组织特征为晶粒尺度小于50 nm的M23C7相及α-Co相,甚至含有少量接近非晶态结构.因而,粘塑性摩擦将激光熔覆合金的硬度由HV600提高至HV997.