Preparation of ultra-fine grain Ni-Al-WC coating with interlocking bonding on austenitic stainless steel by laser clad and friction stir processing

激光熔覆结合搅拌摩擦加工在奥氏体不锈钢表面制备超细晶互锁结构Ni-Al-WC涂层（英文）

The ultra-fine structured Ni?Al?WC layer with interlocking bonding was fabricated on austenitic stainless steel by combination of laser clad and friction stir processing (FSP). Laser was initially applied to Ni?Al elemental powder preplaced on the austenitic stainless steel substrate to produce a coating for further processing. The as-received coating was subjected to FSP treatment, processed by a rotary tool rod made of WC?Co alloy, to obtain sample for inspection. Microstructure, phase constitutions, hardness and wear property were investigated by methods of scanning electronic microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) microanalysis, and X-ray diffraction (XRD), hardness test alongside with dry sliding wear test. The results show that the severe deformation effect exerted on the specimen resulted in an ultra-fine grain layer of about 100μmin thickness and grain size of 1?2μm. Synergy between introduction of WC particles to the deformation layer and deformation strengthening contributes greatly to the increase in hardness and friction resistance. An interlocking bonding between the coating and matrix which significantly improves bonding strength was formed due to the severe deformation effect.

在奥氏体钢表面制备具有超细晶结构且能与基体互锁的Ni-Al-WC涂层。首先采用激光在奥氏体钢表面熔覆Ni-Al涂层,然后采用搅拌摩擦加工(FSP)方法,以WC-Co合金为搅拌头,对激光涂层进行大变形改性,形成Ni-Al-WC超细晶复合涂层。采用扫描电子显微镜、X光能量散射谱仪、X射线多晶衍射、硬度仪及摩擦磨损试验机对样品的显微组织、相组成、硬度及摩擦磨损性能进行表征。结果表明,FSP的大变形效应可形成晶粒尺寸为1~2μm、厚度为100μm的超细晶层。同时,FSP过程还可往变形层中引入WC颗粒,因此变形以及WC颗粒双重强化极大地提高了硬度和耐磨性。另外,FSP大变形使涂层和基体之间形成互锁结构,有利于二者的结合。