304不锈钢局部干法水下激光填丝熔覆层微观组织及性能

采用自行研发的水下激光填丝熔覆装备，在304奥氏体不锈钢板材表面进行激光填丝熔覆试验，并对空气环境和水下环境的熔覆结果进行对比分析，以探索在水下环境进行304不锈钢的缺陷修复. 通过XRD，EDS，光学显微镜分析了熔覆层的显微组织、化学成分和物相组成，采用显微硬度仪进行了硬度测试，利用动电位极化与交流阻抗谱技术研究熔覆层电化学腐蚀行为. 结果表明，在两种环境下均制备了单层多道熔覆层，且无明显气孔、裂纹等缺陷；熔覆层包括熔覆区、搭接区、相变影响区、熔合区、热影响区，显微组织主要由奥氏体、铁素体、马氏体组成；由于各区域内微观组织及晶粒的大小不同，使得熔覆层硬度呈阶梯分布；在3.5%NaCl溶液中，两种环境熔覆层均呈现出明显的钝化行为，且两种熔覆层耐腐蚀性能相近；所研制的水下激光填丝熔覆装备及工艺，可以满足实际工程对于熔覆层高效制备、成形质量控制及耐蚀性能的要求，可用于水下环境304不锈钢表面的防护与修复.

Microstructure and properties of 304 stainless steel coating by local dry underwater laser cladding with filler wire

In the air and underwater environment, 308L stainless steel was clad on the surface of Austenitic 304 stainless steel with self-developed underwater laser cladding equipment to explore the repair of 304 stainless steel with defects in underwater environment. The microstructure, chemical composition and phase composition of the coating were analyzed by XRD, EDS and optical microscope. The hardness of the coating was tested by microhardness tester. The electrochemical corrosion behavior of the coating was studied by potentiodynamic polarization and AC impedance spectroscopy. The results show that single layer and multi-channel cladding layers were prepared in two environments, and there were no obvious pores, cracks and other defects. The microstructure of the cladding layer is mainly composed of austenite, ferrite and martensite. Because of the different microstructure and grain size in each region, the hardness of the cladding layer presents a stepped distribution. The coatings in both environments show obvious passivation behavior in 3.5% NaCl solution, and the corrosion resistance of the coatings in both environments is similar. The designed underwater laser cladding with filler wire process meets the requirements of practical engineering for efficient preparation, forming quality and corrosion resistance of cladding layer, and can be used for surface protection and repair of 304 stainless steel in underwater environment.