激光熔覆制备316L涂层组织及腐蚀行为研究

Microstructure and Corrosion Behaviors of 316L Coating Fabricated by Laser Cladding

为提升金属零件表面耐蚀性,采取激光熔覆技术在45#钢基体表面制备316L涂层。采用光学显微镜、能谱仪、扫描电镜、显微硬度仪等设备对涂层硬度、组织形貌、晶体类型等进行表征。结果显示,在一定加工参数下,涂层与基体呈良好的冶金结合,晶体类型主要为奥氏体组织,在晶间处存在少量的Cr23C6。316L涂层晶体尺寸随着能量密度的增加而增加,硬度则随之降低。当能量密度小于等于19J·mm^-2时,涂层易出现球化与毛化现象,当能量密度过高时,表面则出现涂层过烧,导致部分元素被烧损。通过分析腐蚀形貌可知:316L涂层的腐蚀失效形式主要为晶间腐蚀,同时表面存在少量的腐蚀坑;随着晶间腐蚀的加剧,45#钢基体开始出现腐蚀,表面形成大量的氧化层。

In the present study,a 316L coating is deposited on the surface of 45#steel substrate using laser cladding technology to improve the corrosion resistance of the metal parts.The hardness,microstructure,and crystal morphology of the coating are characterized by optical microscope,energy dispersive spectroscopy,scanning electron microscopy,microhardness tester,and other equipment.The results show that the coating exhibits good metallurgical bonding with the substrate under certain processing parameters,and that the main crystal type is austenite with the existence of a small amount of Cr23C6 in the intergranular region.The crystal dimensions of the 316L coating increase with increase in the energy density,while the hardness of the surface subsequently decreases.When the energy density is less than or equal to 19J·mm^-2,the coating is prone to spheroidization and roughening.However,when the energy density is too high,the surface of the coating will overheat,resulting in the burning of some elements.Thus,some of the elements are lost owing to the degradation in performance.Moreover,according to the analysis of corrosion morphology,the main type of corrosion failure of the 316L coating is intergranular corrosion,and a small number of corrosion pits occur in the coating as well.With increase in intergranular corrosion,the 45#steel substrate begins to corrode,leading to the formation of an oxide film.