双相不锈钢表面激光熔覆钴基合金组织和性能研究

Microstructure and Properties of Laser Cladding Co-based Alloys on Duplex Stainless Steel

目的提高2205双相不锈钢的耐磨性和耐腐蚀性能。方法采用激光熔覆技术,在2205双相不锈钢基体表面制备钴基合金熔覆层。用X射线衍射仪、光学显微镜检测钴基合金熔覆层的相组成和显微组织,用能谱仪测定熔覆层和基体界面区域的Fe和Cr元素分布,确定熔覆层界面过渡区域的宽度。用显微硬度计和湿砂磨粒磨损试验机,测试熔覆层硬度和耐磨性能。采用扫描电镜观察摩擦表面的磨损特性,分析钴基合金熔覆层的磨损机理。用电化学工作站测试熔覆层的电化学腐蚀特性,并用2205双相不锈钢作为对比试样做相应的性能试验。结果熔覆层由γ-Co固溶体和少量的Cr7C3、Cr2Ni3化合物相组成,界面处的熔覆层相组织是少量的平面晶和胞状晶,其他区域是发达的树枝晶。由于熔覆层由多道搭接和多层熔覆形成,树枝晶生长有方向性,但不是成固定的方向,并出现明显的分层现象。熔覆层过渡区范围为50μm左右,熔覆层平均显微硬度达477HV(0.1),远高于2205双相不锈钢基体(265HV(0.1))。当磨程达到3354m时,熔覆层的质量损失仅为10.3 mg,约为基体质量损失的1/3。在3.5%NaCl溶液中,熔覆层具有较高的极化电阻与电荷转移电阻和较小的自腐蚀电流。结论熔覆层组织致密,无气孔、裂纹等缺陷,与基体呈良好的冶金结合,钴基合金熔覆层具有良好的耐磨粒磨损性能和耐腐蚀性能。

The paper aims to improve the wear resistance and corrosion resistance of 2205 duplex stainless steel.A cobalt-based alloy coating was prepared on 2205 duplex stainless-steel substrate by laser cladding technology.The phase composition and microstructure of the cobalt-based alloy coating were analyzed with X-ray diffractometer and opticalmicroscope. The element distribution of Fe and Cr in the coating and substrate interface was detected with energy spectrometer,and the width of the transition region was determined. The hardness and abrasive resistance of the coating were tested withmicrohardness tester and wet sand abrasive wear tester. The wear characteristics of the friction surface were observed underscanning electron microscopy. The wear mechanism of the cobalt-based alloy coating was analyzed. The electrochemicalcorrosion characteristics of the coating were tested with electrochemical workstation. The comparing tests were conducted to2205 duplex stainless steel. The coating consisted of γ-Co solid solution and a small amount of Cr7C3, Cr2Ni3 phases. Themicrostructure of the coating at the interface was composed of cell crystals and a small amount of planar crystals and otherregions were of dendrites. Since the coating was formed by multiple layers of cladding, the dendrites of the coating grew indifferent directions. The transition zone of the coating was very narrow, which was about 50 μm, and the average microhardnessof the coating was 477HV0.1, which was far higher than that of 2205 duplex stainless steel matrix. When the wear distancereached 3354 m, the mass loss of the coating was only 10.3 mg, about one third of the mass loss of 2205 duplex stainless steel.In a 3.5% NaCl solution, the coating had a higher polarization resistance and charge transfer resistance and a lowerself-corrosion current. The coating is dense, free from pore, crack and other defects, and bonded with the substrate properly. Thecobalt-based alloy coating has a much better wear resistance and corrosion resistance.