不锈钢激光熔敷Ni-Cr-B-Si合金涂层的组织及腐蚀行为

Microstructure and corrosion behavior of Ni-Cr-B-Si alloy coating on stainless steel by laser cladding

采用激光熔敷技术在316L不锈钢表面制备成形良好、无宏观裂纹、组织致密的Ni-Cr-B-Si合金涂层。利用扫描电子显微镜、X射线衍射仪分析涂层的显微组织和物相组成,通过动电位极化曲线和电化学阻抗谱测试研究涂层和基材在3.5%Na Cl溶液中的腐蚀行为。结果表明:涂层从底部到顶部,组织形态变化依次为平面晶、胞状晶、柱状树枝晶和等轴树枝晶,涂层主要由γ-(Ni,Fe)固溶体、Fe Ni3、M23C6(M=Fe,Ni,Cr)以及Cr0.19Fe0.7Ni0.11相组成;在3.5%Na Cl溶液环境中,涂层的自腐蚀电位比基材正移了0.14 V,腐蚀电流密度较基材减小71.84%,腐蚀阻抗值也显著高于基材,耐腐蚀性能优于基材,这是由于涂层表面形成钝化膜的致密度和稳定性更高。

The Ni-Cr-B-Si alloy coating with good formation,no macro-cracks and dense microstructure was prepared on 316 L stainless steel surface by laser cladding technology. The microstructure and phase composition of the coating were analyzed by scanning electron microscopy and X-ray diffractometer. The corrosion behavior of the coating and substrate in 3.5% Na Cl solution was investigated by means of potentiodynamic polarization curve and electrochemical impedance spectroscopy.The results show that the microstructure changes are planar crystal,cellular crystal,columnar dendrites and equiaxed dendrites from the bottom to the top of the coating. The coatings are mainly composed of γ-（Ni,Fe）solid solution,Fe Ni3,M23 C6（M=Fe,Ni,Cr）and Cr0.19 Fe0.7 Ni0.11 phases. In the 3.5% Na Cl solution environment,the corrosion potential of the coating moves positively 0.14 V and the corrosion current density reduces by 71.84% compared to the substrate. The corrosion impedance modulus of the coating is also significantly higher than that of the substrate,the corrosion resistance of the coating is better than that of the substrate,which is due to the higher density and stability of the passivation film formed on the surface of the coating.