ZG45钢表面镍钴基熔覆层的显微组织与耐腐蚀性能

Microstructure and Corrosion Resistance of Ni-Co Based Cladding Layers on Surface of ZG45 Steel

采用真空熔覆技术在ZG45钢基体表面制备了不同镍钴配比,以及分别添加不同质量分数WC,石墨(G)+WC的镍钴基熔覆层,研究了熔覆层的显微组织、物相组成,以及在NaCl溶液中的耐腐蚀性能。结果表明:熔覆层的组织致密,与基体实现了冶金结合,G+WC/镍钴合金熔覆层中主要组成相有Cr_7C_3、Cr_(23)C_6、Ni_3Si、CrB、FeC_3W、WC、C和γ-Ni-Co固溶体,镍钴合金熔覆层的耐腐蚀性能比基体的好,且随钴含量增加而提高;随着WC或G含量的增加,WC/镍钴合金熔覆层和G+WC/镍钴合金熔覆层的自腐蚀电流密度均先减小后增大;G+WC/镍钴合金熔覆层表面主要发生局部腐蚀,局部腐蚀坑主要出现在WC与G颗粒集中分布的区域。

The Ni-Co based cladding layers with different proportions of Ni and Co and those with different mass fractions of WC, graphite （G）＋WC were fabricated on the surface of ZG45 steel substrate by vacuum cladding technique. The microstructures, phase composition and corrosion resistance in NaCI solution of the cladding layers were studied. The results show that all the cladding layers had dense microstructures and were metallurgically bonded to the substrate. The main phases of the G＋WC/Ni Co alloy cladding layer were Cr7C3, Cr23C6, Ni3Si, CrB, FeW3C, WC, C and 7-Ni-C solid solution. The corrosion resistance of Ni Co alloy cladding layers was better than that of substrate and increased with the Co content increasing. The free corrosion current density of both WC/ Ni-Co alloy cladding layer and G＋WC/Ni-Co alloy cladding layer decreased and then increased with the increase of WC or G content. I.ocalized corrosion mainly occurred on the surface of G＋WC/Ni-Co alloy cladding layer, and the localized corrosion pits appeared in the WC and G particle concentrated area.