용융 아연과 WC-Co 코팅층 내 코발트의 반응거동에 미치는 아연욕 중의 Al 첨가 영향

• Published in: Biuletyn Uniejowski Vol. 40; no. 1; pp. 23 - 31
• Main Authors: 성병근(Byeong-Geun Seong), 김규영(Kyoo-Young Kim), 권성희(Sung-Hee Kwon), 이기안(Kee-Ahn Lee)
• Format: Journal Article
• Language: Korean
• Published: 한국표면공학회 2007
• Subjects: 기계공학; Co-binder; Al added molten Zinc; Diffusion process of Al atom; Parabolic rate law; CoAl particle; Boundary layer
• ISSN: 1225-8024; 2299-8403; 2288-8403

The objective of this study is to investigate the effect of Al addition on the reaction behavior of cobalt with molten zinc. Pure cobalt specimen was immersion tested in the three kinds of molten zinc (pure, 0.12%Al added and 0.24%Al added) baths at $460^{\circ}C,\;490^{\circ}C\;and\;520^{\circ}C$. For the understanding of degradation processes, specimens were analyzed with scanning electron microscope (SEM) and energy dispersive spectrum (EDS), and electrochemical stripping method. When 0.12% and 0.24% Al was added in molten zinc baths, three intermetallic compounds layers of ${\gamma},\;{\gamma}_1,\;and\;{\gamma}_2$ were formed on the Co matrix and ${\beta}_1$ layer was not formed between the Co matrix and the ${\gamma}$ layer. Particles of CoAl intermetallic compound were formed at the interface between the ${\gamma}_2$ layer and zinc melt and they did not adhere to the Co-Zn intermetallic layer. Weight loss of the Co specimen increased as Al content in the molten zinc increased and the relationship of weight loss vs. immersion time followed parabolic rate law. Rate controlling process for the reaction rate of Co with Al added molten zinc was analyzed as the diffusion process of Al atom through a boundary layer between the ${\gamma}_2$ layer and the Al added zinc melt.