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Ti가 함유된 스테인리스강에서 Ti, Ti/Cr코팅표면과 플라즈마질화표면의 부식특성
최한철(H. C. Choe),이승훈(S. H. Lee),김관휴(K. H. Kim) 한국표면공학회 2002 한국표면공학회지 Vol.36 No.1
Corrosion characteristics of Ti, Ti/Cr coated and plasma-nitrided surface for stainless steel containing Ti have been studied. Stainless steels containing 0.09-0.92wt% Ti were fabricated by using vacuum furnace and solutionized for 1hr at 1050℃. Ti and Cr coatings were done on solutionized stainless steel surface by EBPVD. The Ti coated specimen were coated by Cr and were nitrided by plasma at 450℃ for 5hr. Microstructure and phase analysis were performed using SEM, OM and EDX. Corrosion behavior of the coated specimen was investigated by electrochemical test. The coated surface was of fine columnar structure. The Ti/Cr coated surface was denser than the Ti coated and the Ti coated-nitrided surfaces. The corrosion and pitting potential increased in proportion to the Ti content, coating temperature, coating thickness and formation of stable oxide film. The current density in active and passive region decreased in the case of Ti/Cr coated sample and Ti coated-nitrided samples. Especially the plasma nitrided specimen after Ti coating have a good corrosion resistance compared with the Ti coated specimen. The number and size of pits decreased as Ti content of matrix increased.
Ti-30Ta-(3~15)Nb 합금에 HA/Ti 복합 코팅한 표면의 교류임피던스 특성
정용훈(Y. H. Jeong),이호종(H. J. Lee),문영필(Y. P. Moon),박근형(G. H. Park),장승현(S. H. Jang),손미경(M. K. Son),최한철(H. C. Choe) 한국표면공학회 2008 한국표면공학회지 Vol.41 No.5
A.C. impedance properties of HA/Ti compound layer coated Ti-30Ta-(3~15)Nb alloys have been studied by electrochemical method. Ti-30Ta binary alloys contained 3, 7, 10 and 15 wt% Nb were manufactured by the vacuum furnace system. And then specimen was homogenized at 1000℃ for 24 hrs. The sample was cut and polished for corrosion test and coating. It was coated with HA/Ti compound layer by magnetron sputter. The non-coated and coated morphology of Ti alloy were analyzed by X-ray diffractometer (XRD), energy X-ray dispersive spectroscopy (EDX) and filed emission scanning electron microscope (FE-SEM). The corrosion behaviors were investigated using A.C. impedance test (PARSTAT 2273, USA) in 0.9% NaCl solution at 36.5±1℃. Ti-30Ta-(3~15 wt%)Nb alloys showed the α+β phase, and β phase peak was predominantly appeared in the case of increasingly Nb contents. The microstructures of Ti alloy were transformed from needle-like structure to equiaxed structure as Nb content increased. From the analysis of coating surface, HA/Ti composite surface uniformed coating layer with 750 ㎚ thickness. The growth directions of film were (211), (112), (300) and (202) for HA/Ti composite coating on the surface after heat treatment at 550oC, whereas, the growth direction of film was (110) for Ti coating. The polarization resistance (Rp) of HA/Ti composite coated Ti-alloys were higher than those of the Ti and HA coated samples in 0.9% NaCl solution at 36.5±1℃. Especially, corrosion resistance of Ti-Ta-Nb system increased as Nb content increased.
전자빔 진공증착기를 이용한 muffler재료의 표면코팅과 내식특성
최한철(H. C. Choe) 한국표면공학회 2001 한국표면공학회지 Vol.34 No.1
Fe-Cr-Al alloy has been studied for application in automobile muffler materials due to good corrosion and oxidation resistance. In order to develop the automobile muffler materials, corrosion behaviors of electron beam physical vapor deposition (EB-PVD) coated surface of muffler matericls of muffler materials were investigated using potentiostat. For 0.1M NaCl solution, corrosion potential and pitting potential of Fe-20Cr-10Al was higher than that of Fe-5Cr-10Al samples. Especially, in the case of Ti and Nb coated samples, pitting potential increased remarkably compared with non-coated samples. For 0.1M CaCl₂, solution, Ti-coated Fe-20Cr-10Al showed remarkably improved pitting corrosion resistance in comparison with non-coated Fe-20Cr-10Al and Fe-5Cr-10Al. The number and size of pits were decreased in the case of Ti coated samples in the 0.1M NaCl and 0.1M CaCl₂, solution.