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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.
李昊宗,潘奉贊 순천대학교 공업기술연구소 1990 工業技術硏究所論文集 Vol.4 No.-
The process of graphite formation in solid state was observed after the graphitization heat treatment of the white cast irons artificially made to contain pores or CaO inclusion by means of the additions of Se, gas bubble formation agents or CaO, a compound of oxygen in the hypoeutectic cast iron melts. The process of graphite formation in liquid state was examined after the additions of MmH_2 or Kl in the hypereutectic cast iron melts and cooling either slowly or rapidly. The influences of the amount of MmH_2 addition, different holding times after the additions and different S amount in the melts were also investigated. According to the results obtained, the mechanism of spheroidal graphite formation was studied in the view of the gas bubble theory. The results obtained in this work were as follows: 1. in the case of the graphitization heat treatment of the white cast irons under Se, CaCO_3 additions, temper carbon was preferentially precipitated on the remaining gas pores, but with only CaO addition, little graphite was formed on the CaO inclusion in the samples. From the results the behavior of graphite in solid state was preferred at the defects such as the remained pores in cast iron. 2. In the case of the addition of 0.5wt% MmH_2, a gas bubble formation agent, to the hypereutectic melts with 0.015 and 0.030wt% S, there appeared an increase in the count of spheroidal graphite, the rate of graphite formation and the time for spheroidal graphite to remain in the melts with 0.015wt% S rather than 0.030wt% S. 3. In Kl addition to the hypereutectic melts with 0.030wt% S spheroidal graphite was made when cooling the sample rapidly, but flake graphite was made when cooling slowly. These results were in accordance with the view of the gas bubble theory.