Ti-Ta 합금의 표면특성에 미치는 Ta함량과 TiN 및 ZrN 코팅의 영향

Abstract

Electrochemical characteristics of Ti-Ta alloys coated with TiN and ZrN using RF-magnetron sputtering method were studied. The Ti containing Ta up to 40 wt% were melted by using a vacuum furnace. Ti-Ta alloys were homogenized for 6 hrs at 1000℃ and aged for 2 hrs at 400, 500 and 600℃. The samples were cut and polished for corrosion test and coating. The specimens were coated with TiN and ZrN, respectively, by RF-magnetron sputtering method. The microstructures were conducted by using optical microscope(OM), X-ray diffraction meter (XRD) and field emission scanning electron microscope (FE-SEM). The corrosion behaviors were investigated using potentiostat (EG&G Co, 263A. USA) and electrochemical impedance spectroscopy (10 mHz ～ 100 kHz) in 0.9% NaCl solution at 36.5 ± 1℃. The results were as follows: 1.From the microstructure analysis, homogenized Ti-Ta alloys showed the martensite structure of α + β phase. The micro structure was transformed from lamellar structure(Ti-10 wt% Ta) to needle-like structure(Ti-20 wt% Ta). Aged Ti-Ta alloys showed the needle-like structure and equiaxed structure. In case of aged Ti-40 wt% Ta alloy, β-phase peak was increased with increasing aging temperature. 2.From the corrosion test of Ti-Ta alloy, Corrosion resistance of Ti-Ta alloys increased with increasing Ta content for all sample. Corrosion resistance of aged Ti-Ta alloys decreased in the order of 400℃, 500℃ and 600℃ aging temperature. 3.From the analysis of TiN and ZrN coated layer analysis, TIN and ZrN coated surface showed columlar structure with 600 nm and 640 nm thickness, respectively. 4.The corrosion resistance of TiN and ZrN coated Ti-Ta alloys were higher than those of the non-coated Ti alloys in 0.9% NaCl solution from potentiodynamic test, indicating better protective effect. 5.From the A.C. impedance analysis in 0.9% NaCl solution, Rp values of TiN and ZrN coated Ti-Ta alloys showed 5.19×107 Ωcm2 and 3.55×107 Ωcm2, respectively. TiN and ZrN Coated Ti-Ta alloy was higher than those of non-coated Ti-Ta alloy. Polarization resistance (Rp) values increased with increasing Ta content.