Oxidation behavior and electrochemical corrosion performance of Ti 3 Al alloy with TiAl coating
- PDF / 3,104,349 Bytes
- 6 Pages / 595.276 x 793.701 pts Page_size
- 9 Downloads / 202 Views
OXIDATION BEHAVIOR AND ELECTROCHEMICAL CORROSION PERFORMANCE OF Ti 3 Al ALLOY WITH TiAl COATING Yanjun Xi,1,2 Yongjun Liu,1 Zhixin Wang,1 and Jinbin Lu1 Magnetron-sputter deposition was used to produce a Ti–48Al–8Cr–2Ag (at. %) coating on a Ti–24Al– 17Nb–0.5Mo (at. %) alloy substrate. Oxidation behavior was studied in air at 900–1000°C. The results indicated that the oxidation rate of sputtered Ti–48Al–8Cr–2Ag nanocrystalline coating was lower than that of the Ti 3 Al alloy at 900°C. The former formed a scale of merely Al 2 O 3 , and the latter formed a scale of TiO 2 . However, the Ti–48Al–8Cr–2Ag nanocrystalline coating showed a little bit higher oxidation rate than Ti 3 Al alloy at 1000°C because the outer TiO 2 scale formed and columnar boundaries of the coating gave a larger actual oxidation area than the original alloy. The electrochemical corrosion behavior was investigated in a 3.5% NaCl solution at room temperature. The coating showed excellent electrochemical corrosion resistance in 3.5% NaCl solution because it exhibited stable passive polarization behavior without any overpassivation phenomena. Keywords: Ti 3 Al , TiAlCrAg nanocrystalline coating, high temperature oxidation, electrochemical corrosion.
Titanium aluminides are promising intermetallic compounds for high temperature applications especially because of the possible weight reduction of structural components. Experimental evidence [1–3] showed that titanium aluminides with aluminum content of about 50 at. % form nonprotective TiO 2 + Al 2 O 3 scales rather than a dense protective alumina scale. Therefore, an attempt was made to protect them against oxidation by coating [4–6]. Recently, several investigations have been focused on the oxidation of the Ti–Al alloy by diffusion coatings formed by pack-codeposition of Al and Si [7–8] and Al electrodeposition on the surface of Ti–Al [9]. Since a new class of TiAlCr coatings was proposed and they provided excellent oxidation protection for TiAl intermetallics [10–12], they received a considerable interest. The Ag-containing alloys possess relatively high ductility. TiAlCrAg alloys were investigated to exhibit excellent oxidation resistance [13]. Therefore, TiAlCrAg coatings may become a promising protective coating for Ti 3Al -base intermetallics, and few studies have been focused on it, especially on the electrochemical corrosion. This paper reports on the effect of the TiAlCrAg coating on the high-temperature and electrochemical corrosion performance of the Ti 3Al alloy. Experimental Procedures The Ti–48Al–8Cr–2Ag coating was prepared on the Ti 3Al alloy by magnetron sputtering technique. The target of 380 × 126 × 7 (mm) and the specimens of 10 × 10 × 2.5 (mm) were cut from an alloy ingot. The Ti 3Al alloy specimens were ground down to No. 800 emery paper, peened, and ultrasonically cleaned in ethanol. The 1 2
Zhongyuan University of Technology, Zhengzhou, China. Corresponding author; e-mail: [email protected].
Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 46, No. 6, pp. 113–117, November–De
Data Loading...
