Effects of doping elements on oxidation properties of V–Cr–Ti type alloys in several environments

The alloys examined in this study include V–4Cr–4Ti–0.5Si, V–4Cr–4Ti–0.5Al, V–4Cr–4Ti–0.5Y and V–4Cr–4Ti. Oxidation experiments were conducted in air. After oxidation, tensile tests, hardness measurements and scanning electron microscopy were performed. Surface oxidation layers were identified by X-ray diffraction (XRD) analysis. Based on this study, the alloy doped with Y was excellent in oxidation resistance at 600 and 700 °C. The XRD indicated that V2O5 was the primary oxide phase for the alloys tested at 700 °C, except for the V–4Cr–4Ti–0.5Y alloy. The oxide identified at all temperatures in V–4Cr–4Ti–0.5Y alloy was VO2, that was also observed for the other alloys after testing at 600 °C. It was suggested that the formation of thin and dense VO2 oxide layers had an important role for superior oxidation properties of the V–4Cr–4Ti–0.5Y alloy. From the results of this study, further optimization of the V–4Cr–4Ti alloy could be possible by controlling the small addition of yttrium.