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 V 2 O 5 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 VO 2 , that was also observed for the other alloys after testing at 600 °C. It was suggested that the formation of thin and dense VO 2 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.