EFFECT OF Ni-Al COATING ON HIGH TEMPERATURE OXIDATION BEHAVIORS OF Ti-22Al-26Nb ALLOY

Ni-68.5Al (atomic fraction, %) coatings were prepared on an orthorhombic alloy Ti-22Al-26Nb (atomic fraction, %) by detonation gun spraying (DS). After annealing, the Ni-Al coatings have a good adherence with the substrate, and XRD shows that the coatings mainly composed of β-NiAl. The influence of Ni-Al coatings on the isothermal oxidation behaviors of Ti-22Al-26Nb was studied in static air at 800℃. For the alloy Ti-22Al-26Nb without coating, under high temperature oxidation a mixed oxide scale formed and consisted of TiO2, AlNbO4 and A12O3, in which TiO2 is the dominant oxide phase and exhibits relatively poor oxidation resistance. The high temperature oxidation resistance of the specimens coated with Ni-Al coatings is remarkably improved due to the formation of a dense and adherent Al2O3 scale.