Effect of Coatings on the Heat Resistance of VT-41 and VIT1 Alloys during Isothermal Oxidation

Abstract

The influence of aluminide coatings on high-temperature α + β VT-41 alloy and a VIT1 alloy based on the Ti₂NbAl orthophase on the isothermal heat resistance at 700°C is studied during oxidation in still air. NiCrAlY and Al(Si) coatings are found to substantially increase the heat resistance of the alloys at 700°C. The phase composition of the aluminosilicide layer (TiAl₃ + TiSi₂ + Ti₅Si₃) under the NiCrAlY coating significantly retards the titanium diffusion to the NiCrAlY layer and can be used as a diffusion barrier and a aluminum source for the NiCrAlY layer during high-temperature oxidation.