Oxidation and protection of near-alpha titanium alloys

The near-alpha titanium alloys IMI834 and TIMETAL 1100 form non-protective oxide scales during exposure to air at high temperatures. Furthermore, considerable embrittlement by oxygen solution in the surface degrades the ductility of the materials. Sputtered multilayer and gradient coatings from the Ti-Al system are capable of markedly improving the oxidation resistance and preventing embrittlement of the base material. Whereas gradient coatings transform into multilayer coatings during high temperature exposure, the sputtered multilayer coatings remain stable after 100 hr at 750 degrees C. Both coating systems slightly improve creep life but promote high plastic deformation during exposure to air at 600 degrees C.