Characterization of the Interfacial Reaction between Titanium Castings and Alumina Mold Containing the Alpha-Case Compounds

The interfacial reactions of titanium with investment molds containing alpha-case compound systems were studied. Especially, the alumina molds that are containing titania which is one of the alpha-case compounds were used as a mold material for the alpha-case control. Micro Vickers-hardness and microstructure was analyzed for evaluation of reactivity of titanium with mold material. It was found that the thickness of the alpha-case was effectively reduced, indicating that the titania in the mold can increase the inertness of the alumina mold. The microstructural and compositional characterizations of molds were also analyzed for confirming effect of alpha-case control mechanism. The composition of the mold surface turns titania into oxygen-deficient titania which act as effective barrier on the mold element diffusion.