Effects of coating material on machining graphite casting processforming quality of Titanium alloy

Abstract:

The refractory oxide coating includes Y₂O₃, Al₂O₃, and CaZrO₃ were coated on the inner surface of graphite mold, to study the effect of coating composition on the interface reaction of pure titanium and its microstructure and properties. The results show that the coating can effectively overcome the chilling effect of graphite casting mould. No chemical reactions occur between Y₂O₃ and molten titanium liquid, and Y₂O₃ coating only physically adhere to the surface, so the stability of Y₂O₃ coating and titanium liquid is best. Al₂O₃ and CaZrO₃ coating have interface reaction with molten titanium liquid, and Ti-Al-O and Ca-Ti-O phase form during the interface reaction, respectively. The interface reaction between Al₂O₃ coating and molten titanium liquid is most severe. After the coating, the gain size of the surface layer, the thickness of coarse grain layer and the microhardness all increase. And these changes degree with the coating type from the small to large is Al₂O₃, CaZrO₃, Al₂O_3, respectively.