Effect of Face Coats and Electron-Beam Casting Technology on the Interfacial Reactions Between Titanium and Ceramic Mold.

Electron-beam casting technology has great potential in obtaining high-quality precision titanium castings due to its good ability to remove inclusions from the metal. In this study, the interfacial reactions of titanium with the face coats of the ceramic mold were investigated using microstructural analysis and microhardness measurement. Refractories—Al2O3, ZrO2, ZrSiO4 and Y2O3 were used as fillers for face coats. The study of the microstructure of cast samples from technically pure titanium showed that the Al2O3 face coat led to the formation of an α-case with a thickness of 300–400 μm. The Y2O3 coating in combination with Al2O3 and ZrO2 stucco ensured the formation of a twice-thin α-case. A combined face coat, which contained 70% ZrO2 + 30% Y2O3 slurry fillers and ZrO2 as stucco, ensured the formation of an α-case up to 200 μm thick. Measurement of microhardness made it possible to determine the nature of the interaction of titanium castings with ceramics and the distribution of gas impurities in the surface layers of the metal. Electron beam processing in combination with electromagnetic stirring leads to the formation of a fine structure in titanium castings. The low overheating of the titanium melt specific for EBCT and the low temperature of the mold contribute to reducing the interaction of titanium with ceramics. The combined face coat showed good technological properties and can be recommended for the production of thin-walled castings from titanium alloys by electron-beam casting technology. [ABSTRACT FROM AUTHOR]