Fabrication of Y2O3 doped BaZrO3 coating on Al2O3 applied to solidification of titanium alloy

Abstract The investment casting is one of the most versatile modern technique for metal forming, however, the high chemical stability of ceramic shell materials is required due to the high activity of titanium melt. The Al 2 O 3 is one kind of the common refractory material, which can not be directly used for casting titanium alloys because of its reaction with the melt and contamination caused by this reaction. In this paper, the Y 2 O 3 doped BaZrO 3 coating was fabricated on the Al 2 O 3 matrix in order to develop a novel casting and directional solidification technology. Using the Al 2 O 3 as the matrix, the Y 2 O 3 doped BaZrO 3 coating was prepared by smearing the slurry, dusting the BaZrO 3 powder and sintering them. The reaction between the Al 2 O 3 matrix and the protective coating, the surface quality and chemical stability of the Y 2 O 3 doped BaZrO 3 coating were investigated using the optical microscope (OM), energy dispersive spectrometer (EDS) and scanning electronic microscope (SEM), respectively. Afterward, the interaction between Y 2 O 3 doped BaZrO 3 coating and titanium melt was discussed. Optical microscope and SEM results showed that the BaZrO 3 coating possessed the good surface morphology and high chemical stability, and EDS results showed the thickness of interaction layer between the Al 2 O 3 matrix and the protective coating did not vary with the sintering time and temperature (at 1500 °C and 1600 °C for 2, 4 and 6 h). The thickness of diffusion layer was 10 μm for the rod of Ti-46Al-8Nb with the directional solidification, the same was the counterpart for the casting part of Ti-6Al-4V alloy. This may imply that Y 2 O 3 doped BaZrO 3 is a promising coating for the solidification of titanium alloy.