Interaction between Ti-48Al Alloy and Coating Materials during the Solidification Process

The effect of coating materials on the metal-coating interface, alloy chemical composition and microstructure was evaluated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis. Microhardness variation from the surface to the inside of the samples was compared. The results indicate that inordinate interaction occurs at the interface between the coating and the melt. The crucible layer is found to suffer chemical dissolution and some physical erosion by the molten alloy and the extent of that dissolution depend partly on the coating material. Additionally, the thermodynamics of the TiAl/Oxide reactions have been studied, and the main mechanism responsible for the contamination of the directional solidification samples is diffusion controlled dissolution of the coatings in the melt which increases the oxygen content in the matrix