2013 Volume 54 Issue 8 Pages 1308-1312
Suppression of the reaction between molten Ti and the investment material could limit the formation of the alpha-case layer, which influences the mechanical properties of the casting. This study investigated the influence of the investment material on the composition of the alpha-case layer and the corrosion behavior of Ti castings prepared in Al2O3-based molds by plasma arc melting. The micro-Vickers hardness of the castings was evaluated both on the surface and in the matrix. The corrosion behavior was investigated in 1 M HCl solution by electrochemical tests. The results show that the alpha-case layers formed when using Al2O3–5Ti molds are thinner than those formed when using Al2O3 molds, because the reaction with the molten metal is suppressed. Further, Al2O3–5Ti molds produce castings with better corrosion behavior, although this behavior is still poorer than that of pure Ti. Thus the corrosion behavior of Ti castings is affected by the composition of the alpha-case layer.