Inert calcia facecoats for investment casting of titanium and titanium-aluminide alloys

摘要

A calcia mold facecoat is applied to a mold for casting parts composed of reactive metals such as titanium and titanium aluminide. The facecoat is composed of a calcium carbonate based slurry comprising a dense grain calcium carbonate powder and an aqueous based binder. It is applied to a wax or plastic pattern used in the lost wax process for fabricating a casting shell. The mold is built using multiple dipping of alumina-silicate slurries, and then fired at high temperatures in an oxygen rich environment. The metal part is cast before the fired mold can cool below about 800 DEG C. Organometallic based slurry binders are avoided and significant cost savings are realized owing to the benign nature of the aqueous based suspensions with respect to the environment.