Castability and surface hardness of titanium cast plates obtained from experimental phosphate-bonded silica investment molds.

The effect of 12 different experimental compositions of phosphate-bonded SiO2 investments was examined on cast pure titanium. The mold temperature was 600 degrees C and the casting was conducted with an argon-arc melting and pressure casting machine. Castability was evaluated by the volume of casting porosity, which was calculated from the volume of wax pattern (15 mm x 15 mm x 1.5 mm), the weight of cast plate and the specific density of pure titanium. The existence of inner casting porosities was confirmed by an X-ray non-destructive inspection instrument. Cast plates made in molds with cristobalite had significantly lower castability and higher surface hardness than those in molds with quartz as a refractory material. Cast plates in molds (quartz-cristobalite mixtures) with 20% binder had lower surface hardness and fewer casting porosities than those in molds with 10% binder.