Influence of powder-size matching on the surface quality of ceramic mould shell for investment casting of titanium alloys

The main factors determining the surface quality of the ceramic shell mould for investment casting of titanium alloys include the density of the ceramic powder compact and the viscosity of the slurry. In this work, mixtures of fine/coarse powders with different fine powder contents were prepared and their relation to the density of the compact and to the viscosity of the slurry was studied. Variation in viscosity with the powder/solution ratio was also measured for the different powder mixtures. For the given experimental system, the optimal ratio of the fine/coarse powder and the best powder/solution ratio were determined. Examination of the mould shell made under optimized conditions showed that the surface quality of the mould shell was improved significantly.