Titanium castings using laser-scanned data and selective laser-sintered zirconia molds

Titanium casting molds, made of stabilized and unstabilized zirconium oxide, were created using a combination of selective laser sintering (SLS) and colloidal infiltration. The mold material system was chosen for its thermal shock resistance and low reactivity with molten titanium. The starting material, stabilized zirconia powder mixed with a copolymer binder, was laser sintered into the desired green shape. The binder was removed during pyrolysis and replaced by unstabilized zirconia. As infiltrant weight gain increased, the density, flexural strength, and surface roughness improved to levels adequate for titanium casting trials. A half-scale casting mold for the ball of a human femur bone was produced from laser-scanned data and cast with Ti-6Al-4V alloy. The castings exhibited an as-cast surface roughness (R-a) of 8 mum and a typical microstructure. This work demonstrates a feasible method of producing complex titanium castings for one-of-a-kind and custom components without the necessity of part-specific tooling or wax patterns.