Silica-free investment casting molds based on calcium zirconate

Abstract Investment casting allows the near net shape production of complex cast parts, but the investment casting of high melting and highly reactive titanium alloy melts is very difficult. Calcium zirconate ( C a Z r O 3 ) is a novel ceramic refractory material, which is particularly stable in a highly reducing atmosphere and in contact with extremely reducing titanium alloy melts such as Ti6Al4V. Besides the refractory, the choice of the binder is equally important because conventional silicate binders significantly impair the corrosion resistance. Although there have been successful attempts to develop CaZrO 3 investment casting molds, silica-free CaZrO 3 investment casting molds using a water-based binder have not yet been reported. For the first time, CaZrO 3 investment casting molds using a silica-free water-based binder system were successfully produced. Moreover, the rheological behavior of the slips and the chemical, physical and microstructural properties of the molds were extensively described. Investment casting of Ti6Al4V led to an exceptionally low hardness increase of the cast part, suggesting that only a slight corrosion reaction took place. Thus, the silica-free CaZrO 3 investment casting molds contributed to an improved investment casting of titanium alloys.