Abstract
The application of zirconia (ZrO2), a highly refractory material, to investment material was studied. Various zirconia powders and binders, organic and inorganic, were tested with respect to the conditions for higher temperature casting such as adequately high strength, non-reactivity and good castability. Pure zirconia and zirconia stabilzed with calcia, magnesia, yttria were tried as refractory materials. Zirconia sol, phosphoric acid, phosphates, surfactants, water-soluble acrylic bond and methyl methacrylate (MMA) chemically polymerized at an ambient temperature were used as bonding agents. The properties of investment material such as water/powder ratio, fluidity of slurry, setting time, setting expansion, thermal expansion, thermal conductivity, green and fired compressive strength, surface reactivity and defects contained inside castings were measured. Zirconia was an excellent investment material for the higher temperature casting, which produced titanium castings with a shiny surface without reaction and oxidation as cast, and with fewer casting defects inside.
