Slip Casting of Titanium Powder for Dental Prosthetic Appliances

The feasibility of using slip casting of titanium powder as a method for manufacturing dental prosthetic appliances was examined. Slips with water-powder (W/P) ratios, 0.318, 0.354 and 0.391, and with minimum viscosities were cast in plaster molds. Castings were sintered in an argon atmosphere at 1373, 1473 and 1573 K for 3.6, 7.2 and 10.8 ks, respectively. Green densities and strengths of castings were 2.20 kg/m3 and 2.31—3.82 MPa, respectively. Linear shrinkages and relative densities of sintered castings varied from 17.6 to 20.8% and 0.82 to 0.97 of the theoretical density of titanium, respectively. Tensile strengths and Vickars hardness of the sintered castings were 199.5—315.4 MPa and 233.0—247.7, respectively. There was almost no elongation. Decreasing porosity and crystal grain growth were found in the microstructures of sintered castings and rod-like precipitates of TiC with α-titanium were also observed. Concentrations of carbon and oxygen in the microstructures of sintered castings were higher than those in wrought titanium. Fractured surfaces showed ridge patterns typical of brittle fracture. Further modification of the sintering atmosphere and the additives for the slip is needed to improve the microstructure of slip-cast sintered titanium.