Spark plasma sintering of A[lc]l2O3-T[lc]iC and A[lc]l2O3-T[lc]iC-diamond composites

Abstract

Spark plasma sintering characteristics of Al2O3-TiC and Al2O3-TiC-diamond composites were investigated. Samples prepared in the ratio of 70:30 wt percent of Al2O3-TiC and 67:23:10 vol percent of Al2O3-TiC-diamond were sintered at 1,350 to 1,500 C for 5 min under a pressure of 40 MPa by the spark plasma sintering method. Diamond particles were coated with thin silicon carbide layer. No additive was used. Samples sintered were characterized in respect to microstructural and mechanical properties. The results revealed that nearly 99 percent of theoretical density in Al2O3-TiC composites was obtained, but densities are remarkably lower in samples with diamond. Contrary to this, the toughness of Al2O3-TiC-diamond composite is higher than that of Al2O3-TiC ceramics. Hardness of Al2O3-TiC-diamond composite is also lower than Al2O3-TiC composites. These results were attributed to the lower thermal expansion coefficient of diamond and its tendency to convert to graphite.