Hard particle erosion of silicon carbide and silicon carbide-titanium diboride from room temperature to 1000 degrees C

Two commercially available ceramics, a silicon carbide monolith and a silicon carbide-16 vol.% titanium diboride particle toughened ceramic matrix composite have been subjected to erosion by gas-borne silicon carbide particles over a range of experimental conditions, including erodent particle size and temperature. Material responses to single particle impacts and erosion have been correlated with the behaviour observed when the materials were subjected to quasi-static indentation by a sharp indenter. In all cases, material was lost through the mechanism of lateral fracture. The monolithic ceramic exhibited trends in behaviour which were consistent with the general predictions of wear models based on lateral cracking. The amount of material loss increased with the size of the erodent particles and with the test temperature. The composite material exhibited anomalous behaviour in some regimes. Generally, the composite had a lower wear rate than the monolithic material, as would be expected from its superior fracture toughness. When subject to erosion by the smallest of the three erodent sizes used, however, it exhibited a higher wear rate than the monolith and the wear rate was found to increase with decreasing particle size. This behaviour is not consistent with existing wear models but was consistent with observations of the quasi-static indentation testing. It is clear that the titanium diboride particles have an adverse effect on the short crack properties of the material. The elevated temperature testing employed a single particle size. The composite wear rate was always less than the wear rate of the monolith but the data converged as the temperature was increased, consistant with the decreasing ability of the titanium diboride particle to toughen the silicon carbide matrix. (C) 1997 Elsevier Science S.A.