Correlation of wear behavior and indentation fracture resistance in silicon nitride ceramics hot-pressed with alumina and yttria

Nine kinds of silicon nitrides with different microstructures were fabricated by controlling both sintering conditions and amounts of sintering additives, Al2O3 and Y2O3. The wear behavior of the various Si3N4 ceramics was investigated in sliding contact test without lubricant. The specific wear rate varied notably from 6 × 10−6 to 4 × 10−4 mm3 N−1 m−1 depending on the microstructures, whose ranking was difficult to predict directly from the hardness or fracture resistance obtained by the indentation fracture (IF) technique as well as the single-edge-precracked beam (SEPB) method. A good correlation was obtained between the specific wear rate and both mechanical properties when a lateral-crack chipping model was applied as the material removal process. However, the correlation was lost when the fracture toughness obtained by the SEPB method was employed, indicating that the conventional long-crack toughness is inappropriate for analyzing the wear behavior of Si3N4 exhibiting a rising R-curve behavior.