Abstract
The mechanical properties of hot pressed Y-stabilized α/β SiAlON ceramics have been studied through assessment of hardness, fracture toughness and bending strength measurements. Wear properties were studied by non-lubricated block on ring and ball on disk type wear tests under a range of loads. The effect of the stabilizing cation was also studied by producing identical compositions with the Y cation being replaced by Yb. In the Y stabilized materials there was a slight decrease in hardness with increasing β content but a 2-fold increase in both strength and toughness due to the development of elongated grains in the microstructure. The same trend in fracture toughness and strength was seen for the Yb materials, although lower density and larger grain size resulted in a lower hardness compared to the Y materials. Under low load wear tests the single phase α materials showed better wear properties, possibly as a result of a lower amount of intergranular phase. However under more severe conditions the high β content materials exhibited better wear properties due to resistance to crack propagation. In the single phase materials under low load, despite lower hardness the Yb samples showed an order of magnitude better wear resistance than comparable Y stabilized ones.
