ABSTRACT

The utility of ceramics as wear-resistant materials may be limited by their susceptibility to fracture. In recent years the fracture toughness of ceramics has been improved through the introduction of secondary phases into the microstructure. Zirconia-toughened alumina and whisker-reinforced alumina are two examples of this emerging class of materials. Since the onset of severe wear in ceramics is preceded by fracture, improvements in fracture toughness also imply a potential for improved wear resistance. The studies reported in this chapter indicate that the increased complexity of the toughened ceramic microstructures can result in more complex wear responses. Although the composite body is toughened and fracture suppressed, the wear debris of the secondary phase may abrade the matrix, and the toughening mechanism may depend on a microstructural condition that is detrimental, rather than beneficial, with regard to wear. In addition, the strengthening phase(s) may interact chemically with the environment, producing either desirable or undesirable results. Results obtained on whisker-reinforced alumina and silicon based ceramics are presented and discussed, with reference to the complex microstructural relationship to wear.