A Review of Ceramic Tribology and Application of Si-Based Ceramics to Engine Valves/Seat Inserts

This paper is a review of ceramic tribological characteristics and application of silicon-based ceramics as engine valves and seat inserts. This review has shown that wear of ceramics is not an intrinsic material property or a constant, rather it depends on the operating conditions as well as on microstructure, environment, measurement techniques and material properties. The review also found that the dominant ceramic wear mechanism is a fracture/crack controlled process. There have been many models developed to describe the wear of ceramics, however, the complexity of the wear and the existence of wear transitions suggest that satisfactory results can be obtained for each wear model/equation only for the operating conditions for which it was derived. The application of silicon-based ceramics for engine valves and seat inserts is also reviewed and field engine test results are presented. The advantages and disadvantages of ceramics for engine valves and seat inserts are discussed. The cost and the reliability of ceramic valves remain as the major concerns for engine and valve manufacturers.