Indentation Characterization of Silicon Nitride

Abstract The hardness of hot-pressed silicon nitride ceramics has been measured over a wide range of applied loads, 0.02 to 300 N, for both Vickers and Knoop indenter geometries. The indentation size effect (ISE) was evident for loads less than about 1 N. The Vickers and Knoop hardness values agree provided they are compared at a given penetration of the respective indenter. The influence of the residual stresses of the ceramic surface on the indentation response in the as-machined, polished, and post-annealed state has been investigated. The results are discussed in relation to the characterization of indentation damage in brittle materials and fracture analysis models.