Hardness anisotropy in bimodal grained gas pressure sintered Si3N4

摘要

High hardness and good wear resistance of silicon nitride based ceramics are very attractive for both high and low temperature applications. However, the hardness of these materials is strongly affected by the densification method (hot isostatic pressing (HIP), hot pressing (HP), gas pressure sintering (GPS) etc.), the composition, density and the microstructural parameters. During the past 15 years microhardness and hardness measurements have been used to characterize silicon nitride ceramics [1-3]. Activities in this area can be divided into three main fields: (i) study of the microhardness and its inherent anisotropy in a- and /3-Si3N4 single crystals, [1, 4-6], (ii) study of the impression size effect on the hardness of Si3N4 ceramics and the influence of the chemical composition and micro-structure parameters on its values [7-9] and (iii) "Round Robin" experiment on Si3N4 based ceramic composites in the frame of Versailles Advanced Materials and Standards (VAMAS) [10].