Development of Laminar Type Functionally Graded SiAlON Ceramics

In order to combine high hardness with high toughness, laminar type (two layers) functionally graded (FGM) SiAlON ceramics were developed. In a previous study achieved by the same authors, presence of a sharp transition zone between the two layers was demostrated by SEM analyses. The aim of this study is to eliminate this sharp zone. In addition, the effect of sintering time and temperature on the interaction between the layers was also investigated. For this purpose same metal oxides were added to both layers, which have different compositions. Phase characterisation, microstructural investigation and hardness measurements showed that elimination of the sharp zone was achieved and the laminates sintered at 1700DGC for 1 hour was found to be good enough to obtain continuous change in composition, microstructure and hardness through the thickness of the sample.