Residual Stress Distribution of Si3N4/SiC Gradient Material and the Effect of Residual Stress on Material Properties

The Si3N4/SiC gradient material with a gradient composition structure was prepared by a hot pressing sintering. The sinterability, distribution of residual stress and the effect of residual stress on mechanical properties of Si3N4/SiC gradient materials were studied. The research results show that, at 1 750 °C, Si3N4/SiC gradient materials with different ratios can achieve co-sintering, and the overall relative density of the sample reaches 98.5%. Interestingly, the flexural strength of Si3N4/SiC gradient material is related to its loading surface. The flexural strength of SiC as the loading surface is about 35% higher than that of Si3N4 as the loading surface. The analysis of the residual stress of the material in the gradient structure shows that the gradient stress distribution between the two phases is a vital factor affecting the mechanical properties of the material. With the increase of SiC content in the gradient direction, the fracture toughness of each layer of Si3N4/SiC gradient materials gradually decreases. The surface hardness of the pure SiC side is lower than that reported in other literature.