The effect of silicon carbide on the mechanical and thermal behavior of spark plasma sintered silicon nitride ceramics with Al₂O₃ and Y₂0₃ additives

Silicon nitride-silicon carbide composite ceramics were spark plasma sintered with yttrium oxide and aluminium oxide as additives while varying the percentage weight of silicon carbide from 3 to 12%. Relative density together with Vickers hardness and fracture toughness of the material were measured. Furthermore, holes were drilled using Nd;YAG laser to investigate the thermal stability of the materials. From the results, it was observed that the relative density of the material depended highly on the silicon carbide composition with 99.997% relative density obtained at 12% silicon carbide composition. The Vickers hardness and the fracture toughness slightly increased with increase in the silicon carbide composition from 1943 HV and 8.5 MPa·√m at 3% to 1971 HV and 8.991 MPa·√m at 12%. A huge impact of the silicon carbide composition was observed with thermal behavior in a manner that as the silicon carbide content increased, the material was becoming more thermally stable in high laser energy parameters. (paper)