Cost-Effective Sintered Reaction-Bonded Silicon Nitride for Structural Ceramics

Abstract

Sintered silicon nitride has many superior properties; however, for most applications these materials are too expensive to compete with metal parts. Sintered reaction-bonded silicon nitride (SRBSN) is more ecomonical, with raw material costs < 20% of those of comparable high-purity materials, making it competitive with metal parts. Conventional processing of SRBSN requires long nitridation times and a two-step firing process. Microwave (MW) heating reduces the reaction times and is performed in a one-step process, thereby simplifying the operation. The mecahnical properties of the MW-SRBSN are not equal to those of the higher-cost powders, but are appropriate for a number of applications at lower temperatures and stress levels. At ambient temperature, typical strength, toughness, and hardness values are 480 MPa, 4.8 MPa√m, and 14 GPa, respectively.