Expansion of Silicon Nitride-Boron Nitride Composite by Reaction Bonding

Abstract

A silicon nitride (Si₃N₄)-boron nitride (h-BN) composite is utilized for brazing jig, since it shows low-wettability for brazing metals. Combination of green machining and reaction bonding (RB) is a potential process to reduce machining cost. However, precision is a problem. Thus, in this work, the composite was fabricated by uniaxial die-pressing followed by cold isostatic pressing, green machining and reaction bonding. Precision of green machining and dimensional change (i.e., expansion) after RB were investigated. Green machining was successfully done, and dimensions of the specimen were within the acceptable error range of 100 μm. After RB, the specimen was slightly expanded. Expansions were about 0.5% and 0.9%, respectively, for perpendicular and parallel to the die pressing direction. Ununiform expansion seemed to be due to the alignment of h-BN caused by uniaxial die pressing.