MICROSTRUCTURAL AND MECHANICAL STUDY OF S ILICON-NITRIDE DUCTILE CAST-IRON BRAZED JOINTS

Si3N4 was brazed to ductile cast iron using a reactive filler metal. A microstructural observation of the brazed joint pointed out the prese nce of brittle reaction layers surrounding the eutectic AS-Cu. Finite element modelling of residual stresses in the assembly confirmed the i nfluence of the substrate geometry and the filler metal constitutive b ehaviour on stress distribution. The observed cracking in the samples is interpreted by using the modelling results, and the occurence of su bcritical crack growth in the ceramic phase.