Effect of the Copper Enriched Layer on Relaxation of Thermal Stress

Study on Bonding of Heat-Resisting Fine Ceramics (Report 5)

Abstract

Effects of the insert metals on the crack initiation in Si₃N₄ to SCM435 joints were investigated by paying attention to the thickness of copper enriched layer and the diameter of specimen. The 10 mm diameter joints without crack using Cu-5%Cr, Cu-1%Nb, Cu-3%V, Cu-5%Ti and Cu-10%Zr insert metals were obtained in case that the thickness of copper enriched layers were more than about 0.2 mm, 0.2 mm, 0.3 mm, 0.5 mm and 0.8 mm, respectively. As for Cu-5%Cr insert metal, the 13 mm diameter joints without crack were obtained in case of the thickness of copper enriched layer being more than about 0.4 mm. On the basis of residual stress analysis in Si₃N₄ to SCM435 joint, the critical maximum principal stress in Si₃N₄ to prevent crack in the joint were almost the same level of 350-400MPa in any cases. It was concluded that copper enriched layer had the function of relieving the thermal stress occurred in the bonding process.