CERAMIC-TO-METAL DIRECT BRAZING

The production of important components like first walls of thermonucle ar power reactors advanced automotive or aeronautic turbines and hear exchangers depends on the control of ceramic to metal joining techniqu es, especially direct brazing. Recent advances in two fundamental aspe cts of such techniques are reviewed. thermodynamics and mechanics, Abo ut thermodynamics a general theory of wetting and adhesion of active f iller alloys on oxide ceramics is described This approach allows the d etermination of optimal braze compositions. Some of the concepts of th is approach are used for non oxide ceramics. Due to a complex stress f ield existing in the ceramic at the location of crack initiation and p ropagation, accurate failure prediction of ceramic, to metal assemblie s remains a challenge, Nevertheless, simple analytical calculations ar e often a useful roof. For more advanced analysis, determination of jo int constitutive laws by inverse method and careful finite element enm eshment in the vicinity of the joint allow accurate stress field calcu lations.