Brazing of AlN to SiC by a Pr silicide: Physicochemical aspects

In view of their very different thermomechanical properties, joining of metals to ceramics by brazing is usually performed by means of one or more interlayers. In a recent investigation AlN was chosen as interlayer material for brazing SiC to a superalloy. The aim of the present study is to determine an alloy with a high melting point (close to 1200 °C) enabling brazing of AlN to SiC. Two types of experiments are performed with a Si-17 at.% Pr eutectic alloy (Tm = 1212 °C): sessile drop experiments to determine wetting and brazing of AlN and SiC plates to determine gap filling. Experiments are carried out in high vacuum to promote deoxidation. Interfacial reactivity, joint microstructure and type of failure occurring during cooling are examined by optical and scanning electron microscopy.