INTERMETALLIC TiAl-BASED MATRIX COMPOSITES: INVESTIGATION OF THE CHEMICAL AND MECHANICAL COMPATIBILITY OF A PROTECTIVE COATING ADAPTED TO AN ALUMINA FIBRE

摘要

The investigation of both chemical and mechanical compatibility of a TiAl-based matrix with a ceramic fibre has led to the choice of the "Saphikon" single crystal alumina fibre and to develop a double coating concept consisting of an external yttria layer acting as a diffusion and an internal tungsten coating enabling decohesion at the fibre-matrix interface. Tensile tests performed on monofilament com- posites, i.e. alumina fibers successively coated with W, Y_2O_3 and TiAl, revealed that after the heat treatment (1 h at 1100 deg. C)simulating the consolidation cycle, the double coating provides an 80/100 increase in the mean tensile strength as compared with a monofilament composite without coating.