Plasma-sprayed 2:1-mullite coatings deposited on aluminium substrates

2:1-mullite coatings of (17-23)+ or -6 mu m thickness were deposited by atmospheric plasma spraying (APS) onto flat aluminium coupons. Scanning transmission electron microscopy (STEM) showed that the coatings immediately adjacent to the substrate interface consisted predominately of an aluminium silicate glass with varying Al/Si ratios. Residual compressive coating stresses with in-plane levels ranging from 100 to 300 MPa were determined by Cr (super 3+) photoluminescence piezospectroscopy. The aluminium silicate glass was characterised by wide-angle x-ray scattering (WAXS) using synchrotron radiation to determine the composition (62-63 mole% Al (sub 2) O (sub 3) ) as well as the amount of glass in the coatings (32+ or -2%).