Alumina plasma spraying on 304L stainless steel: Role of a wüstite interlayer

Excellent adhesion values (>70 MPa) of alumina coatings achieved by Atmospheric Plasma Spraying (APS) were obtained on pre-oxidized stainless steel (304L), covered with a continuous layer of wüstite (Fe1−xO) surmounted by a very thin magnetite layer. This is due to epitaxial relationships between alumina, magnetite and wüstite, as shown by Transmission Electron Microscopy (TEM), giving a “crystallographic bonding”.