Comparison of Two Structure Scales of Plasma Sprayed Al₂O₃-TiO₂ Coatings on Mechanical and Tribological Properties

Al₂O₃-13 % wt TiO₂ thermal sprayed coatings exhibit good wear resistance under tribological conditions, thanks to their high toughness. Alumina/titania coatings with two different structures, and similar titania content, have been elaborated by atmospheric plasma spraying (APS). The aim was to compare the effect of the structure on hardness and wear resistance. As feedstocks were used Al₂O₃-13 wt % TiO₂ powders with two different structures: micrometer sized ones, with two size distributions (5 – 30 μm and 15 – 45 μm), and agglomerated nano-meter sized particles (grain diameters between 200 to 500 nm) with a size distribution between 10 and 45 μm. Coatings were sprayed onto low carbon steel (XC38) substrates with several spray parameters, the plasma forming gas used being mixtures of Ar and H₂ (45/15 and 53/17 SLM, respectively). Results show that, with the tribological conditions used in this study, the wear resistance of coatings principally depends of their hardness and not very much on the starting powder morphologies.