Frottement à haute température de revêtements d’oxyde de chrome avec ou sans lubrifiant solide

Sliding friction of chromium oxide (Cr 2 O 3 ) against chromium oxide + solid Lubricants (CaF 2 and BaF 2 ) has been studied at 425° C under different contact pressures. Cr 2 O 3 sliding against itself has always presented the following features : irregularities of the friction curve (slip-stick) ; important variations of the coefficients with contact pressure ; visible damage of the sliding surface. Adding a solid lubricant to Cr 2 O 3 coatings has improved their tribological properties : more regular friction curves ; lower and stable friction coefficients ; prevention of the surface damage ; reduction of the wear rates by 40 to 100 times and higher critical contact pressure. Microscopic observation and analysis show that the improvement of tribological properties results from the presence of a solid lubricant film. Consequently, strong adhesion (in some contact areas) between Cr 2 O 3 / Cr 2 O 3 is prevented. The introduction of a solid lubricant decreases surface energy and improves the shearing behaviour of the ceramic coating.