Tribological behavior of patterned TiAlN coatings at elevated temperatures

Abstract

TiAlN coatings were deposited on stainless steel surfaces with patterns consisting of either wide stripes, narrow stripes or triangular regions. The tribological behavior of these patterned coatings was compared against that of a non-patterned reference in tests which involved rubbing against Al2O3 coated rings at room temperature (RT, ~25), 300, 450 and 600 °C. Results show that patterns can help dissipate frictional heat to decrease surface temperature and the tribo-oxidation degree, thus maintaining the load bearing capacity of the coating and retarding the material softening process. This effect, along with the decreased contact area resulting from the patterning, causes a reduction in adhesive wear. An additional benefit of the patterned surfaces is the accommodation of wear debris to reduce three-body abrasive wear. The lubricious TiO2 formed on the worn surface can also decrease the adhesion and reduce the coefficient of friction, while Al2O3 can protect the coating and reduce wear. This all suggests that, TiAlN patterned coatings are an effective means to reduce adhesive and abrasive wear of sliding components in the engine and other bearing contracts operating at elevated temperatures.