Mechanical strengthening in self-lubricating CrAlN/VN multilayer coatings for improved high-temperature tribological characteristics

• Self-lubricating CrAlN/VN multilayer coatings are fabricated by RF sputtering.
• The multilayer with 16 nm bilayer period exhibits the best plastic deformation resistance.
• Improved wear resistance at elevated temperature is attributed to vanadium oxides and layered configuration.

CrAlN/VN multilayer coatings are periodically fabricated with various bilayer periods by RF magnetron sputtering. Crystalline phases and preferred orientations of thin films are characterized by the X-ray diffractometer. Through SEM and dark-field TEM inspections, a dense and coherent columnar structure is revealed in CrAlN/VN coatings. In the ball-on-disc test at 700 °C, all the multilayer coatings exhibit preferable anti-wear performance, which is attributed to interfacial strengthening and the formation of lubricated vanadium oxide layers on the worn surface. Especially, the lowest friction coefficient of 0.33 and wear rate of 1.6 × 10− 5 mm3 N− 1 m− 1 are revealed in multilayer coating with bilayer period of 16 nm. As compared with CrAlN monolayer, the worn surface in multilayer coating is relatively intact under high-temperature wear torture. A hybrid mechanism including structural strengthening and elemental contribution is proposed to highlight the favorable anti-wear property in CrAlN/VN multilayer coatings at elevated temperature.