Abstract
This article presents the development of hard coatings and new multi-element hard coating systems based on high-entropy alloys (HEAs). Recent design concepts of coatings are exemplified. The preparation and characterization of new multi-element nitride coatings, composed of several nitride and non-nitride forming elements, is presented. Multi-element alloy and nitride coatings tend to form an amorphous phase or solid-solution structure with nanocrystallites, as opposed to a mixture of complicated phases or structures. The high phase stability of the single solid-solution nitride can be retained, even after annealing at 1000°C in vacuum. Smooth surfaces can be obtained from not only HEA metallic coatings but also nitride ones. By the addition of nitrogen, multi-element coatings are found to possess higher hardness, lower compressive stresses and higher hardness-to-modulus ratios than conventional binary nitride materials. © Lavoisier.