Influence of high-temperature ion irradiation on nanostructured TiAlN coatings

Abstract

Nanostructured TiAlN coatings were formed on AISI 304 stainless steel substrates by reactive magnetron sputtering. The studied TiAlN coatings were irradiated with Ar+ ions with an energy of 200 keV in the fluence range from 2.5 ⋅ 1016 to 2.0 ⋅ 1017 ion per 1 cm2 at a temperature of 480 °C. Using energy-dispersive X-ray spectroscopy, scanning electron microscopy and X-ray diffraction phase analysis, the elemental composition, structural-phase state and morphology of the initial and irradiated coatings were studied. Nanoindentation of the obtained structures was carried out according to the method of Oliver and Pharr, the nanohardness (Н) and Young’s modulus (E) were determined, and the impact strength of the coatings under study was calculated as the H/E∗ ratio. The formation of a single-phase structure of the (Ti, Al)N solid solution in the coatings initial state has been detected. The effect of selective sputtering of the lightest component – nitrogen – from the coatings was found. Up to an irradiation fluence of 1.0 ⋅ 1017 ion per 1 cm2, no significant changes were revealed in the structural-phase state of the coatings. When irradiated with a fluence of 2.5 ⋅ 1016 ion per 1 cm2, an improvement in the TiAlN coatings strength properties complex was observed. It has been found that nanostructured TiAlN coatings are radiation-resistant up to an irradiation fluence of 2.0 ⋅ 1017 ion per 1 cm2, at which the onset of segregation of the (Ti, Al)N solid solution as the main phase of the coatings and blistering effect is observed.