Ion beam mixing of AlAlN multilayers for tribological and corrosion protection

Abstract

The changes of the tribological and corrosion protection properties of AlAlN thin film multi-layered structures exposed to 1.8 MeV Ar + ion bombardment were studied. The AlAlN multilayers used in this study had periodic thicknesses ranging from 25 nm/100 nm Al/AlN to 100 nm/25 nm Al/AlN before the bombardment. Ion beam mixing was accomplished by irradiations with relatively low dose and current density (1 × 10 16 Ar + cm −2; 1 μA cm −2). The composition and layer sequence was derived from Rutherford backscattering and Auger electron spectrometric measurements. The corrosion protection potential of the coatings was evaluated by electrochemical methods. The hardness was measured with a dynamic ultramicrohardness tester. It could be shown that ion bombarded multilayers consisting of sequences of 30 nm Al and 100 nm AlN (30/100 thickness ratio) gave the best results as long term corrosion protection and adhesion are concerned. The hardness of these samples was only slightly lower than the one of a single layer AlN film. Therefore these ion beam mixed multilayers represent a new class of protective coatings with excellent properties.