Microstructure and properties of thick nanocomposite TiN/Si3N4 coatings on Vanadis 23 HS steel

Abstract

Abstract The microstructure and selected micro-mechanical properties of a 13.4 μm thick nanocomposite TiN/Si3N4 coating deposited onto Vanadis 23 HS steel by a new gas pulsed magnetron sputtering technique were investigated. Scanning and transmission electron microscopy were employed to investigate the detailed microstructure of the coating. It was found that the coating exhibited a fully nanocrystalline structure and was composed of two zones: the outer zone with columnar structure and the inner one with equiaxed, fine columnar structure. Both zones consisted mainly of the δ-TiN nanocrystallites with a small amount of α-Si3N4 and β-Si3N4. In order to increase coating adhesion to the substrate, a graded intermediate layer consisting of three different phases (pure Cr, CrN and Cr2N) was applied. The hardness of the as-deposited TiN/Si3N4 coating was equal to 48 GPa, whereas it was equal to 40 GPa after annealing. The coatings exhibited very good adhesion to the underlying steel substrate.