Titanium-Doped Powder Coatings with a TiN Layer on 9KhS Steel and VK8 Hardmetal Substrates

Abstract

The phase and chemical compositions, structure, and properties of titanium/aluminum-doped coatings with a TiN layer on 9KhS steel and VK8 hardmetal substrates were studied. A TiN layer 5.0–5.5 μm thick was applied by the physical vapor deposition method. The alloys were doped with titanium and aluminum in fusible containers in a mixture of powders consisting (wt.%) of 40.0 Ti, 5.0 Al, 5.0 Al2O3, and 5 NH4Cl at 1050°C for 4 h. Multilayer coatings including Al2O3, Fe2Ti4O, TiC, and TiN formed on the 9KhS substrate and Al2O3, TiAlCO2, TiC, and TiN coatings on the hardmetal substrate. The TiN layer completely inhibited the penetration of aluminum into the 9KhS substrate and of aluminum and oxygen into the VK8 hardmetal substrate. The coating on 9KhS steel had no Feα(Al) layer, and the coating on VK8 hardmetal had no area containing aluminum and oxygen. Individual layers in the coatings exhibited high microhardness: 35.6 GPa for the TiC layer on 9KhS steel, 29.0 GPa for the TiC layer on VK8 hardmetal, and 23.4–23.6 GPa for the TiN layer on both substrates. The cross-sectional structure of the coatings was virtually porousless, showing good adhesion between the individual layers and the substrate, being characteristic of diffusionhardened coatings. The wear resistance of the coated 9KhS steel was 6.9 times higher than that of the uncoated steel in dry sliding friction conditions. The coated 9KhS steel showed an extreme dependence of the wear on the sliding velocity. Mechanically fastened indexable hardmetal cutting tools with coatings demonstrated 8.3 times higher resistance than uncoated tools tested by 40Kh13 steel cutting. The coatings developed can substantially increase the performance of 9KhS steel and VK8 hardmetal tools.