Producing Multilayer Coatings from the Gas Phase with the Participation of TiC and TiN Compounds on the Hard Alloy VK8

The phase and chemical compositions, structure, thickness, microhardness, operational properties of the VK8 hard alloy with multilayer coatings produced by the methods of diffusion titanizing, titanoalitizing, nitriding, nitridotitanoalitizing have been studied. The last two methods combine the nitriding at a temperature of 540°C for 20 h followed by titanizing or titanonitriding. It has been established that the composition of TiN, TiC layers formed at the nitrotitanoalitizing fulfils barrier functions at the chemically thermal treatment. The produced barrier fully slows down the penetration of aluminium and oxygen into the basis and promotes the surface of the formation on the AlCoTi₂ compound, the microhardness of which due to dissolution of nitrogen, reaches 12.6 GPa. The maximum microhardness of the TiC layers is 31.0–35.5 GPa and of TiN layers 20–21.5 GPa. The stability of the nitrotitanoalitized polyhedral disposable carbide plates VK8 during cutting U8A steel grew by 10.5 times as compared with the initial stability.