Physical and Chemical Conditions of Formation, Structure and Properties of Multicomponent Coatings by the Titanium, Aluminium, Chromium with TiN Barrier Layer on 9HS Steel

Background. Methods of alloy treatment with chloride phases have become widespread in chemical and thermal treatment. Chloride gas environments have been successfully used for titanizing, chromizing, aluminizing of metals and alloys. Diffusion saturation of the gas phase has got significant advantages over other methods: high-quality coatings, flexible process control, high performance and efficiency. Study of factors that affect the state of gas environment and directly the phase and chemical composition, structure and properties of coatings is of the great interest. Objective. The aim of the work is to establish comprehensive thermodynamic conditions of 9HS steel saturation with the layer of nitride TiN by titanium, chromium and aluminum, establishment of the phase composition, structure and properties of coatings and rendering based on the studies of practical recommendations on technical parameters of saturation. Methods. Multiple saturation of 9HS tool steel was realized in a powder mixture of metals Ti, Al, Cr, NH4Cl activator and Al2O3 inert additives. Counterpoise was estimated in the temperature range 300?1500 K for systems involving saturating metals (Ti, Al, Cr), Cl, C, N, O, elements of base (Fe). Samples with coatings were studied by modern me??thods of physical material science. Results. Investigation of gas and condensed state of system Ti?Al?Cr?C?N with different composition in the temperature range 300?1500 K showed a significant probability of 9HS steel saturation by titanium and aluminum, lower by chromium, and formation on surface phases of TiC, TiN. TiN barrier layer inhibits at CTT the division of chromium and aluminum in the outer zones of coatings and promotes on surface layer Cr7C3. Conclusions. Coatings with microhardness of separate components are formed on 9HS steel with TiN layer after titanium-aluminium chromizing: TiC ? 35.6; TiN ? 24.5; Cr7C3 ? 18.5 GPa. Durability of titanium-aluminium chromi-zing 9HS steel with TiN barrier layer in terms of friction without lubrication is in 13.6 times higher than in the same steel after quenching and low tempering.