METHOD FOR SINGLE-STEP DIFFUSION COBALT ALITIZING OF PARTS FROM HEAT-RESISTANT ALLOYS Russian patent published in 2019 - IPC C23C10/52 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular to chemical-thermal treatment, and can be used for protection of parts of gas turbine engine with inner cavities from salt corrosion. Method of single-step diffusion cobalt alitizing of parts from heat-resistant alloys involves stepwise heating of said parts to diffusion saturation temperature with holding at each heating stage in a circulating halide medium formed at contact of initial gas medium with sources of diffusing elements. Initial gaseous medium is generated by evaporating ammonium chloride and iodide while heating, ferrous aluminum and cobalt are used as diffusing elements, diffusion saturation is carried out in a mixture containing components at the following ratio, wt%: ferroaluminium 40–80, cobalt 9.6–19.2, nickel-yttrium 2.4–4.8, ammonium chloride 1.6–3.2, ammonium iodide 0.5–1.0 and aluminum oxide – the rest. At each heating stage diffusion exposure is carried out for 4–6 hours with uniform circulation of halogenide medium, wherein at the first heating stage the diffusion holding is carried out at temperature of 1,000±10 °C and pressure of 0.03–0.05 MPa, and at second step, temperature is increased to 1,050±10 °C, and pressure – up to 0.05–0.07 MPa.

EFFECT: broader possibilities of using cobalt alitizing and high efficiency thereof owing to stepwise variation of pressure during saturation, which provides a shift of the point of thermodynamic equilibrium of chemical saturation reactions towards cobalt Co or aluminum Al with simultaneous cobalt alitizing.

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