METHOD OF CALORIZING OF ARTICLES FROM STEELS AND ALLOYS IN CIRCULATING GAS MEDIUM Russian patent published in 1998 - IPC

FIELD: thermochemical treatment of articles from steels and alloys in circulating gas medium; applicable in aerospace technology, manufacture of power plant machinery. SUBSTANCE: method includes heating of articles in vacuum up to temperature of diffusion saturation and simultaneous vacuum drying of halides at temperature below their evaporation, supply of halides to working surface of plant in gaseous state and subsequent holding of articles in circulating gaseous medium at pressure of 5-30000 Pa. Halide salts are dried in vacuum at temperature of 333-383 K during the entire stage of article heating at pressure corresponding to pressure in the plant working space at this stage of 1-20 Pa, and their supply to plant working space to be begun at temperature 10-100 K below the holding temperature and maintained during the entire holding stage. Halides of diffusing elements may be used in form of aluminum chloride AlClAlCl₃ with consumption of 0.5-1.5 g per liter of working chamber volume. EFFECT: higher quality of diffusion coatings, speed of their formation, reduced consumption of initial materials and improved ecology due to sharp reduction of harmful effluents to atmosphere. 4 cl, 1 dwg, 1 tbl