METHOD TO SILICONIZE PRECISION PARTS OF ALLOYS BASE ON MOLYBDENUM AND TUNGSTEN Russian patent published in 1994 - IPC

FIELD: metallurgy. SUBSTANCE: parts are placed under filling in a container. The filling has silicon, aluminium oxide and 2 to 5 per cent of silicon fluoride sodium. Siliconizing is performed at 950 - 990 C under 10^-3-10^-4 mm Hg vacuum during 2 to 3.5 h. Then the parts are additionally annealed under 10^-4-10^-5 mm Hg vacuum at 1320 to 1370 C temperature during 1 to 1.5 h. Vacuum furnace with stainless steel retort is used for treatment articles. Liquid carbonizer, for example, monoethanol amine, is fed by dropping into the vacuum retort during heating and holding. The same rate of 200 to 250 C/h is used for heating and cooling during the siliconizing. Vacuum annealing is performed with 120 to 250 C/min cooling rate down to 560 to 600 C temperature. Double interim cooling down to 450 to 500 C during 2 to 5 min is used in the course of part vacuum annealing. EFFECT: improved quality of part surface. 9 cl, 1 tbl