National University of Science and Technology “MISiS” (Moscow, Russia):

Ten Е. В., Dr. Eng., Prof., e-mail: edis_ten@mail.ru
Kol O. A., Senior Lecturer

The surface carbonizing of castings from steel 10Cr18Ni9L during producing in the molds from sand-resin mixtures give rise to decrease of their corrosion resistance. The method of applying the protection coatings on the mold and core surface was used for prevention of surface carbonizing of castings. The efficiency of protection action of the passive (glazing) and active aluminophosphate (AF) and aluminochromphosphate (ACrF) coatings has been examined. All these coatings restrict effectively the surface carbonizing of castings, and the glazing coating has the protection action at the same time owing to forming of the dense low gas-permeable layer on the mold and core surface during glazing melting. And the phosphate (AF and ACrF) coatings not only create the low gas-permeable ceramic layer, but also generate the oxidizing gas atmosphere on the casting and mold contact interface due to phosphates decomposition. Therefore the phosphate coatings restrict the surface carbonizing of steel castings more effectively. It was established that the linear relationship between carbon content in the external layer of castings and the factor of carbonizing ability of gas atmosphere, that has been revealed for the castings without protective coatings, is also valid for the same castings with protective coatings.

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