STRUCTURE FORMATION AND PROPERTIES OF Cr₃C₂ – NiCr CARBIDE COATINGS APPLIED BY PLASMA SPRAYING ONTO THE SURFACE OF DUCTILE IRON CASTINGS

The study presents the results of structure examinations and mechanical tests carried out on coatings based on Cr₃Cr2-NiCr chromium carbide, applied onto the surface of ductile iron castings. The chromium carbide-based coatings were applied onto the cast iron substrate by the technique of plasma spraying. Then the coatings were subjected to a remelting treatment. The chemical composition and morphology of the surface layer were examined by optical microscopy and by SEM with EDS analysis. The distribution of microhardness values on the specimen cross-section was determined and cyclic fatigue testing was carried out. Basing on the results of the tests it has been concluded that remelting of Cr₃Cr₂-NiCr coating improves its adherence to the substrate as well as the structure and mechanical properties under the conditions of variable loading. The investigations mainly aimed at the development of technical guidelines for manufacture of protective coatings on ductile iron castings operating under the conditions of heavy dust and cyclic loading.

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