STABILITY OF CHROMIUM CARBIDE IN HEAT-RESISTANT CR3C2-(NI-CR-SI-B) COATINGS

Results of a study of Cr3C2-(Ni-Cr-Si-B) coating applied on steel by a powder-sintering method, are presented. The initial chromium carbide is shown to form complex chromium-based borides (Cr, Ni, Fe)(n)B-m dur ing the process. Chromium carbide (25 wt % Cr3C2) added to the source- mixture drastically promotes dissolution of the substrate in the melt and results in an increase of iron content in the coatings from 3 to 4 0 wt % Fe. Nevertheless, atmospheric heat-resistance (850 degrees C, 3 30 h) of the samples increases, and the oxidation rate constant decrea ses from 6.0 x 10(-4) to 1.6 x 10(-4) g(2)/(m(4)s). Weight gain of the samples during the test follows the parabolic law.