THE INFLUENCE OF GRADIENT SINX IBAD COATING ON CORROSION-RESISTANCE OF ALLOY-STEELS IN OXIDIZING AND SULFIDIZING-OXIDIZING ATMOSPHERE AT HIGH-TEMPERATURE

SiNx IBAD coatings were applied to low-alloy steel (0.4 mu m thick) an d to high-alloy steels AISI 310 and 321 (0.8 mu m) at 90 keV energy ni trogen ions. The samples were subjected to a high temperature corrosio n test for 2000 h; low-alloy steel in air and high-alloy steels in sul phidizing-oxidizing atmosphere at temperatures 500-700 degrees C. In b oth gaseous environments the application of SiNx increased the corrosi on resistance of the tested steels. The protective function of SiNx co ating consists of its barrier effect and in some cases it supports the formation of a compact protective SiO2 layer. (C) 1998 Elsevier Scien ce S.A.