Abstract
Surface modification engineering is a group of processes introducing a foreign material onto the surface of interest. Engineering components with hard coatings usually exhibit improved service behavior and increased lifetime. In this study, hard chromizing process and cathodic arc deposition technique have been employed to deposit chromium containing surface modification layer on ferrous alloys. The thickness of the chromized layer versus the coating time obeys the parabolic law. The primary phase on the chromized surface is (Cr,Fe)2N1-x and the rest is (Cr,Fe)23C6, while (Cr,Fe)7C3 phase is major one in the interior of chromized layer. The chromizing layers and cathodic arc deposited CrN layer on austenitic Fe-Mn-Al alloy and carbon steels exhibit very high hardness, sufficient adhesion strength quality and good wear resistance. A sufficient improvement to the corrosion resistance in 3.5wt% NaCl aqueous solution was obtained by the chromizing process and cathodic arc deposited CrN film on austenitic Fe-Mn-Al alloy. The chromized austenitic Fe-Mn-Al alloy exhibited very good hot corrosion resistance in the 90% Na2SO4 and 10% NaCl mixed molten salt at 877 oC for 48 hours. The diffusivities of chromium in the (Cr,Fe)7C3 phase for AISI 1045 and 1095 steels chromized at 950oC for 4 and 9 hrs were calculated based on the Fick’s second law and the moving boundary model. The mechanisms of chromizing process were discussed and proposed. It was concluded that mechanical properties and corrosion resistance of the chromium containing surface layers modified by chromizing and cathodic arc plasma deposition are superior to ferrous alloys.