Improving the erosion-corrosion resistance of AISI 316 austenitic stainless steel by low-temperature plasma surface alloying with N and C

The erosion-corrosion behaviour of low-temperature plasma surface alloyed AISI 316 austenitic stainless steel has been compared with untreated material using a newly developed slurry pot erosion-corrosion apparatus containing a slurry comprising 20 wt.% silica sand and 3.5%NaCl at 40 degrees C. The total erosion-corrosion wastage, the mechanical erosion under cathodic protection and the electrochemical corrosion were measured directly. Based on the data obtained the synergistic effect of erosion and corrosion was calculated. Post-test examination was conducted to identify material degradation mechanisms involved. It has been shown that the erosion-corrosion resistance of AISI 316 austenitic stainless steel can be effectively improved by low-temperature plasma alloying with carbon (carburising) and nitrogen (nitriding) by 50% and 70%, respectively. The degradation process of the untreated steel is dominated by erosion whilst that of the low-temperature plasma carburised material is by an erosion-corrosion mechanism and that of low-temperature plasma nitrided AISI 316 mainly by corrosion-erosion. The synergy between erosion and corrosion can be ranked from low to high in the order: untreated (1.7%), plasma carburised (30.0%) and plasma nitrided (69.4%) material. (c) 2006 Elsevier B.V All rights reserved.