Nitrogen Modification and Corrosion Analysis of High-Chromium White Iron as Deposited via Welding

High-chromium white iron (HCWI) alloys are often used in industries such as mining which require a high wear resistance. Whilst nitrogen is known as a good austenitic stabiliser, the effects of nitrogen on corrosion properties for welded HCWI have not been studied. Chromium hardfacing alloys were deposited via gas metal arc welding using nitrogen as a shielding gas at flow rates of 5 L/min, 10 L/min, and 15 L/min. The corrosion behaviour of these modified alloys was studied using electrochemical techniques such as potentiodynamic measurements and electrochemical impedance spectroscopy. Higher gas flow rates were found to increase the volume fraction of the eutectic austenite while reducing the amounts of eutectic carbides. Nitrogen did not transform the M7C3 (M = Cr, Fe) carbides into any other form of carbides. The sample without nitrogen as a shielding gas was found to display the worst corrosion resistance after electrochemical testing, such as corrosion resistance parameters in EIS tests. Higher nitrogen shielding gas flow rates were found to produce higher levels of corrosion resistance; this was especially true for the 15 L/min sample with a corrosion resistance parameter to EIS that was more than double that of the sample without nitrogen shielding gas (e.g., 4700 vs. 2325 Ω·cm2 respectively).