Effect of a surface treatment consisting of electron beam remelting and gas nitriding on the corrosion resistance of cast iron

Abstract

AbstractCommercially available gray‐solidified cast iron exhibits reduced load‐carrying capacity under locally concentrated pressure with simultaneous sliding stress. Electron beam remelting dissolves the graphite near the surface, and the surface layer solidifies according to the metastable system. During subsequent gas nitriding, a dense compound layer forms on this white‐solidified, hard surface layer. The phase composition of the compound layer depends not only on the gas nitriding conditions, but also on the chemical composition of the cast iron. The effect of the individual processes of remelting and gas nitriding and their combination on the corrosion behavior of one ferritic and one pearlitic cast iron with different copper contents is investigated using potentiodynamic polarization measurements in 5% sodium chloride solution at room temperature. The remelted and nitrided surface layers exhibit the highest corrosion resistance. The proportion of iron carbonitrides γ' and ε contained in the compound layer influences the corrosion behavior.