The effect of plasma nitriding on the synergism between wear and corrosion of SAF 2205 duplex stainless steel

Abstract

Purpose - his study aims to assess the performance of SAF 2205 duplex stainless steel against pure wear, tribo-corrosion, corrosion and the synergism between wear and corrosion. The effect of plasma nitriding conducted at low temperature (380°C) on SAF 2205 steel was analyzed. Design/methodology/approach - Three systems were used for assessing the synergism between wear and corrosion: tribo-corrosion - wear tests conducted using the micro-scale abrasion test, performed under a slurry of alumina particles containing 3.5% NaCl; pure wear - tests conducted using the previous system but isolated in a glovebox with a 99% N2 atmosphere; and cyclic polarization under 3.5% NaCl solution. A hard nitrided layer of 3 mm thickness was characterized using X-ray diffraction, presenting expanded austenite. Findings - The wear mode after micro-scale abrasion tests changed in the absence of an oxygen atmosphere. During pure wear, a mixed mode was identified (rolling 1 grooving), with the grooving mode more intense for the untreated steel. For tribo-corrosion tests, only rolling wear was identified. For all cases, the nitrided samples presented less wear. The corrosion results indicated a higher repassivation potential for the nitrided condition. Practical implications - The synergism was more positive for the nitrided sample than for the untreated one, which can be considered for surface treatments of duplex stainless steels in practical applications. Originality/value - A detailed description of wear mechanisms showed a significant change in the presence of oxygen atmosphere, a new approach for isolating pure wear.