Metallurgical, Fatigue and Pitting Corrosion Behavior of AISI 316 Joints Welded with Nb-Based Stabilized Steel Filler
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ASS (austenitic stainless steels) are used extensively for a wide variety of service applications in industries such as nuclear, chemical, petrochemical, dairy, fertilizer and so on where conditions imposed on fabrications/ structures are usually harsh.[1] Welded fabrications are usually expected to be sound, reliable as well as dependable to avoid premature failures. Corrosion, as well as the fatigue performance of AISI 316 stainless steel welded fabrications, degrades under certain conditions.[2,3] The primary reason reported for their degradation is the formation of deleterious phases such as second-phase particles owing to the high temperature as well as prolonged exposure. The usage of these steels for critical applications has led to several studies in the recent past as an evaluation of aspects such as corrosion
DIKSHANT MALHOTRA and A.S. SHAHI are with the Department of Mechanical Engineering, Sant Longowal Institute of Engineering & Technology (Deemed to be University), Longowal, Sangrur, Punjab 148106, India. Contact e-mail: [email protected], [email protected] Manuscript submitted August 23, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
and fatigue becomes the key to their service performance. For instance, Caines et al.[4] found pitting corrosion to be the main contributor to corrosion under insulation in marine environments and also identified pit depth as the key parameter to describe the pit stability. ASTM standard F2129 proposes pitting potential (Epit) to be an indicator of pitting corrosion resistance where the breakdown of the passive film and stable pit nucleation occur. The study of pitting corrosion of 304L and 316L austenitic stainless steels in chloride environments by Ghahari et al.[5] extracted several pit propagation parameters such as pit depth, pit width, pit stability product, etc., through synchrotron X-ray radiography studies. The results showed an increase in pit depth with time due to dissolution kinetics inside the pit, whereas lateral development of pits was affected by solution conductivity. The evaluation of corrosion resistance ability of different stainless steels used in vehicle exhaust components and systems considered maximum pit depth and breakdown pitting potential to be the important parameters for material ranking for pitting corrosion susceptibility.[6] Studies on the influence of alloying additions on pitting corrosion are also reported. Higher nickel content in the filler wire than in the base metal improves the pitting corrosion resistance of the weld metal.[7] The effect of niobium addition on the pitting corrosion resistance of Fe-25Ni-15Cr stainless steels was investigated, and results showed the beneficial role of niobium in the formation of denser
protective passive films on these steels in the chloride environments.[8] The influence of nitrogen on the pitting corrosion performance of ASS welds as reported by Jegdic et al.[9] showed that although nitrogen addition improved the pitting potential of welds, detrimental nitrides formed near the HAZ (heat-affec
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