Faculty Publications
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Item Effect of reversion heat treatment on the mechanical properties of thermally embrittled UNS S32760 duplex stainless steel(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Natesh, M.; Shamanth, V.; Ravishankar, K.S.Duplex Stainless Steels contain very high chromium contents (19-30% by weight) and exhibit excellent corrosion resistance and extremely good mechanical properties. Embrittlement of duplex stainless steels due to precipitation of αʹ upon prolonged exposure in the temperature range of 280°C to 500°C has been a serious limiting factor for its long term usage in the nuclear industry, where the operating temperatures of cooling pipes is around 300°C. In this investigation, the effect of reversion heat treatment on the mechanical properties of a thermally embrittled duplex stainless steel has been studied. The specimens were solutionized, aged and then reversion treated for varying periods. The aged specimens showed significant increase in tensile strength and decrease in ductility in comparison to the ones in solutionized condition. The specimens which were reversion treated showed marginal decrease in tensile strength and significant increase in ductility after 5 minutes of holding time. As the holding time increased, the tensile strength rapidly decreased and ductility increased initially up to 30 minutes of reversion, after which there was no significant change in strength and ductility. © (2015) Trans Tech Publications, Switzerland.Item Effect of Heat Treatment on the High Cycle Fatigue Behaviour of S2205 Duplex Stainless Steels(Elsevier Ltd, 2017) Shamanth, V.; Kumar, P.; Ravishankar, K.S.This paper deals with the effect of heat treatment on the high cycle fatigue behavior of duplex stainless steels. In this investigation the specimens were annealed, aged, reversion heat treated and re-aged for varying periods. The results obtained showed that the microstructure plays an important role in the change in fatigue lives. The fatigue resistance was high in the aged and re-aged heat treated condition because of the presence of alpha, alpha prime and some molybdenum rich chromium nitride precipitates in their ferrite matrix. While in the annealed and reversion heat treated condition the samples were free from the precipitates and also there was no much difference in the hardness values of austenite and ferrite phases, hence there was a significant change in their fatigue lives when compared to that of the embrittled samples. © 2017 Elsevier Ltd.Item Dissolution of alpha-prime precipitates in thermally embrittled S2205-duplex steels during reversion-heat treatment(Elsevier, 2015) Shamanth, V.; Ravishankar, K.S.Duplex stainless steels offer an attractive combination of strength, corrosion resistance and cost. In annealed condition duplex steels will be in thermodynamically metastable condition but when they are subjected to intermediate homologous temperature of ~475. °C and below significant embrittlement occurs, which is one of the key material degradation properties that limits its upper service temperature in many applications. Hence the present study is aimed to study the effect of reversion heat treatment and its time on mechanical properties of the thermally embrittled steel. The results showed that 60. min reversion heat treated samples were able to recover the mechanical properties which were very close to annealed properties because when the embrittled samples were reversion heat treated at an elevated temperature of 550. °C which is above the (?. +. ?') miscibility gap, the ferritic phase was homogenized again. In other words, Fe-rich ? and Cr-rich ?' prime precipitates which were formed during ageing become thermodynamically unstable and dissolve inside the ferritic phase. © 2015 The Authors.