Faculty Publications
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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 Weldments of AISI grade 316 stainless steel, having a ferrite content of 4-6% and a variety of nitrogen concentrations were prepared using a modified element implant technique. Charpy impact specimens prepared from these weldments were subjected to a variety of aging treatments. Impact toughness decreases with aging time at all aging temperatures. Nitrogen is found to be beneficial to toughness. An empirical relation connecting the aging temperature, aging time and nitrogen content with toughness has been developed which can be used to estimate the time for embrittlement.(Indian Academy of Sciences, Estimation of embrittlement during aging of AISI 316 stainless steel TIG welds) Nayak, J.; Udupa, K.R.; Hebbar, K.R.; Nayak, H.V.S.2004Item Simulated weldments of AISI grade 304 stainless steel having a ferrite content of 4-6% with three levels of nitrogen (0.03, 0.08, and 0.11 wt-%) were prepared using a modified elemental implant technique. From these weldments, subsize Charpy impact specimens were prepared and subjected to aging treatment at different temperatures, 623-748 K, and for different times, 1000-5000 h. Impact toughness curves for these aged samples were generated by testing at various temperatures from 77 K to 300 K. From the impact curves the upper shelf energy (USE) and lower shelf energy (LSE) were determined. It was observed that both USE and LSE decreased with aging time at all temperatures. Nitrogen seems to offer a beneficial effect as far as impact toughness is concerned, as both USE and LSE values increased with increasing nitrogen content. The worst aging conditions were identified as 748 K, 2000 h at the lowest nitrogen level of 0.03 wt-%. An empirical relation connecting the aging temperature, aging time, and nitrogen content to the LSE was developed, which can be used to predict the time for embrittlement at a given nitrogen level and aging temperature. © 2005 Institute of Materials, Minerals and Mining.(Prediction of embrittlement during aging of nuclear grade AISI 304 stainless steel TIG welds) Nayak, J.; Udupa, K.R.; Hebbar, K.R.; Nayak, H.V.S.2005Item 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.