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Journal ArticleDOI

Effect of weld metal chemistry and heat input on the structure and properties of duplex stainless steel welds

TL;DR: In this article, a low heat input process viz., EBW and another commonly employed process, gas tungsten-arc welding have been employed for welding of duplex stainless steels with and without nickel enhancement.
Abstract: The excellent combination of strength and corrosion resistance in duplex stainless steels (DSS) is due to their strict composition control and microstructural balance. The ferrite–austenite ratio is often upset in DSS weld metals owing to the rapid cooling rates associated with welding. To achieve the desired ferrite–austenite balance and hence properties, either the weld metal composition and/or the heat input is controlled. In the current work, a low heat input process viz., EBW and another commonly employed process, gas tungsten-arc welding have been employed for welding of DSS with and without nickel enhancement. Results show that (i) chemical composition has got a greater influence on the ferrite–austenite ratio than the cooling rate, (ii) and even EBW which is considered an immature process in welding of DSS, can be employed provided means of filler addition could be devised.
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Journal ArticleDOI
01 Mar 2018
TL;DR: In this article, an attempt has been made to weld 2205 duplex stainless steel of 6mm thick plate using conventional gas tungsten arc welding (GTAW) and activated GTLW process using silica powder as activated flux.
Abstract: An attempt has been made to weld 2205 Duplex stainless steel of 6mm thick plate using conventional gas tungsten arc welding (GTAW) and activated gas tungsten arc welding (A- GTAW) process using silica powder as activated flux. Present work is aimed at studying the effect of welding process on depth of penetration, width of weld zone of 2205 duplex stainless steel. It also aims to observe the microstructural changes and its effect on mechanical properties and pitting corrosion resistance of 2205 duplex stainless steel welds. Metallography is done to observe the microstructural changes of the welds using image analyzer attached to the optical microscopy. Hardness studies, tensile and ductility bend tests were evaluated for mechanical properties. Potentio-dynamic polarization studies were carried out using a basic GillAC electro-chemical system in 3.5% NaCl solution to observe the pitting corrosion behaviour. Results of the present investigation established that increased depth of penetration and reduction of weld width in a single pass by activated GTAW with the application of SiO2 flux was observed when compared with conventional GTAW process. It may be attributed to the arc constriction effect. Microstructure of the weld zones for both the welds is observed to be having combination of austenite and delta ferrite. Grain boundary austenite (GBA) with Widmanstatten-type austenite (WA) of plate-like feature was nucleated from the grain boundaries in the weld zone of A-GTAW process. Mechanical properties are relatively low in activated GTAW process and are attributed to changes in microstructural morphology of austenite. Improved pitting corrosion resistance was observed for the welds made with A-GTAW process.

5 citations

Journal ArticleDOI
TL;DR: In this article, the effect of simulated welding thermal cycle on the microstructure and impact toughness of heat affected zone (HAZ) in 2205 duplex stainless steel was investigated by optical microscopy, scanning electron microscopy (SEM) and transmission electron microscope and room temperature impact test.
Abstract: The effect of simulated welding thermal cycle on the microstructure and impact toughness of heat affected zone (HAZ) in 2205 duplex stainless steel was investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and room temperature impact test. The results show that the morphology and volume fraction of austenite change greatly with heat input. The amount of residual austenite and grain boundary austenite (GBA) decreases while Widmanstatten austenite (WA) laths and intergranular austenite increase with the increase in heat input. Only the fine equiaxed austenite exists in the HAZ when the heat input is increased up to 61.8 kJ/cm. WA laths nucleate initially either at the ferrite and GBA phase boundaries or directly in ferrite grains and begin to decompose into diamond-shaped austenite with the heat input larger than 25.2 kJ/cm. The impact toughness shows a non-monotonic variation, which is related to the increase in austenite fraction and the formation and the decomposition of WA laths.

5 citations

Journal ArticleDOI
TL;DR: In this paper, a hyper-duplex stainless steel with 0.47% Niobium was casted using induction melting furnace and then heat-treated under two different heat treatment temperatures of 1160°C and 900°C.
Abstract: Niobium addition to base alloy significantly reduces the formation of deleterious phases, in particular, sigma phase when the material is sensitized at 900 °C. In this paper, hyper-duplex stainless steel with 0.47% of Niobium (Nb + CD3MWN - 7A) was casted using induction melting furnace and then heat-treated under two different heat treatment temperatures of 1160 °C and 900 °C to explore the properties such as microstructure and hardness for further study. The erosion test was carried out in air-jet erosion tester at room temperature with different erodent velocities. The study was done with a constant impact angle of 45°. Microstructure analysis was carried on two different heat-treated samples as well as on eroded samples using scanning electron microscope coupled with energy-dispersive analysis spectroscopy to confirm the presence Niobium carbide precipitation in sensitized sample at grain boundaries. Erosion test results showed that erosion rate is lower in sensitized sample when compared to solutionized sample because of their higher hardness in sensitized sample.

5 citations

Journal ArticleDOI
01 Apr 2019-Silicon
TL;DR: In this article, a three-level Central Composite Design (CCD) based non-linear model was used to establish input-output relationship based on the collected experimental inputoutput data.
Abstract: The present work attempts to study the parameters influencing wear, namely, applied load, heat-treated temperature, sliding velocity, and sliding distance using statistical Design of Experiments (DOE) and Response Surface Methodology (RSM). The wear behavior of super duplex stainless steel was evaluated under dry sliding conditions. A three-level Central Composite Design (CCD) based non-linear model was used to establish input-output relationship based on the collected experimental input-output data. Surface plots were used to study the influence of applied load, heat-treated temperature, sliding distance, and sliding velocity on the wear rate of super duplex stainless steel. The wear rate was observed to vary nearly non-linearly with applied load and linearly with the rest of the input parameters. Analysis of Variance (ANOVA) was conducted to test the statistical adequacy of the non-linear model developed. Applied load and heat-treated temperature were found to have a more positive contribution towards the wear rate than other parameters. Although the sliding velocity had a negligible effect, its interaction with applied load and heat-treated temperature had a significant impact on the wear rate. The regression equation developed was tested for its prediction precision with the help of 20 test cases. Further, attempts were also made to determine the optimum combination of input parameters that minimize the wear rate using the Desirability Function Approach (DFA). The objective of minimizing the wear rate was met with the highest desirability value of 1. Confirmation experiments were conducted for the determined optimal set of input parameters of 20 test cases resulting in an average absolute percent deviation in prediction of 6.34% and 5.58%.

5 citations


Cites result from "Effect of weld metal chemistry and ..."

  • ...The choice of heat treatment cycles was in accordance with the detailed literature survey [9, 13, 21]....

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References
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Book
01 Jan 1997
TL;DR: In this paper, the authors present a non-destructive testing of welds for service experience, based on the application of service experience in metallurgy and metallurgical applications.
Abstract: Developments, grades and specifications Alloy design Microstructure Forming and machining Physical and mechanical properties Corrosion Stress corrosion cracking Welding metallurgy Welding processes Weld properties Non-destructive testing of welds Applications Service experience.

449 citations