This article addresses the weldability, microstructure and mechanical properties of the multi-pass pulsed current gas tungsten arc welding (PCGTAW) of Inconel X750. PCGTA welding was accomplished using two fillers, namely ERNiCrCoMo-1 and ERNiCrMo-3. Interfacial and weld microstructures were characterized using optical and scanning electron microscopy techniques. Migrated grain boundaries (MGBs) were dominating at the fusion zone of both the weldments. Post-weld heat treatment (PWHT) was carried out on the weldments at 705 °C for 22 h and air cooled to assess the microstructural changes and its impact on the mechanical properties. Tensile studies corroborated that all the tensile failures occurred at the fusion zone for both the as-welded and the PWHT samples. Fascinatingly, the weldments after subjected to PWHT resulted in improved tensile strength and the joint efficiency of ERNiCrCoMo-1 and ERNiCrMo-3 weldments improved to 82.2% and 72.5%. However, ERNiCrMo-3 weldments exhibited better impact toughness than ERNiCrCoMo-1 weldments. The structure-property relationships of the weldments are also discussed in the present investigation. © 2015 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.

Devendranath Ramkumar K

Department of Manufacturing Engineering

School of Mechanical Engineering

Vellore Campus

Arivazhagan N

Krishnan S.R

Ramanand R

Logesh S

Satyandas T

Ameer A

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Journal of Manufacturing Processes

In the present study, an attempt has been made to join 5-mm-thick plates of Inconel X750 using autogenous tungsten inert gas (TIG) welds without and with the use of activated compound flux mixture that contains 50%SiO2 + 25%TiO2 + 25%MoO3. The welded coupons were subjected to direct aging at 705 °C for 22 h. The interfacial and fusion zone microstructures were compared for both as-welded and direct aged coupons. It is assimilated that the fusion zone is enriched with Cr23C6 at the grain boundaries along with polygonal γ′ precipitates upon direct aging. Tensile studies show the fact that the fractures occur at the fusion zones of the joints both in as-welded and direct aged conditions. The joint strengths of the autogenous TIG weldments without and with flux addition were reported as 946 and 1162 MPa in the directly aged conditions, respectively. Studies also attested that there is an increase in the tensile strength by 54% of the autogenous weldment employing compound flux upon direct aging compared to as-welded conditions. Further, the fusion zones of both the conditions and the parent metal were subjected to 3.5%NaCl environment. Potentiodynamic polarization plots clearly envisaged that the fusion zone in the directly aged condition exhibits better corrosion resistance than that of the as-welded ones. © 2017, Springer Science+Business Media, LLC and ASM International.

Metallography, Microstructure, and Analysis

Characterization of Microstructure, Tensile Strength and Corrosion Behavior of Autogenous GTA Welds of Inconel X750 With and Without Activated Compound Flux

This study addresses the effect of post weld heat treatment on the fusion zone microstructure and the mechanical properties of activated flux tungsten inert gas (A-TIG) weldments of Inconel X750. In this study, a compound flux of 50% SiO2+50% MoO3 was used for A-TIG welding of the samples. Comparative studies on the microstructure and mechanical properties have been made on the weldments both in the as-welded and post weld heat treated conditions. Direct ageing post weld heat treatment (PWHT) was carried out at 705 °C for 22 h on the A-TIG weldment to assess the structure-property relationships. It was inferred that direct ageing post weld heat treatment resulted in better tensile strength (1142 MPa) compared to the as-welded coupons (736 MPa). The joint efficiencies of the as-welded and post weld heat treated conditions were found to be 60.7% and 94.07% respectively. The impact toughness of the as-welded coupons were found to be greater than the post weld heat treated samples; however the impact toughness of the welds are greater than the parent metal employed in both the cases. This study also attested the detailed structure-property relationships of A-TIG weldments using the combined techniques of optical and scanning electron microscopy, Electron Dispersive X-ray Analysis (EDAX) techniques. © 2016 Elsevier B.V.

Materials Science and Engineering: A

Effect of post weld heat treatment on the microstructure and tensile properties of activated flux TIG welds of Inconel X750

This paper investigates the weldability, microstructure and mechanical properties of 5 mm thick Inconel 718 plates obtained by pulsed current gas tungsten arc welding (PCGTAW) using ERNiCu-7, ERNiCrCoMo-1 and ERNiCr-3 fillers. Post weld heat treatment (PWHT) was also carried out at 720 °C/8 h/furnace cooling followed by 620 °C/8 h/air cooling on the weldments. A comparative evaluation based on the microstructure features and mechanical properties of both the as-welded and aged samples were studied. Further this study addressed the combined effect of filler wires and post weld heat treatment on the metallurgical and mechanical properties of the weldments. The studies showed the improvement in tensile strength and drop in impact toughness for all the weldments after direct ageing heat treatment. © 2015 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.

Effect of filler wires and direct ageing on the microstructure and mechanical properties in the multi-pass welding of Inconel 718

This investigation has been performed to characterize the microstructure and mechanical properties of the GTA and PCGTA welded dissimilar combinations of Inconel 625 superalloy and AISI 304 austenitic stainless steel. These welds were obtained by employing ERNiCrMo-3 filler metal. The weldments were characterized by the combined techniques of optical microscopy and SEM/EDAX analysis. Hardness and tensile studies were conducted to assess the mechanical properties of the weldments. Tensile studies showed that the fracture had occurred at the parent metal of AISI 304 side in both the cases.

Fulltext

ISIJ International

Characterization of Microstructure and Mechanical Properties of Inconel 625 and AISI 304 Dissimilar Weldments

Effects of switching over from gas tungsten arc welding (GTAW) to pulsed current gas tungsten arc welding (PCGTAW) on the quality of joints produced in Hastelloy C-276 material were investigated. Welding was carried out both by autogenous mode and using ERNiCrMo-3 filler wire. Microstructures of weld joints produced with and without current pulsing were studied using optical and scanning electron microscopy. Microsegregation occurring in GTAW and PCGTAW joints was investigated using energy dispersive X-ray spectroscopy (EDS). Strength and ductility of weld joints produced with and without pulsing were evaluated. The results show that pulsing results in refined microstructure, reduced microsegregation and improved strength of weld joints. Secondary phase(s) noticed in GTA weldments were found to be absent in PCGTA weldments. Autogenous PCGTA weldments were found to be the best in terms of: (i) freedom from microsegregation, (ii) strength and (iii) freedom from unwanted secondary phases. © 2014 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.

Journal	Data powered by TypesetJournal of Manufacturing Processes
Publisher	Data powered by TypesetElsevier BV
ISSN	1526-6125
Open Access	No