Effect of friction stir and activated-GTA welding processes on the 9Cr–1Mo steel to 316LN stainless steel dissimilar weld joints

Sunilkumar, D.; Muthukumaran, S.; Vasudevan, M.; Reddy, Madhusudan G.

doi:10.1080/13621718.2019.1695347

Cited by 17 publications

(6 citation statements)

References 18 publications

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“…Narrow HAZ was formed closer to the SZ and LN-type 316 SS owing to the low thermal conductive property. In an EBSD research, 26 it is revealed that the average distribution density of low angle grain boundary (LAGB) and high angle grain boundary (HAGB) of 316LN BM was ∼9.7% and ∼90.3%.…”

Section: Resultsmentioning

confidence: 99%

Unravelling the microstructure – indentation creep resistance relationships for friction stir welded modified 9Cr-1Mo steel and LN-type 316 stainless-steel dissimilar joints

krishna¹,

Lakshminarayanan²,

Vasantharaja

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part L:

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In this article, the indentation creep characteristics and the microstructures are assessed for the friction stir welded modified 9Cr-1Mo steel and LN-type 316 SS dissimilar joint. Microstructures are characterized for the post-weld heat treated and indentation crept samples at different conditions with optical microscopy, scanning electron microscope and energy dispersive X-ray spectroscopy. Distinct heat-affected zones were revealed with the refined and reformed martensite (α′) and austenite (γ) structures that formed in view of the distinct thermal conductivity property and the differences in lower critical(Ac1) and upper critical(Ac3) transformation temperatures. The size of prior austenite grain sizes was found to be varied significantly at the different regions. Indentation creep data were acquired in distinct weld zones at 873, 898 and 923 K. Zone-wise indentation depth, steady-state creep behaviour (SSCR) and activation energy ( Q) were evaluated and correlated with the microstructures. The formation of small prior austenitic grain (PAG) structures and the grain boundary vacancies has led to maximum creep deformation (86.83%) at the heat affected zone of the modified 9Cr-1Mo steel. Furthermore, the reduction in lath structures and the formation of tiny α′ with soft substructures have lowered the hardness values to around 210 ± 21 HV, which is 20 HV less than the post weld heat treated sample. In the stir zone, the presence of dynamically refined and rich γ along with fine α′ layers has improved the steady-state creep rate of 9.112 E-7, which is less than the modified 9Cr-1Mo steel and the heat affected zone at modified 9Cr-1Mo side. The coarse austenite structures that existed in the LN-type 316 base metal have resisted more creep damage and exhibited high activation energy (i.e. 490 kJ mol−1) than the stir zone and heat affected zone of the LN-type 316 SS.

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Section: Resultsmentioning

confidence: 99%

Unravelling the microstructure – indentation creep resistance relationships for friction stir welded modified 9Cr-1Mo steel and LN-type 316 stainless-steel dissimilar joints

krishna¹,

Lakshminarayanan²,

Vasantharaja

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part L:

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“…Specimens welded by the FSW process have HAZs smaller than the specimens joined by fusion welding. For instance, tungsten arc welding was reported to produce HAZs with great widths due to the relatively high heat input [71,72], which may result in the failure of joints created by fusion welding [73]. Comparatively, FSW generates lower heat in the HAZ.…”

Section: Friction Stir Welding (Fsw) Of Steelsmentioning

confidence: 99%

“…This may negatively affect the mechanical properties of the welded joints due to the inhomogeneous distribution of the chemical composition [77,78]. On the other hand, because of the tempered martensite formation and the refined austenite in the SZ, FSW specimens showed higher tensile strength than the specimens joined by activated-gas tungsten arc welding of 9Cr-1Mo and 316LN stainless steel [72].…”

Section: Friction Stir Welding (Fsw) Of Steelsmentioning

confidence: 99%

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Review on the Solid-State Welding of Steels: Diffusion Bonding and Friction Stir Welding Processes

Khedr

Hamada

Järvenpää

et al. 2022

Metals

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Solid-state welding (SSW) is a relatively new technique, and ongoing research is being performed to fulfill new design demands, deal with contemporary material advancements, and overcome welding defects associated with traditional welding techniques. This work provides an in-depth examination of the advancements in the solid-state welding of steels through diffusion bonding (DB) and friction stir welding (FSW). Considerable attention was given to DB of steel, which overcame the difficulties of segregation, cracking, and distortion stresses that are usually formed in liquid-phase welding techniques. The defects that affected DB included two types: two-dimensional defects of a metallic lattice, i.e., phases and grain boundaries, and three-dimensional defects, i.e., precipitation. FSW, on the other hand, was distinguishable by the use of relatively low heat input when compared to fusion welding processes such as tungsten inert gas (TIG), resulting in the formation of a limited heat-affected zone. Moreover, fine grain structures were formed in the FSW interface because of the stirring tool’s severe plastic deformation, which positively affected the strength, ductility, and toughness of the FSW joints. For instance, higher strength and ductility were reported in joints produced by FSW than in those produced by TIG. Nevertheless, the HAZ width of the specimens welded by FSW was approximately half the value of the HAZ width of the specimens welded by TIG. Some defects associated with FSW related to the diffusion of elements, such as C/Cr atoms, through the weld zone, which affected the local chemical composition due to the formation of rich/depleted regions of the diffused atoms. Moreover, the lack-of-fill defect may exist when inappropriate welding conditions are implemented. On the other hand, the stirring tool was subjected to extensive wear because of the high hardness values, which negatively affected the economical usage of the FSW process. A summary of the results is presented, along with recommendations for future studies aimed at addressing existing difficulties and advancing the solid-state technology for steel.

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“…5 GTA welding being the most suitable and trusted on-site welding process in the fabrication of stainless steel structures. 6 Nevertheless, an important inadequacy of the GTAW process is that the welding is carried out in a single pass and limited to a limited plate thickness. 7 In order to overcome this disadvantage, plates with a thickness higher than 6 mm are usually joined with the use of activating flux of oxides or perform multi-pass welding to attain full depth of penetration.…”

Section: Introductionmentioning

confidence: 99%

Double-sided GTAW of nuclear grade steel: Mechanical and microstructure perspectives

Kumar

Shanmugam

2021

Proceedings of the Institution of Mechanical Engineers, Part E:

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This article investigates the microstructural evolution and mechanical integrity of austenitic stainless steel SS321, a titanium stabilized nuclear grade mainly preferred for severe corrosive environments. The double-sided gas tungsten arc welding (DS-GTAW) technique was utilized to fabricate the butt joint having a plate thickness of 6 mm. A heat input of 1.4058 kJ/mm was used to obtain the maximum depth of penetration (DoP) of 3.3 mm with welding speed 120 mm/min and current 220A. Optical microscopy reveals the microstructure of weldment and base metal (SS321). The DS-GTA weldments were subjected to tensile, bend, impact and microhardness tests and the results are evaluated. The fusion zone consists of columnar, equiaxed dendrites, and intermetallic compounds of Titanium carbide (TiC). From EBSD examination the higher fraction of Low Angle Grain Boundaries is corroborated to the increase in tensile strength and reduction in impact toughness of the weldment. The ferrite measurement reveals the increase in ferrite content in the weldment (6.1 FN) and this attributed to the presence of retained δ-ferrite in comparison to SS321 (1.2 FN). X-Ray Diffraction (XRD) pattern reveals austenite and ferrite peaks are present in the SS321 and weldment. Ductile mode of fracture (using SEM-Scanning electron microscope) was observed in the uni-axial tensile and impact test of weldment specimens.

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Effect of friction stir and activated-GTA welding processes on the 9Cr–1Mo steel to 316LN stainless steel dissimilar weld joints

Cited by 17 publications

References 18 publications

Unravelling the microstructure – indentation creep resistance relationships for friction stir welded modified 9Cr-1Mo steel and LN-type 316 stainless-steel dissimilar joints

Unravelling the microstructure – indentation creep resistance relationships for friction stir welded modified 9Cr-1Mo steel and LN-type 316 stainless-steel dissimilar joints

Review on the Solid-State Welding of Steels: Diffusion Bonding and Friction Stir Welding Processes

Double-sided GTAW of nuclear grade steel: Mechanical and microstructure perspectives

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