Other affiliations: Indian Institute of Technology Bhubaneswar
Bio: J.G. Thakare is an academic researcher from VIT University. The author has contributed to research in topics: Ultimate tensile strength & Residual stress. The author has an hindex of 4, co-authored 4 publications receiving 31 citations. Previous affiliations of J.G. Thakare include Indian Institute of Technology Bhubaneswar.
TL;DR: In this paper, a novel approach of measuring through-thickness residual stresses based on the general strain relaxation methodologies has been described, which is an amalgam of the conventional deep hole drilling technique and the contour method with a reduced degree of damage to the component made during measurements.
Abstract: In this present study, a novel approach of measuring through-thickness residual stresses based on the general strain relaxation methodologies has been described. This new method is an amalgam of the conventional deep hole drilling technique and the contour method with a reduced degree of damage to the component made during measurements. The annular deformation of a reference hole made at the measurement location has been interpreted as the displacement boundary conditions in a two-dimensional finite element model. In this regard, a thick, partially plastic four-point bent bar specimen was used to validate the proposed method. Through-thickness axial residual stresses induced in the bar were measured using the proposed technique and were observed to be in a reasonably close match with the theoretical and DHD results.
TL;DR: In this article, the microstructure and mechanical behavior of the Gas Tungsten Arc (GTA) welded joint of ferritic/martensitic (F/M) P91 and austenitic SS304L steel was investigated in as-welded and postweld heat treatment (PWHT) conditions.
Abstract: The microstructure and mechanical behavior of the Gas Tungsten Arc (GTA) welded joint of ferritic/martensitic (F/M) P91 and austenitic SS304L steel was investigated in as-welded and post-weld heat treatment (PWHT) conditions. The microstructural studies included the particle size and its distribution, grain size, and percentage area fraction of the precipitates (%AFP) in different zones of the weldments. In as-welded condition, weld metal showed untempered martensitic microstructure devoid of carbide precipitates. After the PWHT, weld metal was characterized by tempered martensitic microstructure along with the decoration of the coarse carbide particles at PAGBs and fine carbonitride particles inside the matrix region. The mechanical behavior of the dissimilar weld was analyzed in as-welded and PWHT conditions by performing tensile testing, Charpy impact testing, and microhardness testing. A significant variation in microstructure and mechanical properties was obtained across the dissimilar welded joint (DWJ) for as-welded, which was minimized after the PWHT. The minimum%AFP in the coarse grain heat-affected zone was measured due to the formation of the precipitate-free soft δ ferrite patches, which also showed a negligible response to PWHT. The poor Charpy impact toughness (CIT) of 0.8 ± 1.5 J and high tensile strength of 864 ± 12.5 MPa were measured for the as-welded joint. The combination of high strength and low CIT was obtained mainly due to the untempered martensitic microstructure in the weld fusion zone. The DWJ after the PWHT showed a significant increase in Charpy impact toughness (CIT), and it was measured 70 ± 4 J. Improved mechanical behavior with a good combination of ultimate tensile strength and CIT were obtained after the PWHT.
TL;DR: In this article, the microstructural stability of dissimilar welds joint (DWJ) was studied using the optical microscope and field emission scanning electron microscope (FESEM) for as-welded (AW) and postweld heat treatment (PWHT) condition.
Abstract: The dissimilar welds joint of 2.25Cr-1Mo steel and lean duplex LDX2101 steel was prepared using the Gas Tungsten Arc Welding (GTAW) process and employing the Inconel 617 filler. The microstructural stability of the dissimilar welds joint (DWJ) was studied using the optical microscope and field emission scanning electron microscope (FESEM) for as-welded (AW) and post-weld heat treatment (PWHT) condition. The PWHT was employed at 760 °C (PW 1) and 810 °C (PW 2) for 2 h of duration. The application of the heat-treatment resulted in the formation of the soft zone at the interface of weld metal and HAZ in 2.25 Cr-1Mo side, i.e., low Cr side. The mechanical behavior of the DWJs was also studied for AW and PWHT condition. A measurable change in the width and hardness of the soft and hard zones was measured with an increase in PWHT temperature. For weld metal, the minimum average hardness was measured 237 HV in AW and a maximum of 248 HV for PW 2. In the AW condition, the average CIT of the weld metal was measured 46.5 ± 3.5 J, which meets the minimum recommended value as per EN 1557:1999 standards. The PWHT showed a drastic reduction in CIT and a minimum of 34 ± 3 J was measured for PW 2. The CIT of the 2.25Cr-1Mo HAZ (notch adjacent to fusion boundary includes the soft ferrite region) was measured 45 ± 5 J in AW and get increased drastically after the PWHT and maximum was measured for PW 2 (86 ± 5 J).
TL;DR: In this paper, a 3D finite element model was developed, the model was experimentally validated, and the model is used to establish a relationship between applied stress and relaxed strain.
Abstract: Thermal barrier coating (TBC) with Al2O3 and 8YSZ as topcoat constituents has been developed. The commercially available 8YSZ (80% wt.), Al2O3 (17 and 19% wt.) and multiwall carbon nanotubes (MWCNT) (3% and 1% wt.) were plasma sprayed to produce composite coatings. A stress relaxation technique using a slow-speed diamond cutter has been used to relax the strain and determine the through-thickness residual stress in the coatings. A 3D finite element model was developed, the model was experimentally validated, and the model was used to establish a relationship between applied stress and relaxed strain. The addition of alumina increased the compressive residual stress on the surface of the coating by 42%, the addition of 1% MWCNT had a negligible effect on the residual stress on the coating surface. The further addition of MWCNT (3% wt.) resulted in tensile residual stress in the coating as a result of MWCNT agglomeration.
TL;DR: In this paper, the authors present an overview of the dissimilar welded joint's microstructure and mechanical behavior, and the effect of intermetallic phases such as sigma phase, FCC carbides like (M23C6, M6C, and M7C3), laves phase, R and χ-phase, Z-phase on the mechanical property of dissimilar welding joints of each material are reviewed in detail.
Abstract: This review article presents an overview of the dissimilar welded joint's microstructure and mechanical behavior. Dissimilar metal weldings are generally employed in high-pressure tubing/tubing-coupler assembly generally functional in subsea oil-gas production instruments and a wide range of geothermal plants and piping systems for subsea manifolds. Thus, dissimilar metal welding has an essential role in enhancing the subsea oil-gas drilling system's structural integrity. Dual-phase super duplex stainless steel 2507 (super DSS 2507) comprises a balanced phase of austenite and ferrite, establishing great attention of manufacturers and researchers due to its mechanical strength and corrosion resistance properties in several hostile surroundings like marine, offshore, petrochemical, and nuclear power plant. The other most frequently used material in the marine application is nitronic steel (N50), primarily used in subsea oil and gas developments in tube and couplers for its corrosion resistance, high strength, and resistance to galling. Nickel-based superalloy Inconel 625 has significant application in the aviation, petrochemical, and marine industry due to its high tensile, yield, and creep strength with excellent corrosion properties in an unfavorable environment. The dissimilar joining of these materials is repeatedly required in marine and offshore industries. This review focuses on the significant difficulties related to the dissimilar welding of super DSS 2507 with nitronic steel (N50) and Inconel 625. Unlike chemical composition, metallurgical properties, mechanical and physical properties of these steel and nickel alloys lead to the problem like stress corrosion cracking, hydrogen embrittlement, ductility dip cracking and migration of carbon. The other metallurgical problems are deleterious secondary phase formation, carbon diffusion-related problem, δ-ferrite phase present in the fusion zone, and residual stresses are required to be removed or decrease their intensity for the qualification of the weld. The effect of intermetallic phases such as sigma phase, FCC carbides like (M23C6, M6C, and M7C3), laves phase, R and χ-phase, Z-phase on the mechanical property of dissimilar welded joints of each material are reviewed in detail. After the extensive literature review, proper selection of filler metal has also been covered in this article because it plays an essential role in decreasing some of the dissimilar welded joint problems. Heterogeneity across the weldment, unmixed zone formation including peninsula, island, beaches, and filler deficient region, grain boundaries related problems during the dissimilar welded joint of these materials is also discussed thoroughly in this article. The effect of residual stresses in the dissimilar welded joint's distinct condition has also been discussed in detail.
TL;DR: In this article, a detailed study on the relationship of microstructure and mechanical properties of the dissimilar Gas Tungsten Arc Weld (GTAW) joint of heat-resistant ferritic/martensitic P91 and austenitic SS304H steel, prepared using the Ni-grade ERNiCrMo-3 filler, was carried out.
Abstract: The objective of the current investigation to carry out a detailed research study on the relationship of microstructure and mechanical properties of the dissimilar Gas Tungsten Arc Weld (GTAW) joint of heat-resistant ferritic/martensitic P91 and austenitic SS304H steel, prepared using the Ni-grade ERNiCrMo-3 filler. The metallographic characterization of the weldments (P91 HAZ, weld metal, SS304H HAZ) was performed by availing the optical microscope and scanning electron microscope equipped with energy dispersive spectroscopy for precipitate size, their distribution in matrix, morphology and chemical composition. Mechanical properties of the weldments were also evaluated and for that, tensile testing, microhardness testing and Charpy testing were conducted. The metallographic and mechanical characterization of the weldments were also performed after the post-weld heat treatment (PWHT) at 775 °C for 60 min and compared with the as-welded condition. The results indicated that a complete heterogeneous microstructure formation across the weldments which led to variation in the mechanical behaviour of the weldments. The tensile strength and Charpy impact toughness (CIT) of the weld metal were measured 631 MPa and 79 J, respectively, in the as-welded condition. The coarse-grained HAZ region of P91 side showed the peak hardness of 412 HV (as-welded), which was higher than the hardness of the weld metal (303 HV). After the PWHT, an improvement in tensile properties was observed and tensile strength and % elongation was measured 666 MPa and 16.14 %, respectively. After the detailed study, it was concluded that the GTAW process with ERNiCrMo-3 filler offered a better combination of the microstructure and mechanical properties in as-welded condition for the dissimilar welded joint of P91 and SS304H.
TL;DR: In this paper, different finite element (FE) models were prepared to investigate weld induced residual stresses in thick multi-pass butt welded joint of SA516 Gr. 70 plates, and the competence of these FE models on the accuracy of predicting residual stress distribution across the weld cross-section was investigated by comparing it with the experimental results.
Abstract: In the present study, different finite element (FE) models were prepared to investigate weld induced residual stresses in thick multi-pass butt welded joint of SA516 Gr. 70 plates. Both 3D and 2D full geometry models and their axisymmetric half models were taken into consideration. The competence of these FE models on the accuracy of predicting residual stress distribution across the weld cross-section was investigated by comparing it with the experimental results. Blind hole drilling technique and deep hole drilling technique were employed to evaluate the surface and through-thickness residual stress distributions, respectively. In addition, the change in volume and yield strength of weld material due to austenitic phase transformation was also incorporated in the material modeling to observe the effect of solid-state phase transformation (SSPT) on the evaluation of residual stresses. Computed residual stresses obtained from different FE models indicate that the 3D FE models procured the best accuracy compared with the experimental results. On the other hand, 2D models can save a significant amount of computational time with reasonable accuracy. Incorporation of SSPT in the 3D FE full model exhibited a better agreement of predicted results with the experimental measurements.
TL;DR: In this article, a dissimilar butt-welded joint was produced for conventional V groove design by using the gas tungsten arc welding (GTAW) process with the application of an ERNiCrMo-3 Ni-based super alloy filler.
Abstract: This article deals with the dissimilar joining of two different grade Cr-Mo steel (2.25Cr-1Mo: P22 and modified 9Cr-1Mo: P91) for power plant application. The dissimilar butt-welded joint was produced for conventional V groove design by using the gas tungsten arc welding (GTAW) process with the application of an ERNiCrMo-3 Ni-based super alloy filler. A microstructure characterization was performed to measure the inhomogeneity in the microstructure and element diffusion across the interface in a welded joint. The experiments were also performed to evaluate the mechanical properties of the dissimilar welded joint in as-welded (AW) and post-weld heat treatment (PWHT) conditions. An acceptable level of the mechanical properties was obtained for the AW joint. After PWHT, a significant level of the element diffusion across the interface of the weld metal and P22 steel was observed, resulting in heterogeneity in microstructure near the interface, which was also supported by the hardness variation. Inhomogeneity in mechanical properties (impact strength and hardness) was measured across the weldments for the AW joint and was reduced after the PWHT. The tensile test results indicate an acceptable level of tensile properties for the welded joint in both AW and PWHT conditions and failure was noticed in the weak region of the P22 steel instead of the weld metal.
TL;DR: In this paper, the authors examined TIG welded joints processed with friction stir processing at tool rotational speeds (TRSs) of 700, 800, 900, 1000, and 1100rpm, with a constant feed rate of 70mm/min and tilt angle of 1°.
Abstract: In this work, we examine TIG welded joints processed with friction stir processing at tool rotational speeds (TRSs) of 700, 800, 900, 1000, and 1100 rpm, with a constant feed rate of 70 mm/min and tilt angle of 1°. The percentage improvement in the tensile strength of TIG + FSP (TF) weldments was observed to be 78.57 and 75.89%, compared with TIG welded joints with ER4043 and ER5356 filler, respectively, at a TRS of 1100 rpm. A maximum tensile strength of 196 MPa was observed in a TF welded joint with ER5356 filler, and a minimum tensile strength of 98 MPa was observed in the TIG weldment with ER4043 filler. Cleavage facets, tear ridges, and large dimples were observed in fractured specimens of TIG welded joints, whereas fine, equiaxed dimples were observed in TF welded joints. A maximum micro-hardness of 137 HV in the stir zone was observed in TF welded joints at a TRS of 1100 rpm. TF welded joints with ER5356 filler had superior wear resistance compared to TIG and TF welded joints with ER4043 filler.