Hardness Of Weld Metal Research Articles

Selection of the Process of Arc Welding of Sealing Surfaces of Power Valves with a Consumable Electrode in the Shielding Gas

Introduction. One of the main requirements to the methods of weld overlay of sealing surfaces of power valve trim parts is to obtain a high-quality wear-resistant pad with minimal penetration and optimal process performance. Currently, arc, electroslag, plasma, beam, induction and other surfacing techniques have been developed and introduced into production. However, the influence of various arc welding processes with a consumable electrode in shielding gas on the geometric parameters of weld beads and metal hardness of sealing surfaces is understudied. The presented research is intended to fill this gap. The objective of its authors is to select such a process of arc welding of beads on parts of the power valve trim with a consumable electrode in shielding gases, which would provide the best workability of the deposited metal.Materials and Methods. Arc surfacing with a consumable electrode in a mixture of gases was performed on steel plates. The welding torch was moved in a straight line, without transverse oscillations, using the FRC-9 mechanism (Fronius). A microprocessor-controlled inverter-type digital current source TransPulsSynergic 3200 CMT (Fronius) was used as the power supply. The following welding processes were analyzed: MIG/MAG process with self-regulation (Standard mode), synergic process of MIG/MAG method (Synergic mode), short arc process with mechanical separation of electrode metal droplets (CMT-ColdMetalTransfer), and synergic pulse-arc process (PulseSynergic). The short-cut process of bead surfacing was evaluated by the stability of the values of the energy parameters of the bead surfacing mode in time at the same electrode wire feed rates, which were recorded by oscilloscopes, as well as by comparing the geometric characteristics of the deposited beads and the hardness of the deposited metal.Results. The analysis of experimental data of the geometrics of the weld beads and their complex dimensional characteristics made it possible to establish that the welding engineering requirements for the welded beads are most fully met by long-arc surfacing by the PulseSynergic pulse-arc process.Discussion and Conclusion. The study and the resulting data make a certain contribution to solving the problem of the influence of arc welding processes on the parameters of weld beads and on the hardness of the metal of sealing surfaces. A detailed analysis of the modes of arc surfacing of beads with a consumable electrode in shielding gases on the trim parts of power valves can be used in further research on this topic. The conclusions of the authors will not only provide considerable theoretical assistance to scientists, but will also make adjustments to the activities of practitioners.

Influence of welding methods on the microstructure of nickel-based weld metal for liquid hydrogen tanks

This study investigates the microstructure and hardness of weld metals used in liquid hydrogen storage tanks, with a focus on the effects of three welding methods: Gas Tungsten Arc Welding (GTAW), Submerged Arc Welding (SAW), and Shielded Metal Arc Welding (SMAW). Finite element simulations were employed to model the temperature field during welding, aiding in the explanation of observed microstructural differences. The results show that while GTAW and SMAW produce weld metals with similar microstructures, SAW generates significantly larger grains with a pronounced preferential orientation. The use of weaving techniques play a key role in shaping the solidification microstructures. Additionally, the hardness of the weld metal is comparable to that of the base material, with a slight reduction corresponding to increased grain size. This research offers valuable insights into optimizing welding processes for liquid hydrogen storage tanks by addressing the microstructural characteristics that influence weld joint performance.Graphical

Study on the effect of flux composition on the melting efficiency of A-TIG of AISI 316L stainless steel: experimental and analytical approaches

Melting efficiency in welding is determined by various factors, including processing and operational parameters, the thermomechanical and chemical properties of the materials, surface conditions, and the type of energy source. This study uses a dimensionless parameter approach to evaluate melting efficiency by estimating the weld pool area through experimental measurements of the weld bead's diameter and depth. Also, this study investigates surface-active oxide fluxes based on SiO2 with Cr2O3 and Fe2O3 additives in TIG welding of 316L stainless steel. The effects of these fluxes on melting efficiency, weld cross-sectional area, microstructure, and mechanical properties at various currents (100-200A) were evaluated using metallographic, mechanical, and chemical analyses. The results show that using two-component fluxes at steady incident energy increased melting efficiency in the experimental approach by approximately 10% compared to single-component fluxes and by 20% compared to the without flux condition, providing more favorable and realistic outcomes than the analytical approach. This increase in melting efficiency resulted in a rise in the δ-ferrite phase (7.6% volume) and a reduction in the oxygen content (256 ± 10 ppm) in the weld metal. Furthermore, the two-component fluxes caused arc column constriction, which enhanced absorbed energy and led to an equiaxed grain microstructure with increased penetration depth. The weld metal's strength (630 ± 4 MPa) was directly linked to the penetration depth. However, the high absorbed energy caused grain growth, decreasing weld metal hardness (202 ± 2.5 HV) as melting efficiency increased.

Effect of Filler Wire Composition on Weld Metal Microstructure and Mechanical Properties in X80 Steel Laser Welds.

Laser welding was performed using different filler wires, ER70S steel, commercially pure iron, and pure nickel filler, in the context of welding X80 pipeline steel to assess the microstructure and mechanical properties of the weld metal. Introducing an ER70S wire promoted acicular ferrite formation in the fusion zone, compared to a bainitic microstructure in an autogenous laser weld. The use of pure iron wire was considered as a potential strategy for reducing hardenability, as it led to the dilution of alloying elements in the fusion zone, increasing ferrite content and reducing weld metal hardness to a level compliant with API pipeline standards. The addition of pure nickel wire was used to reveal the degree of weld metal mixing imposed by the laser (thus providing an unambiguous tracer element) when it is combined with filler material dilution in the fusion zone, revealing that the upper region contained 38% wire material and the lower region only 12%. This accounts for the differences observed between the upper versus lower portions of the weld metal when other wires are used, and the use of hardness mapping and micro-indentation demonstrates the correlation between the variations in mechanical properties and microstructural differences introduced by incomplete mixing of the filler wire elements.

تأثير الاكاسيد النشطة باستخدام طريقة لحام(TIG) على جودة شكل وابعاد وصلة اللحام للصلب الاوستنيتى المقاوم للصدأ

Active flux welding (A-TIG) is a method that effectively enhances performance and improves penetration in TIG welding by applying a layer of activated flux to the workpiece before welding. The addition of flux results in higher temperatures in the welding arc, leading to increased penetration without the need for multiple passes and groove preparation, thereby significantly boosting productivity. This research explores the impact of various active fluxes (MoO3, Cr2O3, Fe2O3, Al2O3, and CaF2) in A-TIG welding on 6mm thick austenitic stainless steel 304L plates. The investigation focused on surface appearance, weld bead geometry quality, hardness, microstructure, and angular distortion. The findings revealed that utilizing A-TIG welding with Cr2O3, MoO3, and Fe2O3 fluxes notably improved the penetration depth and aspect ratio as well as reduced angular distortion compared to conventional (TIG) welding method. The application of fluxes had a minimal impact on the hardness and microstructure of A-TIG weld metal. Keywords: Activated fluxes (A-TIG), Weld Penetration, Angular distortion, Weld Bead Geometry

조선용 B Gr. 강의 용접부 미세조직과 기계적 성질에 미치는 용접기법의 영향

The microstructurale and mechanical properties of B Gr. steel were evaluated for shipbuilding according to a welding process. The following conclusions were drawn. In tandem submerged arc welding(TSAW), compared to single submerged arc welding(SAW), the grain boundary ferrite was coarsened, and the fraction was higher owing to the high heat input and low flux basicity ; conversely, the volume fraction of acicular ferrite was lower. Fine intragranular acicular ferrite and polygonal ferrite were observed in the weld metal of the electrogas welding (EGW), which had the highest heat input. In the microstructure near the fusion line, as the amount of heat input increased, the prior austenite grain boundary became coarse. Further, both the intergranular grainboundaryferrite and intragranular bainite became coarse, and the heat-affected zone became wider. The hardness of weld metal was independent of the amount of heat input and was demonstrated to be high in the order of EGW, single SAW, and TSAW owing to the microstructure difference caused by the chemical composition of the filler material and the dilution rate of the base metal. Furthermore, the tensile strength of all three welding processes resulted in stable satisfaction with the class society rules.

Flux enhancement with titanium or vanadium oxides addition for superior submerged arc welding of HSLA steel plates

A high-strength low-alloy (HSLA) steel plate of 10 mm thickness underwent submerged arc welding with enhanced fluxes containing additional titanium oxide (TiO2) or vanadium oxide (V2O5). The addition of TiO2 led to the development of a finer acicular ferrite structure but coarsening the carbide and martensite/austenite (M/A) constituents, which marginally improved the hardness, tensile strength, and ductility of weld metal. Conversely, incorporating V2O5 facilitated a substantial vanadium absorption (0.7 wt. %) in the weld metal, giving rise to a distinctive acicular microstructure less reliant on ferrite nucleation at non-metallic inclusions than conventional acicular ferrite. The distinctive microstructure, unique to vanadium steels, combined lath bainite with irregularly shaped granular bainite. The resultant dual-mode bainitic structure, coupled with a more uniform distribution of refined microphase constituents, outperformed the conventional acicular ferrite, delivering more than 20% and 13% improvements in yield and tensile strengths respectively, as evidenced by transverse tensile tests on the weld metals.

Optimization of process parameters of cold metal transfer arc welding of AA 6061 aluminium Alloy-AZ31B magnesium alloy dissimilar joints using response surface methodology

The fabrication of dissimilar metal joints, particularly between AA 6061 aluminum alloy (Al) and AZ31B magnesium alloy (Mg), poses significant technical challenges due to their distinct metallurgical characteristics and the inherent difficulties associated with welding such materials. These challenges include the propensity for intermetallic compound formation, thermal cracking, and differences in thermal and mechanical properties between the two alloys. Cold Metal Transfer (CMT) welding, known for its low heat input and controlled metal transfer, offers a potential solution to these issues. However, optimizing the process parameters to ensure strong, defect-free joints requires a systematic approach. This study aims to optimize CMT welding parameters using parametric mathematical modeling (PMM) to produce high-strength Al and Mg dissimilar joints and to study the effects of CMT parameters on tensile strength (TS) and weld metal hardness (WMH), as well as the microstructural features of AA 6061 aluminum alloy/AZ31B magnesium alloy (Al/Mg) dissimilar joints. Al/Mg dissimilar butt joints were produced by the CMT process using ER4043 as filler wire. CMT, a low-heat input welding technique, was used to mitigate issues such as intermetallic compounds (IMCs), wider heat-affected zone (HAZ), and distortion. The CMT parameters, particularly wire feed speed (WFS), welding speed (WS), and arc length correction (ALC), were optimized using response surface methodology (RSM) to maximize the TS and WMH of the Al/Mg dissimilar joints. Polynomial regression was employed to create PMMs that integrated these CMT parameters to forecast the TS and WMH of the joints. An analysis of variance (ANOVA) was applied to assess the feasibility of the PMMs. The results indicated that the Al/Mg dissimilar joints, produced using a WFS of 4700 mm/min, a WS of 280 mm/min, and an ALC of 10%, exhibited higher TS and WMH values of 33 MPa and 95.8 HV, respectively. The PMMs provided precise forecasts for the TS and WMH of the Al/Mg joints with an error rate of less than 1% and a confidence level of 97%.

Effect of heat input on the microstructure and hardness of AISI 321 stainless steel welds using ER 347 filler metal

Stainless steel is widely used in various fields, one of which is AISI 321, which is used for high-temperature applications because of its high resistance to creep and intergranular corrosion. The type of filler metal and heat input on stainless steel welds play an essential role in determining the microstructure and mechanical properties of the welded joints. The purpose of this experiment was to evaluate the microstructure and mechanical properties of AISI 321 stainless steel welds with variations in heat input. This study is expected to explore the performance of this weld joint, which can be anticipated in relevant fields. The welding method used in this experiment was Gas Tungsten Arc Welding (GTAW) with ER 347 as filler metal. Welding was carried out on three samples with a heat input of 0.92 kJ/mm, 0.64 kJ/mm, and 0.52 kJ/mm, respectively. The tests included tensile strength, Vickers microhardness, and microstructure observations. The tensile test results showed that a fracture occurred in the Base Metal (BM) area, indicating that the strength of the weld joint was higher than that in the BM. The Vickers microhardness test results showed that the Weld Metal's hardness (WM) was the highest, followed by the Heat-Affected Zone (HAZ) and BM. The welding experiment that used three variations in heat input demonstrated that higher heat input lowered the hardness of the weld joint. The microstructure observation results around the fusion line demonstrated the presence of step and ditch structures. The ditch structure indicates intergranular corrosion.

Microstructure evolution and enhanced cryogenic toughness of laser welded dissimilar SA645/AISI304L joints via intercritical tempering

In this study, we explored the impact of intercritical tempering on the microstructural evolution and mechanical properties of dissimilar welds formed through laser welding between 5%Ni steel (SA645) and austenitic stainless steel (AISI304L). Upon tempering at 500 °C, reversed austenite manifested within the weld metal. The volume proportion of reversed austenite in weld metal at room temperature increased first, exhibiting a maximum (∼10%) at ∼600 °C, and then decreased with increasing tempering temperature, which was associated with the diminished stability of austenite. Due to the change in tempering temperatures, two distinct types of reversed austenite were present, with one being located at the high-angle grain boundaries and the other within the martensite blocks. As the tempering temperature increased, the weld metal hardness decreased, reaching a minimum of ∼306 HV at 600 °C, and then increased. The dislocation density within the martensite matrix and the quantity of reversed austenite are the crucial factors to determine the hardness of weld metal. The cryogenic impact toughness of weld metal increased at first and then decreased as the tempering temperature increased. The maximum of ∼40 J for the cryogenic impact toughness was obtained when tempering at 600 °C. The low-temperature impact toughness of the weld metal was determined by the synergy of the TRIP effect of reversed austenite, the compatible deformation capability of dual-phase structure, and the crack propagation behavior.

Pengaruh Variasi Arus Pengelasan SMAW (60, 80 Ampere) Terhadap Kekerasan Logam Las Dan Haz Material Baja ST 37)

This research aims to determine the effect of welding current on the hardness of weld metal and HAZ (heat affected zone) metal which is tested for hardness using the Rockwell method. This research was carried out on ST 37 low carbon steel material which was welded using an E6013 electrode with a diameter of 2.6 mm with a butt joint, then given different welding currents, namely 60, 80, Ampere. For the raw hardness of the low carbon steel material, the average figures were obtained. the average is 48.35 HRB. Specimens that were welded with a current of 60 Ampere had an average weld metal hardness figure of 46.85 HRB and a HAZ of 49.15 HRB. For specimens that were given a welding current of 80 Ampere, the average hardness of the weld metal obtained was 47.05 HRB and the HAZ was 50.3 HRB. The test results show that the increase in hardness numbers in both the weld metal and the HAZ metal is directly proportional to the amount of current used when welding

Comparison of electron-beam-welded joints manufactured by rolled and selective laser melted reduced activation ferritic/martensitic steel

As the core component of China Fusion Engineering Test Reactor (CFETR), the forming and manufacturing of the first wall faces severe challenges due to the constraints of materials, service environment and geometric structure. The microstructure and mechanical properties of welded joints obtained by rolled and laser selective melted (SLMed) reduced activation ferritic/martensitic (RAFM) steel were investigated in depth. The microstructure analysis results showed that the weld metal (WM) was composed of coarse lath martensite and δ-ferrite, while the microstructure were mainly coarse grains in heat affected zone (HAZ) which was easy to break. The average grains size of SLMed RAFM steel (S-RAFMs) was smaller than that of rolled RAFM steel (R-RAFMs), since the rapid melting and solidification of laser in the additive manufacturing process prevented grains to grow. The microstructure of R-RAFMs joint was relatively more uniform and there was no obvious texture and preferred orientation, while the WM of S-RAFMs joint had a weak cubic texture. The results of mechanical properties showed that the S-RAFMs joints exhibited higher strength (UTS = 697.46 MPa) and the R-RAFMs joints exhibited better plasticity (EL = 13.49 %) under the same tensile conditions. The tensile and impact fracture morphologies showed that the fracture mechanism of two joints was ductile-brittle mixed fracture, and the dimples of R-RAFMs joints were finer and denser. It was clearly observed that the hardness of WM (∼390–430 HV0.3) was higher than that of the base metal (BM) (∼190–230 HV0.3) from the hardness distributions along the width directions. The average hardness of BM in R-RAFMs joint (227 HV0.3) was lower than S-RAFMs joint (197.3 HV0.3), which was mainly related to the fine grain strengthening effect during SLM forming. The above results may provide theoretical guidance for the high-performance manufacturing of the first wall and promote the application of SLM and EBW technology in the field of nuclear fusion.

Study on the mechanism of Ni-26W-6Cr alloy solidification cracking: Effect of laser welding heat input

The segregation of P, S, Al, Si and Mo at solidification grain boundary (SGB) results in the formation of the low-melting-point liquid film. As heat input (HI) increases from 76.9 to 214.3 J/mm, upper weld seam width increases by 63 % and lower seam width decreases by 29.3 %. High welding HI generates lower temperature gradient, which could reduce thermal stress. The average hardness of weld metal (WM) drops from 273 to 235 HV and there is a 90 % reduction in the total length of welding solidification crack (WSC). The lower hardness under high HI facilitates the release of thermal stress, which permits the WM to accommodate the tensile stress generated during the solidification phase. Reduced thermal stress decreases the driving force of the formation of WSC.

THE EFFECT OF HARD FACING PROCESS ON THE HARDNESS AND MICROSTRUCTURE OF BUCKET TOOTH FOR DIFFERENT MANGANESE CONTENT

High hardness and wear resistance of bucket tooth are required in the face of abrasion and impact. High manganese steel is hard and ductile, making it more suitable for bucket tooth materials. Bucket tooth can wear out and need to be returned to their original size, so that bucket tooth that have been eroded must be coated with a hard material, using a hard facing process. In this study, the hard facing process was carried out in bucket tooth containing 10.4%, 11.60%, 12.70%, 13.60%, and 14.60% men (manganese) elements, using hard facing electrodes of the AWS A5.13 (JIS Z 3251). Hard facing process was using SMAW welding with an average heat input of 1087.43 J/mm. The hard facing process shown that the hardness of weld metal was always lower than of HAZ (Heat Affected Zone) and base metal. The hardness of the weld metal was almost the same for all types of bucket tooth, which was about 233.478 HVN.

An investigation on the laser welding process parameter effects on the failure mode of tailor welded blanks during the formability testing

The ability to produce high-quality weld with the least distortion and heat affected zone width by the Nd:YAG laser welding process has made it one of the best candidates for steel tailor welded blanks (TWBs). The effect of process parameters including laser peak power, pulse duration, welding speed, and thickness ratio on the mechanical properties and failure modes of TWBs were investigated. TWBs was made of St12 carbon steel sheets with different thickness of 0.5 mm, 1 mm, and 1.5 mm. The weld zone hardness profile in all samples followed a similar pattern, in that the maximum hardness was in the weld metal and gradually fell throughout the heat affected zone (HAZ) until it reached the hardness of the base metal at the end of the HAZ and the hardness of weld metal increased as the average joint thickness increased. Based on the distribution of hardness in different regions of the weld zone a simple model was proposed for failure mode. Weld metal failure mode (WFM) happened as a result of weld metal thickness reduction caused by incomplete weld penetration or excessive penetration. The heat input per unit volume of weld in thin sheet (Hin) was defined as a criterion that determines failure mode. Therefore, a qualitative criterion was proposed for the prediction of failure mode. Based on this simple model, there is an appropriate limit for Hin for all thickness ratios at which the failure mode is base metal failure mode (BFM). The WMF happens at values lower and higher than this appropriate value range. The experiments approved that BFM and the highest formability and joint strength were obtained when 11J/mm3<Hin<37J/mm3.

Residual Stresses of the Laser Welded Abrasion Resistant Steel Butt Joints

This paper investigates residual stresses of the laser welded abrasion resistant steel butt joints. X-ray diffraction (XRD) was used to measure the residual stresses of the laser welded joints. The geometry and mechanical properties of the joints were also investigated. The weld metal hardness of the weld made with the lowest welding energy corresponded to the hardness of the base material. The welding energy had a significant effect on the hardness profiles of the welds. With the lowest welding energy, the tensile strength reached a strength corresponding to the yield strength of the base material. The residual stress results perpendicular to the weld corresponded well to the hardness profiles of the joints. The residual stresses were mainly tensile stress. The measured maximum residual stresses were 480 MPa.

Effect of post weld heat treatment on weld metal microstructure and hardness of HFCA-TIG welded ASTM-B670 high temperature alloy joints

In this investigation, the effect of post weld heat treatment (PWHT) conditions on weld metal (WM) microstructure and hardness of ASTM B670 alloy joints are studied for gas turbine engine applications. This high temperature alloy was joined using high frequency compressed arc TIG (HFCA-TIG) welding process. The precipitation hardening was performed on ASTM-B670 alloy joints directly after welding (DPH); after solutionizing the welds at 980 °C (980ST+PH) and at 1065 °C (1065ST+PH). The WM of ASTM-B670 alloy showed better response to PWHT in minimizing the Laves phases and enhancing the WM hardness of joints. The DPH, 980ST+PH and 1065ST+PH joints showed 55.63%, 58.80% and 64.08% enhancement in hardness of WM compared to as welded (AW) joints owing to the precipitation of hardening phases after PWHT. The 1065ST+PH joints revealed higher hardness of WM than DPH and 980ST+PH joints It is attributed to the complete dissolution of Laves phases in WM causing more Nb available for precipitation hardening of WM. Nevertheless, the PM hardness of 1065ST+PH joints are lower than 980ST+PH joints owing to the severe grain growth. The HFCA-TIG welds showed volume fraction of Laves phase up to 5.10% in WM which is 80.38% and 36.25% lower than constant current TIG (CC-TIG) and pulsed current TIG (PC-TIG) welds. It is attributed to magnetic compression and high frequency pulsation of arc which minimizes input of heat in welding and offers greater refinement of WM.

The effect of heat input in multi-pass GMAW of S960QL UHSS based on weaving and stringer bead procedure on microstructure and mechanical properties of HAZ

Quenched and tempered S960QL (yield strength ≥ 960 MPa) ultra-high strength steel (UHSS) thick plates were joined by multi-pass robotic gas metal arc welding (GMAW) using weaving and stringer bead techniques. The effects of microstructural changes in heat-affected zone (HAZ) of the joint on toughness and hardness were examined. Weaving and stringer bead techniques applied for the multi-pass welding procedure altered average peak temperatures and exposure time to those temperatures. Mechanical properties of HAZs were evaluated by utilizing notch impact and hardness tests, and these results were correlated with microstructural characterizations using optical (OM) and scanning electron microscopes (SEM). Prior austenite grain (PAG) coarsening occurred because of increased exposure time to peak temperature in coarse-grained HAZ (CGHAZ) of the W-5 (weaving pass) joint. CGHAZs at the face pass, which have not been subjected to a second thermal cycle, have the highest hardness in both joints. Hardness of SCHAZ and CGHAZ of S-12 joint was 7% and 1% higher compared with W-5 joint, respectively. Weld metal hardness of W-5 joint was 15% lower than that of S-12 joint. Both joints not only fulfilled the requirements of minimum 50 J per EN ISO 10025-6 at −20 °C but exceeded this limit by 50% (W-5) and 200% (S-12). Lateral expansions for impact toughness specimens were around 17.5% for S-12 joint, whereas it was 4% for W-5 joint. Since HAZ in the S-12 (stringer bead) joint is narrow compared with the one in the W-5 joint, impact toughness values were higher with the S-12 joint due to the locations of the notches of the impact specimens.

Investigation of The Effect of HAZ Width on Weld Metal Electrical Properties in Arc Welded Joints

This study was carried out in order to fill the gap in the literature and to increase the usability of welded joints as electrical connectors. For this purpose, shielded electrode metal arc welding and gas metal arc welding methods, which are frequently used in the industry, were used. In addition to mechanical tests such as microstruc-ture, tensile and hardness of the joints made at different heat inputs, electrical con-ductivity tests were also performed and the results were evaluated together. According to the results obtained, electrical conductivity is lower in arc welding joint with shielded electrode, in other words, the weld metal has reduced conductivity. In the gas arc welding, the electrical conductivity five times more than in the electrode welding. In MAG welding, at the highest heat input 0.78 kJ/mm, 186.33 HV hardness was measured, while 191.33 HV hardness was measured at 0.60 kJ/mm, the lowest heat input. While 386.5 MPa tensile strength was obtained at 0.78 kJ/mm, 377 MPa tensile strength was measured at 0.60 kJ/mm heat input. In SMAW, 163 HV hardness was obtained at the highest heat input as 1.47 kJ/mm, while the tensile strength of the weld metal was measured as 343.5 MPa and the elec-trical resistance was measured as 21.5 Ohm. The electrical resistance was measured as 11.86 Ohm, with a 384 MPa tensile strength and a 174 HV hardness at the lowest heat input 1.17 kJ/mm. It was determined that as the weld metal hardness increased, the electrical conductivity decreased. The relation between the test findings and their interpretation are detailed in the study.

Structural integrity assessment of Inconel 617/P92 steel dissimilar welds for different groove geometry

The work is focused on examining the effect of the weld groove geometry on microstructure, mechanical behaviour, residual stresses and distortion of Alloy 617/P92 steel dissimilar metal weld (DMW) joints. Manual multi-pass tungsten inert gas welding with ERNiCrCoMo-1 filler was employed to fabricate the DMW for two different groove designs: Narrow V groove (NVG) and Double V groove (NVG). The microstructural examination suggested a heterogeneous microstructure evolution at the interface of the P92 steel and ERNiCrCoMo-1 weld, including the macrosegregation and element diffusion near the interface. The interface structure included the beach parallel to the fusion boundary at the P92 steel side, the peninsula connected to the fusion boundary and the island within the weld metal and partially melted zone along Alloy 617 fusion boundary. An uneven distribution of beach, peninsula and island structures along the fusion boundary of P92 steel was confirmed from optical and SEM images of interfaces. The major diffusion of the Fe from P92 steel to ERNiCrCoMo-1 weld and Cr, Co, Mo, and Ni from ERNiCrCoMo-1 weld to P92 steel were witnessed from SEM/EDS and EMPA map. The Mo-rich M6C and Cr-rich M23C6 phases were detected in inter-dendritic areas of the weld metal using the weld’s SEM/EDS, XRD and EPMA study, which formed due to the rejection of Mo from the core to inter-dendritic locations during solidification. The other phases detected in the ERNiCrCoMo-1 weld were Ni3(Al, Ti), Ti(C, N), Cr7C3 and Mo2C. A variation in the microstructure of weld metal from top to root and also along the transverse direction in terms of composition and dendritic structure and also due to the composition gradient between dendrite core and inter-dendritic areas, a significant variation in hardness of weld metal was observed from both top to root and also in the transverse direction. The peak hardness was measured in CGHAZ of P92 while the minimum was in ICHAZ of P92 steel. Tensile test studies of both NVG and DVG welds joint demonstrated that failure occurred at P92 steel in both, room-temperature and high-temperature tensile tests and ensured the welded joint’s applicability for advanced ultra-supercritical applications. However, the strength of the welded joint for both types of joints was measured as lower than the strength of the base metals. In Charpy impact testing of NVG and DVG welded joints, specimens failed in two parts with a small amount of plastic deformation and impact energy of 99 ± 4 J for the NVG welds joint and 91 ± 3 J for the DVG welded joint. The welded joint met the criteria for boiler applications in terms of impact energy (minimum 42 J as per European Standard EN ISO15614-1:2017 and 80 J as per fast breeder reactor application). In terms of microstructural and mechanical properties, both welded joints are acceptable. However, the DVG welded joint showed minimum distortion and residual stresses compared to the NVG welded joint.