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This study analyzes the effects of Post Weld Heat Treatment (PWHT) on the mechanical properties and microstructure of Inconel 617 weldments produced by the Activated Tungsten Inert Gas (A-TIG) welding and Tungsten Inert Gas (TIG) welding. The TIG weld joints considered for this study were in an as-welded condition and underwent two different conditions of heat treatment including 1050∘C for 3 and 5 h, respectively. The A-TIG weld joints studied were the as-welded type and the weldment was heat-treated at 1050∘C for 3 h. The microstructure and the characterization of mechanical properties were performed for all weldments and a comparative assessment was made. Tensile strength and the hardness of the heat-treated samples were considerably higher than that of the as-welded samples. Impact toughness was slightly reduced after PWHT. Improvement in tensile strength could be attributed to the precipitation of the carbides and segregation of Chromium (Cr) and molybdenum (Mo). [ABSTRACT FROM AUTHOR]

The bridge structure of bridge crane is a typical welded structure, and fatigue cracks often appear in the weld area of the main beam during daily service. In order to ensure the service safety of the crane, a multi-level sub model of the dangerous crack region was established based on the multi-scale finite element analysis method. The thermal structural coupling welding finite element model was established on the secondary sub model, and the whole welding process was simulated and analyzed. The influence of post weld heat treatment on residual stress was simulated. Combined with the multiaxial critical interface method, a fatigue analysis method using the strain amplitude as the multiaxial damage parameter was constructed, and the fatigue performance of the dangerous crack region was evaluated. The results show that the proposed method transforms the overall fatigue problem of the structure into the fatigue problem of the local welding position, which not only increases the calculation efficiency, but also considers more influencing factors of the fatigue details, and provides a certain reference for the fatigue life assessment and life extension of the crane weld. [ABSTRACT FROM AUTHOR]

The main objective of this investigation is to study the effect of post weld heat treatments (PWHTs) on tensile properties, hardness, and microstructure of pulsed CMTeMIG (cold metal transfer arcemetal inert gas) welded AA20214-T6 aluminum alloy joints. The welded joints were subjected to PWHT of artificial aging (AA), solution annealing treatment (ST) and ST þ aging (STA). The tensile properties and microhardness of joints were evaluated. The microstructure of joints was studied using optical microscope (OM) and transmission electron microscope (TEM). The fractured surface of tensile specimens was analyzed using scanning electron microscope (SEM). Results showed that the tensile properties and hardness of as welded and PWHT joints are inferior compared to base metal (BM). This mainly refers to the microstructural heterogeneity in different regions of joints and softening of heat affected zone (HAZ) induced by the weld thermal cycle. The PWHTs of AA and ST did not show significant effect on tensile strength and hardness of AW joints. However, the slight reduction in elongation was observed in AA and ST joints. The STA joints showed higher joint efficiency of 71.6%, than other joints by compromising on the elongation. This refers to the greater precipitation of hardening precipitates in STA joints compared to AA and ST joints. It exhibited the higher tensile and yield strength of 326 MPa and 266 MPa and the lowest elongation of 3.8%. The STA joints showed 28.35%, 38.28% and 57.77% reduction in tensile strength, yield strength and elongation compared to BM respectively. All the tensile specimens of joints failed in HAZ owing to the lower hardness. This refers to dissolution of precipitates in HAZ. However, the HAZ softening is less severe in STA joints than AW, AA, and ST joints. [ABSTRACT FROM AUTHOR]

The high entropy alloys (HEAs) are relatively a new class of materials that have attracted significant attention of engineering sector in recent years due to their extensive mechanical properties, high strength to weight ratio, thermal stability and resistance to corrosion and oxidation. HEAs are characterized by their unique composition that is typically composed of five or more elements in equal or somewhat substantial proportions. This leads to the evolution of highly complex microstructure that makes it challenging to weld. To fulfil the key requirements of the design and manufacturing, these HEAs must be capable of being welded in a satisfactory manner. The joining of similar and dissimilar combinations of HEAs and other engineering materials system have been proved to be feasible which further expands their structural applications in aerospace, nuclear and defence sector. Additionally, the fillers of HEAs disclosed greater potential in suppressing the evolution of detrimental intermetallics and enhancing the mechanical properties of joints. So, in this study, a comprehensive review on the current state of research in fusion welding of HEAs particularly AlxCoCrFeNi and CoCrFeMnNi is provided to address the weldability of HEAs under the diversity of composition, initial working condition, welding processes, operating parameters, configuration of joint and operating conditions. The latest challenges, progress and future perspectives in fusion welding of HEAs are reviewed critically with a particular focus on microstructure and mechanical properties of joints. The effect of fusion welding processes such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), electron beam welding (EBW) and laser beam welding (LBW) on microstructural characteristics, mechanical properties and corrosion behaviour of HEAs joints is reviewed and discussed. The effect of post weld heat treatment and HEAs fillers on the mechanical properties and microstructural evolution of welded joints is also discussed. Further, an insight into the potential application of HEAs in advanced engineering applications is provided. The current review article aims to provide an overview of challenges, opportunities, current state of research and main directions in fusion welding of AlxCoCrFeNi and CoCrFeMnNi HEAs and to highlight their potential as high-performance material in a range of applications. [ABSTRACT FROM AUTHOR]

The influence of parameters involved in the pulsed electric arc, used as an energy source in the tungsten inert gas (TIG)-mediated welding of Duplex UNS S31803 stainless steel, to attend the manufacture of flexible pipes for the extraction of oil and gas is presented. A fundamental part in the manufacturing process of flexible pipelines is the welding of these strips so that corresponding TIG welds will be subjected to the same process and work conditions. Therefore, it is necessary to maintain the same properties in the welded regions. Covering the effects of each parameter of the pulsed electric arc such as peak and base current as welds, cyclic ratio, and pulsation frequency is a desirable endeavor. The final objective is the mitigation of problems that have a great impact on production, such as weld breakage during the conformation of the strip in the process and test failures. With this, tensile, bending, and ferrite percentage tests were performed on 12 samples that qualified as satisfactory in the visual aspect. A minimum tensile strength of 734.57 MPa and a maximum of 775.77 MPa were obtained where all values found are above the tensile strength limit of the base material of 620 MPa. With the completion of the study, it is possible to understand not only the response of the process to each parameter but also the tendency when changing them. Moreover, it is possible to explore the possibility of guiding the changes to achieve results about the visual aspect and the mechanical properties of the welded material. [ABSTRACT FROM AUTHOR]

Post weld heat treatment, or PWHT, is often used to improve the mechanical properties of materials that have been welded. Several publications have investigated the effects of the PWHT process using experimental designs. However, the modeling and optimization using the integration of machine learning (ML) and metaheuristics have yet to be reported, which are fundamental steps toward intelligent manufacturing applications. This research proposes a novel approach using ML techniques and metaheuristics to optimize PWHT process parameters. The goal is to determine the optimal PWHT parameters for both single and multiple objective perspectives. In this research, support vector regression (SVR), K-nearest neighbors (KNN), decision tree (DT), and random forest (RF) were ML techniques employed to obtain a relationship model between PWHT parameters and mechanical properties: ultimate tensile strength (UTS) and elongation percentage (EL). The results show that the SVR demonstrated superior performance among ML techniques for both UTS and EL models. Then, SVR is used with metaheuristics such as differential evolution (DE), particle swarm optimization (PSO), and genetic algorithms (GA). SVR-PSO shows the fastest convergence among other combinations. The final solutions of single-objective and Pareto solutions were also suggested in this research. [ABSTRACT FROM AUTHOR]

The Gas Tungsten Arc Welding (GTAW) between P22 (2.25Cr-1Mo) and P91 (9Cr-1Mo) steels are quite common in heavy vehicle structures like; railway locomotives and war (or combat) vehicles. After welding, high hardness values of the Heat-Affected Zones (HAZs) of these dissimilar weld joints are possibly obtained. The uneven hardness in HAZ comes from the austenite transformation to Martensite, because of highly uncontrolled cooling rates. The considerable difference in hardness among various zones leads to prior cracking and is bound to failure during high-temperature operations. Therefore, there is a dire need to establish an appropriate Post Weld Heat Treatment (PWHT) to temper the dissimilar weld joints for required durability. The study investigates the microstructure and mechanical properties of various erupted zones of steel, before and after the application of PWHT. Before and after PWHT, weld zone and HAZ in P22 and P91 are mechanically tested and metallurgically examined. Further PWHT is tried to be optimised strategically and statistically, for the least variation in hardness among different zones. So that any failure due to thermal stresses or strains, during normal running conditions can be avoided. [ABSTRACT FROM AUTHOR]

Residual stress affects the service safety of pipelines, but there are few efficient methods to reduce the residual stress, especially for long-distance pipelines with large diameters. In this paper, a Secondary Post Weld Heat Treatment (S-PWHT) stress reduction method with low temperature and two narrow heating bands is proposed, and this method fully considers the failure of the corrosion resistance layer caused by high temperature. The temperature distribution and stress distribution under different S-PWHT parameters are compared to obtain the optimal S-PWHT parameters using finite element numerical simulation. The thermocouples are conducted to verify the temperature, and the coercivity experiment is used to verify the stress distribution. Results show that two heating bands width of 80 mm and a peak temperature of 120 °C are the optimal S-PWHT parameters with the stress reduced by 61 %. Besides, the levels of stress reduction on the inner surface and the HAZ are higher than those on the outer surface and the base metal, respectively. The high-stress zone is transferred from the inner surface to the outer surface, and from the HAZ to the base metal. Furthermore, the stress reduction mechanism of S-PWHT has been revealed through constraint theory. Temperature change is the initial force, and the constraint is the driving force for stress reduction. [Display omitted] • Established a stress reduction process for the girth welds of the narrow width of the heating bands and the low peak temperature. • This process homogenizes and reduces the stress. The high-stress zone transfers from the HAZ to the base metal. • Constraint theory becomes the supporting theory for this process. [ABSTRACT FROM AUTHOR]

Mandrels for chemical injection are used in the production column of oil and gas wells, a complex system below the Christmas tree, also known as oil country tubular goods. The exploration in the deep water and sub-salt layer brought new problems, such as the increase of the aggressiveness of the transported fluids. Supermartensitic stainless steels (SMSSs) are used to construct mandrels, and the fabrication processes include the joining of forged and seamless tubes by welding. Even containing much less carbon than traditional martensitic stainless steels, the welding of SMSSs requires attention. In this work, the microstructure and sulfide stress cracking resistance of welded joints of a mandrel were analyzed. The objective was to evaluate whether other mandrels from the same supplier can be put into service in mid-sour environments. The results show that even being heat-treated after welding, the weld metal has poor resistance to sulfide stress cracking, and this can be attributed to the excessive hardness of the WM and also to the presence of welding defects (pores). [ABSTRACT FROM AUTHOR]

Nowadays there is an increasing demand to develop light weight defense vehicles, fighter aircrafts and warships in order to enhance their mobility and fuel economy. It can be achieved by using the light weight structures made up of Aluminum and Magnesium plates which will reduce the weight, increase the payload carrying capacity and efficiency of the vehicles. In the present work, experimental ballistic performance of Magnesium (AZ31B) Base Metal (BM), friction-stir-welded (FSW) and post-weld-heat treated (PWHT) target plates have been determined by using the 7.62 mm Armor Piercing Projectiles (APP). Prior to ballistic testing, Magnesium joints were prepared by the FSW process for various tool rotational and welding speeds. Defect-free welds with better tensile and impact properties, were obtained with tool rotational speed of 1200 rpm and the welding speed of 50 mm/min. PWHT was carried out with the annealing temperature at 250 °C for about 1 hour. Microhardness and microstructure of the FSW and PWHT joints were investigated. Highest hardness (67 HV) was obtained for fine grain structure and precipitated particles were observed for PWHT targets. Depth of Penetration of PWHT target plates was approximately 17.55% and 16.31% lower than the BM and FSW target plates respectively. Scanning Electron Microscopic observation of projectile penetrated channel showed the formation of Adiabatic Shear Bands (ASBs). Due to a larger number of ASB lines, ballistic impacted FSW surface showed more number of macro cracks compared to PWHT surface. The PWHT joints showed the absence of fragmentation failure, lesser cracks and ASB lines which increased the ballistic performance. [ABSTRACT FROM AUTHOR]

Underclad cracking in nuclear pressure vessels was of significant concern in the 1970s and 1980s before mitigating adjustments were made both to steel compositions and manufacturing practice. Unfortunately, the cracking mechanisms are still not well understood, and this can undermine confidence when changes to cladding operations are under consideration. In this work, Charpy-sized test coupons of 18MND5 steel were subject to a range of thermal cycles that can be experienced by the substrate immediately adjacent to the interface with the overlay. The Charpy test results are considered in combination with analysis of the samples through field emission gun (FEG) scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDXS). The findings suggest that the heat affected zone subject to the coarse grained plus intercritical thermal cycle, before post weld heat treatment, has a peculiar and potentially brittle microstructure. However, in a steel with no obvious macrosegregation, no clear evidence of intergranular cracking in the early stages of the post weld heat treatment could be found. The second part of the work focuses on the effects of segregation regions in large forgings, more specifically ghost lines, on the tendency for underclad cracking. Ghost line regions that subsequently form a coarse grained heat affected zone (CGHAZ), and are then heated to just under the A 1 temperature, seem to be the most prone to intergranular cracking. Cracking susceptibility appears to be associated with elevated concentrations of alloying and impurity elements at grain boundaries. • The underclad cracking mechanism in 18MND5 seems different from that in Cr-Mo steels. • Solidification segregation, temper embrittlement appear to cause underclad cracking. • Intergranular fracture risk was highest where prior austenite grain size was highest. • The intercritical heat affected zone had intermediate tendency for fracture. • Deposition strategies should aim at maximum refinement of prior austenite grains. [ABSTRACT FROM AUTHOR]

In this study, the effect post weld heat treatment (PWHT) on microstructural evolution and mechanical properties of weld metal of HT700P alloy with Inconel 617 filler metal was investigated. After welding, columnar grain, dendritic microstructure and segregation of Mo, Co and Ti elements related to the equilibrium distribution coefficient were observed in the weld metal. The PWHT was conducted in both direct-aging treatment with different time and solution treatment with different cooling methods. The results showed that direct-aging treatment had a limit impact on homogenization of weld metal, while microstructural homogenization and elemental segregation were significantly improved after solution treatment and massive M 6 C and M 23 C 6 carbides precipitated at the grain boundaries and interdendritic region of weld metal. It was found that the elongation at 700 °C of welded joints after solution treatment was relatively increased, which was related to the decrease of residual stress and the precipitation of Mo-rich carbides at the grain boundaries. The fracture occurred in the weld metal presented interdendritic fracture characteristics, and the fracture mechanism for stress relaxation cracking was the strong grain interior induced by the precipitation of γ′ phase, leading to the stress concentration and nucleation of cavities at grain boundaries. After solution treatment, the creep lifetime of furnace cooling was much greater than that of water quenching. The superior creep properties of furnace-cooled joint could be attributed to the lower residual stress and the migration of carbon element in the fusion line, which inhibited the nucleation and aggregation of cavities in the partially melted zone. • Effect of PWHT on microstructure and properties of welded joints of a Fe-Ni-based alloy is studied. • The segregation of Mo, Co, Ti in the weld metal and fusion line is analyze. • The mechanism for stress relaxation cracking is illustrated after different PWHT. • Residual stress and carbon migration in fusion line dramatically affect creep life of joints. [ABSTRACT FROM AUTHOR]

• HF-ERW welding resulted in the formation of tensile residual stress, resulting in failure of the tube during flattening operation. • Thermo-mechanically heat-affected zone were found to have (1 1 0)[0 0 1],(1 1 0)[1 1 ¯ 0], (0 0 1)[1 1 ¯ 0], (0 0 1)[ 11 ¯ 0] texture. • Post weld heat treatment was found to be effective in alleviating tensile residual stress and preventing tube failure. High-frequency electric resistance welding is used for manufacturing hydro formable tubes. Tube forming and welding results in the formation of residual stress. The hole drilling technique was used to evaluate the residual stress of the welded tube. Tensile residual stress of varying magnitude was observed at different locations on the tube. The weld, heat affected zone was observed to have the highest residual stress as a result of phase transformation, forming and gradually reduced towards the parent material. The generated tensile residual stress led to failure of the tube during mechanical evaluation. Additionally, electron backscattered diffraction studies (EBSD) of the fusion line and the thermo-mechanically heat-affected zone were found to have goss and cube texture. These detrimental textures can lead to easy crack propagation in the presence of defects along the fusion line. A post-weld heat treatment (PWHT) was carried out to alleviate the tensile residual stress and alter the weld microstructure. PWHT helped transform the bainite in the weld to ferrite and pearlite. The inter-critical annealing significantly reduced the tensile residual stress along the circumferential direction resulting in improved formability. [ABSTRACT FROM AUTHOR]

The paper analyses the possibility of post weld heat treatment (PWHT) quality assessment with the help of magnetoacoustic emission (MAE) signal measurements. Two welded superheater tubes, made of high chromium VM12 steel, were analysed—as welded and heat treated one. The analysed sample in the as welded state exhibited significantly higher hardness, accompanied by a big difference in the MAE signal intensity (of order of about 50%). In order to explain that, the influence of tempering on the MAE signal intensity is demonstrated for the very similar X20CrMoV12.1 steel. It is shown that the observed increase of the MAE intensity as a function of annealing time is directly correlated with the change in hardness. The as described dependence allows to propose a method based on the MAE signal measurements as a new tool for the PWHT assessment. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of post-weld heat treatment (PWHT) on the microstructure, microhardness, and sulfide stress corrosion cracking (SSCC) of IN625 weld overlay on AISI 4130. In this paper, cladding was conducted by TIG (tungsten inert gas arc welding) technique, then PWHT was carried out at 650, 750, and 850°C temperatures with the constant time of 1 h. Also, the SSCC test was performed for 720 h. According to the results, columnar dendrites with MC carbide in g solid solution matrix comprise the microstructure. Furthermore, there was not any crack in the Weld Overlay (WO), tempered martensite, bainite in the base metal (BM), coarse tempered martensite, and ferrite in the heat-affected zone (HAZ). The results demonstrate that as the temperature of PWHT rises, the hardness of BM and HAZ reduces while hardness in the WO increases; it can be seen that at 750°C γ'' phase rapidly emerged and changed to stable δ at 850°C by the shearing mechanism. Furthermore, the results of the magnetic test showed stress crack in samples that heat-treated at 850°C. SEM images reveal that stress cracks in BM continued along grain boundaries and reached the WO. [ABSTRACT FROM AUTHOR]

Tn order to obtain a 0.2 mm-thick NiTi shape memory alloy (NiTi-SMA) welded joint with a small difference in phase transformation temperature between the welded metal and the base metal, it will meet the needs of practical applications. Tn this paper, the Nb element is introduced into the weld by adding welding wire, and the welded joint is aging treated after welding to realize the control of the weld metal phase transition temperature, so that it can reach a level similar to that of the base metal. The results show that the weld metal of NiTi joint with Nb wire is mainly R2 phase, R1 S'phase, NbTi phase, Nb phase and (NiTi，Nb) solid solution, and Ni4Ti3 phase precipitates from weld metal after PWHT at 600°C. Through the compound method of "adding 0.1 0mmNb wire+ PWHT at 600 °C"，weld metal with As and Ms very close to that of NiTi base metal was obtained. [ABSTRACT FROM AUTHOR]

Ferritic stainless steel is admired for its corrosion resistance property in chloride atmosphere, and low cost. It is designed as an alternative to carbon steel, and in some applications it has also replaced austenitic stainless steel. Despite its appreciating mechanical properties, it suffers from drawback of low weldability which constraint its utilization. High grain growth is observed at heat affected zone and fusion zone during welding. This degrades its mechanical and microstructural properties. Further, welding of plate above 8mm thickness, with conventional welding process, exhibits high deterioration of properties which restrict the thickness of plate to be welded. In the present research, attempts have been made to weld 18mm thick AISI 409 ferritic steel plate in a single pass weld. Electron beam welding process was used to prepare the joint. The joint was investigated for macro-structural, micro-structural, micro-hardness, impact toughness and tensile strength. The coarse ferrite grains of base metal were converted into fine equiaxed columnar grains in the weld zone. The results revealed higher tensile strength, yield strength and micro-hardness values of weld joint than the base metal. The weld joint properties improved after subjecting to post weld heat treatment at 550°C for 75 minutes. [ABSTRACT FROM AUTHOR]

The present study centres on the effect of post-weld heat treatment (PWHT) on microstructure and mechanical properties of the deep penetration keyhole Tungsten Inert Gas (K-TIG) welded dissimilar joint between creep strength enhanced ferritic (CSEF) steel and austenitic stainless steel (ASS). The as-received normalized and tempered CSEF steel was joined with ASS in a single pass without using any filler materials and edge preparation. Detailed characterization across the welded joint was conducted using stereomicroscope, electron microscopy, energy dispersive spectroscopy (EDS), electron backscattered diffraction (EBSD), hardness test, tensile test and Charpy impact test. Results showed that PWHT had significant effect on the microstructure and mechanical properties of both the weld metal and CSEF steel heat-affected zone (HAZ), while it had little influence on the ASS side. By using proper PWHT, the hardness gradient across the welded joint could be mitigated and toughness in both the weld metal and the CSEF steel HAZ could be restored. 760 °C was considered the most appropriate PWHT temperature for such dissimilar joint in terms of the overall mechanical properties. The tensile properties of K-TIG welded joint after PWHT were comparable to both friction stir welded joint and laser and/or electron beam welded joint, indicating that deep penetration TIG welding technology may provide a good alternative for the nuclear industry. The correlation among welding thermal cycle, various heat treatment, microstructure evolution and mechanical properties was also analysed in detail. [ABSTRACT FROM AUTHOR]

Dissimilar metal welds of austenitic stainless steels are widely used in heat exchangers. In the present study, an attempt has been made to review the Gas Tungsten Arc Welding based dissimilar metal welds of austenitic stainless steels. Dissimilar metal welds of stainless steels and low alloy steels are extensively used in power generation equipment's such as steam generators, super heaters and cooling systems. Dissimilar metal welds of austenitic stainless steel austenitic stainless steel and Nickel alloys are used in heat exchangers in oil and gas industries. Selection of filler wires and welding parameters used in dissimilar metal welds are reviewed and their effect on microstructure is studied. Variation of mechanical properties including micro hardness and tensile properties with welding conditions has been recorded. Corrosion resistance which is very much important in heat exchanger applications is comprised in the study. Post weld treatments are important for stress relieving and improvement of mechanical properties. A comprehensive review on the above characteristics has been made to facilitate ongoing research on dissimilar metal welds of Austenitic stainless steel using Gas Tungsten Arc Welding. [ABSTRACT FROM AUTHOR]

The 9Ni steel low carbon steel is usually applied to pipes, pressure vessels and forged parts working at cryogenic temperatures, due to its high toughness at −196 °C and mechanical strength. Recently, this material was selected to facilities for storage and re-injection of CO 2 gas in modern off shore oil and gas platforms. In this new application the steel may be subjected to high pressures in as environment with condensed water, CO 2 and traces of H 2 S. The effect of such a harsh environment on the simulated heat affected zone (HAZ) was investigated by slow strain rate tensile (SSRT) tests. Two post weld heat treatments (PWHT) were reproduced, single tempering (ST) at 575 °C and double tempering (DT) at 670 °C (2 h) and 600 °C (2 h). Specimens without PWHT were more susceptible to sulfide stress cracking (SSC), while the single tempering at 575 °C decreased both the hardness and the SSC susceptibility. Double tempering also increased the resistance to SSC, but was not more effective than the single tempering. As general conclusion, PWHT is strongly recommended to 9Ni low carbon steels subjected to H 2 S containing environments. • The heat affected zone of 9Ni low carbon steel is susceptible to sulfide stress cracking (SSC). • Single tempering at 575 °C, as post weld heat treatment (PWHT), decreases the susceptibility to SSC. • Double tempering was not better than single tempering as mitigation action to SSC. • PWHT should be mandatory to 9Ni steels handling with H 2 S containing solutions. [ABSTRACT FROM AUTHOR]

Abstract Post weld heat treatment (PWHT) process has an important role on fabrication of advanced ultra-supercritical power plant turbines. This process relieves the residual stresses formed as a result of welding by converting elastic strains into creep strains. In order to analyse the residual stress relief mechanism during the PWHT process, a novel simulation approach based on experimental data was developed for the analysis of residual stress states from complex manufacturing processes which are welding and heat treatment. This model uses permanent plastic strains (eigenstrains) formed as a result of welding process to set the initial mechanical state of the sample. The distribution of eigenstrains in the whole body was determined using displacement data obtained from contour measurements. The use of eigenstrains to set the initial residual stress state of the creep model reduced the number of uncertainties. This allowed the use of the principles of artificial intelligence for the development of a new fuzzy finite element model (fFEM) that determines the eigenstrain-creep model parameters through an evolution process. Subsequent to the determination of the model parameters, conditions of the PWHT process are investigated to analyse residual stress relaxation in Inconel Alloy 740H weldments. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The microstructural evolution and mechanical properties of brazed joints were evaluated before and after the post weld heat treatment. The microstructure and shear strength of brazed joints were improved with the brazing temperature increased, and the highest shear strength of 42 MPa was obtained when brazed at 600 °C. The coarse grains were presented in the joints brazed at the higher brazing temperature, which deteriorated the shear strength dramatically. Post weld heat treatment which including solution treatment and retrogression and re-aging treatment were performed to improve the microstructure and mechanical properties of brazed joints. Through the solution treatment, the brittle intermetallic compounds were reduced significantly and the recrystallization occurred in brazed joints. The coarse lath grains were transformed to the fine grains. After the solution treatment, the retrogression and re-aging treatment were performed and the precipitates which continuously distributed along the grain boundaries were dissolved into the aluminum matrix gradually with the retrogression temperature increased. The fine precipitates were uniformly distributed within the grains and discontinuously distributed on the grain boundaries. When the retrogression temperature was 200 °C, the highest shear strength of 108 MPa was obtained which increased by 160% compared to the shear strength of the brazed joints without post weld heat treatment. [ABSTRACT FROM AUTHOR]

• Simulated HAZ of V-alloyed supermartenstic steel has a microsctructure of martensite, delta ferrite and fine precipitates. • PWHT are necessary to increase the ductility, and decrease the hardness of the HAZ. • Single tempering (620 °C) and double tempering (670 °C and 620 °C), as PWHT, have similar effects in the HAZ. • Base metal and HAZ with PWHT suffered embrittlement in SSRT tests in sour environnments. Supermartensitic stainless steels (SSMSs) with 12–13%Cr, 5%Ni, 2%Mo and microadditions were developed to casings, tubullars and mandrels used in the oil and gas off-shore production. These materials have great resistance to aqueous medium containing large amounts of CO 2 and can withstand high temperatures and large amounts of chloride as well. However, SMSSs have a limited resistance to H 2 S containing solutions, and may fail due to sulfide stress cracking (SSC). This limit is even lower for forged and welded components that used in mandrels. Recent studies have been developed to find an operational envelope for safe use of SMSSs in sour production systems. The present study shows the results of slow strain rate testing (SSRT) of a forged V-alloyed SMSS submited to thermal simulation in Gleeble machine to produce a coarse grain heat affected zone (HAZ). The microstructure of the HAZ is characterized by fresh martensite, intergranular delta ferrite and fine precipitates which increase the hardness to a level above the maximum limit for sulfide stress corrosion cracking. The effects of two post weld heat treatments (PWHT) on the mechanical properties and susceptibility SSC were evaluated. Single and double tempering treatments provoked the decrease of hardness and the increase of ductility parameters. However, specimens representative of the HAZ, base metal, and HAZ with single and double tempering presented high SSC susceptibility parameters in SSRT in saline solution (200,000 ppm NaCl) with 1.0 psia of H 2 S partial pressure, and pH 4.5. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the effect of different temperatures of post weld heat treatments on the residual stress and mechanical properties were investigated for dissimilar joint of ASTM A537CL1 pressure vessel steel to AISI A321 austenitic stainless steel. These joints are commonly used in high temperature services such as boilers, pressure vessels, heat exchangers in petrochemical, oil and gas industries, etc. For this purpose, gas-tungsten arc welding process with ER308L filler metal with diameter of 1.8 mm was used. Then, post weld heat treatment (PWHT) was carried out at 480, 560, 620 and 680 °C for 75 min on the samples. The optical microscope and scanning electron microscope (SEM) were used to study the microstructure and fracture surface of the welded samples. Also, the mechanical behavior of the joint was evaluated by tensile, impact and microhardness tests. The residual stresses of the samples were evaluated with ultrasonic technique. Results showed that the post weld heat treatment had not any significant effect on microstructure of different regions of the joint. Mechanical properties such as ultimate tensile strength and hardness were reduced after post weld heat treatment process. In addition, results of residual stress measurements of the joints showed that the welded sample (without being heat treated) had maximum residual stress, while the sample which was heat treated in 620 °C had minimum residual stress. Impact energy was reduced 52% at this temperature and it was found that 620 °C was the optimum temperature. Highlights • Different post weld heat treatments had no effect on microstructure and grain size. • Hardness of cross samples reduced with applying PWHT. • Tensile strength decreased by increasing PWHT temperature. • Charpy V-notch toughness increased at 480 and 560 °C, but it reduced and at 620 and 680 °C temperatures. [ABSTRACT FROM AUTHOR]

Supermartensitic stainless steels (SMSS) with 11–13%Cr were developed to show higher corrosion resistance, toughness and weldability than conventional martensitic stainless steels (MSS). The main compositional characteristics of SMSS's, in a comparison to common MSS's, are the extra low C content, Ni and Mo addition. This new sub-family of stainless steels has been used in the oil and gas offshore production, as tubulars and casings in the wheel. Despite of the extra low C (<0.03%), the mechanical resistance of SMSS's is maintained high due to the addition of Mo (up to 2.0%wt.), and other elements, such as N, W, Nb and or Ti. As a consequence of the extra low C, the martensite of SMSS's is relatively soft and tough, which makes these steels, in theory, much more resistant to cold cracking in the heat affected zone (HAZ) of welds. Nevertheless, for applications in saline environments with CO 2 and/or H 2 S a post weld heat treatment (PWHT) is necessary to reduce the peak of hardness in the HAZ. In the present work, the failure of a mandril for chemical products injection in the wheel made of SMSS is reported. The failure occurred in a welded joint between two heavy forged pieces. The hardness of the HAZ was higher than the minimum allowable to sour service conditions, indicating that the PWHT was not performed or it was done uncorrectly. [ABSTRACT FROM AUTHOR]

The effects of post weld heat treatment (PWHT) and oil quenching on the metallurgical and mechanical properties of the duplex (UNS S31803) welded joints were evaluated at three different temperatures namely 1080, 1150 and 1200 °C. The microstructural variation, austenite/ferrite phase changes, grain size measurements and microhardness aspects of the welded joint were observed. The fraction of ferrite and austenite phases was equivalent at 1150 °C. Nickel element was more efficient in controlling the twin phase balance. Finer grain structure was achieved at 1150 °C due to recrystallization effect. Twin phase presence and absence of precipitates were confirmed through XRD and TEM which followed Kurdjumov-Sachs relationship. At a heating pressure of 40 MPa, heating time of 4 s, an upsetting pressure of 80 MPa, and an upsetting time of 2 s during a PWHT at 1150 °C, a 50/50 balance between the duplex phases, fine grains, and increased microhardness were obtained. [ABSTRACT FROM AUTHOR]

In the present study, electron beam welding (EBW) was used to join reduced-activation ferritic-martensitic (RAFM) steel to 316L stainless steel. Microstructural evolution and mechanical property variation in the heat-affected zone (HAZ) and weld metal (WM) during the post weld heat treatment (PWHT) was investigated. The results suggested that the hardness of RAFM-HAZ decreased with increased PWHT temperature, while the hardness of WM decreased to minimum at 620 ℃ and then increased at higher PWHT temperatures. This was consistent with strength variation in the WM during PWHTs. Microstructural observations and corresponding phase diagram calculation indicated that blending of two types of base metals increased nickel content of WM, enlarged the two phase-region and lowered A 1 (start of transformation of ferrite to austenite) point of WM, as compared with similar ferritic-martensitic steel weld joint. Thus, reversed austenite transformation and subsequent martensite transformation occurred in WM of sample subjected to higher temperature heat treatment, while there was no transformation in the HAZ. This effect explained the changes in hardness and strength of WM corresponding to PWHT. The optimized properties of both HAZ and WM in the dissimilar weld joint were obtained by a two-step post weld heat treatment. [ABSTRACT FROM AUTHOR]

Gas tungsten arc welding (GTAW) was used to join plates of Inconel 718. The mechanical properties were determined by tensile, microhardness, and instrumented Charpy impact tests. An ERNiFeCr-2 filler metal fed by a semi-automatic mechanism was used. Partial dissolution of the strengthening phases, γ' and γ", induced a soft region (~ 225 HV1.0) in the heat-affected zone (HAZ) during welding. The yield strength (371.3 MPa) of the as-welded joint is approximately 45% of the base material in aged condition (822.7 MPa). The welds were subjected to a hardening recovery post weld heat treatment (HRPWHT). Impact testing of the hardened welds revealed a reduction of 17% in energy absorbed with respect the aged base material. Hardness measurements showed an increase to ~ 410 HV0.1 in the fusion zone; however, due to segregation of Nb and formation of carbides, the precipitation of γ" is not fully completed, and the yield strength (719 MPa) of the heat-treated welded joint is lower than the base material in aged condition. [ABSTRACT FROM AUTHOR]

Increasing the post-weld heat-treating temperature from 600 °C to 840 °C causes a transition of creep rupture locations from the Type IV cracking in the intercritical heat-affected zone to the Type I cracking in the fusion zone in the Grade 91 steel weldments. The specimens following a heat-treatment at temperatures below the A 1 temperature of the base metal failed in the Type IV cracking mode after high-temperature creep tests at 650 °C. The creep-damaged region associated with the Type IV cracking mode is consistently located in a softened zone, which is identified as the intercritical heat-affected zone. In the specimens heat-treated at temperatures close to or above the A 1 temperature of the base metal, the fusion zone enters the intercritical temperature between its A 1 and A 3 temperatures. The fusion zone experienced a partial austenitization to become a mixture of retained ferrite and new martensite, which is believed the most creep-susceptible. The same microstructure, a mixture of retained soft ferrite and new hard martensite, caused nucleation and growth of cavities in the both Type IV and Type I damaged regions. Therefore, it is suggested that the same creep mechanism may have contributed to both cracking modes in Grade 91 steel. [ABSTRACT FROM AUTHOR]

The instrumented indentation test and the microstructure-based finite element analysis were used to study the effect of post weld heat treatment (PWHT) on the mechanical properties of C-Mn weld metal, i.e. the individual microstructures, the heterogeneous deformation distribution and the plastic strain localization under tensile loading. It is found that the PWHT significantly influences the strength of weld metal by changing the strength of individual microstructures: the grain boundary ferrite is softened after PWHT regardless of the holding temperatures; the acicular ferrite is softened after treating at 400 °C and 700 °C, whereas hardened after treating at 600 °C; the variation of the mechanical properties is due to the reduction of dislocation and the precipitation of carbonitride. As a result, the strength variation between grain boundary ferrite and acicular ferrite after the PWHT leads to the distinct distribution of plastic strain localization in weld metal and the critical fracture strain of weld metal. [ABSTRACT FROM AUTHOR]

The techniques of InterPulse magnetic constriction and high frequency pulsation of arc in gas tungsten arc welding (GTAW) were deployed to minimize the detrimental intermetallic laves phase evolution in fusion zone (FZ) of Superalloy-718 welds and enhance the precipitation strengthening of joints. The Superalloy-718 joints were developed by using an advanced variant of GTAW popularly known as InterPulse gas tungsten constricted arc welding (IP-GTCAW). The joints were subjected to the post weld heat treatment (PWHT) cycles of direct aging (DA), solution annealing at 980 °C and 1065 °C followed by aging (980STA and 1065STA) respectively. The tensile properties and hardness of joints were evaluated. The microstructures of joints were analyzed using optical (OM) and scanning electron microscopy (SEM). The elemental analysis of Laves phase and dendrite core of FZ of joints was performed by using energy dispersive spectroscopy (EDS). The tensile fractured surfaces were analyzed using SEM. Results showed that the Superalloy-718 joints developed using IP-GTCAW showed better response to PWHT than GTAW joints because of the greater refinement of FZ microstructure and evolution of finer and discrete Laves phases in FZ. The 980STA joints exhibited superior tensile properties than DA and 1065STA joints. It is correlated to the greater dissolution of Laves phases in nickel austenitic (γ) matrix of FZ resulting in more niobium (Nb) accessible for the precipitation strengthening of FZ. The 1065STA joints showed slightly higher hardness of FZ than 980STA joints because of the almost complete dissolution of Laves phases in FZ. However, the tensile properties of 1065STA joints are lower than 980STA joints because of severe grain growth in FZ and BM. The evolution of microvoids at the interface of Laves phase/weld matrix leading to the development and coalescence of microcracks in FZ on tensile loading is the main mechanism responsible for the premature fracture of joints. [ABSTRACT FROM AUTHOR]

The temperature filed was simulated by use of the established moving heat source model of TIG welded impeller. The obtained computational temperature can be treated as thermal load for the computation of the residual stress near weld. The comparison with experimental data in published literature can validate the proposed models. The effect of the post weld heat treatment (PWHT) was studied by the Norton creep law model. Results indicate that the circumferential residual stress in blade is obviously higher than the vertical residual stress. The final residual stress in the impeller can be greatly decreased by the PWHT. The PWHT temperature is the most important factor in the PWHT process. Higher PWHT temperature can be beneficial to the decrease of the residual stress. But when the PWHT temperature is higher enough, stress concentration occurs at the corner of blade. PWHT process can obviously decrease the residual stress intensity factor. [ABSTRACT FROM AUTHOR]

The effect of postweld heat treatment (PWHT) on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel joints with ER316LMn filler material was investigated. PWHT aging was performed for 1 h at four different temperatures of 600 °C, 760 °C, 870 °C and 920 °C, respectively. The microstructure revealed the sigma phase precipitation occurred in the weld metals heat-treated at the temperature of 870 °C and 920 °C. The PWHT temperatures have the less effect on the tensile strength, and the maximum tensile strength of the joints is about 630 MPa, reaching the 95% of the base metal, whereas the elongation is enhanced with the rise of PWHT temperatures. Meanwhile, the sigma phase precipitation in the weld metals reduces the impact toughness. [ABSTRACT FROM AUTHOR]

Ultrasonic additive manufacturing (UAM) is a solid-state additive manufacturing technique employing principles of ultrasonic welding coupled with mechanized tape layering to fabricate fully functional parts. However, parts fabricated using UAM often exhibit a reduction in strength levels when loaded normal to the welding interfaces (Z-direction). In this work, the effect of post-weld heat treatments (PWHT) on Al-6061 builds fabricated using the UAM process was explored aiming to improve the mechanical strength of the UAM builds. Tensile testing with digital image correlation (DIC) coupled with metallography along with multi-scale structure characterization (SEM-EBSD) was used to investigate and rationalize the mechanical performance of the UAM builds. It was established that PWHTs may improve the Z-strength level by the factor of ~3÷3.5 (from ~46 to 177 MPa). The improvements in the strength level were primarily aided by material aging and grain growth across the bond interface. [ABSTRACT FROM AUTHOR]

In this research, AISI 2507 super duplex/AISI 317L austenitic stainless steels were joined by laser beam welding technique. The effects of heat input and post weld heat treatment (PWHT) on surface, texture, microstructure and mechanical properties were investigated. Based on the experimental results, it has been determined that the weld metal (WM) exhibits a duplex microstructure. Ferrite grains, grain boundary austenite, intragranular austenite and widmanstatten austenite and dislocation formations were detected in WM. In addition, ferrite, austenite grains and stacking faults were detected in the base metal (BM) of 2507 super duplex and 317L austenitic stainless steels. While dislocation and stacking fault formations disappeared after PWHT, Cr 23 C 6 precipitates were formed. While a K-S and N-W orientation relationship (OR) was generally seen in the samples with and without PWHT, no OR was seen in the BM of the 317L side. In addition, the PWHT result of the Bain OR seen in the WM of the welded sample was not seen. The findings showed that while the Oxygen core on the WM surface of the sample without PWHT and PWHT was at the highest level at first, it then became zero as it descended deeper. Moreover, it was determined that the levels of Fe, Cr, Ni and Mo nuclei, which were at low levels at first, increased as one went deeper. It has been determined that as the heat input increases, the tensile strength, hardness and bending force decrement, while the toughness values increase in the welded samples. Based on PWHT, there is a reduction in tensile strength, hardness and bending force; [111] orientation to the grains [101] and [001] grains, a rise in the proportion of grains with a Schmid Factor (SF) value greater than 0.4, a decrement in kernel average misorientation (KAM) values and coincidence site lattice (CSL) boundary ratios, (001)<100> and (112)<111> this component has been caused by changes such as the emergence of recrystallized γ grains causing a rise in austenite content, increase in grain size, disappearance of stacking fault occurrences and dislocations. It was determined that the rise in toughness was caused by the emergence of (113)<332> component and the increase in low angle grain boundary ratios. [Display omitted] • Weld metal microstructure of 2507 super duplex/317L austenitic stainless steels exhibited duplex microstructure. • Due to heat input and PWHT, dislocation, stacking fault and Cr 23 C 6 precipitates were observed as well as δ and γ grains. • Tensile strength was adversely affected due to the orientation of the grains in [001] and [101] directions after PWHT. • The toughness improved due to the appearance of (001)<100>, (112)<111>, (113)<332> components in the texture with PWHT. • Tensile and bending strength decreased due to changes in Schmid Factor ratios, CSL boundary ratios and KAM values after PWHT. [ABSTRACT FROM AUTHOR]

The blanket shield block (SB) shall be required the tight tolerance because SB interfaces with many components, such as flexible support keypads, First Wall (FW) support contact surfaces, FW central bolt, electrical strap contact surfaces and attachment inserts for both FW and Vacuum Vessel (VV). In order to fulfil the tight tolerance requirement, stress relieving shall be performed for dimensional stability after cover welding operation. In this paper, effect of Post Weld Heat Treatment (PWHT) conditions, temperature and holding time, was investigated on the residual stress and hardness. The 316L Stainless Steel (SS) was prepared and welded by manual TIG welding by using filler material with 2.4 mm of diameter. Welded 316L SS plate was machined to prepare the specimen for PWHT. PWHT was implemented at 250, 300, 400 °C for 2 and 3 h (400 °C only) and residual stress after relaxation were determined. The evaluation of residual stress and hardness for each specimen was carried out by instrumented indentation technique. The residual stress and hardness were decreased with increasing the heat treatment temperature and holding time. [ABSTRACT FROM AUTHOR]

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% SiO 2 +50% MoO 3 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. [ABSTRACT FROM AUTHOR]

In the past decade, TWI has been working together with Nagra (the Swiss national cooperative responsible for the disposal of radioactive waste) to develop design concepts for canisters for the disposal of Spent Fuel (SF) and High Level Waste (HLW) in a deep geological repository. The canisters must provide containment of radionuclides for more than 10,000 years. Several different canister designs have been investigated. A forged carbon steel canister is the current reference design. In the framework of options evaluation and optimisation, this study summarises the work carried out to determine the structural integrity of a closure weld during long-term disposal. An analytical study on the lid and weld design for the closure weld and final materials selection have been undertaken. The lid and closure weld designs were refined to avoid heating the nuclear waste above its allowable temperature during post-weld heat treatment (PWHT). Flaw assessments in accordance with the procedures and guidance given in BS 7910, along with finite element analyses (FEA), were used to identify the most suitable combination of PWHT and lid design to ensure no breach of containment within 10,000 years. • A proposed lid design for a nuclear waste canister is evaluated; the requirement is to ensure integrity for 10,000 years. • BS 7910 is successfully used to assess an atypical application. • To achieve this, FEA and ECA are combined in a complementary approach. [ABSTRACT FROM AUTHOR]

In this study, AISI 904L super austenitic - AISI 317L austenitic stainless steel sheets were successfully welded by laser welding method using six different heat inputs. Welded samples went through 1 h of post-weld heat treatment (PWHT) at 1100 °C and then left to cool at room temperature. The effect of PWHT and welding heat input on surface, texture, microstructure and mechanical properties has been examined. According to the results obtained in the study, it was observed that the weld metal microstructure of the samples welded at the lowest and highest heat input values consisted entirely of austenite (dendritic + interdendritic) grains. With PWHT, Cr 23 C 6 precipitation was observed in both grain boundaries and austenite grains. In addition, austenite as well as dislocation and stacking fault formations were observed in the microstructure. While the highest austenite content was observed in the microstructure of AISI 317L, the content of austenite increased in all samples with PWHT. It was observed that most of the grains that were orientated in the [111] direction were orientated in the direction of [101] and [001] after PWHT. However, the KAM values of the dislocation in grain boundaries decreased with the effect of PWHT. In addition, with the reduction of the ratio of dark grains and the effect of re-crystallisation, (112) <111> components representing austenite grains appeared in FCC/BCC texture. It was identified that due to these textural changes, the tensile strength and resistance to bending of the samples were negatively affected but their toughness was positively affected. AB3 sample with the highest tensile strength, hardness, bending strength and lowest toughness had values of 615 MPa, 214 HV, 1100 N and 57 J, respectively, while these values changed to 550 MPa, 181 HV, 720 N and 60 J with the effect of PWHT. Due to the presence of the chromium-oxide layer, it was identified that the density of O− ion and H− ion was at high levels on the surface of the weld metal. It was identified that the density of these ions decreases with increasing depth, while Fe−, Cr− and Ni− ions increase. Excellent K–S and N–W orientation relationship (OR) was observed between FCC/BCC-structured grains present in the microstructure of without PWHT base metals and weld metal, while Bain OR was also observed in weld metal with or without PWHT. In the microstructure of the base metals with PWHT, there was no OR relationship between grains with FCC/BCC structures. • WM consists of almost fully in austenitic and formations such as dislocation and stacking fault have also been observed. • Cr 23 C 6 has precipitated in grain boundaries and austenite grains with the PWHT effect. • Mechanical properties were affected by changes in SF, KAM and grain orientations with the effect of heat input and PWHT. • High density of (112)<111> component emerged representing the γ grains re-crystallising with the effect of PWHT. • Density of O- and H-ions decreased with increasing depth, which was present on the surface of the WM at a high level. [ABSTRACT FROM AUTHOR]

In the present study, numerical and experimental investigation of stress distribution pattern has been performed for thick walled nuclear rotor pipe joint of Alloy 617 and 10Cr steel. Hot wire Tungsten Inert Gas (HW-TIG) welding process has been adopted for multipass narrow groove welding since it yields better mechanical properties at low heat input than manual TIG welding and decreases the accumulation of residual stress significantly. The residual stress generated at the surface of the welded joint was evaluated experimentally using the Blind hole drilling technique (BHD), and consequently, the distribution of stresses along the thickness of the welded joint was masured using the Deep hole drilling (DHD) method. According to the findings, shrinkage at the HAZ area of the weld influences the stresses generated at the cylinder outer surface. The distribution of residual stresses in the weld region is driven mostly by the bending effect produced during the welding process. The influence of post weld heat treatment (PWHT) on residual stress distribution has also been investigated using both experimental and numerical approaches. Numerical investigations have been performed using ABAQUS finite element method. A 2D finite element model has been developed to simulate the welding process and the subsequent heat treatment, using coupled thermo-mechanical analysis. The residual stress results obtained from the numerical approach were validated with the experimentally obtained results and a good correlation has been found. The lumped pass model along with an equal density heat source has been implemented to minimize the computation complexity without affecting the accuracy of the simulated results. The obtained findings revealed that apart from weld centerline, hoop tensile residual stresses were higher around the buttered layer of Alloy 617 and 10Cr steel in an as-welded state. It has been found that nearly 80% of the stresses generated along the weld section have been released after PWHT. • Study of multi-pass dissimilar welded joint of rotor joint of Alloy 617 and 10Cr steel. • Experimental investigation of through thickness residual stresses in the DWJ using the deep hole drilling (DHD) method. • Evaluation of surface residual stresses using blind hole drilling (BHD) method. • Validation of experimental results using numerical analysis. [ABSTRACT FROM AUTHOR]

This work investigates mechanical properties of weld joints of a reduced activation ferritic/martensitic steel, F82H and effects of post weld heat treatment on the welds. Vickers hardness, tensile and Charpy impact tests were conducted on F82H weld joints prepared using tungsten-inert-gas and electron beam after various heat treatments. Although narrow groove tungsten-inert-gas welding reduced volume of weld bead, significant embrittlement was observed in a heat affected zone transformed due to heat input. Post weld heat treatment above 993 K successfully moderated the brittle transformed region. The hardness of the brittle region strongly depends on the heat treatment temperature. Meanwhile, strength of base metal was slightly reduced by the treatment at temperature ranging from 993 to 1053 K. Moreover, softening due to double welding was observed only in the weld metal, but negligible in base metal. [ABSTRACT FROM AUTHOR]

This paper presents a novel technique for evaluation of quality of post weld heat treatment (PWHT) of modified 9Cr–1Mo (P91) steel weld by correlation with its magnetic coercive force (MCF). The MCF of modified 9Cr–1Mo steel was studied in respect of different PWHT cycles involving ordered variations of soaking temperature unto 770 °C and soaking time unto 140 min. It was observed that MCF of the weld metal reduced with increase in both the soaking temperature and soaking time of PWHT. The drop in MCF of welds after PWHT was found to be dependent on the drop in the hardness of the weld and on the degree of carbide precipitations seen in the weld microstructure. Based on the study, a criterion was evolved for evaluation of heat treatment quality of the weld. [ABSTRACT FROM AUTHOR]

The residual stresses in electron beam welded Titanium alloy before and after post weld heat treatment (PWHT) are measured by both of the contour method and X-ray diffraction method. The application of X-ray diffraction method on the surface of welded structure was used to confirm the results of the contour method induced by interpolation from CMM measuring position which is limited near the structure surface. The welding residual stresses are characterized, as well as the residual stress relaxation by PWHT at soaking temperatures of 500 and 650 °C and holding times ranging from 0 min to 2 h respectively. The measured results show that the maximum welding residual stress without PWHT is 550 MPa located inside the plate. The relaxation of the residual stresses from PWHT mainly depend on soaking temperature, and occurs most both in the heating stage and holding stage. The residual stresses are reduced to a limited value after the PWHT with soaking temperature of 650 °C and 2 h. [ABSTRACT FROM AUTHOR]

Welded joints of ASME Gr. 91 steel are subject to post-weld heat treatment (PWHT) to obtain sufficient mechanical properties. However, when the PWHT temperature is higher than the lower critical transformation temperature (AC1) of both the base metal and the weld metal, the mechanical properties of the weld may be degraded. To avoid this, it is important to know the AC1 of the weld. The authors have investigated several methods of measuring the AC1 of Gr. 91 steel weld metals to select the most credible method and examined the effects of the PWHT temperature on the mechanical properties of the weld metal. In addition, the proper PWHT temperature was discussed in consideration of the measurements of AC1 test results of creep-rupture performance, and observation results of precipitates. In the case of a low Mn + Ni weld metal, the upper PWHT temperature limit should be lower than AC1. On the other hand, in the case o f the high Mn + Ni weld metal, remarkable negative effects on the mechanical properties of the weld metal were not found, even though the PWHT temperature exceeds A by about 30 °C. [ABSTRACT FROM AUTHOR]

The so-called thermomechanical steels have undoubtedly reached an important diffusion at industrial level, as a semifinished products for designers and manufacturers, alternative to other comparable and available products, often in contrast to them, obtained with different manufacturing cycles. It's also evident that these steels are mainly used for fabricating structures, while it is less important their role in the pressure vessels construction, where it is not unusual to find specifications issued by major contractors, such as in the Oil & Gas field, for restricting or even prohibiting their application. In the fabrication of welded structures, the post weld heat treatment is notoriously less widespread than in the pressure vessels field: it's not surprising, that behavior and mechanical properties of these steels as a result of the post weld heat treatment are still relatively unknown. This paper was written after an experimental testing performed on FCAW welded joints of API 2W Gr. 60Z steel plates, with thickness 100 mm, compared with several heat treatment conditions and conducted by IIS Progress laboratories. The results are supplemented by a brief state of the art, which considers and summarizes the main references of the national and international technical literature. [ABSTRACT FROM AUTHOR]

Explosion welding is a solid state joining process that allows the manufacturing of corrosion resistant structural composite materials in the form of plates. In the present work, composite bimetal plates of AL-6XN superaustenitic stainless steel and ASME SA516-70 carbon steel produced by explosion welded were studied. Post-weld annealing for stress relief was conducted at 600°C for 30 min and the materials were examined in both the as welded and heat treated conditions. The microstructure of the weld was characterized by optical and scanning electron microscopy and the variation of hardness across the cladded interface was determined by applying Vickers microhardness. The residual stresses generated by the explosion welding process were analyzed by X-ray diffraction using the sin2\j/ technique. The cladded interface exhibited a wavy morphology, characteristic of high bonding strength in explosion welds and the variation of hardness was found to be strongly influenced by strain hardening at the cladded interface. Elevated tensile stresses (700 ± 30 MPa) were present after explosion welding. Application of the proposed heat treatment allowed for significant stress relaxation, with a final tensile stress of 93 ± 10 MPa. [ABSTRACT FROM AUTHOR]

Performing an heat treatment may he necessary in order to satisfy the requirements that the final quality and the service conditions may impose to a welded component. The relevant technical and operational complexity often requires the application of codes and standards (European and International). In this respect, this paper is focused on AWS standard D10.10: "Recommended Practices for Local Heating of Welds in Piping and Tubing". This reference not only provides essential information related to the realization of localized heat treatment on pipes but is integrated with requirements included in other standards both European (e.g. the BS 2633) and International (e.g. ASME B31.1, B31.3). [ABSTRACT FROM AUTHOR]

AA2219 aluminum alloy was successfully welded by variable polarity tungsten inert gas (TIG) welding, and the effect of post weld heat treatment (PWHT) process on the microstructure, mechanical properties, and corrosion behavior of the welded joints was investigated. The PWHT process being used for the welded joints was consisted of solution treatment at 535 °C for 30 min, water quenching, and artificial aging at 175 °C for a soaking time of 12 h. The microstructure and precipitated phase of the as-welded joints and PWHT joints were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X ray diffraction (XRD) and transmission electron microscopy (TEM), while the corrosion behavior was evaluated by intergranular corrosion and stress corrosion cracking. The results showed that, by implementing PWHT, the microstructure of the joint was more homogeneous than the welded joint. Meanwhile, the tensile strength was increased by 44% and the joint efficiency reached 76%. Moreover, the corrosion resistance of the PWHT joint was superior to that of the welded joint. The heat affected zone (HAZ) was observed to be the most critical corroded zone, the susceptibility to corrosion behavior of the HAZ was attributed to the dissolution and segregation of Al 2 Cu phase along the grain boundaries. [ABSTRACT FROM AUTHOR]

Residual stress measurements have been undertaken in a multi-pass circumferential double J butt-weld made from a P92 martensitic steel pipe using an In625 superalloy weld metal. Stresses were evaluated in the as welded condition and after post weld heat treatment. The deep hole drilling and neutron diffraction techniques were used to provide through thickness measurements for the parent, weld metal and heat affected region for the as-welded and the post weld heat treated conditions. The use of multiple residual stress measurement techniques provides an understanding of the stress distributions as well as increasing confidence in the reliability of the measurements. The results presented are discussed with respect to the residual stress magnitude and location as well as with respect to the effectiveness of the post weld heat treatment procedure. [ABSTRACT FROM AUTHOR]