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![Example of stress corrosion cracking of a Type 316 stainless steel under thermal insulation at 50 to 60°C. Rinsing water containing 60 mg/kg of chloride and residual stresses are at the origin of cracking, [During, 1991].](profile/Peter-Rudling/publication/294693732/figure/fig9/AS:526787373682697@1502607305509/3-Example-of-stress-corrosion-cracking-of-a-Type-316-stainless-steel-under-thermal.png)
Example of stress corrosion cracking of a Type 316 stainless steel under thermal insulation at 50 to 60°C. Rinsing water containing 60 mg/kg of chloride and residual stresses are at the origin of cracking, [During, 1991].
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This investigation is purposed to clarify the influence of pilot gas composition to convective pattern on the weld pool surface in Plasma keyhole arc welding process. In order to clarify this, the convective pattern on the top surface of weld pool was investigated in both cases of pilot gas: pure Ar and Ar mixture with 10% hydrogen. For estimating...
The joining of two chemically dissimilar metals is a challenge due to the formation of hard and brittle intermetallic compounds (IMCs) in the diffusion layer. The joining of steel/Fe with aluminum (Al) and zirconium (Zr) alloy is particularly important for the automobile and nuclear industries, respectively. The Al–steel and Zr–steel joints produce...
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... and the formation of various phases in FZ and HAZ regions [1] . In view of these factors, different types of welding procedures such as arc welding (AW), tungsten inert gas welding (TIG), electron beam welding (EBW), electric resistance welding (ERW), and laser beam welding (LBW) have been developed for Zr-based alloys in the nuclear industry over a period of several years [1][2][3][4][5][6][7] . In view of stringent criterion of nuclear industry, during the welding of Zr alloys, contamination of FZ and HAZ regions, and the formation of quenching structures as well as residual stresses should be minimized [7] . ...
... However, it is found that EBW is commercially not viable for welding of the larger components due to limited chamber size and high vacuum requirement [7] . Therefore, in place of EBW, nowadays the laser-based welding process is more preferred for Zr alloys, as it does not require any vacuum chamber [5] . ...
... During early days, the laser welding of zirconium alloys is tried, but fails due to higher porosity and poor corrosion resistance of the weld zone caused by instability of laser process parameters [11,12] . However, with the consistent improvement of the laser development field, the laser welding of zirconium alloys with similar and dissimilar materials has got significant attention over the last decade [3][4][5] . The laser welding of zirconium alloys (Zr-Nb and Zr-Sn) are currently studied with emphasis on defect formation and microstructural evolution across the weld zones [13,14] . ...
In the present study, Zr-2.5 wt.%Nb alloy plates of thickness 4 mm have been welded using pulsed Nd:YAG laser system at different process parameters and characterized in terms of microstructural evolution, hardness, residual stress, and mechanical properties. It has been observed that heat input plays an important role on mode of welding. The full penetration up to a thickness of 4 mm of the alloy has been achieved at a minimum laser heat input of 800 J mm⁻¹ without any crack and porosity formation. For avoiding the porosity formation in the weld zones, a transition mode between conduction and keyhole has been used by optimizing laser process parameters. The microstructural analysis revealed that the fusion (FZ) is consists of predominant lath type α′ martensitic phase with small amount of randomly distributed acicular type of α′ martensite phase. However, the heat affected zone (HAZ) have lath type α′ martensitic phase together with αZr phase. Further, in the FZ and HAZ regions, the presence of retained βZr phase is higher as compared to the base metal (BM). The change in microstructure and phase field of different weld zones has been explained by evaluating the time-temperature profiles and cooling rates using COMSOL multi-physics simulation. In addition, the FZ and HAZ zones have been found to have tensile residual stress of the order of 280 MPa and 145 MPa as compared to the BM (-70 MPa). The microhardness in the FZ region has been observed to be higher (240-260 HV0.1) as compared to the BM (∼185 HV0.1) due to the formation of martensitic phase. The tensile room temperature testing showed that the mechanical strength of as welded sample is significantly higher than the base metal with lower ductility. The fractography of the fractured surfaces confirmed ductile nature of failure in the as welded samples.
... Zirconium alloys are readily weldable but as with all reactive metals need special precautions to prevent pickup of interstitial elements like oxygen, carbon, and nitrogen that can degrade both the mechanical properties and the corrosion performance of the weld. [110][111][112] Vacuum or inert gases (argon, helium, or Ar-He mixtures) can be used to shield zirconium but again, care needs to be taken to ensure sufficient vacuum level or gas purity to prevent contamination. 110,112 Zirconium alloys can be susceptible to both supersolidus and subsolidus (e.g., hydride-type) cracking. ...
... [110][111][112] Vacuum or inert gases (argon, helium, or Ar-He mixtures) can be used to shield zirconium but again, care needs to be taken to ensure sufficient vacuum level or gas purity to prevent contamination. 110,112 Zirconium alloys can be susceptible to both supersolidus and subsolidus (e.g., hydride-type) cracking. Supersolidus cracking is typically solidification-type and many common alloying elements and/or potential contaminants promote susceptibility. ...
Nuclear power systems are constructed from a wide range of metallic alloys, subjected to taxing environmental conditions, and required to resist cracking and degradation of their principal mechanical and physical properties for decades. Fusion welding is, in general, the joining method of choice due to its hermeticity, high joint efficiency, and economic advantages relative to mechanical or brazed joints. However, it is often fusion welds, or their heat affected zones that prematurely degrade or fail due to the complex interplay of physical defects, compositional gradients, metallurgical changes, and residual stresses. This chapter presents the current mechanistic understanding of welding defects, reviews recent developments in assessing residual stresses & plastic strains and relates these factors to the in-service performance of welds. Lastly, the weldability of common structural alloy systems is reviewed.
... As seen in the mass gain plots, breakaway oxidation occurs in all three alloys at temperatures ≥700°C and Zry-4 experiences breakaway the earliest of the three alloys, while Zr-1Nb is the most resistant to breakaway. From Figs. 5-7, and as expected from the discussion above, the HAZ is larger in the TIG welded tubes than in the EBW specimens [18]. The effect of plastic deformation on oxidation behavior is seen in the Sn-Fe containing alloys (Zry-3 and Zry-4); accelerated oxidation on the chamfer regions are clearly visible. ...
The Transient Reactor Test (TREAT) facility is a research reactor designed to simulate rapid transients to test new fuel designs. TREAT's cladding is exposed to unique conditions compared to normal water reactors. These conditions include: exposure to air at high temperatures (≥600 °C), rapid heating (≈700 °C/s), and cladding geometry that includes chamfers and welds. This work investigates the effects of chamfering and welding on the oxidation behavior of zirconium alloys (Zircaloy-3, Zircaloy-4, and Zr–1Nb). Tube specimens were examined under isothermal and transient conditions in dry and humid air. The effect of weld type (tungsten inert gas or electron beam), the number of welds, and alloying elements are compared. Thermogravimetric analysis was used to collect mass gain data during isothermal oxidation and the data was used to quantify the oxidation rate constant and the activation energy of oxidation. Oxide behavior in the weld region, chamfered region, and bulk tube was measured and compared. The microstructure and secondary phase precipitates in EBW tubes before and after breakaway were characterized. The electron beam welded Zr–1Nb specimen was found to have the most favorable oxidation behavior under both isothermal and transient conditions. Zry-4 oxidized the most readily and was the most affected by mechanical deformation. Keywords: Zirconium alloys, Cladding, Breakaway, Transient, Oxidation
... Однако, несмотря на более чем полувековой опыт их производства, высокие надежность и глубину выгорания топлива, количество тепловыделяющих элементов с дефектами сварных швов все еще велико [2]. При изготовлении ТВС для наи-более распространенных ядерных реакторов на тепловых нейтронах (ВВЭР, PWR, CANDU и BWR) в большинстве случаев используют дуговую сварку неплавящимся электродом, стыковую и точечную контактную сварку, а также электронно-лучевую и лазерную [2][3][4]. Лазерная сварка является более предпочтительной по сравнению с электронно-лучевой в связи с отсутствием необходимости использовать вакуумную камеру, а также благодаря лучшим экономическим показателям процесса. В последние годы опубликовано значительное количество работ, посвященных лазерной сварке циркониевых сплавов, легированных оловом (Zircaloy-2, Zircaloy- 4) [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], однако цирконий-ниобиевые и многокомпонентные сплавы (Э110, Э125, M5, Э635, ZIRLO и др.) остаются без внимания. ...
In recent years use of Zr-Nb alloys has increased in nuclear and chemical industry due to its corrosion resistance and enhanced strength compared to tin based ones. Welding of zirconium alloys is one of the most critical manufacturing processes for nuclear assembly production. To select suitable welding parameters to achieve quality weld, understanding of temperature and velocity fields during process in fusion zone and heat affected zone are essential. In the present study the Nd:YAG pulsed laser welding of zirconium alloy E110 was simulated using three-dimensional heat and fluid flow model. The convection mode of heat transfer and Marangoni stresses in fusion zone are two important mechanisms in controlling the heat transfer weld bead size. The calculated heating and cooling rates are of typical in laser welding and useful in microstructure study of fusion and heat affected.
Cite as:
G. Satyanarayana, K.L. Narayana, B. Nageswara Rao, M.S. Slobodyan, M.A. Elkin, A.S. Kiselev, Numerical simulation of the processes of formation of a welded joint with a pulsed Nd:YAG laser welding of Zr–1%Nb alloy, Thermal Engineering 66:3 (2019) 210–218. DOI: 10.1134/S0040601519030066
The paper is available at Springer's web-site https://link.springer.com/article/10.1134/S0040601519030066
... The low strength and low heat resistance of the zirconium can be eliminated by alloying with the niobium, which has a low coefficient of thermal expansion and contributes low distortion during welding. Fusion welding (viz., gas tungsten arc welding, laser beam and electron beam welding) and solid state welding (resistance spot welding) can be processed as candidates for the end plate welding in commercial fuel bundle fabrication [8]. ...
In the nuclear industry, a critical welding process is joining of an end plate to a fuel rod to form a fuel bundle. Literature on zirconium welding in such a critical operation is limited. A CFD model is developed and performed for the three-dimensional non-linear thermo-fluid analysis incorporating buoyancy and Marnangoni stress and specifying temperature dependent properties to predict weld geometry and temperature field in and around the melt pool of laser spot during welding of a zirconium alloy E110 endplate with a fuel rod. Using this method, it is possible to estimate the weld pool dimensions for the specified laser power and laser-on-time. The temperature profiles will estimate the HAZ and microstructure. The adequacy of generic nature of the model is validated with existing experimental data.
... GTAW produces acceptable quality with wider welds due to an inherently higher heat input. The microstructural change that occurs due to thermal treatment can have a negative bearing on the performance of zirconium alloys (Rudling, 2007). The aim of this study is to characterise the complex microstructure that results from autogenous welding and compare the results of the two welding processes. ...
The current study is intended to characterise the complex microstructure that results from autogenous welding of Zr-2.5Nb and its influence on mechanical properties. Laser beam welding (LBW) and gas tungsten arc welding (GTAW) were performed on a 1.5 mm thick samples by applying different combinations of speed and power to vary the heat input. The effect of cooling rate on ß-a phase transformation temperature and the resulting microstructure was investigated using a Bahr dilatometer. In addition, mechanical properties were determined by tensile and hardness testing. The base metal microstructure consisted of a fine structure of Zr-alpha with a small fraction of Nb-beta phase. Both LBW- and GTAW-welded joints displayed similar martensitic microstructures, with the main difference being the weld geometry and strength.
... Relatively complex systems were used as corrosion media, e.g. different binary or ternary alkaline metal fluorides (LiF-NaF-KF-RbF) (Olson et al., 2009;Salanne et al., 2009) (Olson et al., 2009;Rudling et al., 2007) Podor (2007) et al Bernardet et al., 2009;Salanne et al., 2009) or without (Netriová et al., 2009, Boča et al., 2007 ZrF 4 , PbF 2 and BeF 2 . The authors were largely focused on relatively rapid evaluations and analyses of the corrosion losses and corrosion products, due to the fact that the analysis of the thermal corrosion processes itself is rather difficult and, in most cases, not even possible (Marcus, 2002). ...
The interactions of selected zirconium alloys used as special construction materials (Zr-pure, Zry-2, E-110) with the molten system of (LiF-NaF-KF)(eut.) with additions of K2ZrF6 or Na7Zr6F31 were studied. Corrosion losses of pure zirconium decrease sharply with 5 mole % addition of K2ZrF6 to (LiF-NaF-KF)(eut.). The presence of alloying additives (Sn, Nb) has a positive influence on corrosion resistance in the eutectic mixture - up to 60 % increase in corrosion resistance in comparison with pure zirconium. The mass losses of pure zirconium indicate an increasing corrosion attack with increasing Na7Zr6F31 content in (LiF-NaF-KF)(eut.) mixtures.
... Cleaning of Zr-4 plates is essential, as contamination may lead to the welds with poor strength and/or poor corrosion resistance (Rudling et al. 2007). The Zr-4 plates were initially cleaned using ethyl alcohol and the cleaned samples were allowed to dry. ...
Bead-on-plate welding of zircaloy-4 (a reactive material) plates was conducted using electron beam according to central composite design of experiments. Its predictive models were developed in the form of knowledge-based systems in both forward and reverse directions using neural networks. Input parameters considered for this welding of reactive metals were accelerating voltage, beam current and weld speed. The responses of the welding process were measured in terms of bead width, depth of penetration and micro-hardness. Forward mapping of the welding process was conducted using regression analysis, back-propagation neural network (BPNN), genetic algorithm-tuned neural network (GANN) and particle swarm optimization algorithm-tuned neural network (PSONN). Reverse mapping of this process was also carried out using the BPNN, GANN and PSONN-based approaches. Neural network-based approaches could model this welding process of reactive material in both forward and reverse directions efficiently, which is required for the automation of the same. The performance of the neural network models was found to be data-dependent. The BPNN could outperform the other two approaches for most of the cases but not all in both the forward and reverse mappings.
... Le soudage par résistance des gainages combustibles [67] Compte tenu de la forte concurrence dans le domaine, peu d'informations concernant les détails des procédés industriels utilisés par les différents fabricants ont été trouvées. Le soudage par résistance des gainages combustibles en alliage de zirconium donne lieu a un retour d'expérience important du fait de son utilisation depuis les années 70 en Russie. ...
... Nous avons trouvé qu'il valait mieux éviter la présence du chanfrein et ce dans le but de chasser les éventuelles ZF vers le bourrelet extérieur. Enfin, il est à noter que l'optimisation de la géométrie de l'électrode peut aussi être réalisée comme dans le cas du soudage USW (Upset Shape Welding) afin de conserver une taille de bourrelet externe acceptable sans nécessiter un usinage ultérieur [67] (Chapitre 1, paragraphe 1.4.2). ...
ODS steels (Oxide Dispersion Strengthened) are candidate materials for fuel cladding in Sodium Fast Reactors (SFR), one of the concepts at study for the forth generation of nuclear power plant. These materials have good mechanical properties at high temperature due to a dispersion of nanometer-sized oxides into the matrix. Previous studies have shown that melting can induce a decrease of the mechanical properties at high temperatures due to modifications of the nanometer-sized oxide dispersion. Therefore the fusion welding techniques are not recommended and the solid state bonding has to be evaluated. This study is focused on resistance upset welding.Welding experiments and numerical simulations of the process are coupled in this thesis. All the trials (experimental and numerical) are built using the experimental design method in order to evaluate the effects of the process parameters on the welding and on the weld. A 20Cr ODS steel is used in order to conduct the study.The first part is dedicated to the study of the influence of the process parameters on the welding. The simulation shows that the welding steps can be divided in three stages. First, the temperature of the contact between pieces increases. Second, the process is driven by the pieces geometry and especially the current constriction due to the thinness of the clad compare to the massive plug. Therefore, the heat generation is mainly located in the clad part out of the electrode leading to its collapse which is the third stage of the welding step. The evaluation of the process parameters influences on the physical phenomena (thermal, mechanical ...) occurring during the welding step allow to adjust them in order to influence the thermal and mechanical solicitation undergone by the pieces during the welding process.The second part is dedicated to the study of the influence of the physical phenomena on the welds. In the process parameter range, some welds exhibit compactness defects or a modification of the microstructure and of the oxide dispersion. Compactness defects are related to thermal and mechanical phenomena occurring at the contact between pieces. The modification of the microstructure is related to dynamical recrystallization or to a local fusion. The dynamical recrystallization occurring in the clad due to high deformation and high temperature is linked to modification of the oxide dispersion.Using the effects of the process parameters on the welding and on the weld, it is possible to adjust the temperature and the deformation in order to avoid the compactness defects and the modification of the oxide dispersion. All these results are then apply to the welding of a 9Cr ODS steel which is a candidate alloy for the SFR fuel cladding. The effects of the material properties on the welding and the weld are then discussed by comparing the two alloy with a different chromium content but also by comparing results on the 20Cr-ODS with a material of similar chemical composition but without the oxide dispersion.
... Zirconium alloys are readily weldable but as with all reactive metals need special precautions to prevent pickup of interstitial elements like oxygen, carbon, and nitrogen that can degrade both the mechanical properties and the corrosion performance of the weld. [110][111][112] Vacuum or inert gases (argon, helium, or Ar-He mixtures) can be used to shield zirconium but again, care needs to be taken to ensure sufficient vacuum level or gas purity to prevent contamination. 110,112 Zirconium alloys can be susceptible to both supersolidus and subsolidus (e.g., hydride-type) cracking. ...
... [110][111][112] Vacuum or inert gases (argon, helium, or Ar-He mixtures) can be used to shield zirconium but again, care needs to be taken to ensure sufficient vacuum level or gas purity to prevent contamination. 110,112 Zirconium alloys can be susceptible to both supersolidus and subsolidus (e.g., hydride-type) cracking. Supersolidus cracking is typically solidification-type and many common alloying elements and/or potential contaminants promote susceptibility. ...
Nuclear power systems are constructed from a wide range of metallic alloys subjected to taxing environmental conditions and required to resist cracking and degradation of their principal mechanical and physical properties for decades. Fusion welding is, in general, the joining method of choice because of its hermeticity, high joint efficiency, and economic advantages relative to mechanical or brazed joints. However, it is often fusion welds or their heat-affected zones that prematurely degrade or fail because of the complex interplay of physical defects, compositional gradients, metallurgical changes, and residual stresses. This chapter presents the current mechanistic understanding of welding defects, reviews recent developments in assessing residual stresses and plastic strains, and relates these factors to the in-service performance of welds. Finally, the weldability of common structural alloy systems is reviewed.
