Alloy Cladding Research Articles

Solidification behavior of WC particles reinforced nickel alloy cladding layers by plasma surfacing: Simulation and experiment

In this work, a numerical simulation model was developed to investigate the complex heat and mass transfer process inside the molten pool during plasma surfacing. The temperature distribution and fluid flow were employed to depict the evolution of the molten pool. The findings revealed that the maximum temperature is located on the surface of the cladding layer corresponding to the position of heat source, and the temperature distribution follows a Gaussian distribution along the scanning direction. Thermal accumulation is obvious due to the continuous energy input in the initial stage, as a result, the maximum temperature and fluid flow velocity gradually increase with the deposition process. The maximum temperature and fluid flow velocity at 4.0 s are 1893 K and 0.281 m/s in case 110 A, respectively. The predicted shapes and dimensions are consistent with the results of the deposition experiments, with a maximum error of no more than 15 %. In order to investigate the impact of WC particles on the solidification microstructure of nickel composite layers, corresponding plasma surfacing experiment was implemented. The solidification characteristics of the microstructure follow planar-cellular-columnar-equiaxed crystals in the bonding layer and WC particles-columnar-equiaxed dendritic crystals in hard layer, respectively. Furthermore, the Ni dendritic near the retained WC particles transformed into columnar crystals due to temperature gradient in the local area.

Study on fuel management strategy for accident-tolerant fuel on in-pile irradiation test

Within the context of the long-term development plan of batch loading of accident-tolerant fuel assemblies, an equivalent physical model of lead test assemblies is established based on the requirements of radiation testing and the applicability of analysis software. The quantitative assessment has been conducted on the impacts of parameters including zirconium alloy cladding coating and pellet additives on reactivity of fuel assembly. Concurrently, the fuel management strategy is optimized in alignment with the irradiation test objectives of ATF assemblies, leading to the creation of an evaluation process tailored for ATF assembly loading pattern. Focusing on the irradiation of the lead test assemblies into a nuclear power plant in China, three-cycle nuclear reactor loading pattern are designed, which are taking into account the economic, safety, and irradiation testing goals of the nuclear power plant. Simultaneously, the neutronic characteristics are also evaluated, quantitatively. The results show that the established equivalent physical model can effectively represent the characteristics of the lead test assemblies. The loading patterns designed based on the Optimised fuel management strategy achieve the desired goals in terms of economy, safety and radiation test requirements. The designed loading pattern evaluation process and equivalent model analysis method in this work provide guidance for the subsequent engineering design and application of irradiation testing for lead test assemblies.

Effect of diffusion barriers on steam oxidation properties and interface evolutions of Cr coating for zirconium alloy at 1200 °C

Currently, Cr-based coatings are considered the most promising protective coatings for zirconium alloy claddings under the ATF design concept. However, the primary factor affecting the oxidation resistance of Cr coatings is the interdiffusion of Cr and Zr. In this study, Cr coatings with three refractory metal interlayers of Nb, Mo, and Ta were deposited on zirconium alloy surfaces using closed-field unbalanced magnetron sputtering. The study investigated the effects of different interlayers on the microstructure, oxidation properties, and interface evolution process of Cr coatings under steam conditions at 1200 ℃, and compared them with Cr coatings without intermediate layers. The results indicate that the refractory metal interlayer influences the orientation and growth rate of Cr coating grains. The formation of a Laves phase mixed layer in the interlayer during oxidation effectively hinders the diffusion of O and Cr to the zirconium alloy matrix, enhancing its oxidation resistance. Furthermore, the diffusion rate and vacancy concentration of Mo and Ta elements to the Zr layer exceed that of diffusion to the Cr layer. During the cooling process, a precipitate phase forms in the Zr-4 matrix, while the Nb coating forms an infinite solid solution in the β-Zr.

Evolution of fretting wear behavior of zirconium alloy cladding tube under gross slip regime in simulated primary water of pressurized water reactor

The evolution of fretting wear behavior of zirconium alloy cladding tubes mated with dimples under the gross slip regime (GSR) was investigated. The findings revealed that the primary wear mechanisms under GSR were delamination, surface fatigue wear and abrasive wear, and the fretting damage rate mainly depends on delamination. The cross-sectional microstructure of the worn area could be divided into the third-body layer, tribologically transformed structure layer, and general deformation layer, with their formation mechanisms analyzed. Furthermore, the mechanism of wear-induced grain refinement was identified as dynamic recrystallization (DRX), including both continuous DRX and discontinuous DRX. Additionally, the processes of fretting wear and DRX were discussed.

High-strength and wear-resistant Babbitt alloy coatings prepared through in-situ alloying

Babbitt alloy, a commonly used wear-resistant coating material, has a low hardness. This causes severe plastic deformation, detachment or heavy wear to easily occur under low speed and heavy-load service conditions, reducing its service life. To solve these problems and improve the bonding strength and wear resistance of the tin-based Babbitt alloy coating, a higher laser cladding power was adopted to achieve in-situ alloying of the cladding layer and enhance the strength of the coating. The increase in strength was verified through the Fleischer theory and Orowan empirical formula to mainly result from the enhancement of solid solution strengthening and dispersion strengthening. Meanwhile, due to dispersion strengthening and the presence of dendritic FeSn, the occurrence of delamination wear was effectively prevented. The bonding strength of the final sample reached 147 MPa, and the wear rate was as low as 4.24 × 10–5 mm3/N・m. Thus, a high-strength and wear-resistant Babbitt alloy cladding layer was obtained.

Achieving low-porosity AlSi10Mg cladding layers for the additive repair of aluminum alloy parts by directed energy deposition

Directed Energy Deposition (DED) has broad application prospects for repairing damaged aluminum alloy parts such as piston aero-engine casing. However, due to the low laser absorptivity and the complex thermal cycle process, it is challenging to obtain aluminum alloy cladding layers with high-quality morphology and low-porosity by DED method. In this work, a series of individual stages of DED process are studied during single-tracks overlapping and layers stacking. Correspondingly, the within layer scanning strategy, inter-layer stacking strategy, and process parameters are examined carefully. Using the proposed DED processing flow that combines substrate preheating with intermittent process, the deposited layers without balling and collapse are successfully achieved. Furtherly, the bi-directional scanning strategy for single-tracks overlapping within layer is proposed to compensate the thickness nonuniformity caused by heat accumulation. The inter defects identified as “lack of fusion” and “gas pores” are observed in the cladding layers with uniform surface. By analyzing the pore formation mechanism and considering the energy distribution and re-melting, the multi-layer offset stacking strategy is proposed to inhibit the porosity to 0.25 %. Combined with the optimized process parameters, the porosity is reduced up to 0.09 %, ensuring the density of the DED deposition coating. This work provides new pathway and direct guidance for fabricating high-quality AlSi10Mg cladding layers during the DED repairing of valuable aluminum alloy parts.

The effects of Nb on the microstructure and performance of laser-cladded Fe50-xMn30Co10Cr10Nbx high entropy alloy coatings

A laser cladding technique was employed to produce a Fe50-XMn30Co10Cr10NbX (X = 2.5, 5, 7.5, 10at%) high entropy alloy coating. This study delved into the influence of Nb concentration on the coating’s phase constitution, microstructural features, hardness, and wear resistance. The high entropy alloy coating exhibited a multifaceted structural composition, encompassing FCC (Face-Centered Cubic), HCP (Hexagonal Close-Packed), and BCC (Body-Centered Cubic) structures, along with the presence of Laves phase. Notably, the incorporation of Nb led to an augmentation in the Laves phase and modifications within the microstructure. The hardness of the cladding layer is higher than that of the substrate. With the increase of Nb content, the hardness of the cladding layer increases first and then decreases; the average hardness of the Fe42.5Mn30Co10Cr10Nb7.5 cladding layer is the highest, the maximum hardness is 429.8Hv, and the average hardness is 382.3Hv. The friction coefficient and weight loss of the cladding layer decreases first and then increases with the increase of Nb content. The friction coefficient and weight loss of the Fe42.5Mn30Co10Cr10Nb7.5 cladding layer are the smallest, which are 0.0132 g and 0.5974, showing the best wear resistance. The wear types of high entropy alloy cladding layer are both adhesive wear and abrasive wear. The addition of Nb into high entropy alloy will form the Laves phase, which can improve the mechanical properties of high entropy alloy.

Review on hard particle reinforced laser cladding high-entropy alloy coatings

Since their advent in 2004, high-entropy alloys have allured the field of materials science and engineering. Laser cladding technology, with its advantages of a small heat-affected zone and rapid heating and cooling, has become a popular technique for preparing high-entropy alloy coatings. Traditional high-entropy alloys have the problem of strength-plasticity mismatch, which limits the further application of laser cladding high-entropy alloys in industry. As a method to solve these challenges, hard particle reinforced alloy coating technology can effectively control the comprehensive properties of high-entropy alloy coatings. This paper first explores and analyzes the five strengthening mechanisms and four main influencing factors of hard particle reinforced laser cladding alloy coatings. Then, from the perspective of introducing particle types, the research status of ceramic particles, rare earth particles and other types of hard particle reinforced laser cladding high entropy alloy coatings is introduced. Finally, the characteristics of hard particle reinforced laser cladding high-entropy alloy coatings are summarized, and future recommendations for hard particle reinforced alloy coatings technology and its application in laser cladding high-entropy alloys are proposed, which will be helpful for researchers and producers in this field.

Effect of multi-element synergistic addition on the microstructure evolution and performance enhancement of laser hot-wire cladded Fe-based alloy

To satisfy the requirements of hardness and corrosion resistance for laser additive manufacturing of hydraulic supports, this study applied the synergistic addition of C, B, Cr, Ni, Nb and Mo elements in Fe-based alloys. The multi-phases, martensite + austenite + ferrite were designed. The microstructure, hardness and corrosion resistance of the coatings were analyzed. Increasing the C and B contents could significantly increase the hardness of the coatings, while the corrosion resistance was decreased. The corrosion resistance of the coatings was determined by the Cr contents. However, increasing the Cr contents to 20.0 wt % resulted in the ferrite structure with lower hardness (21 HRC). The coatings with 0.25 wt % C, 1.2 wt % B and 19.0 wt % Cr showed the optimal matching of hardness (56 HRC) and corrosion resistance (survived in neutral salt spray test≥300h). The resulted coatings were mainly consisted of dendritic structure. Fine lath martensite phase was dominant in the dendrite regions. The interdendritic regions were consisted of nano-sized intermetallics with a mixture of σ+Nb + FeNb + Cr2Nb+(Fe,Cr)2B + NbC compounds. These interdendritic regions (14.2 GPa) showed higher hardness than that of the dendritic regions (7.1 GPa). The high Cr contents with finer dendritic structures were the major mechanisms for the excellent combination of hardness and corrosion resistance. The precipitation and growth mechanisms of the interdendritic phases were elaborated. This work provides a valuable reference for laser hot-wire cladding to prepare Fe-based alloys with high hardness and excellent corrosion resistance.

Expansion deformation mechanism and cracking behaviours of chromium-coated zirconium alloy cladding at room temperature

The deformation of the cladding tube triggered by the expansion of the internal plug is used to investigate the hoop deformation behaviour of the Cr-coated zirconium alloy cladding tube at room temperature. A thin-walled pressurized cylinder model is used to transform the axial load-displacement curve working on the expansion plug into the hoop stress-strain curve working on the cladding tube, and it is found that the Cr coating can be able to restrain the cladding tube from hoop deformation. Observation of the Cr-coated cladding tube after different amounts of hoop deformation revealed that the strain corresponding to the generation of the first crack was a ranged from 0.48 % to 0.59 %, the density of cracks started to grow very fast and then entered a saturation stage. The fracture strength of the Cr coating and maximum interfacial shear strength when the Cr coating crack density reaches saturation were calculated by the shear-lag model. Twins and a large number of dislocations were generated in the Zr matrix and a small number of dislocations in the Cr coating after the hoop deformation. The behaviour of crack initiation and propagation occurring in Cr coating is revealed.

Autoclave grid-to-rod fretting corrosion behaviors of the Zr alloy fuel cladding with and without Cr coating through advanced characterization

The fretting corrosion behaviors and the associated mechanisms of Zr alloy claddings with and without Cr coating in the primary water (310 °C/15.5 MPa) of the simulated pressurized water reactor were studied and compared. The results demonstrated that the fretting corrosion resistance of Zr alloy cladding was improved significantly by the introduction of Cr coating. The increased fretting corrosion resistance of the Cr-coated Zr alloy cladding was mainly attributed for two reasons. Firstly, the metallic Cr had much greater hardness than the Zr alloy and the formation of the ultra-fine grains layer under the worn scar further increased its hardness. Secondly, the metallic Cr had much better plasticity than the ZrO2 layer, resulting in better resistance to fatigue failure.

Influence of high-reactivity energetic materials on microstructure and performance on iron-based cladding layer under low laser power

Abstract Under low laser power conditions, the cladding layer is constrained by inadequate energy density, resulting in incomplete melting of certain powder particles and the occurrence of defects such as cracks and pores within the layer. This paper utilizes a QT500 substrate and synergistically integrates high-reactivity energetic materials (H-REMs) with metal powder. By external laser energy ignition, the localized combustion of the H-REMs (Al + Fe2O3) is induced, thereby providing additional heat input during the laser cladding process. Through in-depth analysis of extensive experimental data, the influence of H-REMson microstructure and performance of alloy cladding layerhas beenrevealed. The research results demonstrate that the inclusion of H-REMs leads to a 450 K increase in the maximum temperature of the molten pool. By incorporating high-reactivity energetic materials, the energy density utilization of the composite material increased from 0.2663 to 0.7375. The combustion wave generated by H-REMs induces mixing in the molten pool, resulting in cladding layer grain refinement and an average hardness increase of 80 HV1. The friction coefficient decreases from 0.71024 (prior to the addition of H-REMs) to 0.35809, representing a reduction of approximately 49 %.

Finite Element Modeling and Experimental Verification of a New Aluminum Al-2%Cu-2%Mn Alloy Hot Cladding by Flat Rolling

The roll bonding of an experimental Al-2%Cu-2%Mn alloy with technically pure 1050A aluminum at true deformations of 0.26, 0.33 and 0.40 has been simulated using the QForm 10.3.0 FEM software. The flow stress of the Al-2%Cu-2%Mn alloy has been measured in temperature and strain rate ranges of 350–450 °C and 0.1–20 s−1, respectively. The simulation results suggest that the equivalent strain in the cladding layer is more intense than that in the base layer, reaching 1.0, 1.4 and 2.0 at strains of 0.26, 0.33 and 0.40, respectively. The latter fact favors a decrease in the difference between the flow stresses of the rolled sheet layer contact surfaces by an average of 25% at the highest strain. The experimental roll bonding has achieved good layer adhesion for all the test samples. The average peeling strength of the samples produced at strains of 0.26 and 0.33 proves to be 12.6 and 18.4 N/mm, respectively, and at a strain of 0.40, it has exceeded the flow stress of the 1050A alloy cladding layer. The change in the rolling force for different rolling routes has demonstrated the best fit with the experimental data.

Chromium Coatings Applied to Zr Alloy Claddings by Cathodic Arc Ion Plating: Effect of Nitrogen Inclusion on Limiting Columnar Defects

The effect of nitrogen on an anticorrosive Cr coating for the Zr alloy cladding of nuclear fuel rods is investigated. It is aimed to reduce the number of typical columnar defects generated in Cr‐based coatings when using the cathodic arc ion plating method through reactive nitrogen inclusion and improve the oxidation resistance. Under a working pressure of 5 Pa and an arc current of 60 A in a chrome target, Cr‐based coatings are fabricated under varying N2/Ar gas flow ratios and substrate biases. The growth structures, crystallography, and corrosion behavior of the coatings are characterized using scanning electron microscopy, X‐ray diffraction, and potentiodynamic polarization tests. The Cr coating exhibits a typical columnar structure with voids, pores, and columnar defects. In comparison, through nitrogen inclusion, when the nitrogen content of the Cr‐based coating is less than 15 at%, the Cr(N) coating shows a “featureless structure” similar to an amorphous structure, resulting in fewer voids and defects. Potentiodynamic polarization tests reveal that the Cr(N) coating, featuring a distorted body‐centered cubic‐Cr structure, exhibits a significantly low corrosion current in the passive region. The protection efficiency of the Cr(N) coating is calculated to be 96.9%, confirming its superior substrate protection capabilities compared with chromium nitride coatings.

Effects of drawing speed on microstructure and properties of Cu-Ni-Si alloy clad AA8030 alloy composites prepared by continuous casting composite technology

The Cu-Ni-Si alloy clad AA8030 alloy rod was prepared by continuous casting composite technology with gradient-varying drawing speeds, and the influences of drawing speed on the casting quality and microstructure of Cu-Ni-Si alloy clad AA8030 alloy rod were systematically studied. The drawing speed at which satisfactory continuous casting quality could be obtained was 90–120 mm/min. Meanwhile, axial columnar grains favorable for subsequent plastic processing were obtained, although the angle between columnar grains and axial direction increased with the increases of drawing speed. Moreover, with the drawing speed increasing from 90 mm/min to 120 mm/min, the thickness of composite interfacial layers was significantly increased, and the morphology of interfacial phases was gradually changed. The Cu-Ni-Si alloy cladding layer was cut from the composite to perform solution and aging experiments. The results showed that the solid solution effect of the as-cast Cu-Ni-Si alloy was consistent with that of the solution-treated Cu-Ni-Si alloy because of the rapid cooling characteristics of continuous casting composite technology, which solved the problem that the composite rod could not be solution treated as a whole due to the lower melting point of the Al core.

Triboinformatic Machine Learning Model for Frictional Behavior and Wear Volume Loss Prediction of SS316L Alloy Clad with WC/NiCrBSi

Triboinformatic Machine Learning Model for Frictional Behavior and Wear Volume Loss Prediction of SS316L Alloy Clad with WC/NiCrBSi

Numerical Simulation and Crack Suppression Study on High-Speed Laser Cladding of ZL101 Aluminum Alloy

Numerical Simulation and Crack Suppression Study on High-Speed Laser Cladding of ZL101 Aluminum Alloy

Optimization and high-temperature wear characterization of Stellite alloy claddings developed using TIG welding on 56NiCrMoV7 die steel

In this study, Stellite 6 and Stellite 12 claddings were deposited on 56NiCrMoV7 hot-worked die steel using the Tungsten Inert Gas (TIG) welding process. Initially, single tracks were deposited using a full factorial design varying two process parameters - current (65, 75, and 85 A) and scan speed (400, 600, and 800 mm/min). The single tracks were then optimized based on dilution rate and microhardness. The optimized parameters were used to develop Stellite 6 and 12 multi-pass clad layers on 56NiCrMoV7. The evaluation of the microstructure of the claddings was done using an optical microscope, XRD, FESEM, EDX, and EBSD. The microstructure of the claddings consists of α-Co matric with M7C3, M23C6, and W2C carbides precipitated along the grain boundaries. Further microhardness and tribological performance were analyzed using Vicker's hardness tester and ball-on-disc tribometer, respectively. Stellite 12 claddings exhibited superior wear resistance and indicated reduced wear volume by 51.3 % at room temperature, 69.2 % at 450 °C, and 32 % at 550 °C compared to the base material and 53.2 % at room temperature, 37.3 % at 450 °C, and 24.1 % at 550 °C compared to Stellite 6 claddings. The KAM mapping showed higher dislocation density for Stellite 12 cladding. The combination of finer grains, higher hardness, and higher dislocation density resulted in higher wear resistance.

Corrosion Behavior of CMT Cladding Layer of AZ91 Magnesium Alloy Subjected to Friction Stir Processing.

Friction stir processing (FSP) was performed on an AZ91 magnesium alloy cladding layer fabricated by a cold metal transfer (CMT) technique. Electrochemical properties and immersion corrosion behavior of the cladding layer before and after FSP in 3.5 wt.% NaCl solution were investigated. After applying the FSP, the corrosion potential and corrosion current density of the cladding layer increased from -1.455 V to -1.397 V and decreased from 4.135 μA/cm2 to 1.275 μA/cm2, respectively. The results of OM and SEM displayed the refinement of grains and the dispersion of β-Mg17Al12 second phase in the friction stir processed (FSPed) cladding layer and more severe corrosion of the unprocessed sample. The corrosion rate of the FSPed cladding layer was lower, and a more compact corrosion product film was formed on the surface of the FSPed cladding layer. EDS results and XRD patterns showed that the corrosion products was mainly composed of Mg(OH)2. The increase in Al content in the α-Mg matrix, grain refinement, and fragmentation and dispersion of the β-Mg17Al12 second phase induced by FSP were the main factors that led to the improvement in corrosion resistance of the cladding layer of the AZ91 magnesium alloy fabricated by CMT.

Novel photocatalysis-assisted mechanical polishing of laser cladding cobalt-based alloy using TiO2 nanoparticles

This paper presents a novel photocatalysis-assisted mechanical polishing method for cobalt-based alloy cladding layers using TiO2 nanoparticles. By leveraging the active oxygen species generated by the photocatalyst under illuminated conditions, surface oxidation reactions on cobalt-based alloys are initiated, thereby enhancing material removal efficiency. The underlying principles of photocatalytic oxidation are elucidated, particularly the promotion of oxidation by •OH when it interacts with the metal surface, leading to the formation of a CoO oxide film on the cladding layer surface and a subsequent reduction in surface hardness. An experimental platform was established, and research findings identified an etching time of 60 min and a TiO2 concentration of 10 wt% as optimal process parameters. Comparative analysis with pure mechanical polishing and chemical mechanical polishing revealed that photocatalysis-assisted mechanical polishing yielded superior surface roughness of 60 nm and a material removal rate of 63.8 μm/min.