Single Clad Research Articles

Production and characterization of laser cladding coating of Fe66Co7Nb4B23 (at.%) gas-atomized and ball-milled powders

In this study, a new Fe 66 Co 7 Nb 4 B 23 (at.%) alloy was produced from commercially graded precursors. Gas atomized powder of this alloy was produced, and coarser particles (“splat plates”, size ranges > 5 cm) were subsequently submitted to high-energy ball milling. Laser cladding coating of Fe 66 Co 7 Nb 4 B 23 (at.%) gas-atomized and ball milled powders was produced. Powders and laser cladding coatings were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Gas-atomized and ball milled Fe 66 Co 7 Nb 4 B 23 (at.%) powders showed a glassy matrix with some crystalline phases such as α-(Fe,Co) and Fe- and Co-containing borides. Both were employed as feedstock powders (<45 μm) to produce single tracks and laser cladding (LC) coating. Optimizing of the LC parameters allowed to obtain and to evaluate single tracks, aiming the production of LC coatings from the optimized parameters. The single tracks were composed of α-(Fe,Co), M 2 B and M 3 B phases, and displayed high microhardness, ranging from of 980 ± 150 to 1480 ± 70 HV 0.5 , depending on the powder and LC parameters. The resulting LC coatings were dense and free from excessive defects such as cracks, porosity and insufficient metallurgical bonding to the AISI 1020 steel substrate. These findings open perspectives to produce protective wear-resistant and affordable coatings on conventional steel components.

Fragility Comprehensive Assessment of Low-Rise Cold-Formed Steel Framed Wall Structure Subjected to Wind Load

This paper presents a comprehensive assessment method of the fragility of low-rise cold-formed steel (CFS) framed wall structures subjected to wind hazards considering the fragility of both the main structure and the cladding system. The effects of wind directions on the fragility of CFS framed wall structures were also studied. For the main structure, the fragility curve is established using the maximum interstory drift ratio (ISDRmax) as the performance index for assessing the wind fragility of the structure. For the cladding system, the probabilistic models of the wind load and the cladding component resistance are established based on Monte Carlo simulation, and then methods for the fragility assessment of single cladding components and the cladding system under wind hazards considering the influence of the number and arrangement of the cladding components are proposed. The results indicated that, under strong wind, the cladding system may be damaged before the required wind resistance capacity of the main structure is exhausted. In particular, the roof sheathing is the most prone to damage, followed by the stud wall. That is, before the main structure is severely damaged or collapses, the cladding systems may be severely damaged, rendering the structure unusable. Therefore, the comprehensive assessment of the fragility of this type of structure subjected to wind hazard considering the fragility of both the main structure and the cladding system is more accurate. This study is of great significance for the improvement of the wind resistance performance of CFS structures and the popularization of this type of structure.

Parametric investigation and optimization for CO2 laser cladding of AlFeCoCrNiCu powder on AISI 316

Abstract The purpose of the current investigation is to analyze the effect of the operating parameters of laser-assisted cladding process on clad height, clad depth, clad width and the percentage dilution in a cladding of AlFeCuCrCoNi high-entropy powder on SS-316 through CO2 laser and to optimize the cladding process parameters for optimum dilution. The experiments were designed by the full factorial method and analyzed by ANOVA. The analysis results indicate that dilution is most influenced by scanning speed followed by the powder feed rate. The outcomes of the single clad profile in terms of dilution, microhardness, composition and the microstructures produced in various cladding conditions are investigated briefly, and through which the optimum set of laser cladding operating parameters for maximum hardness of the clad material is determined. The optimum cladding conditions in the experimental range were obtained at 4 g/min powder feeding rate, 500 mm/min laser scanning speed and 1.1 kW laser beam power through multi-response optimization. Furthermore, the multi-track coating with 60% overlapping ratio was deposited using optimized parameters. The wear behavior of multi-track coating was determined using pin on disk wear apparatus with applied load of 20 N, sliding speed of 300 RPM and test duration of 15 min. The pin on disk wear test results indicates that the friction coefficient of SS-316 is larger than that of high-entropy alloy cladded SS-316. The wear resistivity of SS-316 improved by 40.35% after laser-assisted high-entropy alloy coating, which confirms that the laser cladding layer plays an essential role in enhancing the wear resistance capability of austenite steel.

Регрессионные модели показателей технологического процесса послойного выращивания изделия из порошка стали 316L методом коаксиального лазерного плавления

Coaxial laser melting is a method of manufacturing metal parts related to additive manufacturing processes significantly reducing the manufacturing time and cost of complex geometry parts in single and small batch production, as well as reducing material losses during machining. The typical objects of this technology are parts containing thin-walled structures. Determining coaxial laser melting regimes of such structures when grown under conditions of varying heat sink is a daunting task, and numerous papers devoted to the analysis of the influence of process parameters on the geometry of the forming clads are contradictory and do not always take into account the limited heat capacity of the thin walls. Based on the results of the experiment using the mathematical planning method, regression models for calculating the dimensions of the upper forming clads for thin-walled structures made of corrosion-resistant steel 316L were obtained. The relationship between the main parameters of the coaxial laser melting regime and the geometric characteristics of single clads has been established. A complete correlation of the experimental and calculated data was found, as well as a high accuracy in predicting the results. The analysis of regression characteristics allowed finding the optimal regimes of coaxial laser melting i.e. the maximum cross-sectional area with the minimum substrate penetration.

All-fiber transient phase noise characterization of polarization maintaining Yb-doped fiber amplifiers

We demonstrated an all-fiber phase noise measurement technique to detect transient phase variation of polarization maintaining Yb-doped fiber amplifier based on active phase locking of an optical heterodyne detection system. The root mean square, power spectral density, and drift velocity in the phase noise were analyzed for both core-pumped single clad fiber amplifier and clad-pumped double-clad fiber amplifier. The phase noise was further analyzed in terms of the seed laser power, amplifier output power, and fiber optic component configurations. The phase drift velocity measurements at various amplifier output powers indicated the optical phase were closely related to the temperature variations.

Coupled heat transfer, fluid flow and solidification kinetics for laser additive manufacturing applications

Abstract A new coupled heat transfer and solidification kinetics model is developed for the optimization of microstructure during laser additive manufacturing applications. The Johnson–Mehl–Avrami–Kolmogorov equation is applied in a self-consistent manner for modeling of the rapid phase change on the substrate. The numerical simulations using the OpenFOAM framework are conducted for Ni-based superalloy single track laser cladding. Single track laser cladding experiments were carried out to verify the results of our calculations. A rather good coincidence with the experimental data is shown for the developed model. The influence of processing parameters on the macro and micro parameters of the tracks is analyzed. A method for changing the average crystalline size and simultaneous preservation of the height and width of the track is presented. The possibility of controlling the microstructure of similar tracks gives an opportunity to preserve the scanning strategy for building parts with a defined quality.

Simulation Research on Temperature Field of IN 625 Alloy by Micro-arc Plasma Additive Manufacturing Using Gaussian Heat Source

As a rising star in the field of additive manufacturing, micro plasma additive manufacturing technology has attracted more and more attention because of its unique heat source advantages. However, the simulation method based on micro plasma additive manufacturing technology is not mature enough to reveal the law and guide the experiment. In this paper, the single pass single-layer cladding process of in625 alloy manufactured by micro arc plasma additive is simulated by computer simulation method. The temperature field distribution in the manufacturing process of micro arc plasma additive is studied and the thermal process of characteristic points is output. The results show that: the finite element simulation method can better restore the heat source moving process of micro arc plasma additive manufacturing, and the Gaussian surface heat source has good applicability in the micro arc plasma additive manufacturing. The simulation results can provide theoretical basis and data support for the organizational evolution in the manufacturing process of micro arc plasma additive.

Advances in the understanding of the annular laser beam wire cladding process

This paper experimentally studies the influence of conventional process parameters (laser beam power, P, workpiece, and wire feeding velocities), and the nominal workpiece irradiation proportion WIPN parameter, on ALB-WC process stability and generated clad geometry. The study was based on an extensive set of single clad experiments using stainless steel AISI 316L wire of 0.6 mm diameter and a stainless steel AISI 304 workpiece. The results show that the laser beam power required for a stable process increases non-linearly with WIPN, and this relationship can be described by quadratic regression. An increase in either the workpiece or wire feeding velocity respectively causes a reduction or enlargement of the stability region in the P-WIPN stability diagrams. The influences on stability diagrams are explained by means of the increase in the nominal WIPN to the effective WIPE, as a result of the clad height generated. With respect to clad geometry, it was shown that an increase in the WIPN causes a decrease in the dilution ratio, which is linearly correlated with the workpiece and melt pool temperatures, while clad width and height are not influenced by the WIPN. The paper further explains the complex influences of the process parameters observed on process stability and generated clad geometry using a phenomenological description of the ALB-WC process at a low and high nominal WIPN. For this purpose, heat transfer, Marangoni flow, and laser beam reflections are considered qualitatively and supported by IR and visual images of the wire-end and melt pool as well as the workpiece and melt pool temperatures.

Laser Cladding of PAC 718, Tribaloy T-700 and METCO 41 C Hard Facing Powders on AISI SS 304L Substrate

The present investigation aims to deposit the three different hard facing powder (Triboloy T-700 and PAC 718, and TETCO 41 C) on SS 304L using laser cladding technique. The single and overlapped clad track was deposited using 2 kW laser power system. The optimized laser process parameters and 50% overlap clad track was used to deposit a large surface area. The optimum laser process parameters were finalised using single clad structure study. The cross-sections of the clad layers were used to obtain the microstructure and micro-hardness from different regions namely, clad layer, diffusion layer, and substrate. Throughout the study, the laser power was kept constant i.e. 1.2 kW. For single clad deposition, the scanning speed and powder feed rate varied from 0.3 to 0.5 m/min and 4 to 9 g/min, respectively. T-700 and PAC 718 shows uniform developing micro-structure while METCO 41 C shows the development of mixed dendritic and cellular type microstructure. The Triboloy shows the maximum surface hardness of 534 Hv, 321 Hv for PAC 718, and 294 Hv for METCO 41 C.

On the heterogeneous cooling rates in laser-clad Al-50Si alloy

Abstract The local microstructural heterogeneities in a single layer of laser clad hypereutectic Al-50Si alloy over Al7075 substrate has been studied over different applied laser powers. The general microstructure of the laser clad layer, irrespective of the applied laser power, could be described by three distinctive regions from the deposited bead/substrate interface to the top – i) columnar primary Al-dendritic region, ii) Al-Si near-eutectic region, and iii) non-equilibrium three phase region composed of Si primary particles, fine Al-rich dendrites and interdendritic Al-Si eutectic. A spatial heterogeneity in the cooling rates is inferred within the single clad layer based on the microstructural length scales – the bulk Al-Si shows two orders of magnitude higher cooling rate than interface. A distinct difference in the orientation of the clad microstructure near the bead/substrate interface and size and distribution of Si particles in the deposited layer is seen with different applied laser power. Such microstructural differences have been explained on the basis of the melt pool solidification conditions of the hypereutectic alloy under different laser power.

Lossy mode resonance sensor assisted by dual long-period fiber gratings with core-mode blocker

A novel sensor configuration consisting of TiO2 film and dual long-period fiber gratings (LPFG) with an in-between core-mode blocker (CMB) is proposed and numerically investigated. TiO2 film is on the cladding surface of separation fiber between two identical LPFGs and lossy mode resonance (LMR) is induced by a single cladding mode which is coupled from core mode by the first grating. Afterwards, the cladding mode influenced by LMR is recoupled into core mode by the second grating. As a result, the output spectrum is characterized as a dip in the top of a bandpass spectrum curve. The central wavelength of this dip is sensitive to surrounding refractive index and the numerical analysis reveals that the sensitivity reaches 5075 nm/RIU with excellent linearity. In this configuration, the bandwidth of attenuation dip is reduced in a great manner since LMR is induced by a single cladding mode. Moreover, this sensor configuration synthesizes the advantages of both LMR and LPFG, which offers additional degrees of freedom in the sensor design.

Failure behaviour of cladding made from Sv 07Kh25N13 austenitic stainless steel

Sv 07Kh25N13 is austenitic stainless steel used in nuclear industry. Due to its excellent corrosion resistance in the environment of WWER type nuclear reactor primary circuit, it is applied as anticorrosive cladding of the reactor pressure vessel. In this paper, results of detailed experimental research of failure behaviour of the cladding are presented. Static fracture toughness values J0.2 exhibited an extreme scatter. Metallographic analysis performed on the fractured specimens revealed large variations of structure within every single cladding layer. Fractographic analysis performed on fracture surfaces revealed considerable variations of micromechanisms taking place during ductile crack propagation. Conclusions on the relationship between the local microstructure, the failure mode and the fracture toughness of the cladding were drawn. Results indicate that the fracture toughness of the cladding was primarily determined by local amount of sigma phase in the area of crack propagation.

Interlayer Dilution Zone Elemental Profiling and Microhardness Measurements for Individual Laser Clads

A detailed study of microstructure and microhardness distribution at clad-to-substrate interlayer dilution zone as well as elemental profiling were carried out for individual laser clads. Tungsten carbide (44 712-10) and nickel alloy (1560) powders were used for individual clad synthesis at the surface of low alloy steel by coaxial laser cladding technique. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed partial tungsten carbide (WC) melting and secondary chromium carbides formation near WC grains. Iron and nickel elemental profiles were quantified by EDX technique to estimate interlayer dilution zone dimensions. Interlayer zone depth in the clad center increased from 15 to 80 µm when laser power was changed from 0.8 to 1.5 kW while at the outer clad regions it varied in 3–20 µm range. Interlayer clad-to-substrate zone microhardness study revealed a non-uniform dependence of hardness distribution for single clads synthesized with varying laser power.

Selection of modes for laser cladding of PR-08Kh17N8S6G powder

A brief analysis of powders used in the industry for surfacing on the work surfaces of critical parts is given in order to increase their wear resistance. The results of experimental studies on the choice of parameters of gas-powder cladding modes are presented. The cladding process was carried out by a laser robotic complex with a coaxial feed of powder to the surfacing zone. The substrate used steel grade 08H18N10T, which was applied to the melt of wear-resistant powder grade PR-08H17N8S6G. The use of ytterbium fiber laser allowed to reduce the heat supply to the surfaces, which significantly reduced the residual stresses in the workpiece. Variable parameters of the laser cladding process were the output power of laser radiation, processing speed, and powder mass flow rate. During visual inspection, the absence of pores and cracks were used as the estimated indicators of the cladding. The study of macro geometry single clad track was conducted on cross section of the clad. During measurements, the quality of a single clad track was determined by its geometric dimensions: clad height, clad width, contact angle between the tangent to the cladding surface and the substrate plane, as well the depth of the mixing layer of the surfaced and substrate materials. According to the results of experimental studies of the selected optimal mode, providing a cladding track with a clad height above 1 mm; clad width 2.5 mm; the depth of the mixing layer – 0.2 mm; contact angle between the tangent to the clad surface and the substrate more than 50º. This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation. Agreement on the provision of subsidies No. 075-15-2019-1833 dated December 03, 2019. Unique identifier PNI RFMEFI60419Kh0245.

Experimental Investigation on Laser Metal Deposition of Ti-6Al-4V Alloy with Coaxial Local Shielding Gas Nozzle

An inert gas environment is required during the laser metal deposition of titanium alloys due to oxidation. A nozzle with local shielding device is more flexible than the inert gas chamber, and size of the components produced is not restricted. In this study, a coaxial double-deck gas shielding nozzle was designed to provide a local shielding for the laser metal deposition of Ti-6Al-4V alloy. Numerical simulation of flow field under four different gas flow rates was carried out, and the corresponding Ti-6Al-4V single clads as well as components were produced. Experimental results revealed that the effective protection length increased and then became steady with the gas rate getting larger. Every component showed significant change in the degree of surface discoloration. Among that when the gas flow rate exceeded 30 L/min, surface of the formed bulk components showed yellowish and shiny silver and the internal oxygen content was below 2000 ppm, which had a minimal raise from the powder. In addition, the microhardness of the components showed little increase compared with the rolled substrate.

Selection of rational modes of laser powder cladding

A brief overview of the surfacing used on the working surfaces of industrial equipment parts is given. The most universal method of laser surfacing is considered laser powder cladding. The results of experimental studies on the choice of parameters of surfacing modes for a single track are presented: laser power, mass flow rate of powder for deposition, and surfacing speed. Samples made of 08H18N10T steel were used as a substrate for testing. Laser powder cladding was performed on a robotic complex with an ytterbium fiber laser and a coaxial powder feed. When measuring macrogeometry, the quality of a single track was evaluated by its geometric dimensions: height, width, and depth of the layer mixing of the surfaced and base materials (substrate). Variable parameters of the surfacing process were the output power of laser radiation, processing speed, and mass flow rate of the powder. The quality of a single clad track was evaluated by its geometric dimensions: height, width, and depth of the layer mixing of the surfaced and base materials (substrate). it is Shown that the value of d depends on the mass flow rate and the power of the laser radiation: when increasing mass flow rate, it is necessary to increase power of the laser radiation to ensure a constant value of depth of the layer mixing. The shape of the deposited clad track is close to a half-ellipse only when the laser power not more than 1000 W and mass flow rate 15 g/min. The height of depends on the value of mass flow rate and the laser power: when increasing mass flow rate, an increase in laser power is required in approximately the same ratio. The width of the surfacing with increasing mass flow rate at a constant power of laser radiation decreases due to the fact that the cooling rate of the liquid phase of the metal melt is very high and only superheated melt can increase the width of the clad track.

2D thermal model of laser cladding process of Inconel 718

Abstract Layer by layer deposition in laser based metal additive manufacturing process causes accumulation of high thermal residual stresses. This may sometimes lead to dimensional inaccuracy and warping of the deposited clad layer. Additive manufacturing being expensive process, simulation may reduce the number of experimental trails. In the present work, 2D thermal model of Direct Metal Laser Deposition process taking Inconel 718 as deposited material was solved using the finite element software package COMSOL MULTIPHYSICS and the phase change of the material was incorporated. The thermal model is carried out for a 2D single clad bead to estimate HAZ and melt depth. The proposed 2D thermal model can predict the melt pool boundary at the interface of the clad layer and the substrate as a function of time for a given set of laser process parameters and found to be in good agreement with the experimental results.

Strategy Development for the Manufacturing of Multilayered Structures of Variable Thickness of Ni-Based Alloy 718 by Powder-Fed Directed Energy Deposition

In this study, a manufacturing strategy, and guidelines for inclined and multilayered structures of variable thickness are presented, which are based on the results of an own-developed geometrical model that obtains both the coating thickness and dilution. This model is developed for the powder-fed directed energy deposition process (DED) and it only uses the DED single-track cladding characteristics (height, width, area, and dilution depth), the overlap percentage, and the laser head tilting-angle as inputs. As outputs, it calculates both the cladding geometry and the dilution area of the coating. This model for the Ni-based alloy 718 was improved, based on previous studies of the single clad working both vertically and at an inclined angle, adding the equations of the single clad characteristics with respect to the main process parameters. The strategy proposed in this paper for multilayered cladding consisted of both adding an extra clad at the edges of the layer and using a variable value of the overlap percentage between clads for geometric adaptations. With this strategy, the material deposition is more accurate than otherwise, and it shows stable growth. Manufacturing a multilayered wall of wider thicknesses at higher heights was utilized to validate the strategy.

Supercontinuum generation directly from a random fiber laser based on photonic crystal fiber.

Supercontinuum (SC) can be generated directly from a random fiber laser (RFL). However, its spectral bandwidth and flatness need to be further optimized for many practical applications. To solve this issue, a RFL based on random distributed Rayleigh scattering in photonic crystal fiber is demonstrated for the first time in this paper. The experimental results revealed that compared with the traditional single or double clad fiber, photonic crystal fiber not only can provide random distributed feedback effectively, but is also a superior nonlinear medium for SC generation which can realize better spectral width and flatness. A flat SC covering 400 nm to 2300 nm is obtained directly from a RFL based on photonic crystal fiber and the corresponding 20 dB bandwidth is more than 1600 nm, which is the widest ever reported to the best of our knowledge. The optical rogue waves caused by solitonic collisions can explain the instability of the output pulses in the time domain. This work proves that photonic crystal fiber can be used in RFL to provide random distributed feedback as well as nonlinear medium for spectrum broadening, and the spectral width and flatness of the generated SC is as good as the conventional method of using a high peak power pulsed laser to pump a piece of photonic crystal fiber, which can greatly reduce the cost of the SC and enrich the research scope of SC as well as RFL.

Globular Crystals in the Center of Roll Cast Aluminum Alloy Strips

This study investigated the crystallization position and formation mechanism of globular crystals at the center area in the thickness direction of aluminum alloy strips cast by a high-speed twin roll caster. Twin roll casters for single strips and clad strips were used, as well as twin roll casters equipped with a cooling slope. The globular crystals were formed from dividing arms of dendrites of the solidified layer facing the center area at the roll gap. The arms of isolated dendrite also divided. No globular crystals were formed at the interfaces of clad strips with different solidification temperatures because of the temperature gradient at the interface which inhibited division of the dendrite arms. It was demonstrated that globular crystals at the center area of the thickness direction were formed by dendrite-arm-dividing at the roll gap by the strip casting clad strip. Experiments by semisolid-strip casting with the cooling slope showed that globular crystals in the molten metal existed in the solidification layers.