Laser Cladding Method Research Articles

Numerical simulation and experimental analysis of thermal conduction and stress in laser cladding repair of thin-walled parts

To minimize the deformation of thin-walled parts during the laser cladding process and enhance the quality of the repaired parts, the Finite Element Abaqus software was used to develop a thermal conduction and 3D stress model, the heat source used in the experiments was a double ellipsoid heat source model. This model simulates the thermal process and the deformation resulting from residual stresses in the laser cladding process on a titanium alloy substrate with a thickness of 2 mm. Through the simulation, the temperature field of the substrate at the end of each pass was obtained, and the cladding sequence with the smallest temperature gradient during the multi-pass laser melting process was determined. By combining simulation and practice, the multilayer stacking pattern was optimized to achieve deformation control. Analog simulation experiments indicate that the optimized single-layer multi-pass laser cladding method results in less heat accumulation and thermal stress compared to the unidirectional sequential scanning method. The flatness test results show that the specimens have less deformation with the optimized multilayer stacking method. In addition, the metallographic organisation of the two cladding specimens is analysed in this paper, and the results show that the optimised specimens exhibit excellent microstructures and properties.

Combating Cl− and SO42−-induced molten salt corrosion by laser cladding FeCrNiMoAl high-entropy alloy coating

FeCrNiMoAl high entropy alloy coating was successfully prepared by laser cladding method with phases of dominant face-centered cubic (FCC) and minor intermetallics (AlFe and AlNi). After 144 h of corrosion in the molten salt mixture of 40 % NaCl + 40 % KCl + 10 % Na2SO4 + 10 % K2SO4 at 600 °C, FeCrNiMoAl exhibited a much lower corrosion rate than conventional Inconel 625 by a reduction of 34 %. XRD and SEM were used to characterize the corroded samples. To combat Cl-induced active corrosion and S-induced sulfidation, Inconel 625 develops a single Cr2O3 layer while FeCrNiMoAl developed dual layers of outer Cr2O3 and inner Al2O3, which effectively prevents penetration of Cl and S.

Research on rapid prediction method of laser cladding deposited layer state based on molten pool texture sequence

A texture sequence feature combining texture statistical characteristics with time series is proposed for rapid prediction of the state of laser cladding deposited layer. Texture features in the molten pool images are extracted using high-order dense texture descriptor operators and transformed into probability sequences with the aid of multi-cell histograms. Texture features are screened based on the types of points of interest to improve the sequence, enhancing the prediction accuracy and speed for deposited layer. For different types of points of interest, the optimal texture sequence obtained achieves an improvement of more than 6% in prediction accuracy for deposited layer state compared to the full-texture sequence. The proposed texture sequence features, when compared with molten pool image features, exhibit an average improvement in prediction speed of more than 17 times across different deep learning models. Overall, the results indicate that this method significantly improves prediction speed while maintaining accuracy, satisfying the requirements of high-speed monitoring in laser cladding.

Effect of WC particle size on the microstructural evolution and tribological properties of laser cladding Ti-bearing Co-based WC reinforced coating

To improve the wear resistance of 300 M steel under reciprocating wear in landing gear shock strut, Ti-bearing Co-based WC reinforced coatings with three different WC particle sizes (280 mesh, 200 mesh, and 150–300 mesh) were successfully fabricated by laser cladding method. The effect of WC particle size on phase composition, microstructure, microhardness and tribological properties were systematically investigated. The results show that the phase composition of these coatings consists mainly of γ-Co, TiC, WC, Cr23C6 and CrCo, and that varying the WC particle size changes the morphologies of the second phases. With the increase of WC particle size, the morphology of TiC is dendritic, ellipsoidal and block, respectively; the morphology of Cr23C6 changes from discontinuous fine particles to grid-like at grain boundaries. And the TiC-WC composite phases appear when the particle size of the added WC particles is a mixture. The coating with a mixture of 150–300 mesh WC particles, has the highest hardness range, the lowest average friction coefficient of 0.372, and the lowest wear rate of 9.61 × 10−5 mm3/N·m. The wear mechanisms of all three coatings are abrasive wear and oxidation wear, and the oxide film on the worn surface of the coatings gradually becomes denser and more continuous with increasing WC particle size.

The Process Optimization Analysis of CBN Abrasive Cu-Sn-Ti Coating Fabrication via the Ultrasonic-Vibration-Assisted Laser Cladding Method

Ultra-precision machining has higher requirements for the performance of abrasive tools, but the traditional grinding wheel has some problems such as irregular grain arrangement, limited chip space, and high grinding temperature. Therefore, a structured grinding wheel suitable for ultra-precision machining is proposed. In this study, the laser cladding method and ultrasonic vibration technology were combined to study the preparation process of a structured grinding wheel. Firstly, the quality evaluation system of the printing layer was established, and the shape coefficient and dilution rate were used to evaluate the laser cladding quality. The effects of laser power, sweep speed, powder feeding speed, and ultrasonic power on the shape coefficient and dilution rate of the printing layer were analyzed by single-factor experiments. The level range of each factor in the orthogonal experiment was established to optimize the process parameters. The surface morphology was observed, and the influence of ultrasonic vibration on the morphology was analyzed. The structured grinding wheel was prepared according to the optimized parameters.

Dilution induced variation of microstructure and mechanical properties on Co-Cr-Fe-Ni high entropy alloy coatings prepared by laser cladding

The remarkable properties of some series of high entropy alloys (HEAs) have garnered extensive interest in the development of HEA coatings. In this study, we prepared non-equiatomic Co-Cr-Fe-Ni HEA coatings using laser cladding method with Co-Cr-Fe-Ni cable-type welding wire (CTWW) as the filling material and investigated the effect of dilution rate on the microstructure evolution of coatings. By changing the wire feeding speed, a large dilution rate range was obtained which is from over 80 % to below 20 % and a variation of the coating's microstructure and mechanical properties was discovered within this large dilution rate range. All of the coatings are dense and uniform, with good metallurgical bonding. A pivotal discovery was made when the dilution rate decreased from approximately 35 %–40 % to below this threshold. The coating transitions from face centered cubic (FCC) and body centered cubic (BCC) dual-phase to FCC single-phase, accompanied by a precipitous drop in hardness from approximately 425 HV to below 175 HV. The interlaced distribution and dislocation pile-up of the layered BCC eutectic structure within the FCC phase are the main reasons for this dramatic change. Therefore, controlling the dilution rate is an effective way to regulate the performance of Co-Cr-Fe-Ni HEA coatings.

Effect of solution and artificial aging heat treatment on the hardness, friction and wear properties of laser cladding and roll-formed 18Ni300 materials

Abstract 18Ni300 is widely used in precision moulds, national defence, and other engineering fields due to its high strength and toughness, and because its properties can be greatly changed after heat treatment. In this research, the 18Ni300 cladding layer was fabricated on 18Ni300 substrate using the laser cladding method and a solid solution artificial aging treatment was carried out to analyse its macro morphology and metallographic organization. Comparison of hardness, friction, and wear of cladding layers manufactured by laser cladding and of materials produced by rolling was performed before and after heat treatment. The results show that the solution and artificial aging heat treatment has a significant effect on the microstructure of the cladding layer fabricated by laser cladding. There are obvious differences in the organization and morphology of different parts of the cladding layer before heat treatment; the metallographic organization and morphology of different parts of the cladding layer after heat treatment are the same. The trend of change of material hardness before and after heat treatment is the same in that the cladding layer is greater than the rolled material and the hardness of the material after heat treatment is much greater than the hardness of the material before heat treatment. The hardness and wear resistance of the material after solution and artificial aging heat treatment has been significantly improved, and the impact on the rolled production material of the melted cladding layer manufactured by laser cladding is even greater.

Effect of laser power on morphology, microstructure and mechanical properties of CBN abrasive block prepared by two-step laser cladding

The preparation of cubic boron nitride (CBN) grinding tools using laser cladding has the advantages of strong bonding, short time consumption and customizable abrasive arrangement. In this paper, a two-step laser cladding method was used to prepare CBN abrasive blocks with the aim of reducing laser damage to CBN grits during the laser cladding process. The cross-sectional morphology of CBN abrasive blocks under different laser power conditions was characterized, and the relationship among laser power, preparation method, and forming quality of Cu–Sn–Ti/CBN cladding layer was investigated. Then, the microstructure at the Cu–Sn–Ti/CBN interface under different laser power conditions was characterized, and the main phase compositions at the Cu–Sn–Ti/CBN interface were analyzed. Finally, the grinding tests were carried out on CBN abrasive blocks. The results show that as the laser power increases from 250 W to 400 W, the fracture ratio of CBN grits increases dramatically from 4.3 % to 17.3 %. TiN, TiB2, and TiB compounds are all detected at the Cu–Sn–Ti/CBN interface under different laser power conditions. The mass loss of the TC4 wheel caused by the CBN abrasive block initially increases and then decreases as the laser power increases from 250 W to 400 W. The CBN abrasive block has the optimum material removal performance at the laser power of 300 W using two-step laser cladding. The results provide a theoretical basis for the preparation of high-performance CBN grinding tools using laser cladding.

Wear resistance optimized by heat treatment of an in-situ TiC strengthened AlCoCrFeNi laser cladding coating

Abstract An AlCoCrFeNi high-entropy alloy coating containing 20 % mass fraction of TiC was prepared using the laser cladding method. The effect of heat treatment on the coating’s microstructure was analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and transmission electron microscopy (TEM). It was observed that following high-temperature heat treatment, the phase transition of AlCoCrFeNi–20%TiC shifted from BCC to FCC at 750 °C. Through microhardness and wear resistance tests, the increased diffusion of carbon post-heat treatment led to a higher precipitation of TiC-reinforced phases, resulting in exceptional wear resistance with a notable 128.3 % enhancement.

Effect of processing parameters on the microstructure of laser-clad Stellite 6 on the X19CrMoNbVN11-1 stainless-steel substrate

This investigation aims to study the effect of laser cladding parameters on the microstructure of Stellite 6 on the X19CrMoNbVN11-1 stainless-steel substrate. First, Stellite 6 powder was coated on the X19CrMoNbVN11-1 substrate using the laser cladding method. The effect of laser cladding parameters (i.e., laser power, scanning speed, and powder feed rate) was studied on the microstructure of deposits. The secondary dendritic arm spacing was assessed, and the structural defects were studied (e.g., lack of bonding, porosity, and crack). The results revealed that the microstructure has changed from coating/substrate interface to coating surface, from plate-cellular to columnar and equiaxed dendrites. Also, an increase in the laser power increased the cellular structure in the coating/substrate interface and equiaxed dendrites in the coating surface. The cooling rate (G × R) increased by increasing the scanning and powder injection rates. The microstructure of the Stellite 6 was composed of cobalt solid-solution γFCC.

Microstructure and Wear Resistance of Si-TC4 Composite Coatings by High-Speed Wire-Powder Laser Cladding.

The hardness and wear resistance of the surface of TC4 titanium alloy, which is widely used in aerospace and other fields, need to be improved urgently. Considering the economy, environmental friendliness, and high efficiency, Si-reinforced Ti-based composite coatings were deposited on the TC4 surface by the high-speed wire-powder laser cladding method, which combines the paraxial feeding of TC4 wires with the coaxial feeding of Si powders. The microstructures and wear resistance of the coatings were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers hardness tester, and friction and wear tester. The results indicate that the primary composition of the coating consisted of α-Ti and Ti5Si3. The microstructure of the coating underwent a notable transformation process from dendritic to petal, bar, and block shapes as the powder feeding speed increased. The hardness of the composite coatings increased with the increasing Si powder feeding rate, and the average hardness of the composite coating was 909HV0.2 when the feeding rate reached 13.53 g/min. The enhancement of the microhardness of the coatings can be attributed primarily to the reinforcing effect of the second phase generated by Ti5Si3 in various forms within the coatings. As the powder feeding speed increased, the wear resistance initially improved before deteriorating. The optimal wear resistance of the coating was achieved at a powder feeding rate of 6.88 g/min (wear loss of 2.55 mg and friction coefficient of 0.12). The main wear mechanism for coatings was abrasive wear.

Study on Microstructure and High Temperature Stability of WTaVTiZrx Refractory High Entropy Alloy Prepared by Laser Cladding.

The extremely harsh environment of the high temperature plasma imposes strict requirements on the construction materials of the first wall in a fusion reactor. In this work, a refractory alloy system, WTaVTiZrx, with low activation and high entropy, was theoretically designed based on semi-empirical formula and produced using a laser cladding method. The effects of Zr proportions on the metallographic microstructure, phase composition, and alloy chemistry of a high-entropy alloy cladding layer were investigated using a metallographic microscope, XRD (X-ray diffraction), SEM (scanning electron microscope), and EDS (energy dispersive spectrometer), respectively. The high-entropy alloys have a single-phase BCC structure, and the cladding layers exhibit a typical dendritic microstructure feature. The evolution of microstructure and mechanical properties of the high-entropy alloys, with respect to annealing temperature, was studied to reveal the performance stability of the alloy at a high temperature. The microstructure of the annealed samples at 900 °C for 5-10 h did not show significant changes compared to the as-cast samples, and the microhardness increased to 988.52 HV, which was higher than that of the as-cast samples (725.08 HV). When annealed at 1100 °C for 5 h, the microstructure remained unchanged, and the microhardness increased. However, after annealing for 10 h, black substances appeared in the microstructure, and the microhardness decreased, but it was still higher than the matrix. When annealed at 1200 °C for 5-10 h, the microhardness did not increase significantly compared to the as-cast samples, and after annealing for 10 h, the microhardness was even lower than that of the as-cast samples. The phase of the high entropy alloy did not change significantly after high-temperature annealing, indicating good phase stability at high temperatures. After annealing for 10 h, the microhardness was lower than that of the as-cast samples. The phase of the high entropy alloy remained unchanged after high-temperature annealing, demonstrating good phase stability at high temperatures.

Microstructure and Wear Resistance of Ti6Al4V Titanium Alloy Laser-Clad Ni60/WC Composite Coating.

In this paper, Ni60/WC wear-resistant coatings have been created on the Ti6Al4V substrate surface using a pre-layered powder laser cladding method by deploying various scanning speeds of 8, 10, 12, and 14 mm/s. The coatings are characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), and a high-speed reciprocating fatigue wear tester. It is found that the phase composition of the coating comprises the synthesized, hard phase TiC and TiB2, the silicides WSi2 and W5Si3, and NiTi and γ-Ni solid solutions. At different scanning speeds, there is a metallurgical fusion line in the bonding area of the fused cladding layer, indicating a good metallurgical bonding between the substrate and the powder. At a low scanning speed, the coating develops into coarse dendrites, which shows significant improvement with scanning speed. The microhardness first increases and then decreases with the scanning speed, and the coating's average microhardness was 2.75-3.13 times higher than that of the substrate. The amount of mass wear has been reduced by 60.1-79.7% compared to the substrate. The wear behavior of the coatings was studied through detailed analysis of wear surfaces' microstructures and the amount of wear to identify the optimum scanning speed.

Effect of WC on the microstructure and mechanical properties of laser-clad AlCoCrFeNi2.1 eutectic high-entropy alloy composite coatings

AlCoCrFeNi2.1/WC eutectic high-entropy alloy composite coatings were prepared on a 316 L stainless steel substrate via the laser cladding method. The effects of the WC content on the phase composition, microstructure, and mechanical properties of the composite coatings were investigated. The results revealed that the laser-clad AlCoCrFeNi2.1/WC eutectic high-entropy alloy composite coating mainly consisted of FCC and BCC phases. As the WC content increased from 0 wt% to 30 % wt%, the Cr7C3 and Cr21W2C6 phases were gradually precipitated from the composite coating. Consequently, the microhardness of the composite coating increased from 318.6 to 572.3 HV1.0. The strengthening mechanism of composite coatings mainly comprised solid solution strengthening, second-phase strengthening, and fine-grain strengthening. Additionally, the high dislocation density, caused by rapid condensation during the laser cladding process, contributed to the improvement in the coating hardness. Wear experiments revealed a significant improvement in the wear resistance of the composite coating with increasing WC content. The composite coating with 30 wt% WC exhibited the highest hardness and wear resistance with an average friction coefficient of 0.535, as well as a wear rate and wear volume loss of 4.4 × 10−7 mm3N−1 mm−1 and 5.44 mm3, respectively.

Increasing the wear resistance of the ICE’s valves with the laser cladding method

BACKGROUND: There is plenty of factors leading to failure and expensive repair of piston engines at their operation. One of the widespread factors capable of affecting the engine operation is combustion chamber sealing failure. During the engine operation, gases combusting in a chamber bring pressure on working surfaces of a valve and a valve seat. If these surfaces do not ensure sealing, exhaust gases begin to leak in the exhaust manifold untimely, in some cases in the intake manifold as well. In addition, filling of cylinders with inlet charge worsens. In majority of cases, combustion chamber sealing failure caused by defect formation at working surfaces of the valve — valve seat coupling. In order to avoid combustion chamber sealing failures and other issues of operation of piston engines, it is necessary to minimize working surfaces wearing by means of wear-resistant coating. AIMS: Wear- and corrosion-resistant coating of valve’s working surface to increase service life. METHODS: The factors affecting the reliability of the valve — valve seat coupling were defined by means of literary sources analysis. Laser cladding at the valve’s chamfer was conducted with the laser robotized facility based on ytterbium fiber laser. Quality of the coated surface at the valve’s working chamfer was defined by means of metallographic study and liquid penetrant test. RESULTS: After laser cladding of the PR-08Kh17N8S6G powder material at the valve’s working chamfer, the uniform coated surface with microhardness of 435–485 HV (44–48 HRC) was obtained. CONCLUSIONS: The study results may be used for development and implementation of new kinds of wear-resistant surfaces that make it possible to increase the service life and to repair worn-down surfaces of components.

Epitaxial growth of single crystal superalloy by a novel spot-cutting laser cladding method

A spot-cutting laser cladding process was proposed to repair the thin wall single crystal superalloy in this paper. The effects of spot cutting and its gap width on the dimensions and microstructure of cladding layers were studied. The results demonstrate that the cladding layers exhibit directionally epitaxial dendrites throughout the layer, reducing the formation of “stray grains” and significantly decreasing the machining allowance compared to samples without spot cutting. By optimizing the parameters, continuous epitaxial grains were achieved in the cladding layer, reaching a height of 1173 μm. The layer dimensions increased initially with weld height, but then decreased with a flattening morphology as the base metal width increased.

Optimization on laser cladding parameters for preparing Ni60 coating along with its friction and wear properties

Ni60 coating was prepared on Q235 substrate by using laser cladding method, and the optimization of processing parameters was performed based on response surface methodology. Laser power, scanning speed and powder feeding rate were considered as input variables, while dilution ratio, ratio of width to height, and hardness were considered as output responses. Then, the influence of processing parameters on cladding quality was studied by single track cladding experiments, and the optimal parameters were obtained by regression analysis. Subsequently, Ni60 coating was successfully prepared and its friction and wear properties were investigated. Results show that the optimal parameters are: laser power 540 W, scanning speed 30 mm/s, powder feeding rate 0.2 r/min and overlapping step 0.4 mm. The microhardness of coating is 499.4 HV0.5, which is 5 times higher than that of the substrate. Correspondingly, the wear loss of the coating is 68.3% and 82.1% lower than that of Q235 substrate at room temperature and 400 °C respectively, indicating that the Ni60 coating can improve the wear resistance of Q235 steel significantly.

Parameters optimization for single-track laser cladding based on MPA-SVR and A-NSGA-III

Laser cladding as an emerging surface modification technology, the morphology of the single-track cladding layer is directly affected by the process parameters. To obtain the ideal cladding layer morphology, it is necessary to build the mapping relationship between the process parameters and the morphology and optimize the process parameters. A method for predicting the morphology of the single-track cladding layer is proposed by using the support vector regression optimized by the marine predators algorithm. Then, the adaptive non-dominated sorting genetic algorithm III is used for process parameter optimization to determine the optimal process parameters of laser cladding. The results of the validation experiments show that the aspect ratio of the optimized cladding layer has been improved by 41.78%, the dilution rate has been improved by 22.30%, and the wetting angle has been reduced by 35.20%. The proposed process parameters optimization method of laser cladding can significantly improve the morphology of the cladding layer.

Microstructure and properties of W0.5Ta0.3MoNbVAlTi1-xZrx high entropy alloy coatings by laser cladding on the surface of 45# steel

W0.5Ta0.3MoNbVAlTi1-xZrx (x = 0, 0.25, 0.5, 0.75, and 1.0) high entropy alloy coatings were prepared on the surface of 45# steel in this study using a laser cladding method. The resulting data demonstrate that increasing x changed the proportion of the phases but not the type of phases. Additionally, for all HEA coatings consisting of the BCC solid solution phase, Laves phase, MC phase, and unmelted W, the content of Laves phase was gradually decreased, and the HEA coatings microstructure was gradually transitioned from equiaxed to dendritic crystals. Solid solution strengthening, precipitation strengthening, and diffusion strengthening significantly increased the microhardness of the HEA coatings. The microhardness of the coating was the highest when x = 0.25, approximately 1.1–1.4 times that of other coatings. The wear mechanism of the HEA coatings was abrasive wear, and the wear rate first decreased and then increased with increaseing x. The combined resistance of the coating to micro-cutting and brittle debonding was the strongest when x = 0.5 with maximal wear resistance. The wear rate was only 43.8–82.9% that of other coatings. The increase in Zr content and decreasing Laves phase content reduced the number of defects and the formation of unstable oxides at the phase boundaries. The stability of the oxide layer was enhanced, and the coating exhibited the best high-temperature oxidation resistance when x = 0.75, approximately 1.4–6.3 times that of the other coatings.

A modified Fe–Ni alloy coating in pure iron combined of surface mechanical attrition treatment and spark plasma sintering approach

To overcome the shortage of long processing time, high energy consumption, and complex controlling in fabricating Fe–Ni alloy coating, this paper was modified Fe–Ni alloy coating based on the mechanical alloying, electrodeposition, laser cladding and DC arc plasma method. Here, Surface Mechanical Attrition Treatment (SMAT) had been chosen as a pre-treatment to fabricate uniform Fe–Ni alloy coating by Spark Plasma Sintering (SPS). After the well-designed coating approach of SMAT + SPS, a homogeneous and continuous Fe–Ni alloy coating was fabricated on a pure iron plate. During study of the effect of SMAT and the subsequent process of SPS on microstructure and mechanical properties of Fe–Ni alloy coating, a valid set of process parameters were investigated. The results show that the thickness of Fe–Ni interface layer was enhanced significantly by SMAT. In comparison, the depth on the SMAT-sample was approximately twice as thick as on the untreated coarse-grained (CG) sample. The relative densification, microhardness and friction and wear performance are significantly related to the sintering temperature, which also affects the microstructure of interface between iron matrix and alloy coating. It has been evidently proved that, the sintering temperature just within 800–900 °C, the optimum performance Fe–Ni alloy coating on the SMATed iron matrix could be obtained, which has higher density, better wear resistance and tighter bonding.