Search Results (590)

This study examines in situ induction-heating thermal field assistance during laser cladding of Stellite 6 on 17-4PH stainless steel. Single-layer, multi-track coatings (~2.3 mm) were produced at induction powers of 0, 300, 600, and 900 W while keeping laser parameters constant. Surface morphology, phase constituents, and microstructures were characterized by LSCM, OM, XRD, SEM, EDS, and EBSD, and nanoscale features were probed by TEM for the 600 W condition; microhardness and coating-only tensile properties were evaluated. Thermal assistance improved surface finish (minimum Sa = 16.67 μm at 600 W) and suppressed hot cracking. XRD/EBSD revealed a γ-Co matrix with interdendritic carbides and an increased ε-Co fraction under thermal assistance; TEM further showed stacking-fault lamellae and a distinct FCC/HCP interface, supporting a fault-assisted, diffusionless γ → ε transformation. Increasing induction power coarsened the microstructure (larger D_E and SDAS), decreasing hardness from 537.1 to 461.5 HV_0.1 and lowering yield/ultimate strengths from 1046 MPa and 1512 MPa to 849 MPa and 1423 MPa, while elongation increased from 4.37% to 6.27%. Considering crack-free valve hardfacing with acceptable strength loss and improved ductility, 600 W provides the best overall performance. Full article

cBN-reinforced particle Ti-based composite coatings were deposited by high-speed laser cladding technology to enhance the wear resistance of Ti alloy. In this work, the influence of Ag addition on the microstructure and tribological behavior was systematically investigated. The microstructure and phase composition of the coatings were characterized using SEM/EDS and XRD. And the microhardness and tribological performance of coatings with Ag addition were assessed from room temperature up to 500 °C. The results show that the solidification process evolves with different Ag content. At lower Ag concentrations, Ag dissolves in the Ti-based solid solution, whereas higher Ag concentrations lead to the precipitation of Ag and Ag-Ti intermetallic. Due to the solid-solution strengthening effect and the formation of high-hardness intermetallic phases, the hardness of the coating increases with increasing Ag content. However, excessive Ag addition (>2.5 wt.%) results in a decrease in hardness. Tribological tests reveal that the friction coefficient and wear volume at room temperature decrease with increasing Ag content. With 10 wt.% Ag added, the friction coefficient of the coating decreases by 15% to 0.56, and the wear volume reduces by 28%, with the wear mechanism evolving from adhesive and fatigue wear to oxidative wear. At elevated temperatures (300 °C–500 °C), the friction-reducing effect is further enhanced due to the “sweating” of Ag and the formation of an oxide film, leading to reductions in the friction coefficient of 18%, 13%, and 7% at 300 °C, 400 °C, and 500 °C, respectively, for coatings with 5 wt.% Ag compared to coatings without Ag. Moreover, the formation of hard phases improves the coating’s high-temperature softening resistance and wear resistance property, as evidenced by an 85% reduction in wear volume at 500 °C for coatings containing 5 wt.% Ag. Full article

As a critical component of scraper conveyors, the middle trough operates under harsh conditions for extended periods, making it prone to failure and thus reducing the overall service life of the equipment. To address this issue and extend its service life, this study incorporated different amounts of CeO₂ into Cr₃C₂/Fe-based composite coatings. It investigated the effects of CeO₂ on the coating’s phase composition, microstructural evolution, wear resistance and corrosion resistance. Results show that CeO₂ addition did not alter the coating’s phase composition. The composition remained α-Fe, M₂₃C₆ (M: Fe, Cr) and vanadium carbides. However, CeO₂ promoted the transformation from columnar grains to equiaxed grains and refined the grains. With increasing CeO₂ content, the composite coating’s mechanical properties gradually improved. The Ce2 coating exhibited the highest microhardness (923.08 HV_0.5), the lowest friction coefficient (0.31) and the lowest wear rate (0.00217 mm³/N·m). Its dominant wear mechanisms were abrasive wear and mild adhesive wear. In 3.5% NaCl solution, the Ce2 coating showed the highest corrosion potential (−0.82 V) and the lowest corrosion current density (2.04 × 10⁻⁶ A/cm²), indicating excellent corrosion resistance. This study provides theoretical support for preparing high-performance Cr₃C₂/Fe-based composite coatings. It clarifies the key mechanism by which CeO₂ regulates coating properties. The developed composite coating has broad application potential due to its excellent combined wear and corrosion resistance. It can be widely used for surface strengthening of vulnerable components in mining machinery such as scraper conveyors, offering important theoretical and technical support for improving the service life of scraper conveyor middle troughs. Full article

Very-high-cycle fretting fatigue (VHCFF) behavior at elevated temperatures is critical for the safety and longevity of aerospace components. This study investigates the VHCFF mechanisms of laser-clad IN718/20%WC composite coatings at 650 °C. Fatigue tests were conducted to generate S-N data, and the resulting wear and fracture morphologies were characterized. Crack initiation was found to preferentially occur in grains exhibiting higher Schmid factors, lower elastic moduli, and larger equivalent sizes. To simulate fretting fatigue, a crystal plasticity finite element model (CPFEM) incorporating the actual microstructure was developed. An improved fatigue indicator parameter (FIP) was proposed, which integrates multiple physically significant factors including plastic strain, dislocation density, elastic modulus, and grain size. Life predictions based on a critical FIP value demonstrated high accuracy, with 97.6% of the results falling within a ±3.5 scatter band of the experimental data, confirming the model’s effectiveness in predicting crack initiation life. Full article

The nickel (Ni)-based alloy cladding layers on the surface of 6061 aluminum alloy are fabricated successfully using an optimized laser cladding process. An analysis has been conducted to compare the influence of two types of Ni-based powders on the phase composition, macroscopic morphology and microstructure of the cladding layers. The study also elucidates the micro-hardness and friction property of the cladding layers fabricated by two types of Ni-based powders. The results reveal that phases including Al₃Ni, Al₃Ni₂, and α-Al are formed in the pure Ni cladding layer. Nonetheless, in the Ni–Cr–B–Si cladding layer, a new phase characterized by needle-shaped Cr₇C₃ is observed. Mechanical properties characterization of the cladding layers reveals a notable improvement in microhardness and friction properties compared to the 6061 aluminum alloy substrate. The best properties are achieved in the Ni–Cr–B–Si cladded layer, which demonstrates a microhardness of 714 HV, almost 8.1 times superior to that of the substrate. Its friction and wear rate is merely 21% of that of the base aluminum. Our results are expected to provide significant insights into the design and production of aluminum materials with great resistance to wear. Full article

In order to improve the wear resistance of titanium alloy and apply it to the high-speed train brake disc, TiNbZrV_x (x = 0, 0.2, 0.4, 0.6, 0.8) refractory medium-entropy alloy coatings were prepared on Ti-6Al-4V (TC4) substrate. The effect of V content on the microstructure, mechanical properties, and friction and wear properties of the coatings was studied. TiNbZrV_x coatings achieved good metallurgical bonding with the substrate, forming BCC and B2 phases and AlZr₃ intermetallic compound (IMC). From TiNbZr coating to TiNbZrV_0.8 coating, V promotes element segregation and new phase formation, which decreased the average grain size from 85.055 μm to 56.515 μm, increased the average hardness from 265.5 HV to 343.4 HV, and reduced the room temperature (RT) wear rate by 97.8%. However, the ductility of the coatings decreased from 15.7% to 5.8% because the grain boundary precipitates changed the dislocation arrangement, and the tensile fracture mode changed from ductile fracture to brittle fracture. Abrasive wear was the main wear mode at RT, and adhesive wear and oxidation wear were the main wear modes at elevated temperature. The COF at elevated temperature was lower than that at RT, because a large number of friction pair components were transferred to the coating surface at high temperature and were repeatedly rolled to form a dense film, which played a certain lubricating role. Full article

Sliding bearing alloy layers must combine excellent tribological performance with reliable metallurgical bonding, but conventional fabrication methods often suffer from coarse grains, chemical segregation and poor interface adhesion. Annular coaxial laser wire-feed cladding, by providing more uniform heat input and rapid solidification, is expected to mitigate these deficiencies; however, systematic studies of this technique applied to tin-based Babbitt alloy layers remain limited. In this work, Babbitt layers produced by conventional casting and by annular coaxial laser wire-feed cladding were compared in terms of microstructure, phase constitution, hardness and tribological behavior. The results indicate that laser cladding can produce continuous, dense and well-bonded coatings and markedly refine the SnSb phase, reducing grain size from approximately 100 μm in the cast material to 10-20 μm. Hardness increased from 25.3 HB to 27.6 HB, while tribological performance improved substantially: the coefficient of friction decreased by about 38.19% and the wear volume was reduced by approximately 10.46%. These improvements are attributed mainly to the rapid solidification, low dilution and more uniform phase distribution associated with annular coaxial laser cladding, demonstrating the strong potential of this process for fabricating high-performance tin-based Babbitt bearing layers. Full article

Laser cladding is an effective surface engineering technique to enhance the high-temperature performance of metallic materials. In this work, a Cr-Al-C composite coating was in situ fabricated on H13 steel by laser cladding to alleviate the performance degradation of H13 steel under severe thermomechanical conditions, particularly in high-temperature piercing applications. The phase composition, microstructure, microhardness, high-temperature oxidation behavior, and tribological performance of the coating were systematically investigated. The coating is mainly composed of a B2-ordered Fe-Cr-Al phase reinforced by uniformly dispersed M₃C₂/M₇C₃-type carbides, which provides a synergistic combination of oxidation protection and mechanical strengthening, offering a microstructural design that differs from conventional Cr-Al or Cr₃C₂-based laser-clad coatings. Cyclic oxidation tests conducted at 800–1000 °C revealed that the oxidation behavior of the coating followed parabolic kinetics, with oxidation rate constants significantly lower than those of the H13 substrate, attributed to the formation of a dense and adherent Al₂O₃/Cr₂O₃ composite protective scale acting as an effective diffusion barrier. Benefiting from the stable oxide layer and the thermally stable carbide-reinforced microstructure, the wear rate of Cr-Al-C coating is significantly reduced compared to H13 steel. At room temperature, the wear rate of the coating is 6.563 × 10⁻⁶ mm³/(N·m), about two orders of magnitude lower than 8.175 × 10⁻⁴ mm³/(N·m) for the substrate. When the temperature was increased to 1000 °C, the wear rate of the coating remained as low as 5.202 × 10⁻⁶ mm³/(N·m), corresponding to only 1.9% of that of the substrate. This work demonstrates that the Cr-Al-C laser-cladded coating can effectively improve the high-temperature oxidation resistance and wear resistance of steel materials under extreme service conditions. Full article

Carbon steel components used in aluminum alloy casting are prone to severe corrosion by molten aluminum, which significantly shortens their service life. To address this limitation, protective coatings were applied to improve corrosion resistance and extend durability. In this study, laser-clad TiB₂–TiC reinforced ferroboron coatings were fabricated on carbon steel substrates. The microstructure, phase composition, and interface characteristics were systematically analyzed. Electrochemical and immersion tests were conducted to evaluate corrosion resistance in molten aluminum. The results demonstrate that the composite coating forms a dense barrier layer that effectively prevents aluminum infiltration and suppresses intermetallic compound growth. Consequently, the coated carbon steel exhibits markedly enhanced resistance to molten aluminum attack, providing a promising solution for extending the lifetime of steel components in aluminum alloy casting environments. Full article

To enhance the operational damage resistance of hydraulic machinery, this study employed laser cladding technology to fabricate a Co_37.4Cr₃₀Ni₂₀Al₅Ti₅Nb_2.6 high-entropy alloy coating on 04Cr13Ni5Mo substrate. The influence of laser power on the microstructure and properties of the coating was systematically investigated. Based on preliminary research, the friction-wear performance and cavitation erosion behavior of the coatings prepared at 3000 W, 3200 W, and 3400 W were specifically examined. Results indicate that as the laser power increased from 3000 W to 3400 W, the microhardness of the coating gradually decreased from 345.3 HV_0.2. At 3000 W, the precipitation of trace strengthening phases significantly enhanced the mechanical properties. In wear tests under a 20 N load for 30 min, the wear rate of the coating prepared at 3000 W was 1.41 × 10⁻⁴ mm³/(N·m), which is 13.5% lower than that of the 3200 W coating (1.63 × 10⁻⁴ mm³/(N·m)) and 16.07% higher in wear resistance compared to the substrate. Cavitation erosion tests revealed that after 20 h of ultrasonic vibration, the mass loss of the 3000 W coating was only 2.35 mg, representing an 88.89% reduction compared to the substrate (21.15 mg), and significantly lower than that of the 3200 W (4.57 mg) and 3400 W (3.85 mg) coatings. This study demonstrates that precise control of laser power can effectively optimize the cavitation erosion resistance of high-entropy alloy coatings, providing technical support for their application in harsh environments. Full article

As high-end equipment manufacturing advances, demand for improved surface performance in critical components has increased. Laser cladding is an advanced surface strengthening technique that affords effective surface modification. During the laser cladding process, obtaining a fine grain microstructure usually helps to enhance the microhardness, wear resistance, and corrosion resistance of the cladding layer. However, conventional laser cladding often yields coarse columnar grains that limit further performance improvements, so process optimization to achieve grain refinement is necessary. In this study, oscillating laser cladding was combined with a pulsed-wave (PW) laser mode to deposit a fine-grained Al₂CrFe₂Ni₄Ti_1.5 high-entropy alloy cladding on Q550 steel substrates. Compared with continuous-wave (CW) laser cladding, the PW mode produced markedly refined grains and concomitant improvements in microhardness, wear resistance, and corrosion resistance. Specifically, the microhardness of the PW cladding layer reached approximately 673.34 HV_0.5, the wear volume was approximately 0.06 mm³, the wear rate was approximately 0.21 × 10⁻⁴ mm³/N·m, and the corrosion current density decreased to approximately 1.212 × 10⁻⁵ A·cm⁻². This work presents a novel approach for producing high-performance, wear-resistant, and corrosion-resistant high-entropy alloy cladding layers, and offers both theoretical insight and potential engineering applications. Full article

This study systematically investigates the influence of laser power (1000 W, 1400 W, 1800 W) on the microstructure and properties of Ni25 alloy coatings prepared by laser cladding to optimize process parameters for enhanced comprehensive performance. Through the analysis of multi-dimensional characterization, it is found that the laser power significantly changes the thermal cycle, thus determining the evolution of microstructure. At 1000 W, a fine dendritic structure with dispersed hard phases (BNi₃, BFe₃Ni₃, CrB₂, Cr₇C₃) yielded the highest hardness (442.52 HV) but poor wear (volume loss: 0.3346 mm³) and corrosion resistance (Icorr: 2.75 × 10⁻⁴ A·cm⁻²) due to microstructural inhomogeneity. The 1400 W coating, featuring a uniform γ-Ni dendrite/eutectic network and increased B solid solubility, achieved an optimal balance with the lowest wear rate (0.0685 mm³), superior corrosion resistance (Icorr: 2.34 × 10⁻⁵; A·cm⁻²), and a stable friction coefficient (0.816), despite lower hardness (342.00 HV). At 1800 W, grain coarseness and Cr₇C₃ decomposition led to blocky hard phases, recovering hardness (415.36 HV) and reducing the friction coefficient (0.757), but resulting in intermediate wear and corrosion resistance. This study demonstrates that the uniformity and continuity of the microstructure are the key determinants governing the comprehensive service properties of the laser cladding layer, with their importance outweighing a single hardness index. 1400 W is identified as the optimal laser power, providing critical insights for fabricating high-performance Ni25 coatings in demanding service environments. Full article

TC4 alloy coatings were fabricated on a titanium alloy substrate using laser cladding. The influence of laser power ranging from 1000 W to 2200 W on the microhardness, wear resistance, and electrochemical corrosion behavior in 3.5% NaCl solution was systematically investigated. Results demonstrate that the TC4 coating exhibited a 35.17% enhancement in microhardness compared to the substrate, with an average value reaching 500 HV. As the laser power increased from 1000 W to 2200 W, the maximum wear depth progressively decreased, indicating significantly improved wear resistance, with fatigue wear being identified as the dominant mechanism. The coating prepared at 1400 W showed the best corrosion performance, displaying the highest self-corrosion potential of −0.110 V, the lowest corrosion current density of 0.125 μA·cm⁻², and the largest polarization resistance of 2.057 × 10⁶ Ω·cm². The charge transfer resistance initially increased and then decreased with increasing laser power. Numerical simulations revealed that when exposed to seawater, galvanic couples formed between the α and β phases on the TC4 titanium alloy surface, resulting in preferential dissolution of the β-phase. Full article

Co-Cu-Ti composite coatings were fabricated on Ti6Al4V substrates by laser cladding. The Criteria Importance Through Intercriteria Correlation–Technique for Order Preference by Similarity to Ideal Solution methodology was employed to determine the optimal parameters. The effect of varying the scanning speed, a critical parameter, was investigated to evaluate its influence on the coating’s microstructure and performance. The phase composition of the coatings comprises Co-Ti phases and Cu-Ti phases. The microhardness and wear resistance of the coatings initially increase as the scanning speed rises, reaching a peak before subsequently declining. The predominant wear mechanisms of the coatings are abrasive wear, with minor contributions from adhesive wear and fatigue wear. The wear resistance of the coating is superior to that of the TC4 substrate, primarily due to the synergistic enhancement from the strengthening effect of the Co-Ti phase and the lubricating effect of the Cu-Ti phase. The composite coatings fabricated at a scanning speed of 3 mm/s exhibited superior properties. Specifically, the microhardness measures 788 HV_0.2, the coefficient of friction is approximately 0.57, and the wear cross-sectional area is 3.57 × 10⁻⁹ mm². At this speed, these two effects achieve an optimal balance, making it the best process parameter for wear resistance. Full article

In this study, a multiphysics coupling numerical model was developed to investigate the thermal-fluid dynamics and microstructure evolution during the laser metal deposition of AlCoCrFeNi high-entropy alloy (HEA) coatings on 430 stainless steel substrates. The model integrated laser-powder interactions, temperature-dependent material properties, and the coupled effects of buoyancy and Marangoni convection on melt pool dynamics. The simulation results were compared with experimental data to validate the model’s effectiveness. The simulations revealed a strong bidirectional coupling between temperature and flow fields in the molten pool: the temperature distribution governed surface tension gradients that drove Marangoni convection patterns, while the resulting fluid motion dominated heat redistribution and pool morphology. Initially, the Peclet number (Pe_T) remained below 5, indicating conduction-controlled heat transfer with a hemispherical melt pool. As the process progressed, Pe_T exceeded 50 at maximum flow velocities of 2.31 mm/s, transitioning the pool from a circular to an elliptical geometry with peak temperatures reaching 2850 K, where Marangoni convection became the primary heat transfer mechanism. Solidification parameter distributions (G and R) were computed and quantitatively correlated with scanning electron microscopy (SEM)-observed microstructures to elucidate the columnar-to-equiaxed transition (CET). X-ray diffraction (XRD) analysis identified body-centered cubic (BCC), face-centered cubic (FCC), and ordered B2 phases within the coating. The resulting hierarchical microstructure, transitioning from fine equiaxed surface grains to coarse columnar interfacial grains, synergistically enhanced surface properties and established robust metallurgical bonding with the substrate. Full article