Cladding high-hardness In718 alloy onto ductile iron emerges as an effective solution to mitigate interfacial degradation, owing to the alloy’s superior resistance to corrosion, oxidation, wear and thermal fatigue. Herein, the effects of laser cladding parameters on the tribological performance of laser-cladded In718 coatings were investigated. Simulation results demonstrated that optimized cladding parameters effectively homogenize the molten pool’s temperature gradient and significantly reduce the residual stress within the cladding layer, thereby enhancing the cladding quality. In718 alloy coatings were cladded on ductile iron substrates using simulation-optimized cladding parameters, achieving a microcrack-free morphology with minimal powder inclusions, negligible pores, and refined metallographic structures. The coatings demonstrate a substantial hardness enhancement of 46.7%–58.9% compared to the substrate, attributed to hard carbide formation and metallurgical grain refinement. The coatings generate a stable coefficient of friction across varying loads, with values of 0.63–0.77 (10N), 0.58–0.77 (12N) and 0.63–0.72 (15N), demonstrating enhanced hardness and wear resistance. The wear severity of the coatings exhibits minimal variation, but intensifies remarkably with increasing loads. The dominant wear mechanisms include abrasive wear, fatigue wear and plastic deformation, with oxidative wear becoming a significant factor under higher loads. This study provides a technical foundation for developing high-hardness In718 alloy coatings with enhanced tribological performance.

Nickel-based superalloys are widely employed in critical service scenarios of mechanical engineering, owing to their excellent creep strength and superior high-temperature corrosion resistance. However, their intrinsically low microhardness easily causes abnormal wear and fatigue cracking, threatening service safety. Herein, WC-reinforced In718 composite coatings were laser-cladded on In718 substrates, and their tribological enhancement mechanisms were systematically elucidated. Localized critical melting occurs at WC particle peripheries, promoting complex multiphase metallurgical microstructures that enhance interfacial bonding strength. The coatings consist of face-centered cubic γ-Ni, (Ni, Cr) and (Ni, Fe) solid solutions, with in-situ precipitated hard phases and precipitation-strengthening phases. Due to the synergistic strengthening from WC dispersion, grain refinement, and multiphase in-situ precipitation, the coatings exhibit 49.3%–70.7% higher microhardness, stable 0.66–0.72 coefficient of friction, and 38.2%–70.4% lower wear mass loss. In-situ precipitated Fe3W3C hard phases and WO3 oxides induced by frictional heat further enhance wear resistance. Dominant wear mechanisms include abrasive wear, adhesive wear, and fatigue wear, with oxidative wear increasing remarkably under high loads. Progressively enhanced dispersion and grain refinement strengthening from higher WC content, coupled with in-situ precipitated hard phases, synergistically improve tribological performance. This study provides a new technical reference for fabricating high-tribological-performance In718/WC coatings, addressing the poor wear resistance of nickel-based superalloys.

The formation and degradation of the white layer are critical factors governing the operational lifespan of cannon barrels. Nevertheless, the correlation between its microstructural characteristics and mechanical behavior remains inadequately elucidated, thereby constraining the development of robust protective strategies for barrel materials. In this study, microstructural characterization reveals that the white layer undergoes pronounced plastic deformation, manifested as grain refinement, orientation clustering, elevated dislocation density, and twinning-induced phase transformations (gamma -> alpha'-> w -> alpha't). These features suggest that the formation of the white layer is predominantly driven by coupled thermo-mechanical effects during firing, leading to the development of a gradient microstructure proximal to the bore surface. Moreover, micro-mechanical testing demonstrates that the white layer exhibits a significantly higher hardening coefficient and pronounced temperature sensitivity relative to the substrate. The elevated hardening tendency facilitates the nucleation of microcracks and micropores, while the pronounced thermal softening enhances local erosion in the vicinity of these defects, thereby exacerbating crack propagation. As a result, the synergistic action of thermal, mechanical, and chemical processes during service promotes interfacial delamination of the white layer, ultimately contributing to bore enlargement and the consequent degradation of barrel integrity. These findings underscore the imperative for the design and application of advanced materials possessing improved structural stability, superior erosion resistance, and enhanced high-temperature mechanical performance, in order to extend the service life of cannon barrels under extreme operational environments.

Laser cladding uses a high-energy laser to rapidly melt cladding materials with the substrate surface， forming a metallurgically bonded coating upon solidification. It is a key technology for producing high-performance surface coatings and remanufacturing metallic components. Recently， laser cladding has evolved from a surface coating technique into a comprehensive process integrating coating fabrication， repair of damaged parts， and additive manufacturing， showing great potential in new material development. This review first elaborates the metallurgical characteristics of laser cladding metals， then highlights process innovations in four directions： high efficiency， hybridization， specialization， and intellectualization. It further addresses the role of laser cladding in material development and fabrication， systematically reviewing research progress on conventional alloys， high-entropy alloys， amorphous alloys， metal matrix composites， and functionally graded materials， and summarizing their strengthening mechanisms and typical applications. However， challenges remain for laser cladding fabricating materials， including incomplete non-equilibrium solidification theories， lack of quantitative process-microstructure-property models， and inadequate monitoring and evaluation techniques. Future efforts should prioritize data-driven intelligent optimization， novel material system design， extreme-environment adaptability， and integration of multi-energy-field hybrid processes and combined process chains.

This study investigates the effect of three additives (Al2(SO4)3, Ce(SO4)2, and a Ce(SO4)2-citric acid C6H8O7 composite) on the microstructure and properties of ceramic films formed on 2024 aluminum alloy in H2SO4 electrolyte. The films were characterized by scanning electron microscopy, x-ray diffraction, and electrochemical analysis to evaluate their microstructure, phase composition, and corrosion resistance. Results show that the film formed in the H2SO4 electrolyte had a higher surface pore density, while the films with additives exhibited a smoother surface with smaller, more uniform pores. The addition of Al2(SO4)3, Ce(SO4)2, and the composite additive increased the microhardness by 60, 59.2, and 94.7 HV, respectively, compared to the sulfuric acid system. Additionally, these additives raised the self-corrosion potential by − 0.16, − 0.07, and − 0.42 V, respectively. The composite additive film showed the highest self-corrosion potential (−0.18 V) and largest impedance arc radius, with the thickest barrier layer (369 nm). The inclusion of C6H8O7 in the composite additive delayed the dissolution of Ce(OH)4 precipitates, significantly enhancing both microhardness and corrosion resistance.

In this study, a Stellite 6/WC composite coating was applied to the surface of 45 steel using various laser cladding rates. The phase composition, microstructure, microhardness, and corrosion resistance of the composite coating were examined using XRD, SEM, a micro-Vickers hardness tester, and an electrochemical workstation. The analysis revealed that the composite coating predominantly consists of Co3W3C and Co4W2C phases. At a cladding rate of 8 mm/s, the WC particles within the coating exhibit significant cracking, resulting in numerous fragments. As the cladding rate increases, the spherical WC particles maintain better integrity, but more cracks extend from within the WC particles to the surrounding structure. The coating produced at a 16 mm/s cladding rate exhibiting the highest hardness at 950 HV. The composite coating fabricated at a cladding rate of 10 mm/s demonstrated excellent corrosion resistance.

Laser additive manufacturing is a revolutionary advanced manufacturing technology that has rapidly developed and been applied in fields such as aerospace, automotive, and medical. However, when using LAM to form metals, it is easy to form defects such as pores and cracks, as well as microstructural issues such as coarse columnar crystals and composition segregation, affecting the performance of the metal. The addition of nano-ceramic particles can effectively improve alloy formability, refine microstructure, and thereby enhance mechanical properties of the metal. This research discussed the addition method of nano-ceramic particles during laser additive manufacturing of metals, the evolution behavior of nano-ceramic particles in the molten pool, and the impact of nano-ceramic particles on formability, microstructure, and mechanical properties. The existing problems and future research in this field were also summarized and prospected.

The adhesion force of water-droplet sliding on superhydrophobic surface is essential for the wettability characterization. Direct measurement causes the deformation of water-droplet and other unfavorable factors to decrease the accuracy, and the published simulation method is generally used for qualitative characterization. Herein, we proposed a simulation method to characterize the adhesion force. Three types of superhydrophobic surfaces were designed and fabricated with femtosecond laser ablation and chemical fluorination. Wettability and structure were quantitatively characterized for establishing the simulation model. Wettability data were accurately acquired by analyzing the morphology characteristics of sliding water-droplet and superhydrophobic structures, and six types of adhesion forces were calculated. Sliding angle of simulation and measurement was adopted to analyze the availability of simulation method, and exhibited an unignorable difference (1.02 degrees - 1.85 degrees), which results from the simplification of structure model. The simplification decreases the super- hydrophobicity and accordingly increases the sliding angle, causing the deviation of adhesion force with its real value. Improving the accuracy of structure model can reduce the deviation. This study offers a novelty and available method to characterize the adhesion force of water-droplet sliding on superhydrophobic surface, and greatly promotes the development of superhydrophobic surfaces with controllable adhesion properties.

During the braking process, temperature of brake disc in high-speed light-load vehicles sharply increases, causing the thermal fatigue crack. Therefore, it is necessary to design new brake disc and study its thermomechanical and friction properties. Here, authors designed new brake discs by way of constructing biomimetic nonsmooth structures in contact surface, then conducted simulation and experiment to quantify their effect on thermomechanical and friction properties. Compared with the smooth brake disc and under the initial velocity 120/160/200 km/h, the brake disc with straight grooves reduces the friction temperature that exhibits the reduction rate of 27.16%, 36.25% and 31.20%. Equivalent stress shows the increase rate of 61.64%, 46.92% and 71.58%, but these values are within the material yield strength. Experiment results showed the biomimetic brake discs have slightly smaller friction coefficient (0.32-0.48) but significantly lower friction temperature (41.7 degrees C-77.9 degrees C) than the smooth brake disc (0.56, 96.7 degrees C). The biomimetic brake disc with straight grooves and air inlets exhibit relatively better performance, resulting from the superior capability in dissipating heat. This study demonstrates biomimetic nonsmooth structures can improve brake disc's thermomechanical properties, which provides an available design approach for brake discs in high-speed light-load vehicles.

Titanium alloys have great applications in the fields of medical devices, orthopedic implants and aerospace components due to their excellent physicochemical properties, and endowing their surface with superhydrophobic properties is very necessary. Inspired by the wax crystals of Nepenthes, superhydrophobic microstructures on titanium alloy were designed and then fabricated via femtosecond laser ablation and chemical fluorination. This innovative method attributes a programmable laser micro-processing technique that realizes the facile fabrication of superhydrophobic microstructures with the advantages of simple design and multiple functions. The fabricated superhydrophobic surfaces achieved the contact angle of 163.45° and the sliding angle of 5.13°, and exhibited ultralow adhesion, good bouncing behaviors, excellent anti-icing capability and strong functional durability. Moreover, analyses based on experiment results demonstrated that the microstructure characteristics have a significant effect on the superhydrophobicity, and appropriate parameters can improve the superhydrophobic properties. Additionally, due to the insufficient accuracy and uncontrollability of femtosecond laser ablation, irregular pores resembled the wax crystals were fabricated which can cause the formation of stable air-film and accordingly enhances the superhydrophobicity, therefore becomes the crucial technique of this study. This study offers an innovative method for the fabrication of multi-functional superhydrophobic surfaces on titanium alloys, and promotes their applications in engineering fields.

The damage to brake discs in heavy-duty vehicles caused by uneven wear is usually repaired with milling method, which reduces their radius and accordingly shortens their service life. Laser cladding repair can maintain the radius, thereby gradually becoming a promising method for brake disc repair, but the complexity of the laser cladding process causes the cladding layer to generate defects that decrease the repair quality. Here, we studied the regulation mechanism of laser power, beam diameter and scanning speed in the cladding layer’s quality via simulation and experiment. Simulation results showed that with the increase of laser power and the decrease of beam diameter or scanning speed, the molten pool’s temperature and flow rate, and the cladding layer’s residual stress have varying degrees of increase. We then fabricated laser cladding samples (Ni60/WC on ductile iron) and acquired their micromorphology, dilution rate and microhardness, and analyzed their regulation mechanism. Experiment results exhibited that the cladding process with laser power 1400 W, beam diameter 3 mm and scanning speed 10 mm/s can make the cladding layer have a better quality. This study provides an available reference for the laser cladding repair of uneven wear in brake discs from heavy-duty vehicles.

In this study, anodized aluminum oxide (AAO) films were fabricated in situ on the surface of a high-strength and robust 2024 aluminum alloy using step voltage and constant voltage modes, respectively. Our study included examination of the microstructure, thickness, microhardness, and electrochemical characteristics of the AAO films. Cross-sectional morphology analysis revealed that the AAO film produced via the step-voltage approach exhibited remarkable density, uniformity, and good quality. In contrast, conspicuous cracks were observed in the AAO film generated under constant-voltage conditions when applied to the 2024 aluminum alloy substrate. Notably, the microhardness of the AAO film prepared using the step voltage method surpassed that of its constant-voltage counterpart. Specifically, the microhardness of the AAO film produced at 30 V via the step voltage reached 289 HV, whereas the equivalent AAO film produced at a constant voltage of 30 V registered only 174 HV. Furthermore, the self-corrosion potential and polarization resistance of the AAO films created using the step voltage were markedly higher than those achieved using a constant voltage. Specifically, the AAO films produced under step voltage conditions, specifically at 30 V and 60 min, exhibited the highest self-corrosion potential and polarization resistance values of namely -0.52 V and 34,888.6 omega, respectively. In contrast, AAO films prepared under constant voltage conditions displayed values of -0.61 V and 23,292.0 omega, respectively. Conducting AC impedance measurements and subsequent fitting calculations, the maximum thickness of the AAO film generated via step voltage and constant voltage methods amounted to 132.43 nm and 106.70 nm, respectively. Overall, the microstructure and corrosion resistance of the AAO film formed on the surface of the 2024 aluminum alloy using the step voltage approach demonstrated that it outperformed that of the AAO layer prepared under constant-voltage conditions. Chinese library classification number:TG178 Document ID:A Article ID.

This study applied a stellite6/WC composite coating, renowned for its wear and corrosion resistance, onto Q960 high-strength steel through laser cladding technology. The study aimed to investigate the influence of varying WC content and cladding power on the microstructure and properties of the coating. Findings indicated that the microstructure of the stellite6/WC coating evolved from planar crystals at the bonding interface to dendritic and cellular crystals in the central region, ultimately resulting in equiaxed crystals at the top. Despite the increased WC content, the dilution rate of the composite coating remained approximately 15%. Under the combined influence of a high-energy laser and high-temperature molten pool, WC particles experienced fracture and recrystallization, resulting in phases such as WC, W2C, Co3W3C, Co4W2C, and Co-rich. For example, at WC content levels of 10 wt.%, 20 wt.%, and 30 wt.% in the 550 W cladding, the average microhardness values were 457 HV, 535 HV, and 1045 HV, respectively. Likewise, the average wear loss for the composite coating and substrate stood at 12.5 mg, 9.2 mg, 5.8 mg, and 30.2 mg, respectively. Additionally, the recrystallization of elements such as Co, Cr, and Ni markedly enhanced the corrosion resistance of the Q960 steel after cladding. At a cladding power of 550 W, the corrosion resistance of the composite coating is superior. However, an increase in WC content slightly diminishes the composite coating's corrosion resistance, with the 30 wt.% WC coating exhibiting a self-corrosion potential of - 732 mV. The study demonstrates that a stellite6/WC composite coating can substantially enhance the wear and corrosion resistance of a shock absorber piston rod, thereby extending the service life of the automobile shock absorber piston rod.

7075 aluminum alloy is a type of lightweight metal material with high mechanical properties. Due to the intricate solidification process that produces the coarse grains and cracks, it is challenging to produce 7075 aluminum alloy using additive manufacturing techniques like laser metal deposition (LMD). Due to its similar crystal structure to the 7075 aluminum alloy, ZrH2 powders were used in this study as the nucleation particles during the laser metal deposition process. The results demonstrated that the addition of ZrH2 particles allowed the grains to be clearly refined, and that maximum tensile strength was above 330 MPa, which represents promising performance among the reported LMD-fabricated Al alloys

Selective laser melting (SLM) is a promising technique for achieving function-driven design as well as unique performances of parts. This article focuses on the frictional behavior of the SLMed brake disc under high-speed conditions, aiming to reveal the inherent wear mechanisms. A bench test of the SLMed disc was conducted using a full-scale flywheel brake dynamometer. The initial braking speed ranged from 50km/h to 380km/h, and the clamping force was from 18 kN to 37 kN. The relationship between instantaneous friction coefficient and multiple variables was explored, including clamping force, initial braking speed, and temperature. With rising temperature, the wear mechanism shifted from abrasive wear to adhesive wear. Compared to a cast disc, SLMed disc is better for high-speed conditions, as it exhibits a more stable friction coefficient, shorter braking distance, and higher braking energy efficiency. The average friction coefficient distribution of the SLMed disc is relatively more concentrated, ranging from 0.333 to 0.417, while it is from 0.277 to 0.426 for cast disc. The braking distance of the SLMed disc is 20% shorter when clamping force is 37 kN. Moreover, the braking amplification factor is proposed to enhance the accuracy of brake performance evaluation. Additionally, a preliminary utilization principle is established for SLMed discs.

Femtosecond laser has been an important processing technique for micro/nano structures in recent years. It can modify and ablate materials, and is capable of machining high-precision three-dimensional structures in specific areas. Femtosecond laser machining has broad application prospects in micro/nano processing. In this paper, the general interaction process between femtosecond laser and metals is described, and the methods for the preparation of micro/nano structures are introduced, such as femtosecond laser direct writing, femtosecond laser induced surface periodic structure, and femtosecond laser composite chemistry method. Then, the applications of femtosecond laser for the preparation of micro/nano structures on metal surfaces in environmental engineering, aerospace, and biomedicine are discussed. Finally, the shortcomings and future research directions of preparation of micro/nano structures by femtosecond laser are summarized and prospected.