Cold spray (CS)，as a low-temperature solid-state deposition technique，can avoid oxidation and phase transformation problems associated with conventional thermal spraying processes. However，it still has limitations，such as insufficient deposition density，difficulty in depositing high-strength and high-hardness materials，and dependence on helium. Laser-assisted cold spray (LACS) introduces synchronous laser heating to achieve localized thermal softening of particles and the substrate deposition zone. While maintaining the characteristics of solidstate deposition，LACS reduces the critical deposition velocity and enhances plastic deformability. This effect improves deposition efficiency，interfacial bonding strength，and coating density，and expands the processing window for cold spraying of difficult-to-deposit materials. This review systematically reviewed the working principle and deposition mechanism of LACS，summarized its research progress in pure metals，structural alloys，high-entropy alloys，and metal-matrix composites，and analyzed the governing mechanism of laser heat input on microstructural evolution and property regulation. Finally，future development directions concerning equipment integration，multi-parameter regulation，and mechanism research were prospected.
Titanium alloys have become core structural materials for aero-engines due to their low density，high specific strength，and excellent corrosion resistance. However，they exhibit low surface hardness and poor wear resistance. Surface micro-damage often occurs under fretting wear，inducing the initiation and propagation of fatigue cracks. Meanwhile，titanium alloys show high crack sensitivity，strong chemical activity，and low thermal conductivity，and their fatigue performance can be easily degraded during processing. For titanium alloy components characterized by large size and irregular geometry，traditional surface strengthening processes are limited by temperature，structural adaptability，and coating uniformity，making it difficult to meet the requirements of high-performance surface strengthening for components with complex morphologies. Cold Spray (CS)，as a solid-state deposition technology，has the advantages of low deposition temperature，small heat-affected zone on the substrate，controllable coating residual stress，and strong adaptability to large and special-shaped components. It enables efficient and high-quality coating preparation while avoiding high-temperature oxidation and thermal distortion of titanium alloys.In this study，IN718 and IN718＋WC10Co4Cr nickel-based wear-resistant coatings were prepared on Ti55531 titanium alloy by cold spraying. The microstructure，hardness，bonding strength，fretting wear performance，and high-cycle bending fatigue performance of the coatings were systematically characterized，and the action mechanism of the coatings on substrate wear and fatigue behavior was revealed. The results showed that the cold-sprayed nickel-based coatings had uniform and dense microstructure with good bonding to the substrate. The porosities of the two coatings were 0.21％ and 0.17％，respectively，and the bonding strengths were both higher than 70 MPa. The addition of WC10Co4Cr hard phase increased the hardness of the IN718＋WC10Co4Cr coating by 29 HV compared with the IN718 coating.The Ti55531 titanium alloy substrate suffered the most severe wear，with a wear rate of 9.81×102μm3/(N·m). Deep and wide plowing grooves were observed on its worn surface，with significant material spalling and delamination，accompanied by a large amount of wear debris. The wear mechanisms of the two cold-sprayed nickel-based coatings were both mild adhesive wear and abrasive wear. Among them，the IN718＋WC10Co4Cr coating exhibited the best wear resistance，with a wear rate of (55±28) μm3/(N·m) and a wear volume of (14540±7428) μm3，increasing the wear resistance by a factor of44.39 compared with the substrate. Its worn surface presented a typical tribo-layer morphology，which could partially fill the plowing grooves，inhibit crack initiation and propagation，and exert significant buffering and protective effects on the substrate.After deposition of the IN718＋WC10Co4Cr nickel-based coating，the high-cycle fatigue strength of the titanium alloy substrate decreased.Analysis of fatigue fracture，substrate hardness，and grain size variation indicated that interface defects，work hardening，and grain coarsening were not the main causes of fatigue degradation. Residual stress was identified as the primary factor reducing fatigue performance. The residual stress on the coating surface was compressive under both single-pass and multi-pass spraying，with the compressive stress in multi-pass coatings significantly higher. At a depth of50 μm within the coating，the residual stress transformed into tensile stress along the RD direction，and the residual tensile stress in single-pass coatings was significantly higher than that in multi-pass coatings. The fatigue strength of multi-pass coated specimens (560 MPa) was significantly higher than that of single-pass coated specimens (400 MPa). The lower internal tensile stress reduced the initiation and propagation of fatigue cracks at the substrate interface，which was consistent with the better high-cycle rotating-bending fatigue performance of multi-pass specimens.
Aluminum (Al)，titanium (Ti)，and their alloys are ideal materials for aerospace applications owing to their excellent properties，but conventional forming methods still suffer from problems such as oxidation and cracking. In addition，as a lightweight material，magnesium alloy requires further investigation regarding its response mechanism to particle impact. As a low-temperature solid-state deposition process，cold spray technology can effectively alleviate the above problems. However，systematic research on the co-deposition of Al and Ti particles under low-pressure conditions remains insufficient. Spraying distance and particle size are key parameters affecting the quality of cold spray deposition，while experimental optimization is costly. In this study，numerical simulation and experiments were combined to investigate the effects of spraying distance and particle size on the deposition behavior of Al and Ti particles in low-pressure cold spray. The optimal process parameters were determined to provide a basis for preparing composite coatings on light-alloy surfaces by low-pressure cold spray technology.Fluent software was used to simulate the impact velocity and temperature distribution of Al and Ti particles under a compressed-air pressure of0.9 MPa，spraying temperatures of200-500 ℃，and spraying distances of 10-30 mm. The optimal spraying distance was determined by preliminary screening at 5 mm intervals，followed by refined simulation within the range of 17-25 mm. Meanwhile，ABAQUS software was used to establish a quarter Lagrangian model for the impact of single Al and Ti particles with particle sizes of 10-30 μm on an AZ31 magnesium alloy substrate. The equivalent plastic strain (PEEQ) during the impact process was analyzed to determine the critical deposition velocity. The results showed that，when the spraying temperature was 500 ℃，the particle velocity first increased and then decreased with increasing spraying distance，reaching its maximum at a spraying distance of 20 mm. The maximum velocity of 20 μm Al particles was 418.33 m/s，while that of 25 μm Ti particles was 366.29 m/s. At these particle sizes，the velocities of Al and Ti particles were closest to their critical deposition velocities，resulting in the best deposition effect. Under low-pressure conditions，Ti particles were difficult to deposit independently and required Al particles as carriers to achieve co-deposition.To verify the reliability of the simulation results，supersonic low-pressure cold spray experiments were conducted under a compressed-air pressure of0.9 MPa and a spraying temperature of500 ℃. First，ball-milled mixed powders with an Al-to-Ti mass ratio of 1∶1 were sprayed at spraying distances of 10，20，25，30 mm. Subsequently，five mixed powders with different particle-size combinations were prepared for comparison. The experimental results showed that，at a spraying distance of20 mm，theA20-T25combination，namely Al with aD50of approximately 20 μm and Ti with aD50of approximately 25 μm，exhibited the best comprehensive properties. Its deposition efficiency was 29.97％，average hardness was 154.01 HV0.05，porosity was only 0.59％，friction coefficient was approximately 0.59，and mass wear rate was 1.46×10-11kg/(N·m). The soft Al phase played a filling and bonding role，while the hard Ti phase provided strengthening and support. The experimental results were in good agreement with the simulation predictions.Through numerical simulation and experimental verification，this study explored the optimal process window for preparing Al/Ti composite coatings by low-pressure cold spray. At a spraying distance of20 mm and a gas temperature of500 ℃，Al and Ti particles reached their maximum impact velocities of418.33 m/s and 366.29 m/s，respectively. The optimal deposition particle size was approximately 20 μm for Al and approximately 25 μm for Ti. This study provided a theoretical basis and process reference for preparing high-performance composite coatings on light-alloy surfaces using low-pressure cold spray equipment.
Cold spray technology is based on a low-temperature solid-state deposition mechanism and can effectively suppress oxidation and phase transformation，thereby enabling the preparation of coatings with high bonding strength and low porosity. It is particularly suitable for temperature-sensitive material systems such as Al and Cu. Although Al alloys have the advantages of light weight and excellent corrosion resistance，their thermal conductivity and wear resistance are relatively low. Depositing Cu coatings on Al substrates enables property complementarity between the two materials. However，cold-sprayed Cu coatings usually suffer from severe work hardening，insufficient strength，and weak interfacial bonding. Previous studies have shown that subsequent heat treatment can effectively promote recrystallization，reduce porosity，and improve interfacial bonding，but the underlying atomic-scale mechanism remains unclear. Molecular dynamics simulations can reveal key processes such as diffusion behavior and dislocation evolution at the atomic scale. At present，atomic-scale studies on the heat-treatment mechanism of cold-sprayed Cu coatings on Al substrates are still limited. Therefore，this study combined experiments and molecular dynamics simulations to systematically investigate the microstructural evolution of cold-sprayed pure Cu coatings on 6061-T6 Al alloy substrates during heat treatment.In the experimental part，a PCS-100 cold spray system was used to deposit pure Cu coatings on 6061-T6 Al alloy substrates using nitrogen as the working gas at 600 ℃ and 4.5 MPa，followed by heat treatment at 400 ℃. X-ray diffraction (XRD) and scanning electron microscopy(SEM) equipped with energy dispersive spectroscopy (EDS) were used to characterize the phase composition and microstructural evolution of the coatings. In the molecular dynamics simulation，a model of a Cu particle with a diameter of 140 Å impacting an Al substrate with dimensions of400 Å×400 Å×200 Å at an impact velocity of 540 m/s was constructed using LAMMPS software and the embedded atom method(EAM) potential. The heat-treatment process at 427 ℃ was simulated，and the atomic-scale structure was analyzed using OVITO software.The experimental results showed that the cold-sprayed Cu coating underwent obvious recrystallization after heat treatment at400 ℃，and the intermetallic compound CuAl2was formed，resulting in a significant improvement in interfacial bonding. The molecular dynamics simulation results showed that，after cold spray deposition，the Cu particle contained a relatively low proportion of disordered structures，but the dislocations were highly entangled and dominated by Shockley dislocations，which accounted for approximately 72％ of the total dislocation length，showing typical work-hardening characteristics. In the early stage of heat treatment (100 ps)，enhanced atomic thermal vibration reduced lattice stability，leading to a significant increase in disordered structures，a rapid decrease in dislocation density，and a sharp increase in the number of vacancies. As the heat-treatment time increased to 800 ps and then 1600 ps，the disordered structures gradually transformed into face-centered cubic (FCC) structures. FCC grains continued to grow as recrystallization proceeded，and the disordered structures decreased and became more uniformly distributed. The number of grains generally exhibited a trend of first decreasing and then increasing，indicating that the microstructure transformed from a highly distorted state to a recrystallized structure. Atomic diffusion analysis showed that Cu atoms preferentially diffused into the Al matrix. This behavior was mainly attributed to the higher diffusion coefficient and larger atomic radius of Al (1.43 Å)，as well as the smaller atomic radius (1.27 Å) and higher binding energy of Cu. Heat treatment further strengthened the preferential diffusion tendency of Cu into the Al matrix. The dislocation evolution results showed that the total dislocation length decreased rapidly in the initial stage of heat treatment and then tended to stabilize. Shockley dislocations remained dominant throughout the process，and their variation trend was consistent with that of the total dislocation length，whereas perfect，stair-rod，and Hirth dislocations remained at low levels. The number of vacancies showed a “rapid increase followed by slow growth” trend，while the dislocation density decreased significantly in the early stage and then tended to stabilize. The synergistic evolution of vacancies and dislocations drove the transformation of the Cu coating from a high-energy non-equilibrium state to a thermodynamically stable state.In summary，this study systematically revealed the microstructural evolution and atomic diffusion mechanism of the cold-sprayed Cu/Al system during heat treatment by combining experiments with molecular dynamics simulations. The results showed that heat treatment significantly promoted coating recrystallization，increased the proportion of FCC structures，and caused the number of grains to exhibit a dynamic evolution trend of first decreasing and then increasing. The preferential diffusion of Cu atoms into the Al matrix was significantly enhanced，whereas the reverse diffusion of Al atoms was relatively limited. Meanwhile，the dislocation density decreased rapidly in the initial stage and then tended to stabilize，with Shockley dislocations being dominant，while the number of vacancies continued to increase with time. The synergistic evolution of dislocations and vacancies promoted defect reorganization and annihilation through a thermally activated mechanism，thereby effectively improving the structural stability and interfacial bonding performance of the coating.
To address the poor wear resistance of4340 steel components，WC-10Co4Cr coatings were successfully deposited on4340 steel substrates via high-velocity oxy-fuel (HVOF) spraying and cold spray (CS)，with process parameters optimized for each. The microstructure，phase composition，porosity，microhardness，bonding strength，sliding wear，and fretting wear of the two coatings were systematically characterized using a scanning electron microscope (SEM)，an optical microscope (OM)，a X-ray diffractometer (XRD)，a Vickers microhardness tester，an universal testing machine，a tribometer，and a 3D profilometer. The effects of CS and HVOF processes on coating structure and properties were compared and analyzed. The results showed significant differences in microstructure，mechanical properties，and wear behavior between the two coatings. The porosity of the CS coating was below 0.1％，whereas that of the HVOF coating was approximately 0.3％. Phase analysis indicated that the WC phase remained stable in the CS coating，while the HVOF coating experienced decarburization of WC and the formation of a new W2C phase. The average microhardness of the CS coating reached 1 617.2 HV0.3，about 52.4％ higher than that of the HVOF coating (1 061.3 HV0.3). In sliding wear tests，the wear rate of the CS coating was 1.7×10-6μm3/(N·m)，only 39.5％ of that of the HVOF coating. Its fretting wear rate was 1.28 μm3/(N·m)，37.6％ higher than that of the HVOF coating. However，the bonding strength of the CS coating (35 MPa) was significantly lower than that of the HVOF coating (73.5 MPa). In conclusion，compared with the traditional HVOF process，WC-10Co4Cr coatings prepared by the CS process exhibited higher hardness，denser microstructure，and superior sliding wear performance，demonstrating promising potential for engineering applications.
Aluminum sheaths of high-voltage (HV) cables are susceptible to localized damage induced by the combined effects of environmental corrosion and mechanical stress during long-term service，posing a severe threat to the safe and reliable operation of power grids. Accordingly，efficient and reliable in-situ repair techniques are urgently needed. To solve the problem that traditional hot brazing often causes thermal damage to insulation layers during in-situ repair of HV cable aluminum sheaths，cold spray solid-state additive manufacturing (CSAM) has become an optimal adternative owing to its superior low-temperature solid-state deposition characteristics. Particle impact velocity is the core parameter determining the deposition and repair quality of cold spray. However，the corrugated curved structure commonly adopted in HV cable aluminum sheaths severely disrupts the distribution of the supersonic flow field，significantly affecting the kinetic behavior of particles. In this study，a three-dimensional numerical model was established based on a coupled computational fluid dynamics-discrete phase model (CFD-DPM) method. The shock wave evolution characteristics on both flat and corrugated curved substrates were comparatively investigated. The velocity attenuation of 5-45 μm particles passing through the shock waves under normal incidence was quantitatively characterized，and comparative deposition experiments using powders with different classified size fractions were conducted. Simulation results revealed that in the near-wall region of the curved substrate，influenced by shock waves，gas velocity gradients increased sharply；particle velocities decreased most markedly when the particle size was below 15 μm. Experimental results demonstrated that by removing fine powders (optimizing the particle size range to 15-45 μm) and synergistically adjusting the carrier gas pressure to 0.65 MPa，the adverse effects of shock waves were effectively mitigated，yielding denser coatings. By revealing the kinetic energy dissipation mechanism of particles during cold spray onto curved substrates，this study confirmed the feasibility of improving the repair quality of corrugated aluminum sheaths through particle size gradient optimization，providing theoretical support for the development of in-situ repair processes for power equipment.
Suspension plasma spraying (SPS) has emerged as a transformative technology for fabricating next-generation thermal barrier coatings (TBCs)，driven by the growing demands for higher operating temperatures and efficiency in advanced gas turbines and aero-engines. Conventional atmospheric plasma spraying (APS) and electron beam physical vapor deposition (EB-PVD) face inherent limitations in achieving an optimal combination of thermal insulation，strain tolerance，and long-term durability，whereas SPS provides a promising alternative. This technique fundamentally departs from powder-based feedstock routes by injecting a liquid suspension of sub-micron or nano-sized ceramic particles directly into the plasma jet. This review provides a comprehensive and systematic analysis of SPS technology，clarifying its underlying mechanisms，key factors governing coating architecture，resultant performance advantages，and future potential，thereby serving as an authoritative technical reference for both research and engineering communities.The deposition mechanism of SPS involves a complex sequence of events:penetration and primary atomization of the suspension jet，followed by secondary fragmentation and rapid evaporation of solvent droplets within the plasma plume. This exposes the fine particles to high temperatures，leading to melting or partial melting. The ultrafine molten droplets subsequently impact the substrate or previously deposited layers，where they spread，rapidly solidify，and accumulate. Compared with APS，the use of nanoscale feedstock alters the thermal and momentum history of particles in the plasma，facilitating the formation of unique non-lamellar microstructures. These structures are characterized by finely segmented columns，dense networks of vertical cracks，and high inter-columnar porosity，which are critical to superior performance.The final coating microstructure and properties result from the interplay between suspension characteristics and process parameters. Suspension formulation is critical:solvent type (e. g.，water vs. ethanol)，through its latent heat of vaporization，affects suspension stability，atomization behavior，and the thermal load on the plasma. Solute particle size and distribution primarily govern columnar grain refinement and microstructural homogeneity. Solid loading must balance flowability against deposition efficiency；typically，lower concentrations favor more porous structures with higher strain tolerance. Key process parameters，including plasma power，jet chemistry，stand-off distance，suspension feed rate，and substrate conditions (temperature and roughness)，must be precisely optimized to control particle melting，adhesion，and coating densification. Through precise regulation of these variables，diverse microstructures ranging from dense vertically-cracked architectures to highly porous columnar-dominated morphologies can be designed.These customizable microstructures endow coatings with excellent functional properties. Their defining features—fine columns and vertical cracks—act as intrinsic strain-relief mechanisms and effectively mitigate thermal expansion mismatch and growth stresses. This results in dramatically enhanced strain tolerance and thermal cyclic fatigue life，farexceeding those of standard APS coatings. The inherent micro-porosity also improves thermal insulation. Furthermore，the architectural flexibility of SPS allows the engineering of surface layers with higher density and tortuosity，improving resistance to infiltration by corrosive media such as molten CMAS (calcium-magnesium-alumino-silicate) or water vapor.Mechanically，although SPS coatings may exhibit intermediate hardness and bond strength relative to APS and EB-PVD coatings，their unique fracture behavior provides improved resistance to spallation and erosion.In conclusion，SPS successfully integrates the most desirable characteristics of existing mainstream TBC technologies:within a single scalable process，it achieves the high strain tolerance and columnar structure reminiscent of EB-PVD while retaining the high deposition rate，geometric adaptability，and cost-effectiveness of APS，making SPS a unique spraying technology.
Materials are inevitably affected by various factors in natural environments and undergo corrosion. Predicting their corrosion behavior and evolution patterns can provide references for material applicability evaluation and the formulation of protection measures. With the development of algorithm theory，computer technology，and related software and hardware capabilities，prediction models for material corrosion behavior have developed rapidly and attracted wide attention. To improve the understanding of different models and promote their application in corrosion research，this paper briefly introduced the principles of typical corrosion prediction models，including gray prediction models (GM)，support vector machine models (SVM)，and artificial neural network models (ANN)，and reviewed their application progress in the corrosion field. At present，the theories of the above typical corrosion prediction models have become relatively mature. Their applications primarily involved optimizing key algorithmic parameters and computational procedures by incorporating optimization algorithms，thereby improving model prediction accuracy，training speed，and generalization ability. This paper also summarized the model principles and application status of machine learning methods such as deep learning，including convolutional neural networks and long short-term memory networks，and ensemble learning，including random forests and gradient boosting trees. Compared with typical prediction models，these models have more complex structures and stronger prediction and generalization abilities，but they also require larger amounts of data and more computational resources.On this basis，the applicable scenarios，methodological advantages，and limitations of various models were summarized. Finally，the future development directions of model algorithms were discussed. First，the quality of modeling data samples should be improved by deepening the identification of key corrosion data and standardizing data acquisition and governance. Second，for single-model applications，multiple optimization algorithms should be jointly used to overcome model limitations and improve model learning efficiency and prediction accuracy. Third，with the wider adoption of big data concepts and the explosive growth of data，the application advantages of algorithms such as deep learning and ensemble learning are becoming increasingly prominent，and theoretical innovation and computing power optimization are important development directions. The integration and complementarity of multiple algorithms to continuously improve the comprehensive prediction ability，generalization ability，and interpretability of models will be the main development trend of corrosion prediction models.
Thermoplastic ethylene-methacrylic acid copolymer (EMAA) has attracted widespread attention in fields such as self-healing coatings，anti-corrosion coatings，and functional composite coatings because of its good film-forming ability，interfacial adhesion，toughness，and thermally triggered self-healing characteristics. As the demand for adaptability to complex service environments increases in marine engineering，aerospace，oil and gas mining，new energy，and other fields，the mechanical properties，wear resistance，corrosion resistance，erosion resistance，and characteristic functionalities of bulk EMAA materials under complex service conditions still require further improvement. This review focused primarily on recent research progress in EMAA polymer coatings，and systematically reviewed the material properties of EMAA，chemical and physical modification methods，powder manufacturing technologies，coating preparation processes，and the current status of application research in typical fields. First，EMAA mainly includes two categories:bulk-polymerized acid copolymers and ionomers modified by metal-ion neutralization. Bulk-polymerized acid copolymers retain more free carboxyl groups and therefore exhibit better polarity，interfacial activity，and substrate adhesion. In contrast，neutralization-modified ionomers form reversible ionic association structures through the partial neutralization of carboxyl groups by metal ions，showing outstanding structural recoverability and functional responsiveness. Current chemical modification of EMAA mainly alters the chemical structure of EMAA macromolecules and the types and distribution of functional groups through chemical reactions；however，related studies on chemical modification remain relatively scarce both domestically and internationally. Physical modification remains the main approach for improving the performance and functionality of EMAA coatings. In this review，the roles of micro/nano particles，such as Al2O3，ZrO2，SiO2，TiO2，and CaCO3，in improving mechanical properties，wear resistance，erosion resistance，and barrier capability against media were systematically summarized. It was also pointed out that one-dimensional or two-dimensional reinforcing phases，such as CNTs，graphene，and boron nitride，are more conducive to increasing the tortuosity of medium transport pathways，inhibiting the penetration of water，oxygen，and corrosive media，and enhancing characteristic functionalities. In terms of fiber reinforcement，carbon fibers，glass fibers，basalt fibers，aramid fibers，and other fibers can provide skeletal support for the EMAA matrix，thereby suppressing coating cracking and peeling and improving its mechanical properties，wear resistance，and erosion resistance. Composite modification can achieve multi-component and multidimensional structural optimization through the complementary effects among components with different material systems and dimensionalities，thereby realizing synergistic modification and reinforcement. It can compensate for the insufficient balance in overall performance caused by single-filler modification，allowing the comprehensive performance of EMAA coatings to be fully optimized. Second，in terms of powder manufacturing and coating preparation，EMAA powder preparation techniques mainly include ball milling，screw melt extrusion followed by cryogenic pulverization，as well as emerging technologies such as supercritical CO2-assisted processing and spray drying. The ball milling technique involves a simple process and is suitable for small-batch preparation in laboratories. Screw melt extrusion，combined with cryogenic cooling，pulverization，and sieving，offers stronger component-mixing capability，better compositional uniformity，and a more favorable particle size distribution. Moreover，it has the capacity for large-scale production and is currently the most widely used technical route. In contrast，supercritical CO2-assisted processing and spray drying are highly promising emerging technologies，but their scale-up still requires further investigation. Regarding coating preparation，thermal spraying technologies，such as flame spraying，are suitable for rapid or convenient on-site construction；electrostatic spraying is suitable for continuous industrial processing of different components；and hot-press molding is more applicable to regular substrates and laboratory sample preparation.
To address the engineering problem that hot-dip galvanized coatings are prone to corrosion and have insufficient protective service life in high-humidity and high-salt corrosive environments such as marine and industrial environments，this study adopted an organic-inorganic composite superhydrophobic protective system as the design direction. Nano-SiO2with three particle sizes (30，100，500 nm) was hydrophobically modified with hexamethyldisilazane (HMDS). HMDS-SiO2/PDMS superhydrophobic coatings were then controllably fabricated on hot-dip galvanized substrates by a one-step spraying method. The effects of SiO2particle size on the microstructure，wettability，wear resistance，and corrosion resistance of the coatings，as well as the intrinsic regulation mechanism，were systematically investigated. Transmission electron microscopy (TEM)，scanning electron microscopy (SEM)，Fourier transform infrared spectroscopy (FTIR)，contact angle measurement，and electrochemical testing were used to comprehensively analyze the structure and properties of the modified particles and coatings. The results showed that low-surface-energy methyl groups were successfully grafted onto the SiO2surface through chemical bonding by HMDS，causing SiO2of all three particle sizes to transform from hydrophilic to hydrophobic，with no obvious change in particle size after modification. The optimal HMDS-SiO2/PDMS mass ratio required to achieve stable superhydrophobicity increased with increasing particle size:1∶2，1∶1，and 2∶1 for 30，100，and 500 nm SiO2，respectively. The water contact angles of the coatings prepared at the optimal ratios were all higher than 150°. Small-sized HMDS-30SiO2had a large specific surface area and readily constructed a dense micro/nano rough structure，giving the best initial hydrophobicity with a contact angle of 155.1°. However，insufficient PDMS encapsulation led to poor coating compactness and weak interfacial adhesion，and the coating lost its superhydrophobicity after only 15 abrasion cycles. In contrast，large-sized HMDS-500SiO2had a smaller specific surface area and could be fully encapsulated by PDMS，resulting in a continuous and compact coating structure with strong interfacial bonding. Its wear resistance was significantly improved，and the contact angle decreased by less than 2％ after 30 abrasion cycles.Electrochemical tests showed that the low-frequency impedance modulus of the HMDS-30SiO2/PDMS coating in 3.5％ NaCl solution reached 3.69×105Ω·cm2，which was three orders of magnitude higher than that of pure zinc. The self-corrosion current density was as low as 1.87× 10-8A/cm2，and its corrosion resistance was significantly better than that of the pure PDMS coating. Saltwater immersion tests showed that the coating maintained its superhydrophobic state for up to 18 h，and its impedance modulus remained higher than the initial value of pure PDMS after 24 h of immersion. The excellent protective performance originated from the synergistic barrier effect between the coating's physical barrier and the air film trapped by the micro/nano structure:the air film dominated short-term efficient protection，while the physical barrier provided long-term fundamental protection. This study clarified the structure-property relationship between SiO2particle size and the performance of superhydrophobic coatings，and established a trade-off law whereby small particle sizes favored high hydrophobicity and large particle sizes favored high stability. The findings provide systematic experimental evidence and theoretical support for particle size selection，formulation design，and engineering application of superhydrophobic protective coatings on hot-dip galvanized components，and were of great significance for improving the durability and practicality of metal-based protective coatings.
WC-based cermet coatings are widely used in marine equipment and chemical valve applications owing to their high hardness，excellent wear resistance，and corrosion resistance. Among them，WC-10Co-4Cr (86WC) is a typical commercial wear-resistant coating system，whereas WC-20Cr3C2-7Ni shows potential advantages in corrosive environments. Studies on the friction-wear-corrosion coupling behavior of these two WC-based coatings in marine environments remain limited. Based on this，73WC and 86WC coatings were prepared on 2507 duplex stainless steel substrates by high-velocity air-fuel (HVAF) spraying，and their microstructures，friction and wear properties，and corrosion resistance were investigated.The 73WC and 86WC coatings were prepared by HVAF spraying. The microstructure and phase composition were analyzed by scanning electron microscopy (SEM)，energy dispersive spectroscopy (EDS)，and X-ray diffraction (XRD). The hardness，friction and wear properties，and electrochemical corrosion behavior in 3.5％ NaCl solution were tested using a microhardness tester，a pin-on-disk tribometer，and a CHI660E electrochemical workstation，respectively.The results showed that the 73WC coating was mainly composed of WC，Ni，Cr7C3，and (W，Cr)2C phases，whereas the 86WC coating was mainly composed of WC，Co，and a small amount of Co6W6C，with a small amount of W2C also present. Both coatings exhibited dense lamellar structures and good bonding with the substrate. The thicknesses of the 73WC and 86WC coatings were approximately 179 μm and 212μm，respectively，and their porosities were only 0.16％ and 0.31％，respectively. The average hardness values of the 73WC and 86WC coatings reached 1 182 HV0.3and 1 286 HV0.3，respectively，both of which were approximately six times those of the substrate. The Weibull modulus mof the 73WC coating was 16.80，higher than that of the 86WC coating (8.69)，indicating a more stable hardness distribution.Friction and wear results showed that the average friction coefficient of the 73WC coating was approximately 0.32，lower than that of the 86WC coating (0.51). However，its wear rate[(4.26±0.09)×10-5mm3/(N·m)] was higher than that of the 86WC coating [(2.54±0.06)× 10-5mm3/(N·m)]. During sliding，Cr2O3and NiO oxide films formed on the 73WC coating surface，reducing interfacial shear stress. However，the Ni binder phase had relatively low load-bearing capacity，which readily led to WC particle pull-out. In contrast，the Co binder phase in the 86WC coating formed a stable supporting structure，giving better wear resistance.Electrochemical tests showed that the 73WC coating exhibited better corrosion resistance in 3.5％ NaCl solution. Its corrosion potential was-421 mV，higher than that of the 86WC coating (-913 mV). Its corrosion current density was only 2.87×10-7A/cm2，approximately oneeighth that of the 86WC coating. This was mainly attributed to the lower porosity of the 73WC coating and the formation of passive films consisting of NiO，Cr2O3，and Cr(OH)3.In summary，highly dense WC-based cermet coatings were prepared on 2507 duplex stainless steel substrates by HVAF spraying. The 73WC coating had a lower friction coefficient and better corrosion resistance，making it suitable for marine and chemical corrosive environments. In contrast，the 86WC coating exhibited better wear resistance owing to its higher hardness and stable Co-based supporting network，making it more suitable for high-load wear conditions. This study revealed the nonsynchronous relationship between friction coefficient and wear resistance in WC-based coatings and clarified the synergistic effects of binder phase stability，microstructural densification，and oxide film evolution on comprehensive performance. These findings provide a theoretical basis for the engineering application of WC-based coatings in marine and chemical equipment.
High-γ′nickel-based superalloys are widely used in hot-section components of aero-engines because of their excellent high-temperature strength，oxidation resistance，and corrosion resistance. However，conventional cast nickel-based superalloys such as IN738LC usually contain relatively high Al and Ti contents，which readily lead to a wide solidification temperature range，severe elemental segregation，and increased cracking susceptibility during laser additive manufacturing. Therefore，reducing the precipitation tendency of detrimental phases and crack formation while maintaining high-temperature strengthening capability is key to realizing the application of IN738LC alloy via laser additive manufacturing. In this study，the Al and Ti contents were each controlled at approximately 3.0％，and the W content was designed at four levels:7.41％，8.41％，9.41％，and 10.41％. The effects of W content on γ′phase stability，detrimental phase precipitation，microstructural evolution，and mechanical properties were investigated.Thermodynamic calculation，laser directed energy deposition (L-DED)，heat treatment，phase analysis，microstructural characterization，and mechanical property testing were combined. First，JMatPro software was used to calculate the equilibrium phase constitution of the designed IN738LC alloys. The results showed that increasing W content had a relatively limited effect on the mass fraction of the γ′phase at 900 ℃.When W content increased from 7.41％ to 10.41％，the mass fraction of the γ′phase at 900 ℃ increased only from 39.14％ to 40.77％. This indicated that，compared with typical γ′-forming elements such as Al and Ti，W was not the dominant element directly increasing the γ′phase content；its main role was to dissolve in the γ matrix and produce solid-solution strengthening. In contrast，increasing W content significantly enhanced the formation tendency of topologically close-packed (TCP) phases. With increasing W content，the mass fraction of TCP phases increased from 0 to 4.85％，and their equilibrium precipitation temperature increased from 839 ℃ to 1 051 ℃. This indicated that excessive W significantly increased the risk of detrimental TCP phase precipitation during high-temperature service.Optical microscopy (OM) observations showed that the as-deposited samples exhibited good overall forming quality，with only a small number of pores in local regions and no obvious macrocracks. This indicated that the optimized IN738LC alloy had relatively low cracking susceptibility under the selected L-DED process conditions. After solution treatment and two-stage aging，microstructural uniformity improved，and the γ′phase was uniformly and dispersively precipitated in the matrix. However，relatively obvious second-phase precipitation features remained in the interdendritic regions of the high-W samples. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS)analyses further showed that W content had a significant effect on elemental segregation and carbide formation. In the as-deposited state，Al and Ti were mainly related to γ′phase formation and were relatively stably distributed in the dendrite cores or intragranular regions. With increasing W content，the enrichment of W，C，and part of Nb in the interdendritic regions became more pronounced，promoting the formation and coarsening of MC-type carbides. When W contents were 7.41％ and 8.41％，the samples showed relatively uniform microstructures with fewer detrimental phase precipitates. When W content increased to 9.41％ and 10.41％，carbide precipitation became more obvious，and a small amount of needle-like TCP phases were observed after heat treatment. This indicated that excessive W promoted carbide coarsening and TCP phase precipitation，thereby reducing microstructural stability.Mechanical property testing showed that increasing W content improved the hardness and tensile strength of the samples. The Rockwell hardness (HRC) of the as-deposited samples increased from 40.18 HRC (7.41％ W) to 42.22 HRC (10.41％ W). After solution＋two-stage aging，the hardness values of the four samples increased to 40.82，41.64，42.88，43.32 HRC，respectively. The increase in hardness was mainly attributed to the solid-solution strengthening of W and the precipitation strengthening of the γ′phase. Tensile testing showed that the 9.41％ W sample exhibited the most pronounced strengthening，with tensile strengths of 1 403 MPa at 25 ℃ and 618 MPa at 900 ℃. However，thermodynamic calculations showed that the TCP phase mass fraction at 900 ℃ for this composition had already reached 2.68％，indicating a clearly increased risk of detrimental phase precipitation. When W content was further increased to 10.41％，grain-boundary carbide continuity and TCP phase precipitation became more significant，leading to decreased plasticity. Fracture morphology observations showed that，with increasing W content，the fracture mode gradually shifted from ductile fracture dominated by fine dimples to mixed ductile-brittle fracture.W played a dual role in IN738LC alloy fabricated by laser additive manufacturing. An appropriate amount of W improved alloy strength through solid-solution strengthening，whereas excessive W aggravated interdendritic segregation and promoted MC-type carbide coarsening and TCP phase precipitation，thereby reducing microstructural stability and plasticity. Although the 9.41％ W sample exhibited the highest strength，its TCP phase precipitation tendency had already increased significantly，which was unfavorable for long-term high-temperature microstructural stability. In contrast，the 7.41％ and 8.41％ W samples showed a better comprehensive balance among strength，plasticity，cracking resistance，and microstructural stability. Therefore，the W content in L-DED-fabricated IN738LC alloy is recommended to be controlled within 7.41％-8.41％，namely approximately 7.4％-8.4％. This composition range maintains the high-temperature stability of the γ′phase while suppressing carbide continuity and excessive TCP phase precipitation，providing a reference for the composition design of nickel-based superalloys specifically intended for laser additive manufacturing.
Background and objective:Zn-Al-Mg (ZAM) coated steel sheets are prone to black spot and blackening defects due to Mg oxidation，which limits their high-end decorative applications. In this study，a copper nitrate-phosphate chemical oxidation process was used to prepare a uniform black decorative film on a medium-Al ZAM coated steel sheet，and its microstructure，mechanical properties，corrosion resistance，and coloration mechanism were systematically investigated.Methods:The substrate was a Pangang ZAM coated steel sheet (Mg 2.0％，Al 11.2％，Zn balance；coating thickness 5-8 μm). Specimens (50 mm×50 mm×3 mm) were ultrasonically cleaned in acetone，degreased in alkaline solution (15-20 s)，activated in 10％ HCl (3-12 s)，and then chemically oxidized at 37 ℃ for 180-360 s in an aqueous solution containing Cu(NO3)2·3H2O (1.5-3.0 g/L)，Zn(H2PO4)2(4.0-7.0 g/L)，anhydrous citric acid (1.5-3.0 g/L)，sodium dodecylbenzenesulfonate (0.15-0.30 g/L)，and H2O2(5-8 mL/L). Surface and cross-sectional morphologies were observed by scanning electron microscopy (SEM)，and elemental distribution was analyzed by energy dispersive spectroscopy (EDS). Phase composition and chemical states were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS)，respectively. Blackness was quantified using a colorimeter based on the LAB system according to|L|＋|a|＋|b*|，where a lower value indicates a darker color. Film thickness，roughness，and micro-Vickers hardness were measured using a coating thickness gauge，a roughness tester，and a micro-Vickers hardness tester (load 0.1 kgf，dwell 15 s)，respectively. Corrosion resistance in 3.5％ NaCl solution was evaluated by potentiodynamic polarization (scan rate 1 mV/s，±0.5 V vs open-circuit potential) and electrochemical impedance spectroscopy (EIS，105-10-2Hz). Neutral salt spray (NSS) tests were conducted per GB/T 10125-2021 [5％ NaCl，35 ℃，deposition rate 1-2 mL/(h·80 cm2)]，and macroscopic morphologies were recorded at 0，24，312，1 440，1 500，1 600 h.Results:(1) Oxidation process:At 4 min oxidation，the film exhibited a uniform black appearance，with a minimum blackness value of 29.07，thickness 2.63 μm，roughness 0.458 μm，and microhardness 189.2 HV0.1，which was 71.5％ higher than that of the substrate (110.3 HV0.1).(2) Microstructure and composition:The film was dense and bundle-like，fully covering the substrate，with a tightly bonded filmsubstrate interface and no delamination. EDS analysis (mass fraction) gave Zn 56.9％，O 28.6％，Al 5.8％，Cu 2.4％，P 1.6％. XRD and XPS confirmed that the film mainly comprised ZnO，Al2O3，and CuO，among which CuO was the key black-coloring component.(3) Coloration mechanism:Pure ZnO is white；the black color originated from CuO absorption of visible light，with phosphate playing a synergistic regulatory role. Insufficient CuO yielded brick-red Cu2O (reddish tint)，while excess phosphate precipitated white Zn3(PO4)2(whitish tint).(4)Corrosion resistance:In 3.5％ NaCl，after oxidation the corrosion potential shifted positively from -0.381 V to -0.346 V，the corrosion current density decreased from 2.806×10-6to 2.219×10-6A/cm2，and the polarization resistance increased from 1.389×107to 1.682×107Ω·cm2. EIS showed a significantly enlarged capacitive arc radius and enhanced low-frequency impedance modulus，indicating an improved barrier effect.NSS testing showed no red rust within 1 440 h. After 1 500 h，local film dissolution occurred with reddish-brown rust (Fe2O3/FeOOH)；after 1 600 h，corrosion further aggravated.Conclusion:A uniform，dense black film with blackness 29.07，thickness 2.63 μm，and hardness 189.2 HV0.1was successfully prepared on medium-Al ZAM coated steel sheets via the copper nitrate-phosphate chemical oxidation process. The film structure was dominated by ZnO，while CuO and phosphate synergistically regulated black coloration. The film significantly improved corrosion resistance，with no red rust after 1 440 h NSS testing. This study provides an effective technical route for eliminating surface defects on ZAM coated steel sheets and developing high-quality black decorative films.
Titanium alloys are widely used in aerospace，medical devices，chemical equipment，and other fields owing to their high specific strength and excellent corrosion resistance. However，their low thermal conductivity，high chemical reactivity，and low elastic modulus lead to extremely severe tool wear during machining. TiAlN-coated cemented carbide tools are commonly used for cutting titanium alloys，and this coating provides oxidation resistance and a thermal barrier effect. In practical machining processes，cutting tools may be subjected to high temperatures，resulting in changes in coating microstructure，release of internal stress，and degradation of the coating-substrate interfacial bonding state. However，the coupled effects of quenching pretreatment，which simulates thermal cycling during interrupted cutting or tool regrinding，and cutting conditions，including dry/wet cutting and cutting speed，on the wear behavior of TiAlN-coated tools have not been systematically investigated. This study aimed to systematically investigate the effects of quenching temperature and cutting parameters on the wear performance of TiAlN-coated cemented carbide turning tools，with emphasis on the rake face wear mechanism，coating adhesion，and cutting temperature rise.TiAlN coatings were deposited on WC-Co cemented carbide substrates by multi-arc ion plating. The deposition process included surface cleaning under a vacuum of5×10-3Pa，heating to480 ℃，and Ar glow cleaning for 60 min，followed by the sequential deposition of a TiAlN bottom layer for 30 min，an intermediate layer for 25 min，and an outer layer for 20 min using Ti33Al67targets. The coating thickness was observed to be approximately 0.97 μm using a scanning electron microscope (SEM；Hitachi Regulus 8100). The coating hardness was measured to be 32.5 GPa using a nanoindenter (Keysight G200). The coated tools were quenched at 200，400，600，and 800 ℃ in a muffle furnace，held for 30 min，and then cooled in a water-oil mixture with a volume ratio of 1:10. The hardness values were measured using an HVS-50Z digital Vickers hardness tester under a load of294 N and were 2057 HV at 200 ℃，2062 HV at 400 ℃，2061 HV at 600 ℃，and 1 986 HV at 800 ℃，while that of the unquenched sample was 2048 HV. These results indicated that the hardness changed only slightly except after quenching at 800 ℃.It was shown by grazing incidence X-ray diffraction (GIXRD；Bruker D8) that，with increasing quenching temperature，the diffraction peaks of both the WC substrate and TiAlN coating weakened，and the full width at half maximum increased，indicating grain refinement but increased crack susceptibility. Scratch testing using a WS-2005 tester under a load of 150 N and a scratch length of6 mm showed that the critical load for coating delamination decreased from 47 N at 200℃ to 26 N at 600 ℃，confirming that the coating adhesion gradually decreased.Cutting tests were conducted on a CK6140S CNC lathe using Ti6Al4V titanium alloy bars with dimensions of φ100 mm×300 mm. The cutting parameters were a feed rate of0.12 mm/r，a cutting depth of 1.4 mm，and cutting speeds of60，90，150 m/min under dry and wet cutting conditions. The quenched tools treated at 200，400，600 ℃ were tested at 90 m/min under dry cutting conditions. The tool quenched at 800 ℃could not be clamped because of thermal deformation of the mounting hole. The cutting temperature rise was monitored using an embedded thermocouple. Under dry cutting conditions，the temperature was 313 ℃ at 60 m/min and 400 ℃ at 90 m/min (a 27.8％increase)，and reached 466 ℃ before failure at 150 m/min (a 48.9％ increase over 60 m/min).After the tests，the wear regions on the rake face were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Regarding the effect of quenching temperature at 90 m/min under dry cutting conditions，the wear areas were 0.561 1 mm2at 200℃，0.612 7 mm2at 400 ℃，and 0.595 5 mm2at 600 ℃. At 600 ℃，an obvious W signal was detected，indicating substrate exposure and crack formation. Regarding the effect of cutting speed under dry cutting conditions using unquenched tools，the wear areas were 0.473 1 mm2at 60 m/min and 0.6764 mm2at 90 m/min，while the tool failed after only 152 m of cutting at 150 m/min. Under wet cutting conditions using the same water-oil mixture with a volume ratio of 1∶10 and a flow rate of approximately 0.125 L/s，the wear areas were significantly reduced to 0.374 7 mm2at 60 m/min and 0.399 8 mm2at 90 m/min，corresponding to 79.2％ and 59.1％ of those under dry cutting conditions，respectively. At 150 m/min under wet cutting conditions，the wear area was 0.915 5 mm2，but the cutting length reached 375 m，approximately 2.5 times that under dry cutting conditions. EDS analysis showed that the atomic percentage of oxygen on the surface ranged from 12.72％ to 19.30％，and Ti and Al elements caused by workpiece adhesion were also detected.The quenching temperature had a significant effect on the material properties and wear resistance of TiAlN-coated tools. As the quenching temperature increased from 200 ℃ to 600 ℃，the coating adhesion gradually decreased，and substrate exposure and cracks appeared on the rake face at 600 ℃. Cutting speed played a dominant role in the cutting temperature rise，and higher cutting speeds aggravated tool wear，especially under dry cutting conditions. The use of cutting fluid effectively reduced wear. At 60 and 90 m/min，the wear areas were reduced to 79.2％ and 59.1％ of those under dry cutting conditions，respectively，and the tool life was extended by approximately 2.5 times at 150 m/min. Quenching at 800 ℃ caused severe thermal deformation of the tool mounting hole，making cutting tests impossible. These results provide a quantitative basis for optimizing the quenching process and cutting parameter selection of TiAlN-coated cemented carbide tools in titanium alloy machining.
In the field of power transmission and transformation，aluminum components exhibit more complex corrosion behavior under currentcarrying conditions. Traditional corrosion prediction methods based on experiments and empirical formulas have limited accuracy and low efficiency. In this study，a multimodal prediction method integrating Mamba and a temporal convolutional network (TCN) was proposed. Through the deep fusion of numerical time-series data and surface morphology images，the weight loss of aluminum under current-density and time-gradient conditions was accurately predicted. Experimental results showed that the proposed method could effectively capture both short-term fluctuations and long-term evolution trends in the corrosion process，even under small-sample conditions. Its prediction accuracy was significantly higher than that of traditional empirical models and unimodal deep learning methods，and the proposed method demonstrated good application potential in material corrosion prediction and intelligent monitoring.
Coiled tubing nitrogen operation is a practical technology with broad application prospects. However，due to the presence of oxygen in nitrogen，coiled tubing is prone to corrosion failure in downhole high-temperature and high-pressure environments，posing significant wellcontrol risks. In this study，high-temperature and high-pressure weight-loss corrosion tests were conducted，and scanning electron microscopy(SEM)，energy dispersive spectroscopy (EDS)，and X-ray diffraction (XRD) were used to investigate the corrosion behavior of CT90 and CT110 coiled tubing in a simulated downhole nitrogen operation environment (nitrogen purity 95％-99％，temperature 80-120 ℃，pressure 50-90 MPa). The results showed that，in the corrosive nitrogen operation environment，the corrosion rates of CT90 and CT110 in both gasand liquid-phase environments gradually decreased with increasing nitrogen purity. The change in the liquid phase was more significant，and the corrosion rates of CT90 in both gas and liquid phases were higher than those of CT110. With increasing pressure，the corrosion rates of CT90 and CT110in the liquid-phase environment both increased. In the gas-phase environment，CT110 showed a gentle upward trend，whereas CT90 first increased slightly and then increased sharply. With increasing temperature，the corrosion rates of CT90 and CT110 in both gasand liquid-phase environments increased significantly，with the increase in the liquid phase much greater than that in the gas phase. Microscopic analysis of corrosion products showed that the main corrosion products on liquid-phase specimens of CT90 and CT110 were Fe3O4and Fe2O3.The corrosion product films formed in the liquid phase were loose and porous，indicating relatively severe corrosion. Under a single downhole operation time of 10 h and a minimum tensile safety factor of 1.5，evaluation based on the residual tensile strength criterion showed that higher nitrogen purity permitted more downhole operation cycles. Under the same conditions，the maximum number of downhole operation cycles of CT110 was approximately 2.4 times that of CT90. This study analyzed the corrosion morphology and corrosion products of coiled tubing under different conditions，and evaluated the safe service life of coiled tubing in combination with service conditions and failure theory，providing technical guidance for the safe operation of coiled tubing in oilfield production.
Founded in 1960, Monthly
ISSN：1001-1560
CN：42-1215/TB
Governed by:
China Machinery Industry Federation
Sponsored by:
China Academy of Machinery Wuhan Research Institute of Materials Protection Co.,Ltd.
Editor-in-Chief: LEI Mingkai
Tel.:
027-83641679 (Editorial Department);
027-83615846 (Editorial Department);
027-83638752 (Operation Department);
E-mail: bjb@mat-pro.com
