Search Results (1,325)

HVOF coatings based on tungsten and chromium carbides are widely used in aerospace, energy, and oil and gas industries. However, the selection between the wear resistance of WC–Co and the corrosion resistance of Cr₃C₂–NiCr is often hindered by a lack of systematic data on the effect of powder particle size. In this study, WC–12Co and Cr₃C₂–NiCr coatings were deposited onto 12Kh18N10T stainless steel substrates by HVOF spraying using three particle size fractions: <20, 20–32, and 32–40 μm. Individual spray parameters were selected for each material to ensure high-quality deposition (standoff distance 350 mm, one pass for WC–12Co; 250 mm, two passes for Cr₃C₂–NiCr). The influence of powder particle size distribution on coating properties was investigated using a comprehensive set of methods, including scanning electron microscopy, X-ray diffraction with Rietveld quantitative phase analysis, microhardness testing, tribological testing, electrochemical measurements, and numerical modeling of particle in-flight motion. It was found that the 20–32 μm fraction is optimal for both materials. Different degradation mechanisms were identified: for WC–Co, decarburization of WC with the formation of W₂C and η-phases dominates (maximum for the <20 μm fraction); for Cr₃C₂–NiCr, oxidation and carbide dissociation prevail (in the <20 μm fraction—13.7% Cr₂O₃ and 38.6% Cr₇C₃), leading to low coating thickness (~16 μm) due to loss of ductility and wettability. Numerical modeling confirmed that the high velocity of fine Cr₃C₂–NiCr particles (~680–720 m/s) does not compensate for their overheating, whereas for WC–12Co all fractions have velocities above the critical threshold, but coarse particles (32–40 μm) give porosity up to 3.15% due to insufficient deformation. Corrosion tests showed that under spraying conditions optimized for each material, the Cr₃C₂–NiCr coatings (corrosion rate 0.066–0.102 mm/year) are an order of magnitude superior in corrosion resistance to WC–12Co coatings (corrosion rate 0.353–0.651 mm/year), owing to the passivation of the γ-Ni(Cr) matrix; for WC–Co, the main protective barrier is provided by the structural density. Full article

Heat-resistant superalloys (HRSA) offer good oxidation, corrosion, and creep resistance and exhibit better rupture strength characteristics. These HRSA are used under cyclic loads and high-temperature environments such as turbine blades, pressure vessels, turbocharger rotors, seals, boilers, and high-temperature fasteners. Inconel 718, Inconel 825, Nimonic 80A, Nimonic C263, Incoloy/Inconel 800, and Inconel 617 are some of the most used superalloys. Despite several advantages and applications, poor thermal conductivity, a tendency towards work hardening, and outstanding metallurgical consistency all adversely affect the machining of these alloys. This study reviews the various machining possibilities for Incoloy 800 superalloys to date. The present article aims to investigate multiple conventional and non-conventional machining studies on Incoloy 800 in terms of machining conditions, surface roughness (SR), Tool wear (TW), and the optimization of process parameters. Furthermore, this article summarizes the developments in machining Incoloy 800 over the past few years and identifies a prominent research gap for future studies. Full article

Rolling bearings in modern wind turbines operate under demanding tribological conditions that include high contact stresses, mixed lubrication, transient loads, electrical discharge, corrosion, and hydrogen-assisted damage. These factors contribute to premature failures such as micropitting, scuffing, white etching cracks (WECs), and electrical fluting, which remain major reliability challenges in both onshore and offshore turbines. Surface-engineering technologies have emerged as effective tools to mitigate these failure modes. Carbon-based coatings improve sliding performance and reduce wear under boundary-lubricated conditions; black oxide conversion layers enhance the corrosion resistance, lubricant retention, and early-life running-in behavior; and insulating ceramic coatings protect generator bearings from electrical discharge damage. Additional solutions, including polymer overlays, composite films, and hybrid ceramic architectures, offer further improvements in friction, surface fatigue resistance, and environmental robustness. This manuscript reviews the current state of coated bearing technologies relevant to wind turbine applications, synthesizing findings from tribological research, industrial practice, and emerging material developments. While only a limited number of coating suppliers provide documented evidence of coating use in wind turbine drivetrain bearings, the collective progress in surface engineering demonstrates clear potential for improving reliability and extending service life across the installed turbine base. The analysis highlights the mechanisms by which coatings enhance performance, the conditions under which they are most effective, and the gaps that remain in field validation and large-scale deployment. Coated bearings represent a promising pathway toward higher turbine availability, reduced maintenance costs, and improved drivetrain durability. Continued advances in carbon-based films, multilayer architectures, and insulating coatings, combined with better integration of lubrication strategies and condition-monitoring technologies, will play an increasingly important role in enabling the next generation of high-power wind energy systems. Full article

This study investigates the microstructural, tribological, and corrosion properties of electrodeposited Zn-Co nanocomposite coatings reinforced with graphene and TiO₂ nanoparticles on Selective Laser-Melted (SLM) Ti6Al4V alloy. Systematic characterization using XRD, SEM, and Raman spectroscopy revealed that the incorporation of graphene and TiO₂ significantly refined the grain structure, resulting in a dense and defect-free surface morphology. Reciprocating wear tests demonstrated that the optimized hybrid coating (Zn-Co-GTi) exhibited superior tribological performance. Electrochemical impedance spectroscopy (EIS) tests conducted in simulated body fluid (SBF) at 37 °C demonstrated that the optimized hybrid coating (Zn-Co-GTi) also provided enhanced corrosion resistance. Specifically, the coefficient of friction decreased from 0.79 to 0.24, while the wear rate was reduced to 5.1 × 10⁻⁴ mm³/Nm. Electrochemical evaluations further confirmed a significant improvement in corrosion resistance, with the Zn-Co-GTi coating exhibiting the lowest corrosion current density (0.0059 μA cm⁻²) and the highest charge transfer resistance (Rct). However, increasing the reinforcement content beyond the optimum level resulted in partial nanoparticle agglomeration, leading to a slight deterioration in both tribological and corrosion performance. Overall, the optimized Zn-Co-Graphene-TiO₂ nanocomposite coating provides an effective and scalable surface engineering strategy for improving the durability and corrosion resistance of SLM-produced Ti6Al4V components for advanced engineering and biomedical applications. Full article

Ti–6Al–4V alloy is widely used in aerospace and other high-performance engineering components, but its service reliability is often constrained by surface-initiated fatigue, fretting damage, wear, and corrosion. Ultrasonic surface rolling process (USRP) couples a static rolling force with high-frequency mechanical impacts to introduce severe plastic deformation while retaining relatively low surface roughness, thereby producing a gradient-strengthened surface layer. This review systematically summarizes advances in USRP strengthening of Ti–6Al–4V alloy within a “process–microstructure–surface integrity–service performance” framework. The effects of static load, ultrasonic amplitude and frequency, feed rate, spindle speed, processing passes, treatment temperature, and lubrication conditions are first compared. Particular attention is then paid to the mechanisms governing dislocation multiplication and rearrangement, grain subdivision, gradient nanostructure formation, the responses of the α and β phases, deformation-induced phase transformation, and the evolution of depth-dependent residual compressive stress. The intrinsic relationships between these mechanisms and surface roughness, hardness, strengthened layer depth, wear and corrosion resistance, fatigue performance, and fretting fatigue performance are subsequently clarified. Control strategies involving electropulsing, laser/temperature assistance, deep cryogenic treatment, and coating combinations are further reviewed, together with methods for contact dynamics analysis, residual stress prediction, and data-driven optimization. The combined evidence indicates that the performance gains from USRP are jointly controlled by surface defects, gradient microstructure, and residual compressive stress; excessive load, processing passes, or heat input may weaken or even reverse the fatigue benefit because of defect accumulation, gradient mismatch, and residual stress relaxation. Current limitations include inconsistent reporting of process parameters, difficulty in quantitatively separating the contributions of different strengthening mechanisms, insufficient investigation of residual stress stability, and limited validation on complex components. Full article

Three kinds of surface treatments, including permanganate, molybdate, and phytic acid conversion films, were fabricated on La-Ce mischmetal containing AM60B magnesium alloy. Their effects on the corrosion and tribological behaviors of the alloy in 3.5 wt% NaCl solution were systematically investigated via Mott–Schottky analysis, electrochemical measurements, and friction–wear tests. The results show three surface treatments shift the flat band potential in the negative direction, reduce the corrosion current density, enlarge the electrochemical impedance arc radius, and decrease the friction coefficient, conferring remarkably enhanced corrosion and wear resistance to the alloy substrate. The performance enhancement is ascribed to the formation of uniform, dense conversion films that act as effective physical barriers, which impede the penetration of corrosive species, isolate the substrate from the aggressive aqueous environment, and improve the chemical and electrochemical stability of the alloy–solution interface. The comprehensive performance ranking of the three surface treatments in terms of corrosion and wear resistance is as follows: permanganate conversion film > molybdate conversion film > phytic acid conversion film. Full article

Although the duty cycle is an important parameter in pulsed plasma nitriding, its role in simultaneously controlling the microstructure, mechanical performance, tribological behavior, and corrosion resistance of 12Kh18N10T stainless steel remains insufficiently understood. Therefore, this study systematically investigates these relationships under otherwise fixed nitriding conditions. The samples were nitrided at 500 °C, a pressure of 400 Pa, a voltage of 700 V, and a treatment duration of 5 h, with duty cycle (DC) values of 30, 60, and 90%. The surface microstructure and composition were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. The mechanical properties were evaluated by instrumented nanoindentation, the tribological properties were evaluated using the coefficient of friction and wear rate, and the corrosion resistance was investigated using potentiodynamic polarization. The maximum nitrided layer thickness of 91.29 μm was obtained at DC30, whereas the layer thickness at DC60 and DC90 was approximately 65.07 μm. Fe₄N and Cr₂N phases were identified in all samples. The DC60 regime provided the highest hardness of 740.6 HV, an elastic modulus of 215.9 GPa, the lowest coefficient of friction of 0.333, and the lowest corrosion current density of 0.000665 mA/cm². The minimum wear rate of 2.276 × 10⁻⁵ mm³/(N·m) was achieved at DC90. These results show that the optimal processing condition depends on the required combination of hardness, wear resistance, coefficient of friction, and corrosion resistance. The obtained results demonstrate that the functional properties of the steel can be effectively tailored by controlling the duty cycle. Full article

Corrosion-resistant coatings with a double-layer structure are deposited on the surface of S30408 stainless steel at welding currents of 170 A, 200 A, and 230 A using metal active gas (MAG) arc welding technology. The influence of welding current on the microstructure, microhardness, wear resistance, and electrochemical corrosion behavior of the coating is systematically studied. The results show that the coating produced at 200 A exhibited the finest martensitic structure, the highest microhardness (~450 HV), and the lowest mass loss (139.9 mg), indicating its superior wear resistance. In contrast, the coating fabricated at 230 A displayed the most positive corrosion potential (−0.302 V vs. saturated calomel electrode (SCE)) in 3.5 wt.% NaCl solution, which is attributed to enhanced elemental homogenization arising from the higher heat input. This paper clarifies the critical role of welding current in balancing wear and corrosion performance and provides a practical guideline for the cost-effective surface enhancement of S30408 steel components. Full article

Laser cladding technology is a widely applied surface modification technique; but its inherent process characteristics render it susceptible to cracking. The addition of rare earth oxides has proven to be an effective approach for curbing crack formation and enhancing the comprehensive performance of the coating. This review summarizes the mechanisms by which rare earth additives improve the coating microstructure, molten bath behavior, and interfacial bonding strength, including adjusting surface tension, purifying the molten bath, and forming interatomic chemical bonding. The addition of rare earth oxides significantly improves the forming quality of materials, which contributes to a finer and more uniform microstructure and directly enhances material hardness and resistance to plastic deformation, thereby altering wear behavior and improving wear resistance. The increased hardness provides better support for the surface oxide film, while the improved microstructure mitigates galvanic corrosion and intergranular corrosion susceptibility, leading to enhanced corrosion resistance. In addition, the article incorporates relevant quantitative analysis to provide a reference basis for the type selection, content optimization, and particle size selection of rare earth additives. This article provides a coherent framework for understanding how the addition of rare earths transfers its effects from the process to the performance. However, the industrial application of rare earth oxide laser cladding faces key bottlenecks such as additive deactivation under extreme conditions, threshold effects, nano-agglomeration, and cost constraints. Full article

Silver (Ag)-based conductive coatings are widely used in electrical contacts due to their excellent electrical conductivity, low contact resistance, good thermal stability and oxidation resistance, although their susceptibility to sulfidation and environmental corrosion is a concern under certain service conditions. In recent years, significant progress has been achieved in both the manufacture and performance optimization of Ag-based coatings to satisfy the demanding requirements of modern electrical and electronic systems. This review summarizes recent advances in fabrication techniques and processing parameters for Ag-based coatings, including electroplating, electroless deposition, magnetron sputtering, electrospark deposition, thermal spraying, and electrical explosion spraying on metallic substrates, particularly on copper and steel substrates. More attention is given to microstructural design strategies, such as the incorporation and homogeneous dispersion of reinforcement or solid lubricant phases within the Ag matrix, to enhance contact reliability and operational endurance. The performance of Ag-based coatings is analyzed in terms of their physical, chemical and mechanical properties, electrical contact resistance, friction and wear behavior, arc erosion resistance, and environmental durability under different service conditions. Key challenges, including coating degradation under high electrical loads, mechanical wear, and corrosive environments, are highlighted. Future research directions are outlined, focusing on multifunctional coating structures that enhance surface performance and ensure the long-term durability of electrical contacts. Full article

Methanol compression-ignition engines are vital for transport carbon neutrality, yet methanol’s low cetane number, corrosivity, low viscosity, and cavitation tendency compromised piezoelectric injector reliability. This study proposed systematic optimization strategies tailored to methanol’s fuel properties. A sealed thin-walled metal encapsulation, fabricated from precipitation-hardening martensitic stainless steel, was designed to isolate corrosive methanol media. The geometry of the tubular spring was optimized to meet the stiffness requirements for high-frequency injections. A monolithic nozzle without side pin holes, also upgraded to the same precipitation-hardening martensitic stainless steel, effectively suppressed stress corrosion cracking by leveraging the material’s combined high strength and excellent corrosion resistance. A dedicated return-line backpressure valve compensated for hydraulic leakage and improved fuel replenishment, and nozzle hole taper and inlet fillet radius were optimized to mitigate cavitation. Cold-motoring reliability tests showed the optimized injector maintained flow deviation within 3% after 100 million cycles, whereas the unoptimized prototype reached 8% deviation at 60 million cycles. The single-cycle injected fuel quantity coefficient of variation dropped from 4% to 1.3%. Spray characteristic comparison tests further confirmed that the optimized injector maintained stable flow consistency and atomization quality after prolonged cyclic operation. These optimizations effectively resolved corrosion, wear, and hydraulic instability caused by methanol, significantly enhancing flow consistency and durability over the service life. The results provided critical component-level technical support for advancing methanol compression-ignition engines from laboratory research to industrial application, addressing key reliability barriers that previously hindered engineering deployment of methanol-fueled powertrains. Full article

Compacted graphite iron (CGI) is widely used in thermomechanically demanding engineering applications owing to its high thermal conductivity, vibration-damping capacity, and machinability. However, its surface performance can be limited under the simultaneous effects of elevated temperature, sliding contact, and corrosive environments. In this study, CGI surfaces were subjected to pack boriding using a silica-free B₄C–NaBF₄ powder mixture at 800, 900, and 1000 °C for 4 h, and the microstructural characteristics of the resulting boride layers, together with their wear behavior at room temperature and 500 °C and their electrochemical corrosion resistance, were systematically investigated. Cross-sectional SEM/EDS analyses revealed the formation of boride layers exhibiting a saw-tooth interface morphology, with thickness increasing from 44 ± 4 µm to 108 ± 9 µm with increasing boriding temperature. XRD results indicated the formation of a dual-phase FeB/Fe₂B structure in all borided specimens, with the Fe₂B phase dominant at 800 °C and the FeB phase becoming dominant at 1000 °C. Boriding increased the surface hardness from approximately 470–480 HV to a range of 2122–2550 HV. In room-temperature wear tests, specimens B1 and B2 exhibited specific wear rates approximately 13-fold lower than that of the untreated CGI, whereas B3 showed a higher wear loss attributable to the brittle character of the FeB phase. At 500 °C, B1 maintained the most balanced tribological performance, with the lowest volumetric wear loss and coefficient of friction, while microcracking and three-body abrasion effects became more pronounced in B2 and B3. In electrochemical tests conducted in 3.5 wt.% NaCl solution, B1 exhibited more stable open-circuit potential behavior, whereas B3 showed the highest resistance in terms of Tafel kinetics, with the lowest corrosion current density and corrosion rate. Overall, the results demonstrate that the Fe₂B-dominant boride layer obtained at 800 °C provides the most balanced performance among hardness, wear, and corrosion behavior, whereas the thick, FeB-dominant layer formed at 1000 °C, despite offering high hardness and favorable corrosion kinetics, may compromise tribological reliability owing to its brittleness, increased surface roughness, and tendency toward microcracking. Full article

TiAl alloy exhibits excellent strength, oxidation resistance and creep resistance, making it a preferred candidate material to replace high-temperature alloys. Currently, TiAl alloy has been widely applied in aerospace, the marine industry and other fields involving high-stress contact or highly corrosive environments. Selective laser melting (SLM) technology provides a brand-new approach for the fabrication of TiAl alloys, which enables direct forming of workpieces with complex structures and significantly reduces manufacturing cycles. However, the quality and performance of SLM fabricated TiAl alloys are highly dependent on laser energy input. Therefore, this study fabricated TiAl4822 alloy under different SLM process parameters, and systematically conducted investigations on its tribological properties and electrochemical corrosion behavior. The experimental results show that the SLM process did not alter the basic phase composition of TiAl4822 alloy, with Ti_0.6Al_0.4 as the dominant phase. TiAl4822 alloys fabricated under the parameter combinations of 1000 mm/s + 140 W exhibited outstanding wear resistance, and the wear mechanism transformed from severe adhesion and abrasive wear to mild oxidative wear. When the laser power was 100 W and the scanning speed was 1200 mm/s, the alloy achieved the highest corrosion resistance, with the corrosion potential reaching the maximum value of −390.065 mV and the corrosion current density decreasing to the minimum value of 8.73 × 10⁻⁶ A/cm². Thus, different parameter combinations can realize the optimization of tribological properties and electrochemical corrosion performance respectively. This study lays a theoretical foundation for promoting the high-performance engineering application of this alloy in harsh wear-resistant and corrosion-resistant environments. Full article

Steel is the most fundamental material used in structural system elements in the construction industry. It needs to be coated with materials that provide resistance to high temperatures, wear, and corrosion. Ni-Al powder is preferred in coatings because nickel increases corrosion resistance and aluminium forms an oxide layer to reduce oxidation. In the long term, the protective effect of coatings decreases, and corrosion resistance declines. In this study, a random forest model was evaluated using experimental data on the corrosion performance of A36 steel coated with Ni-Al powder for corrosion prevention, after exposure to a 3.5% NaCl solution for 1 h and 30 days for short- and long-term electrochemical response prediction. The impedance and phase angle characteristics, which represent the electrochemical response of coated and uncoated steel, have been predicted. In addition, the model’s reproducibility was investigated using the multi-seed (30 seeds) method to analyse the stability and consistency of the random forest model. The aim of this study was to develop a machine learning model that learns the frequency-dependent electrochemical impedance (Bode) response of graphene oxide-enriched Ni–Al coatings on steel, which reflects the corrosion-related electrochemical behaviour of the coating system, and to evaluate the model for predicting the impedance magnitude and phase angle of reference coatings over the investigated frequency range. The developed artificial intelligence model predicted the Bode response (impedance magnitude and phase angle) of coated and uncoated steel to NaCl solution after 1 h and 30 days as a function of frequency and coating type. The predicted impedance spectra reflected the deterioration of the corrosion protection performance of the Ni–Al coatings with increasing exposure time. The predicted EIS responses were subsequently used to assess changes in the corrosion-related electrochemical behaviour of the coatings over short- and long-term exposure. According to the findings, the random forest models can predict the frequency-dependent electrochemical response (impedance magnitude and phase angle) with high accuracy. Full article

In this work, the microstructural evolution and comprehensive performances (mechanical, wear, and corrosion resistance) of LDED-fabricated 2205 DSS subjected to heat treatment at 1000 °C for different holding durations (5 min, 10 min, 30 min, and 60 min) were systematically investigated. The results indicate that the austenite content gradually increases with the extension of heat treatment time, reaching a peak value of 51% at 30 min. Meanwhile, the austenite morphology transforms from dendritic grains to equiaxed grains, accompanied by the massive precipitation of intragranular austenite (IGA) and obvious elemental enrichment behavior. In terms of mechanical and functional performances, the microhardness decreases slightly with prolonged heat treatment, with a total reduction of only 7%. The elongation increases continuously, while the yield strength and tensile strength remain relatively stable. Additionally, the wear coefficient and wear rate present a trend of first decreasing and then increasing. The minimum wear rate of 48.32 × 10⁻⁶ mm³/(N·m) is obtained at the heat treatment duration of 30 min, which is 83.4% lower than that of the untreated sample. Moreover, the optimal corrosion resistance is achieved after 30 min of heat treatment, with the corrosion current density decreasing by 45.8% relative to the as-built specimen. These results demonstrate that heat treatment at 1000 °C for 30 min is an optimal processing parameter to significantly optimize the microstructure and comprehensive performances of LDED-2205 DSS. Full article