Key Takeaways & Executive Findings
- •• • At a modulation period of 186 nm, TiAlN/VN multilayers achieved a maximum hardness of 25.46 ± 0.69 GPa and a minimum residual compressive stress of 0.88 GPa, surpassing the rule-of-mixtures hardness of monolithic TiAlN and VN films. This hardness-stress combination is critical for connecting rods subjected to cyclic loading, where stress-induced cracking would otherwise accelerate fatigue failure. • • The multilayer with Λ = 280 nm delivered the highest H/E and H³/E² ratios, correlating with superior fracture toughness and film-substrate adhesion, and maintained a stable friction coefficient of 0.5 with optimal wear resistance. These metrics indicate that a moderate interface density balances hardness and toughness, preventing premature delamination under sliding contact. • • The Λ = 186 nm multilayer exhibited increased self-corrosion potential and reduced corrosion current density compared to the TC4 substrate, owing to a higher interface count and lower porosity that effectively sealed micro-pores and micro-cracks. This barrier effect impedes corrosive media diffusion, directly extending the service life of titanium alloy connecting rods in chloride-rich or acidic environments. • • Decreasing the modulation period while holding total film thickness constant increased the number of interfaces, which absorbed energy from TiAlN layers and relaxed their strain fields, producing lower residual stress. This interface engineering strategy offers a scalable route to tailor residual stress and mechanical properties without altering chemical composition.
China Advanced Materials & Deep-Tech Radar
Get verified English translations, SEM micrographs & open-access PDF alerts from China's leading state key laboratories delivered to your inbox every Monday at 08:00 EST.
Abstract
TiAlN/VN multilayer films with modulation periods (Λ) of 186, 280, and other values were deposited on TC4 titanium alloy connecting rods via microwave-enhanced magnetron sputtering to address the inadequate tribological and corrosion performance of monolithic TiAlN and VN coatings. X-ray diffraction confirmed coherent epitaxial growth of a face-centered cubic structure across all multilayers. As Λ decreased from 280 to 186 nm, hardness increased to a maximum of 25.46 ± 0.69 GPa and residual compressive stress decreased to 0.88 GPa, attributed to increased interface density and alternating stress fields that inhibit dislocation motion and relieve internal strain. The multilayer with Λ = 280 nm exhibited the highest H/E and H³/E² ratios, yielding superior fracture toughness, film-substrate adhesion, a stable friction coefficient of 0.5, and optimal wear resistance. Electrochemical testing revealed that the Λ = 186 nm multilayer, with its higher interface count and lower porosity, effectively blocked micro-pores and micro-cracks, increasing the self-corrosion potential and reducing corrosion current density relative to the TC4 substrate. These results demonstrate that TiAlN/VN multilayers provide a dual-function barrier against wear and corrosion, extending the service life of titanium alloy connecting rods in harsh environments and offering a theoretical basis for broadening titanium alloy applications.
1. Introduction
TC4 titanium alloy connecting rods are widely used in automotive and aerospace applications due to their high specific strength and corrosion resistance. However, their poor tribological performance—characterized by low hardness, high friction coefficients, and susceptibility to adhesive wear—and inadequate corrosion resistance in aggressive environments limit their service life. Monolithic hard coatings such as TiAlN and VN have been applied to mitigate these issues, but each suffers from intrinsic drawbacks: TiAlN films develop high residual compressive stresses that promote cracking and spallation, while VN films exhibit lower hardness and inferior wear resistance. These limitations stem from the inability of single-layer architectures to simultaneously optimize hardness, toughness, and stress management.
Multilayer architectures with alternating nanoscale layers offer a solution by introducing interfaces that impede dislocation motion, relax residual stresses, and block corrosive pathways. This study employs microwave-enhanced magnetron sputtering to deposit TiAlN/VN multilayers with controlled modulation periods on TC4 substrates. By systematically varying the modulation period, the research establishes quantitative relationships between interface density, residual stress, hardness, fracture toughness, wear resistance, and corrosion protection. The findings provide a design framework for engineering multilayer coatings that extend the operational lifespan of titanium alloy connecting rods under combined mechanical and electrochemical degradation.
Loading authentic research manuscript (Pages 1–5)...
WU Jie, XU Zhaoying, WANG Jiarong, ZHANG Tengfei, WANG Jinbiao, SU Yongyao (2026). Microstructure and Wear-Corrosion Properties of TiAlN/VN Multilayer Films on Titanium Alloy Connecting Rods. Surface Technology (表面技术). https://doi.org/10.16490/j.cnki.issn.1001-3660.2026.08.004
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntelare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the dominant failure mechanism of TiAlN/VN multilayers under sliding wear, and how does modulation period influence it?
The dominant failure mechanism is crack initiation and propagation at interfaces, followed by delamination. At Λ = 280 nm, the multilayer exhibits the highest H/E and H³/E² ratios, which correlate with superior fracture toughness and film-substrate adhesion, resulting in a stable friction coefficient of 0.5 and optimal wear resistance. Reducing Λ to 186 nm increases hardness to 25.46 GPa but lowers toughness, making the film more susceptible to brittle fracture under high contact stresses. Therefore, Λ = 280 nm provides the best balance for wear resistance.
How does the multilayer architecture mitigate residual stress compared to monolithic TiAlN films?
Monolithic TiAlN films typically develop high residual compressive stresses that promote cracking. In TiAlN/VN multilayers, decreasing the modulation period from 280 to 186 nm increases the number of interfaces, which absorb energy from TiAlN layers and relieve their strain fields. This results in a residual stress reduction to 0.88 GPa at Λ = 186 nm, significantly lower than the average value for monolithic TiAlN films. The alternating stress fields at interfaces inhibit dislocation motion and accommodate strain, preventing stress accumulation.
What electrochemical metrics demonstrate the corrosion protection of TiAlN/VN multilayers on TC4, and what is the underlying mechanism?
The Λ = 186 nm multilayer exhibits a higher self-corrosion potential and lower corrosion current density compared to the TC4 substrate. This is attributed to its higher interface count and lower porosity, which effectively seal micro-pores and micro-cracks, blocking the diffusion of corrosive media. The dense, coherent epitaxial structure acts as a physical barrier, reducing the exposed substrate area and suppressing electrochemical reactions. These results indicate a significant corrosion protection effect, extending service life in harsh environments.
Can the TiAlN/VN multilayer deposition process be scaled to industrial production for connecting rods, and what are the cost implications?
The microwave-enhanced magnetron sputtering process used in this study is compatible with industrial-scale batch coating systems. The deposition parameters—modulation period, total thickness, and target power—are controllable and reproducible. While multilayer deposition adds process steps compared to monolithic coatings, the improvement in service life (reduced wear and corrosion) can offset the initial cost by lowering maintenance and replacement frequency. The use of standard TiAl and V targets ensures material availability and cost parity with existing hard coatings.
What are the limitations of the current study regarding long-term durability and thermal stability of TiAlN/VN multilayers?
The study focuses on room-temperature mechanical and electrochemical performance. Long-term durability under cyclic loading and elevated temperatures (e.g., engine operating conditions) was not evaluated. Thermal stability of the multilayer, particularly interdiffusion at interfaces and oxidation resistance above 500°C, remains unquantified. Future work should assess phase stability, hardness retention, and corrosion resistance after thermal exposure to validate suitability for high-temperature connecting rod applications.
Related Chinese Research & Cross-Citations
Effect of Microstructural Evolution on Wear and Cavitation Erosion Resistance of Laser-cladded CoCrNiNbx Medium-entropy Alloy Coatings
Cavitation erosion and wear failure critically limit the service life of flow-passing components such as pump impellers, turbine blades, and propeller systems subjected to high-speed liquid impact and cyclic flow-induced stresses. This work aims to design a high-performance surface coating with enhanced hardness, wear resistance, and cavitation erosion resistance by tailoring the Nb content in a CoCrNi medium-entropy alloy (MEA) system. CoCrNiNbx (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2) coatings were fabricated on 316L stainless-steel substrates with an FL020 fiber laser under identical processing parameters. The effect of Nb addition on the phase constitution, microstructure, mechanical properties, tribological behavior, and cavitation performance of the coatings was comprehensively investigated to determine the optimal composition for balanced mechanical and anti-erosion properties. Phase analysis by X-ray diffraction (XRD) showed that increasing Nb content promoted a transition from a single face-centered cubic (FCC) solid solution to a dual FCC + hexagonal close-packed (HCP) phase structure. The emergence and growth of the Nb-rich HCP phase were accompanied by pronounced lattice distortion and precipitation strengthening. Microstructural characterization using field-emission scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy (EDS) revealed that Nb preferentially segregated along interdendritic regions, where fine HCP-phase precipitates gradually formed a semi-continuous strengthening network. Electron backscatter diffraction (EBSD) analysis further quantified grain size and phase distribution. The average microhardness of the coatings initially increased and then decreased with increasing Nb molar ratio x, peaking at 689 HV0.1 for x = 0.6, approximately 3.7 times that of the substrate. Wear performance followed the same trend. Cavitation erosion tests demonstrated that the CoCrNiNb1.0 coating exhibited optimal cavitation erosion resistance, with mass loss significantly lower than that of the 316L substrate, achieving an order-of-magnitude improvement. The optimal Nb addition (x = 0.6–1.0) balances strength and toughness, significantly enhancing the wear and cavitation erosion resistance of CoCrNi-based MEA laser-cladded coatings. This study provides experimental evidence and process references for engineering applications of CoCrNi-based MEA coatings in high-flow-velocity liquid impact environments.
Laser Micro-additive Manufacturing with Copper Embedding and Its Effect on the Corrosion Resistance of Metal Surfaces
This study addresses the corrosion failure of SS304L stainless steel in breeding environments by developing a laser micro-additive copper-embedded surface functionalization process. A 355 nm nanosecond laser with 60 W average power, 40 kHz repetition rate, and 16 ns pulse width was used to embed a 0.12 µm Cu foil onto SS304L substrates under three coating strategies: single-layer, double-layer, and double-pass, each at scanning speeds of 400, 800, and 1200 mm/s. Surface characterization via 3D profilometry, SEM, EDS, and XPS revealed regular grooves and micro-concave structures with height differences increasing from 0.1 µm (untreated) to 1.6–3.8 µm, with the double-pass sample achieving the maximum 3.8 µm. Cu particles were successfully embedded, forming CuO and Cu2O oxide layers. Electrochemical tests in 3.5 wt.% NaCl solution showed that the optimal sample (double-layer coating at 800 mm/s, designated b2) exhibited the highest corrosion potential (increased by ~0.04 V), a one-order-of-magnitude reduction in corrosion current, and a maximum charge transfer resistance (Rct) of 6954 Ω·cm². These results demonstrate that laser micro-additive embedding of copper synergistically enhances the corrosion resistance of stainless steel through surface texturing, copper particle incorporation, and oxide film formation.
Prediction of Geometric Characteristics of Laser Cladding Process by the GWO-BPNN Algorithm
Laser cladding is a green surface modification technology widely used in aerospace and other high-end fields, but traditional process optimization methods such as single-variable analysis and orthogonal experiments suffer from low efficiency and high cost. The geometric characteristics of the cladding layer—dilution rate, forming coefficient, and wetting angle—directly determine service performance. Existing machine learning models often fail to achieve multi-objective optimization and comprehensive prediction. This study proposes a hybrid algorithm combining Grey Wolf Optimizer (GWO) with Backpropagation Neural Network (BPNN) to predict geometric quality indicators. Full-factorial single-track laser cladding experiments were conducted on 316L stainless steel with 316L alloy powder. A polynomial regression model predicted clad width and height with relative error below 4.2%. The GWO-BPNN model predicted dilution rate, forming coefficient, and wetting angle with an average coefficient of determination (R²) of 95.28%, a 12.4% improvement over traditional BPNN (82.93%). Experimental and inverse validation confirmed stable predictive performance across different parameter ranges, meeting engineering tolerance requirements. The method provides a quantitative basis for multi-dimensional optimization of cladding quality and demonstrates practical applicability in industrial scenarios.
Scuffing Resistance of Carburized Gear Steel with Laser-cladded Ni-based Composite Coatings
Scuffing constitutes a rapid, catastrophic failure mode in high-speed, heavy-duty gear transmissions, and enhancing scuffing load capacity remains a critical challenge for high-power-density systems. This study investigates the feasibility of laser cladding to improve scuffing resistance and repair scuffed tooth surfaces on 18CrNiMo7-6 gear steel. Three substrate conditions—tempered, carburized, and carburized with pre-induced scuffing damage—were coated with NiCr20-3%ZrO2-1%MoS2 (mass fraction) via a MobiMRO-2 laser cladding system with synchronous powder feeding. The cladded layer, approximately 1.2 mm thick, exhibited a dendritic, cellular, and irregular particulate microstructure with hardness of 690–730 HV0.1, comparable to the carburized case. Laser cladding induced significant heat-affected zone (HAZ) transformations: tempered steel formed lath martensite and lower bainite near the coating, with spheroidized structures in the lower HAZ; carburized steel developed coarse acicular martensite at the top, refined structures in the middle, and troostite at the bottom, with overall temper softening. Scuffing tests using a two-disc rolling contact rig under step-wise loading revealed that cladded tempered, cladded carburized, and repaired samples achieved 94.4%, 61.3%, and 50.7% increases in scuffing load capacity, respectively, relative to uncladded carburized baseline. This enhancement stems from increased hardness and the self-lubricating effect of the coating, which reduced interfacial friction coefficient and delayed critical failure. Failure analysis showed that the cladded layer altered crack initiation and propagation paths, significantly raising the critical failure load. The repaired samples, however, exhibited poor bonding at the original damage interface, leading to localized coating detachment. These findings confirm laser cladding as an effective method for enhancing gear scuffing resistance and repairing scuffed surfaces, providing experimental and theoretical support for surface strengthening and damage repair.
Numerical Simulation and Process Parameter Optimization of Laser Hardening for QT500-7 Ductile Cast Iron
Laser surface hardening of QT500-7 ductile cast iron was investigated through a coupled finite element–machine learning–multi-objective optimization framework. A phase-transformation heat-transfer finite element model screened process windows for laser power (100–400 W), scanning speed (5–15 mm·s⁻¹), and overlap rate (60%–90%). A three-factor, three-level Box-Behnken design yielded hardened layer depth and fused layer depth as response variables. Four predictive architectures were benchmarked: Random Forest (RF), XGBoost, RF-XGBoost ensemble, and Bayesian-optimized RF-XGBoost (BO-RF-XGBoost). The BO-RF-XGBoost model achieved superior accuracy, with relative errors of 6.52% for hardened layer depth and 9.09% for fused layer depth. Multi-objective optimization compared Advantage Actor-Critic (A2C), Multi-Objective Particle Swarm Optimization (MOPSO), and Non-dominated Sorting Genetic Algorithm II (NSGA-II). A TOPSIS-entropy weight method ranked the Pareto front, identifying optimal parameters: laser power 230 W, scanning speed 14 mm·s⁻¹, overlap rate 75%. Experimental validation at these parameters produced a hardened layer depth of 230 μm and fused layer depth of 66 μm, with finite element model errors of 9.13% and 3.03%, respectively. Microhardness measurements showed the fused layer at 940 ± 40 HV0.5 and the hardened layer at 630 ± 30 HV0.5, both significantly exceeding the substrate hardness of 166 ± 15 HV0.5. The framework provides a reliable tool for parameter optimization in laser surface hardening of ductile cast iron.
Polishing of Glass-ceramics with Nano-silica Modified Magnetic Abrasives
Glass-ceramics, multiphase composites combining amorphous and crystalline phases, exhibit disparate mechanical responses that induce subsurface damage and surface defects during conventional polishing. This study fabricates magnetic abrasive particles (MAPs) via a bonding process with three variants: unmodified, hydrophilic nano-silica (20 nm) modified, and hydrophobic nano-silica (20 nm) modified. Base composition comprises iron powder (75 μm) and CeO2 abrasives (15 μm) at a 12:3 mass ratio. Polishing tests on glass-ceramics using an N-S array tool reveal that hydrophobic modified MAPs achieve the lowest surface roughness (Sa = 17 nm) and highest material removal depth (2.5 μm), compared to hydrophilic (Sa = 24 nm) and unmodified (Sa = 48 nm) MAPs. Dynamic friction coefficients measured in situ are 0.31, 0.35, and 0.42 for hydrophobic, hydrophilic, and unmodified MAPs, respectively. Surface and subsurface damage analyses show hydrophobic MAPs minimize pits, micro-cracks, and brittle fractures, while hydrophilic MAPs exhibit brittle spalling and unmodified MAPs show point defects. Wear tests confirm that nano-silica addition enhances bond strength and extends abrasive lifespan. The hydrophobic modification promotes surface hydration and formation of a lubricating silicate gel layer, reducing mechanical plowing and friction, thereby enabling high-quality surface integrity. These findings demonstrate that nano-silica modification effectively tunes MAP hydrophobicity, offering a viable route for ultra-smooth, low-damage polishing of glass-ceramics.