Properties Of Coatings Research Articles

Terahertz Nondestructive Measurement of Heat Radiation Performance of Thermal Barrier Coatings Based on Hybrid Artificial Neural Network

Effective control of the micro- and nanostructure of thermal barrier coatings is essential to enhance the thermal radiation performance of the coating, which helps to determine the remaining service life of the coating. This paper proposed a method to measure the radiation properties of thermal barrier coatings by terahertz nondestructive testing technique, using APS-prepared thermal barrier coatings as the object of study. Radiative properties were a comprehensive set of properties characterized by the diffuse reflectance, transmittance, and absorptance of the thermal barrier coating. The coating data in actual service were obtained by scanning electron microscopy and metallographic experiments, and the data were used as the simulation model critical value. The terahertz time-domain simulation data of coatings with different microstructural features were obtained using the finite-different time-domain (FDTD) method. In simulating the real test signals, white noise with a signal-to-noise ratio of 20 dB was added, and fast Fourier transform (FFT), short-time Fourier transform (STFT), and wavelet transform (WT) were used to reduce the noise and compare their noise reduction effects. Different machine learning methods were used to build the model, including support vector machine algorithm (SVM) and k-nearest neighbor algorithm (KNN). The principal component algorithm (PCA) was used to reduce the dimensionality of terahertz time-domain data, and the SVM algorithm and KNN algorithm were optimized using the particle swarm optimization algorithm (PSO) and the ant colony optimization algorithm (ACO), respectively, to improve the robustness of the system. The K-fold cross-validation method was used to construct the model to improve the adaptability of the model. It could be clearly seen that the novel hybrid PCA-ACO-SVM model had superior prediction performance. Finally, this work proposed a novel, convenient, nondestructive, online, safe and highly accurate method for measuring the radiation performance of thermal barrier coatings, which could be used for the judgment of the service life of thermal barrier coatings.

Study on the Optimization of the Preparation Process of ZM5 Magnesium Alloy Micro-Arc Oxidation Hard Ceramic Coatings and Coatings Properties

Hard ceramic coatings were successfully prepared on the surface of ZM5 magnesium alloy by micro-arc oxidation (MAO) technology in silicate and aluminate electrolytes, respectively. The optimization of hard ceramic coatings prepared in these electrolyte systems was investigated through an orthogonal experimental design. The microstructure, elemental composition, phase composition, and tribological properties of the coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and tribological testing equipment. The results show that the growth of the hard ceramic coatings is significantly influenced by the different electrolyte systems. Coatings prepared from both systems have shown good wear resistance, with the aluminate electrolyte system being superior to the silicate system in performance. The optimized formulation for the silicate electrolyte solution has been determined to be sodium silicate at 8 g/L, sodium dihydrogen phosphate at 0.2 g/L, sodium tetraborate at 2 g/L, and potassium hydroxide at 1 g/L. The optimized formulation for the aluminate electrolyte solution consists of sodium aluminate at 5 g/L, sodium fluoride at 3 g/L, sodium citrate at 3 g/L, and sodium hydroxide at 0.5 g/L.

Optical properties of germania and titania at 1064 nm and at 1550 nm

One of the main noise sources in current gravitational-wave detectors is the thermal noise of the high-reflectivity coatings on the main interferometer optics. Coating thermal noise is dominated by the mechanical loss of the high-refractive index material within the coating stacks, Ta2O5 mixed with TiO2 . For upgrades to room-temperature detectors, a mixture of GeO2 and TiO2 is an interesting alternative candidate coating material. While the rather low refractive index of GeO2 increases with increasing TiO2 content, a higher TiO2 content results in a lower threshold temperature before heat treatment leads to crystallisation, and potentially to a degradation of optical properties. For future cryogenic detectors, on the other hand, a higher TiO2 content is beneficial as the TiO2 suppresses the low-temperature mechanical loss peak of GeO2. In this paper, we present the optical properties of coatings—produced by plasma-assisted ion-beam evaporation—with high TiO2 content at 1550 nm, a laser wavelength considered for cryogenic gravitational-wave detectors, as a function of heat-treatment temperature. For comparison, the absorption of pure GeO2 was also measured. Furthermore, results at the currently-used wavelength of 1064 nm are presented.

Reinterpretation of Salodik Group Performance Based on Facies and Diagenesis Approaches to Classify Reservoir Quality

An integrated study of several methods to characterize a carbonate reservoir provides a comprehensive result on carbonate facies and diagenesis. Therefore, a study on the Tertiary carbonate reservoir at the East Arm of Sulawesi area, Banggai – Sula Basin, is intended to determine the Salodik Group carbonate reservoir facies and diagenesis. Moreover, the purpose of this study is to determine the intensity and implication of syn-depositional or post-depositional processes, and to provide the reservoir final properties values, such as porosity and permeability to classify the reservoir quality. The methods of the study are based on carbonate fieldwork mapping to obtain samples on distributed traverses. Further analyses are the laboratory works to determine facies and diagenesis features on a more detailed scale. This study shows several facies, dominantly classified into reefal packstone, planktonic foraminifera packstone-wackestone, large foram packstone-mudstone, skeletal packstone-wackestone, planktonic-large foraminifera packstone-wackestone, and large foraminifera-red algae packstone. The dominant diagenesis processes are cementation and dissolution. Moreover, meteoric vadose and meteoric phreatic are predominantly the main diagenesis environment of Salodik Group formations. Furthermore, the dominant diagenesis stage is Eogenetic. The post-depositional process or the diagenetic processes, provides a more significant impact on carbonate reservoir properties than the syn-depositional process as shown on lithofacies texture. However, in general, from the younger to the oldest formation of Salodik Group, this shows a decreasing trend of reservoir properties due to the dominantcementation process in the oldest formation. Overall, the reservoir quality referring to porosity value is classified as negligible to excellent. While, based on permeability data, it is classified as the tight to good reservoir.

Zwitterionic Hydrogel Coating with Antisediment Properties for Marine Antifouling Applications.

Biofouling is a serious issue affecting the marine industry because the attached micro- and macrocontaminants can increase fuel consumption and damage ship hulls. A hydrophilic hydrogel-based coating is considered a promising antifouling material because it is environmentally friendly and the dense hydration layer can protect the substrate from microbial attachment. However, sediment adsorption can be an issue for hydrogel-based coatings. Their natural soft and porous structures can trap sediment from the marine environment and weaken the antifouling capability. There is still little research on the antisediment properties of hydrogels, and none of them deal with this problem. Here, we report on optimizing zwitterionic hydrogel-based coatings to improve their antisediment properties and achieve comparable performance to commercial biocidal coatings, which are the gold standard in the antifouling coating area. After 1 week of sediment contamination and 2 weeks of diatom coculturing, this optimized zwitterionic hydrogel coating maintained its antifouling properties with a few diatoms on the surface. Its large-scale samples also achieved antifouling performance similar to that of biocidal coatings in the Atlantic Ocean for 1.5 months. More importantly, our research provides a universal strategy to improve the antisediment properties of soft hydrogel-based coatings. For the first time, we report that the introduction of interfacial electrostatic interactions enhanced the antisediment properties of hydrogels.

Preventing columnar grains growth during hybrid wire arc additive manufacturing of austenitic stainless steel 316L

AbstractWire arc additive manufacturing (WAAM) is an efficient technique for producing medium to large‐size components, due to its accessibility and sustainability in fabricating large‐scale parts with high deposition rates, employing low‐cost and simple equipment, and achieving high material efficiency. Consequently, WAAM has garnered attention across various industrial sectors and experienced significant growth, particularly over the last decade, as it addresses and mitigates challenges within production markets. One of the primary limitations of WAAM is its thermal history during the process, which directly influences grain formation and microstructure heterogeneity in the resulting part. Understanding the thermal cycle of the WAAM process is thus crucial for process improvement. Typically, fabricating a part using WAAM results in a microstructure with three distinct zones along the build direction: an upper zone (thin surface layer) with fine grains, a middle zone dominated by undesirably long and large columnar grains covering more than 90% of the produced part, and a lower zone with smaller to intermediate columnar grains closer to the substrate material. These zones arise from variations in cooling rates, with the middle zone exhibiting the lowest cooling rate due to 2D conduction heat transfer. Consequently, producing a component with a microstructure comprising three different zones, with a high fraction of large and long columnar grains, significantly impacts the final mechanical properties. Therefore, controlling the size and formation of these grain zones plays a key role in improving WAAM. The aim of this work is to investigate the formation of undesired columnar grains in austenitic stainless steel 316L during WAAM and propose a simple hybrid technique by combining WAAM with a hot forging process (with or without interlayer cooling time). This approach targets the disruption of the solidification pattern of columnar grain growth during deposition progression and aims to enhance the microstructure of WAAM components.

Correlative In Situ Spectro-Microscopy of Supported Single CuO Nanoparticles: Unveiling the Relationships between Morphology and Chemical State during Thermal Reduction.

The activity, selectivity, and lifetime of nanocatalysts critically depend on parameters such as their morphology, support, chemical composition, and oxidation state. Thus, correlating these parameters with their final catalytic properties is essential. However, heterogeneity across nanoparticles (NPs) is generally expected. Moreover, their nature can also change during catalytic reactions. Therefore, investigating these catalysts in situ at the single-particle level provides insights into how these tunable parameters affect their efficiency. To unravel this question, we applied spectro-microscopy to investigate the thermal reduction of SiO2-supported copper oxide NPs in ultrahigh vacuum. Copper was selected since its oxidation state and morphological transformations strongly impact the product selectivity of many catalytic reactions. Here, the evolution of the NPs' chemical state was monitored in situ during annealing and correlated with their morphology in situ. A reaction front was observed during the reduction of CuO to Cu2O. From the temperature dependence of this front, the activation energy was extracted. Two parameters were found to strongly influence the NP reduction: the initial nanoparticle size and the chemical state of the SiO2. substrate. The CuOx reduction was found to be completed first on smaller NPs and was also favored over partially reduced SiOx regions that resulted from X-ray beam irradiation. This methodology with single-particle level spectro-microscopy resolution provides a way of isolating the influence of diverse morphologic, electronic, and chemical influences on a chemical reaction. The knowledge gained is crucial for the future design of more complex multimetallic catalytic systems.

Development of Diffraction Research Methodologies for Mediloy S-CO Alloy Speciments Made Using LPBF Additive Manufacturing

Abstract This study focuses on the application and improvement of diffraction measurement methodologies for the optimization of manufacturing parameters of CoCr alloy components made by additive manufacturing (AM) – particularly for Mediloy S-Co alloy specimens made using Laser Powder Bed Fusion (LPBF) additive manufacturing. We measured the phase composition of specimens obtained in AM processes, the measurement of residual stresses resulting from the manufacture of these printed parts, as well as the effectiveness of stress relaxation through the use of heat treatments dedicated to this type of material. Findings reveal several insights into how printing strategies affect the porosity and residual stresses in additive manufacturing. Specimens with higher porosity, particularly those created using specific strategies that resulted in lower energy densities, exhibited lower residual stresses. Notably, printing direction and energy density were found to significantly affect the mechanical stresses within the specimens, with directional choices playing a critical role in the final properties of the parts. Additionally, our findings underscore the complex relationship between various printing parameters and the development of mechanical stresses, highlighting the impact of adjustments in printing strategy on the properties of printed components.

Mechanical recycling of poly(lactic acid)/agave fiber biocomposites

This paper focuses on evaluating the mechanical recycling potential of poly(lactic acid) (PLA) biocomposites reinforced with agave fibers (AF). The biocomposites were prepared by extrusion using 5, 15, and 30 wt.% of agave fibers and reprocessed up to eight times. The results show that the fiber dimensions substantially decrease during reprocessing, especially after the first extrusion cycle, followed by a more gradual decrease in each subsequent cycle. The melt flow index (MFI) and the mechanical properties (except impact strength) tend to decrease as the fiber concentration increases. On the other hand, the glass transition temperature ( T g) and the crystallinity ( X c) of the biocomposites increased with increasing fiber concentration. It is important to highlight that closed-loop reprocessing does not significantly affect the overall behavior of the biocomposites under the conditions investigated. Therefore, PLA reinforced with AF is suitable for primary recycling since the final properties are mainly influenced by the fiber concentration and less by the number of reprocessing cycles.

Temperature distribution analysis and mechanical property prediction of wire loops in the Stelmor air-cooling system

During the Stelmor air-cooling process, the temperature distribution has a significant impact on the wire loops' final mechanical properties. The temperature distribution during air-cooling process is accurately solved by establishing three-dimensional model and Computational Fluid Dynamics (CFD) simulation. It is also found that the heat transfer coefficient on the cross section of the wire loop is very different, with a difference of 70–100 Wm−2K−1. The average value of the surface heat transfer coefficient of the wire loops section is used to replace the surface heat transfer coefficient of the wire loops, which improves the temperature distribution calculation accuracy, which is not considered by previous scholars. The finite difference method is used to calculate the mathematical model of the temperature distribution during the Stelmor air-cooling process. It is found that the maximum temperature difference of the wire during the cooling process is 90–110 K. The prediction model of mechanical property of wire after air-cooling was established, and distribution of mechanical property of the wire loops was obtained, and the reason for the uneven distribution of mechanical property of the wire loops was found.

Tailoring structure, morphology, and tribo-mechanical properties of HiPIMS-deposited CrxNy coatings for enhanced performance in wear and corrosion protection

During reactive sputtering of CrxNy, precise regulation of nitrogen gas is crucial to control the properties of the deposited coating. In the present work, we investigate the influence of nitrogen content on CrxNy characteristics, including morphology, crystalline structure, hardness, corrosion protection, and wear protection performances. Our findings reveal that the hexagonal Cr2N coatings, although slightly lower in hardness (19 GPa) compared to stoichiometric CrN, exhibit superior corrosion resistance with a protection efficiency of 82%, and a reduced sliding wear behavior at 1.35E-09 mm3/N/m. Conversely, stoichiometric CrN shows the highest hardness at 22.8 GPa. Using high-power impulsed magnetron sputtering as a deposition technique, we were able to design CrxNy protective coatings with desired microstructure and phase composition, enabling the production of performance-tailored CrxNy coatings suitable for a diverse range of applications.

Optimization of the extrusion rate for different layer thicknesses to achieve controlled mechanical properties in MEX 3D printing of low-alloy steel

Composite extrusion modeling is an advanced material extrusion additive manufacturing process that requires fine-tuning of printing parameters for printing injection molding feedstocks. In order to achieve comparable high-quality parts at different layer thicknesses, the parameters must be optimized for the respective layer thicknesses. In this work, the printing parameters for AISI 8740 low-alloy steel injection molding material are optimized for four different layer thicknesses. The extrusion multiplier values for each layer thickness are tuned, allowing fine adjustment of the printer's screw rotation speed at every layer thickness, resulting in all final parts' maximum densities (≥ 98 %) with high accuracies. Scanning electron microscope images, surface roughness measurements, and printing precision tests proved the good and comparable high-quality of all optimized printed parts. Young's modulus, tensile and yield strengths also raised by ∼24 %, ∼16 % and ∼15 %, respectively, compared to the non-optimized printed sintered part. The achieved tensile strength range of (∼888–947) MPa and yield strength range of (∼574–586) MPa of all optimized printed sintered parts were also higher than those provided by the feedstock manufacturer. This promising approach significantly reduces printing time and manufacturing costs without compromising the printed final parts' quality and mechanical properties. The adjusting screw rotation speed methodology allows broader applicability across diverse material extrusion processes.

Effect of B addition on the microstructure and tribological properties of laser cladding FeCoCrNiCu composite coatings

The high-entropy alloy coatings of FeCoCrNiCuBx (x = 0, 0.1, 0.3, 0.5, x values are molar ratios) were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, and surface energy of the FeCoCrNiCuBx coatings were investigated, and the tribological property and wear mechanism of the composite coatings at room temperature (RT) and 600 ℃(HT) were analyzed. The FeCoCrNiCu coating consists of a single FCC-type solid solution. When x = 0.3, 0.5, the composite coatings appear the Cr2B phase. The x = 0.5 (B5) coating has the lowest surface energy (27.45mN/m), which is one of the reasons it has excellent tribological properties. The tribological properties of FeCoCrNiCuBx composite coatings were improved at both RT and HT. The B5 coating has excellent tribology at both RT and HT. At RT, the wear resistance of the B5 coating (wear rate is 8.54 ×10−5 mm3/N∙m, coefficient of friction (COF) is 0.51) was improved by 54.79%, 50.89%, and 12.86% compared with x = 0(HEA), x = 0.1(B1), and x = 0.3(B3), respectively, the COF reduced by 42.69%, 41.39%, 22.73%. At HT the wear resistance of the B5 coating (wear rate is 6.69 ×10−5 mm3/N∙m, COF is 0.24) was increased by 71.53%, 52.91%, and 49.42% compared to HEA, B1, and B3, respectively, the COF reduced by 29.41%, 25.00%, 17.24%. The wear mechanisms of coatings that add B element at RT are abrasive wear and fatigue wear, and at HT are mainly oxidative wear, moderate abrasive wear and fatigue wear.B2O3 melts at HT to form a low-viscosity liquid that forms a lubricating film that isolates the contact surfaces and reduces direct contact and adhesion. This is the main reason for the excellent friction properties of B5 coating at HT.

Glucono-Delta-Lactone-Induced Alginate Gelation: New Insights into the Effect of the Cross-Linker Carrier Type on the Hydrogel Mechanics.

Physical alginate hydrogels commonly rely on "internal gelation" to introduce the cross-linker, e.g., calcium (Ca(II)) ions. These are released in a homogeneous manner by using a pH-sensitive Ca(II) carrier and glucono-delta-lactone (GDL) as the acidifier. Yet, it remains unclear how the carrier of the cross-linker affects the gelation process and final hydrogel properties. We therefore investigate two internal gelation methods using either Ca(II)-chelating ligand complexes or insoluble Ca(II)-based salts. Ionometry coupled with pH measurements reveals the release process of Ca(II) ions upon acidification, which is well described by simulations using the Hyperquad Simulation and Speciation program. We show that these findings correlate well with the evolution of the mechanical properties of the hydrogels. Although the two pH-triggered gelation methods appear to be similar, we demonstrate their differences in terms of the gelation kinetics and final cross-link density. The nature of the ligand or the salt significantly affects the fraction of the released Ca(II) ions and, hence, the mechanical properties of the final hydrogel for a given GDL concentration. Furthermore, for the first time, we demonstrate the competition between GDL and alginate in binding with Ca(II) ions. This study therefore provides different tools for the efficient formulation of alginate hydrogels.

Tailoring electroless Ni-W-P polyalloy coatings: Unveiling the synergistic impact of cerium addition and annealing on surface functional properties

Electroless deposition of Ni-based coatings is a cost-effective solution to augment the surface mechanical and electrochemical properties of engineering components. This work explores the influence of addition of rare-earth element Ce on the characteristics of Ni-W-P coatings. The concentration of Ce salt in the deposition bath was varied in the range 0–14 mg/L, and the highest deposition rate was for the solution with 8 mg/L Ce. A homogeneous distribution of Ce over the coated surfaces was observed, and the share of Ce in the composition of the deposition varied monotonically with the Ce concentration in solution. Further, the coating surface compositions also depended on the Ce-content. Coating obtained using 8 mg/L Ce was found to have significantly improved scratch hardness (8.49 GPa), fracture toughness (7.05 MPa.m1/2), specific wear rate (3.1 × 10−6 mm3/N.m) and corrosion protection efficiency (94.16 %) as compared to the coating without Ce (3.87 GPa, 3.39 MPa.m1/2, 9.03 × 10−6 mm3/N.m, and 45.44 %, respectively). Interestingly, the ability of the coating to inhibit biofilm formation on the surface initially increased with increasing Ce content, but this effect also diminished above 8 mg/L Ce. Additionally, annealing the coatings caused further alterations in the microstructures, resulting in improvement in the microhardness, scratch, wear, and biocorrosion resistance, but at the cost of compromised corrosion resistance. Properties of such annealed coatings also depended on the annealing temperature. Therefore, this study indicates that a wide spectrum of combinations of surface physical, mechanical, and electrochemical properties can be achieved by controlling only two processing conditions, i.e., the Ce concentration, and the annealing temperature.

SYNTHESIS OF COPOLYMERS FOR PROTECTIVE COATINGS

Copolymers were obtained in this work and the methodology for their synthesis was worked out. Various fillers were selected for the polymer coating. Resulting copolymers have good adhesion required for composite protective coatings. An experiment was conducted to determine the corrosion resistance of metals coated with copolymers when exposed to aggressive environments, as well as to determine the hardness and thickness of the polymer coatings obtained. It was found that the polymer coating filled with bronze powder, despite the small thickness of 43.4 μm, hasthe best adhesion and corrosion properties, as well as having the highest hardness values of 80.5 HB. Such physical and mechanical properties of polymer coatings allow them to be used as protective coatings for metal products working under the influence of aggressive media.

Effect of hydrophobic modification of chitin nanocrystals on role as anti-nucleator in the crystallization of poly(ε-caprolactone)/polylactide blend

Biodegradable polymer blends filled with rod-like polysaccharide nanocrystals have attracted much attention because each component in this type of ternary composites is biodegradable, and the final properties are more easily tailored comparing to those of binary composites. In this work, chitin nanocrystals (ChNCs) were used as nanofiller for the biodegradable poly(ε-caprolactone) (PCL)/polylactide (PLA) immiscible blend to prepare ternary composites for a crystallization study. The results revealed that the crystallization behavior of PCL/PLA blend matrices strongly depended on the surface properties of ChNCs. Non-modified ChNCs and modified ChNCs played completely different roles during crystallization of the ternary systems: the former was inert filler, while the latter acted as anti-nucleator to the PCL phase. This alteration was resulted from the improved ChNC-PCL affinity after modification of ChNCs, which was due to the ‘interfacial dilution effect’ and the preferential dispersion of ChNCs. This work presents a unique perspective on the nucleation role of ChNCs in the crystallization of immiscible PCL/PLA blends, and opens up a new application scenario for ChNCs as anti-nucleator.

Effect of Acrylic Resin on the Protection Performance of Epoxy Coating for Magnesium Alloy

The low toughness of epoxy resin can influence its shielding performance against a corrosive medium and strength of adhesion to metal surfaces. Extensive efforts have been made to modify epoxy resin. In this research, acrylic resin was synthesized by the solution method, and 1 wt.%, 2.5 wt.%, and 5 wt.% were added to epoxy resin (E44 brand) to prepare coatings on the surface of AZ31B magnesium alloy. The effects of acrylic resin on the mechanical and protective properties of epoxy coatings were investigated via experiments measuring impact resistance, flexibility, and adhesion as well as the electrochemical impedance technique. Compared with the pure epoxy coating, the adhesion between the coating and the substrate increases by 1.37 MPa after the addition of 2.5 wt.% acrylic resin. Meanwhile, the pencil hardness has a slight change from 5B to 6B, and the flexibility significantly improves. Therefore, the epoxy coating exhibits enhanced anticorrosive properties after the addition of 2.5 wt.% acrylic resin.

Characteristics of mountain vs. lowland dairy products

SummaryBesides the clean environment, mountain pastures are important sources of bioactive compounds that contribute to the quality of dairy products resulting from animals grazing there. This review aimed to compare the main differences among mountain and lowland dairies in terms of chemical composition, physical and sensory properties and microflora. The most important factors influencing final product properties are the biodiversity of pastures and the abundance of plants in terpenes and fatty acids, farm practices, animal breeds and climatic conditions. Differences between dairies from lowland and mountain products were observed regarding the sensory profile, microflora and nutritional and functional value. The comparisons of the results presented in the literature concluded that some mountain dairies presented more than 50% higher content of terpenes compared to lowland products. Furthermore, the amounts of polyunsaturated fatty acids (PUFA) were more than 15% greater in mountain products compared to lowland ones, conjugated linoleic acids more than 35%, n−6 and n−3 PUFA more than 10%, while the saturated fatty acids content was reported to be more than 3% lower in mountain dairies. In conclusion, mountain dairy products can be distinguished from lowland ones, especially by their content of terpenes and fatty acid profile, along with the microflora which are influenced by livestock management.

Preparation and self-lubricity investigation of CNTs/Ni composite coatings under severe conditions

Carbon nanotubes (CNTs) demonstrate the potential to improve the tribological properties of nanocomposite coatings. Herein, CNTs/Ni composite coatings were quickly fabricated by the direct current (DC) electrodeposition. The adhesion strength was estimated by the scratch test incorporation with an acoustic emissive signal. Much attention was paid on the self-lubricity of the CNTs/Ni composite coating under severe conditions. Results indicated that presence of CNTs enhanced the adhesion strength of the pure Ni coating. Notably, CNTs contributed towards 54.5 % of friction reduction in comparison to the pure Ni coating at dry friction. The improvement of tribological properties was attributed to that under high contact stress the embedded CNTs were crushed to tiny lubricating particles and produced protective film on rubbing surfaces.