Tribological properties of nanostructured Al_2O_3-40%TiO_2 multiphase ceramic particles reinforced Ni-based alloy composite coatings

The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.

CeO_2/Zn NANOCOMPOSITE COATING BY ELECTRODEPOSITION

The nanocomposite coating is obtained by electrochemical deposition of the zinc plating solution with ceria nanoparticles (mean diameter 30 nm). The effect of ceria nanoparticles on the electrodeposited zinc coating is stu died by weight loss test, inductively copuled plasma quantometer (ICP), scanning electron microscopy (SEM) and X ray diffraction (XRD), respectively. It is found that under the same electrodeposition conditions, the corrosion resistance of the nanocomposite coating increases obviously while that of the micron composite coating only improves slightly; The ceria content of the nanocomposite coating is more than that of the micron composite coating. Ceria nanoparticles modify the surface morphology and crystal structure of the zinc matrix in correlation with the increase of corrosion resistance.

Preparation and oxidation behaviour of electrodeposited Ni-CeO_2 nanocomposite coatings

Ni-CeO2 nanocomposite coatings with different CeO2 contents were prepared by codeposition of Ni and CeO2 nanoparticles with an average particle size of 7 nm onto pure Ni surfaces from a nickel sulfate. The CeO2 nanoparticles were dispersed in the electrodeposited nanocrystalline Ni grains （with a size range of 10-30 nm）. The isothermal oxidation behaviours of Ni-CeO2 nanocomposite coatings with two different CeO2 particles contents and the electrodeposited pure Ni coating were comparatively investigated in order to elucidate the effect of CeO2 at different temperatures and also CeO2 contents on the oxidation behaviour of Ni-CeO2 nanocomposite coatings. The results show that the as-codeposited Ni-CeO2 nanocomposite coatings have a superior oxidation resistance compared with the electrodeposited pure Ni coating at 800 °C due to the codeposited CeO2 nanoparticles blocking the outward diffusion of nickel along the grain boundaries. However, the effects of CeO2 particles on the oxidation resistance significantly decrease at 1050 °C and 1150 °C due to the outward-volume diffusion of nickel controlling the oxidation growth mechanism, and the content of CeO2 has little influence on the oxidation.

A brand new green coating technology for realizing the regulation of spherical propellant energy release process

To achieve the controllable release of energy of nitrocellulose-based propellants,this paper combines the cellulose-based nanocomposites aqueous coating(Surelease®-NC)with fluidized bed coating equipment to successfully prepare the coated spherical propellant for the first time.The effects of fluidized bed coating temperature,air velocity,flow speed and atomization pressure on the adhesion rate,coating integrity and coating uniformity of the coated spherical propellant were investigated,and the preparation of coated spherical propellant with homogeneous size and structural integrity was achieved for the first time.The microscopic morphology,chemical structure,water vapor adsorption behavior,combustion performance,and ageing resistance property of the coated spherical propellant were systematically investigated by,Fourier transforms infrared spectroscopy(FTIR),Micro confocal raman spectrometer,field scanning electron microscopy(SEM),dynamic vapor adsorption techniques,and closed bomb test,confirming the surface core-shell structure and the tightly bonded interfacial structure of coated spherical propellant.Meanwhile,the coated spherical propellant has good hygroscopic,excellent progressive burning and long storage stability.

CeO2/Zn NANOCOMPOSITE COATING BY ELECTRODEPOSITION

The nanocomposite coating is obtained by electrochemical deposition of the zinc plating solution with ceria nanoparticles (mean diameter 30 nm). The effect of ceria nanoparticles on the electrodeposited zinc coating is stu died by weight loss test, inductively copuled plasma quantometer (ICP), scanning electron microscopy (SEM) and X ray diffraction (XRD), respectively. It is found that under the same electrodeposition conditions, the corrosion resistance of the nanocomposite coating increases obviously while that of the micron composite coating only improves slightly; The ceria content of the nanocomposite coating is more than that of the micron composite coating. Ceria nanoparticles modify the surface morphology and crystal structure of the zinc matrix in correlation with the increase of corrosion resistance.

Crystalline texture evolution, control of the tribocorrosion behavior, and significant enhancement of the abrasion properties of a Ni-P nanocomposite coating enhanced by zirconia nanoparticles

This paper describes an investigation of the effect of ZrO2 nanoparticles on the abrasive properties,crystalline texture developments,and tribocorrosion behavior of Ni-P nanostructured coatings.In the investigation,Ni-P and Ni-P-ZrO2 nanostructured coatings are deposited on St52 steel via the electroless method.Transmission electron microscopy(TEM),field emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),cyclic-static polarization tests in 3.5wt%NaCl solution,the tribocorrosion test(by back-and-forth wear in electrochemical cell),and the microhardness test using the Vickers method were performed to characterize and analyze the deposited coatings.The results of this study showed that the addition of ZrO2 nanoparticles to the Ni-P electroless bath produced the following:a sharp increase in wear and hardness resistance,the change of the wear mechanism from sheet to adhesive mode,the reduction of pitting corrosion resistance,significant reduction in the tribocorrosion protective properties,change in the preferred orientation of the crystalline texture coating from(111)to(200),increase in the sedimentation rate during the deposit process,and a sharp increase in the thickness of the Ni-P nanostructured coatings.

Amorphous Co-B/Al nanocomposites prepared by electroless coating technique and their excellent catalytic activity

To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum （Co-B/M） nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of ammonium perchlorate （AP） and AP-based solid state propellants. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, inductive coupled plasma emission spectrometry （ICP）, differential scanning calorimetry （DSC） as well as strand burner method were employed to characterize the crystal phase, morphologies, chemical composition, and catalytic activity of the as-synthesized material. The results show that a continuous layer of about 100 nm amorphous Co72.6B27.4 covers the surfaces of M particles. Addition of the as-synthesized Co-B/A1 nanocomposites as catalysts promotes AP decomposition, enhances the burning rate, and lowers the pressure exponent of the AP-based propellants considerably.

Fluidized bed coating efficiency and morphology of coatings for producing Al-based nanocomposite hollow spheres

Abstract： We performed fluidized bed coating ofAl-based nanoeomposite powder-binder suspensions onto polymer substrates. The effects of the type and amount of the binder and nanoparticle additive on the coating process efficiency and coating characteristics were investigated. The efficiency decreased from 52% to 49% as the processing time increased from 15 to 20 min. However, the amount and thickness of the coating also increased as the processing time and amount of the binder were increased. The addition of nanoparticles to the system decreased the thickness of the coating from 222 to 207 μm when polyvinyl alcohol （PVA） was used as a binder. The suspension containing 3wt% R-4410 binder exhibited the greatest efficiency of 60%.

Improvement of wear and corrosion resistance of AZ91 magnesium alloy by applying Ni-SiC nanocomposite coating via pulse electrodeposition

To improve the surface properties of AZ91 magnesium alloy, Ni-SiC nanocomposite coatings with various SiC contents were pulse electrodeposited in modified Watts baths containing SiC nano-particles with the concentration of 0-15 g/L. The morphology of the coatings was studied by scanning electron microscope （SEM）. The SiC content of the coatings was measured by energy dispersive spectroscopy （EDS） analyzer. Microhardness measurement of the coatings showed up to 600% enhancement for the sample produced from the bath with 15 g/L SiC. The corrosion behavior of the coated AZ91 alloy was investigated by potentiodynamic polarization method. The results reveal a significant improvement in the corrosion resistance, that is, the corrosion current density decreases from 0.13 mA/cm2 for uncoated specimen to 1.74x10-6 mA/cm2 for the sample coated from the bath containing 15 g/L SiC and the corrosion potential increases from -1.6 V for uncoated specimen to -0.31 V for the sample coated from the bath. The wear resistance of both coated and uncoated samples was evaluated by pin-on-disc tribotester. The results show that the wear volume loss of coated sample is 8 times less than the bare alloy.

Characterization of NbSi_2–Al_2O_3 nanocomposite coatings prepared with plasma spraying mechanically alloyed powders

The present study characterized NbSi2-Al2O3 nanocomposite powders plasma-sprayed on Ti-6Al-4Vsubstrates. The powders were agglomerated to obtain suitable particle sizes for spraying. The agglomerated powders were then plasma-sprayed using atmospheric plasma spraying. The structural transformations of the powders along with the morphological and mechanical changes of the coatings were examined by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and hard- ness testing. The results showed that after plasma spraying, the grain size increased, and the lattice strain decreased. However, the grain size of this compound after spraying was still in the nanometer range. The coating was uniform and exhibited good adhesion to the substrate. The microhardness and fracture toughness of the nanocomposite coating were higher than those of a nanostructured NbSi2 coating.

Fabrication of in-situ synthesized ceramic reinforced Ni-based alloy composite coatings by reactive braze coating processing

In-situ synthesized ceramic such as TiC,Cr7C3 and Cr5B3 reinforced Ni-based alloy composite coating was fabricated on the surface of mild steel substrate by reactive braze coating processing with colloidal graphite,Cr,Ni,ferro-boron,Si and titanium powders as the raw materials at low temperature of 1000℃,and a new kind of coating materials was developed.By means of SEM,EDS,XRD and surface hardness tester,the microstructures,phases,hardness and wear-resistance of the coating were analyzed,respectively.The results revealed that the coating was mainly composed of the ceramic in-situ synthesized reinforcement phases of TiC,Cr7C3 and Cr5B3 and the binder phases in-situ synthesized of Ni31Si12 and(Ni,Fe)solid solution;The ceramic reinforcement phases of TiC,Cr7C3 and Cr5B3 were randomly distributed in the binder phases of Ni31Si12 and(Ni,Fe)solid solution;The coating had about 15vol%pores and can possibly be applied as a self-lubrication coating;The coating and the substrate were integrated together by metallurgical bonding;The coating had a hardness up to 91-94HR15N.

Effect of WO3 Nanoparticle Loading on the Microstructural, Mechanical and Corrosion Resistance of Zn Matrix/TiO2-WO3 Nanocomposite Coatings for Marine Application

In this study, for marine application purposes, we evaluated the effect of process parameter and particle loading on the microstructure, mechanical reinforcement and corrosion resistance properties of a Zn-TiO2-WO3 nanocomposite produced via electrodeposition. We characterized the morphological properties of the composite coatings with a Scanning Electron Microscope （SEM） equipped with an Energy Dispersive Spectrometer （EDS）. We carried out mechanical examination using a Dura Scan hardness tester and a CERT UMT-2 multi-functional tribological tester. We evaluated the corrosion properties by linear polarization in 3.5% NaCl. The results show that the coatings exhibited good stability and the quantitative particle loading greatly enhanced the structural and morphological properties, hardness behavior and corrosion resistance of the coatings. We observed the precipitation of this alloy on steel is greatly influenced by the composite characteristics.

Effect of cathode composition on microstructure and tribological properties of TiBN nanocomposite multilayer coating synthesized by plasma immersion ion implantation and deposition

Nanocomposite multilayer TiBN coatings were prepared on Si(100) and 9Cr18Mo substrates using TiBN composite cathode plasma immersion ion implantation and deposition technique(PIIID). Synthesis of TiBN composite cathodes was conducted by powder metallurgy technology and the content of hexagonal boron nitride(h-BN) was changed from 8% to 40%(mass fraction). The as-deposited coatings were characterized by energy dispersive spectrometer(EDS), grazing incidence X-ray diffraction(GIXRD), Fourier Transform Infrared Spectroscopy(FTIR) and high resolution transmission electron microcopy(HRTEM). EDS results show that the B content of the coatings was varied from 3.71% to 13.84%(molar fraction) when the composition of the h-BN in the composited cathodes was changed from 8 % to 40%(mass fraction). GIXRD results reveal that the TiBN coatings with a B content of 8% has the main diffraction peak of TiN(200),(220) and(311), and these peaks disappear when the B content is increased. FTIR analysis of the multilayer coatings showed the presence of h-BN in all coatings. TEM images reveal that all coatings have the characteristics of self-forming nanocomposite multilayers, where the nanocomposites are composed of face-centered cubic Ti N or h-BN nanocrystalline embedded in amorphous matrix. The tribological tests reveal that the Ti BN coatings exhibit a marked decrease of coefficient at room temperature(~0.25). The improved properties were found to be derived from the comprehensiveness of the self-forming multilayers structure and the h-BN solid lubrication effects in the coatings.

EFFECT OF SURFACTANTS ON Ni-TiN NANOCOMPOSITE COATINGS PREPARED BY ULTRASONIC ELECTRODEPOSlTION

Ni-TiN nanocomposite coatings were prepared by ultrasonic electrodeposition, and the effects of the surfactants on the coatings were investigated and the microstructure and micro rigidity of the coatings were characterized. Samples were also submitted to corrosion tests in 3% NaCl solution. The results showed that the surfactants had great effects on Ni-TiN nanocomposite coatings. The composite coatings prepared by ultrasonic electrodeposition with the surfactants were better than that of the coatings prepared without surfactants. The favorable properties of Ni-TiN nanocomposite coatings were prepared with the mixing of the non-ion and positive ion surfactants. The concentration of the mixing was 80 mg/L, and the ratio of the non-ion and positive ion surfactants was 1： 2.

Fabrication and wear properties of co-deposited Ni-Cr nanocomposite coatings

Ni-Cr nanocomposite coatings with different Cr particles contents were developed by electrodeposition method from a nickel sulfate solution containing different concentrations of Cr nanoparticle with an average particle size of 40 nm. The characteristics of the coatings were assessed by scanning electron microscopy and microhardness test. The friction and wear performances of Ni-Cr nanocomposite coatings and pure Ni film were comparatively investigated, with the effect of the Cr content on the friction and wear behaviors to be emphasized. The results indicate the microhardness, friction and wear behaviors of Ni-Cr nanocomposite coatings are closely related with Cr particles content. The Ni-Cr nanocomposite coating with a lower Cr content of 4.0% shows somewhat increased microhardness and wear resistance than the pure Ni coating, while the Ni-Cr nanocomposite coating with a higher Cr content has much better wear resistance than the pure Ni coating. The effect of Cr nanoparticles on the microhardness and wear resistance was discussed.

Dependence of Microstructure and Hardness of Nanocomposite Coatings of nc-(Ti_(1-x)Al_(x)N)/a-Si_(3)N_(4) on Aluminum Contents

Super-hard nanocomposite coatings have been received a great attention during recent years. Based on our previous investigations onto the several super-hard nanocomposite coating systems including nc-TiN/a-Si3N4, nc-TiN/a-BN. This paper reports on the nc-(Ti1.xAlxN)/a-Si3N4 nanocomposite coatings prepared by direct current plasma enhanced chemical vapor deposition (PECVD). And the effect of aluminum contents on the microstructure and hardness of the coatings have been mainly investigated. The coatings were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive analysis of X-rays (EDX), and the hardness measurements were done by means of the automated load-depth sensing technique using Vickers diamond indenter. The thermal stability of nanocomposite coatings of TiN/a-Si3N4 was evaluated by annealing at elevated temperatures up to 1000°C. The results shows that super hardness of nc-(Ti|_xAlxN)/a-Si3N4 could be obtained with a wide aluminum content from 10at.% to 86at.% in (Ti^AlJN phase, while the silicon content can be kept at 4-5 at.%. These nanocomposite coatings shows a relatively better thermal stability of nanocrystallite size and therefore high hardness up to 1000°C, which further support our earlier concept for the design of super-hard nanocomposite coatings. These results are suggested mainly due to the formation of nanostructure, and this indicates that the aluminum has also the role of controlling the crystallite size within nc-(Ti1.xAlIN)/a-Si3N4 besides its known well property of the super anti-oxidation.

Sand-wear resistance of brush electroplated nanocomposite coating in oil and its application to remanufacturing

Sand-wear resistance of nano scale alumina particle reinforced nickel matrix composite coating （n-Al2O3/Ni） prepared by brush electroplating technique was investigated via wear tests in sand-contaminated oil lubricant, comparing with that of AISI1045 steel and brush electroplated Ni coating. Effects of testing load, sand content and sand size on worn volume of the three materials, and also coating surface roughness on worn volume of the brush electroplated coatings were accessed. Results show that the worn volume of all the three materials increases with increasing of testing load, sand content and sand size. In the same conditions, n-Al2O3/Ni composite coating has the smallest worn volume while AISI1045 steel has the largest because of the n-Al2O3 particle effects. As to n-Al2O3/Ni and Ni coatings, the surface-polished coatings have obviously lower worn volume than the as-plated coatings. The brush electroplated n-Al2O3/Ni composite coating was employed to remanufacture the sand-worn bearing seats of a heavy vehicle and good results were gained.

FABRICATION OF TRANSPARENT PU/ZrO_2 NANOCOMPOSITE COATINGS WITH HIGH REFRACTIVE INDEX

Transparent ZrO2-polyurethane nanocomposites with high refractive index were prepared by dispersing ZrO2 nanoparticles in a polyurethane matrix via ligand molecule engineering. TEM showed that the inorganic particles were well dispersed within the polymeric network with no significant macroscopic agglomeration. By controlling the phase separation it was possible to obtain transparent zirconia nanostructured coatings, characterized by improved mechanical and thermal properties. UV-Vis spectra indicated that the coatings still maintained transparency in the visible light. The refractive index of the UV-cured films depends linearly on the ZrO2 content and varies from 1.475 to 1.625 （20 wt%） at 633 nm. These coatings could find advanced applications in coatings of optical and electronic devices.

Superhard Nanocomposite Coatings

The recent development in the field of nanocomposite coatings with good mechanical properties is critically reviewed in this paper. The design principle and materials selection for the nanocomposite coatings are introduced. Different methods for the preparation of superhard nanocomposite coatings are described with emphasis on the magnetron sputtering. Based on recent theoretical and experimental results regarding the appearance of superhardness in nanocomposite coating, lattice parameter changes, crystallite size, microstructure and morphology are reviewed in detail. Also emphasized are the mechanical properties (especially on hardness) and the ways by which the properties are derived.

Improving Anti-frosting Performance for Super-hydrophobic Nanocomposite Coatings

New super-hydrophobic nanocomposite coatings were formed from modified nano-sized CaCO3 particles and polyacrylate at weight ratio of 9/1-8/2. SEM and XPS analysis indicated that such hydrophobicity could be attributed to the surface nano-microstructure and the surface enrichment of fluorine atoms. As the surface hydrophobicity increased, longer time was required for formation the initial frost, which makes super-hydrophobic coatings suitable for anti-frosting purpose.