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.

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%.

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.

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

在这研究，为海洋的申请目的，我们评估了在微观结构，机械加强和经由电极淀积生产的 Zn-TiO 2-WO3 nanocomposite 的腐蚀抵抗性质上装载的过程参数和粒子的效果。我们与与一个精力散分光计(版本) 装备的一台扫描电子显微镜(SEM ) 描绘了合成涂层的词法性质。我们用一个 Dura 扫描坚硬测试者和一件必然发生的事情执行了机械检查 UMT-2 多功能的 tribological 测试者。我们在 3.5% NaCl 由线性极化评估了腐蚀性质。结果证明涂层展出了好稳定性，极大地装载的量的粒子提高了结构、词法的性质，坚硬行为和涂层的腐蚀抵抗。我们观察到钢上的这合金的降水被合成特征极大地影响。

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.

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.

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.

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.

Structure and Performance of TiC-containing Diamond-like Carbon Nanocomposite Coatings Deposited by Rectangular Cathodic Arc Ion-plating

TiC-containing diamond-like carbon （TiC-DLC） nanocomposite coatings were deposited by a rectangular cathodic arc ion-plating system using C2H2 as reacting gas. Raman spectroscopy and transmission electron microscopy analysis show that with increasing flow rate of C2H2, the structure of nanocomposite coatings changes from TiC nanograin-containing to graphite nanograin-containing DLC. The harness measurements show that the hardness decreases from 28 GPa to 18 GPa with increasing C2H2 flow rate. The scratch test show that a high critical load （〉40 N） was obtained and exhibited a good adhesion between the coating and the substrate. Wear experiment shows that the friction coefficient of TiC-DLC nanocomposite coatings decreases with increasing C2H2. A low friction coefficient of 0.07 was obtained at 480 sccm C2H2.

Relationship between dispersibility of ZrO2 nanoparticles in Ni-ZrO2 electroplated nanocomposite coatings and mechanical properties of nanocomposite coatings

Ni-ZrO2 nanocomposite coatings with monodispersed ZrO2 nanoparticles were prepared from the composite plating bath containing dispersant under DC electrodeposition condition. It is found that the morphology, orientation and hardness of the composite coating with monodispersed ZrO2 nanoparticles have lots of difference from the composite coating with agglomerated ZrO2 nanoparticles and pure nickel coating. Especially, the result of hardness shows that only a very low volume fraction (less than 1%) of monodispered ZrO2 nanoparticles in Ni-ZrO2 composite coatings will result in higher hardness of the coating. The hardness of Ni-ZrO2 nanocomposite coatings with monodispersed and agglomerated ZrO2 nanoparticles are HV 529 and HV 393, respectively. The hardness value of the former composite coatings is over 1.3 times higher than that of the later. All these composite coatings are 2 - 3 times higher than that of pure nickel plating (HV 207) prepared under the same conditions.

Thermal Sprayed CNT Reinforced Nanocomposite Coatings – A Review

This review is done essentially to study results in the field of synthesis and characterization of Carbon Nanotubes (CNT’s) reinforced nanocomposite coatings using thermal sprayed coatings. CNT reinforced nanocomposite coatings produced by thermal spray process are being developed for a wide variety of applications, e.g. aerospace, automotive and sports equipment industries. It is anticipated that, if properly deposited, nanocomposite ceramic coatings could also provide improved properties like wear resistance and thermal barrier coatings. These results clearly demonstrate that the significant improvement in coating performance can be achieved by utilizing proper thermal sprayed nanocomposite coatings. Thermal sprayed nanocomposite coatings shows improvement of resistance to wear, erosion, corrosion and mechanical properties. The purpose of this paper is to review CNT reinforced nanocomposite coatings using thermal spray by various researchers.

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.

Mechanical assisted electroless barrel-plating Ni-P coatings on magnesium alloy

A mechanically assisted electroless barrel-plating Ni-P was carried out in a rolling drum containing Mg alloy specimens and ceramic balls, which was submerged in a bath containing electroless plating solution deposited by this novel technique have a It is demonstrated that the Ni-P coatings crystallized Ni-P solid solution structure, showing fine-grains, higher hardness, and higher corrosion resistance compared with the conventional electroless plated amorphous Ni-P coatings. After heat treatment at 400 ℃ for 1 h, the structure of such Ni-P coatings were transformed to a structure with Ni-Ni3P double phases, and cracks in these coatings could not be observed, whereas cracks appeared seriously in the conventional electroless plated Ni-P coating after same heat treatment. Therefore, both hardness and corrosion resistance of these Ni-P coatings can be improved further by heat treatment. All of these beneficial effects can be attributed to the role of mechanical attrition during the mechanically assisted electroless barrel-plating process.

High-temperature tribological properties of Ni-P alloy coatings deposited by electro-brush plating

High-temperature tribological properties of Ni-P alloy coatings processed by electro-brush plating on 20CrMo steel have been investigated. A baU-on-disc configuration was employed and 4 mm diameter Si3N4 balls were used as static counterpart. All the wear tests were carried out at 450℃ for 180 rain without lubricants. The electro-brush plating Ni-P coating is amorphous in as-deposited condition, and it becomes polycrystalline with the formation of Ni and Ni3P after heat treatment at 450℃for 1 h. The friction coefficient of the Ni-P coating is just 50% of that of the 20CrMo steel at the friction temperature of 450℃. A mild adhesive wear mechanism was found for the electro-brush plating Ni-P coating tested at 450℃, whereas for the 20CrMo steel at the same temperature a mixed adhesive and abrasive wear mechanism was observed.

Erosion and Toughening Mechanisms of Electroless Ni-P-Nano-NiTi Composite Coatings on API X100 Steel under Single Particle Impact

The addition of superelastic NiTi to electroless Ni-P coating has been found to toughen the otherwise brittle coatings in static loading conditions, though its effect on erosion behaviour has not yet been explored. In the present study, spherical WC-Co erodent particles were used in single particle impact testing of Ni-P-nano-NiTi composite coatings on API X100 steel substrates at two average velocities—35 m/s and 52 m/s. Erosion tests were performed at impact angles of 30°, 45°, 60°, and 90°. The effect of NiTi concentration in the coating was also examined. Through examination of the impact craters and material response at various impact conditions, it was found that the presence of superelastic NiTi in the brittle Ni-P matrix hindered the propagation of cracks and provided a barrier to crack growth. The following toughening mechanisms were identified: crack bridging and deflection, micro-cracking, and transformation toughening.

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.

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.

Quality of Electroless Ni-P (Nickel-Phosphorus) Coatings Applied in Oil Production Equipment with Salinity

The corrosion resistance of nickel-phosphorus (Ni-P) coatings and their mechanical properties in seawater have led inestigations into the development of new technologies and the replacement of some special alloys in equipment used in oil production, such as valves, tubing, sucker rod joints, pumps, riser, manifolds and subsea Christmas trees. These studies began with Brenner and Riddel who developed, in the 1940s, formulations for Ni-P deposition on carbon steel without using an electric current. Joint deposition of nickel and phosphorus on a metallic surface (carbon steel) without applying an external current is accomplished using cathodic reduction with hydrogen (H) from a reducing agent (sodium hypophosphite) and nickel salts. To assure good performance of a Ni-P coating, the deposit quality must be inspected and evaluated during the chemical deposition process or in the end product. The recommended test parameters are: thickness, layer uniformity, hardness, adhesion, porosity, corrosion resistance and chemical composition of the nickel-phosphorus coating. The purpose of this paper was to investigate the Ni-P coating process, to evaluate the b?haviour of Ni-P in a saline environment using aqueous brine (3.5% - 30% sodium chloride by mass) and to present possible defects that could compromise the coating.