MECHANICAL PROPERTIES AND ANTI-WEARABILITY STUDIES OF MULTILAYER THIN COATINGS ON CUTTING TOOLS

The naniondentation fracture of multilayer hard coatings, such as TiN, TiN/Ti(C, N)/TiC, TiN/Ti (C,N)/TiC/Ti (C, N)/TiC and TiN/Ti (C, N)/TiC/Ti (C,N)/TiC/Ti(C,N)/TiC coating, deposited on cemented carbide using a CVD technique are studied. It is found that these coatings have high hardness. Based on the analysis of the energy release in cracking, the fracture toughness of these coatings are calculated. The observations clearly establish a step occurs in the force-displacement curves at the onset of coating fracture and a straight line segment in the load-penetration depth squared curves to idenntify the interfacial failure of coatings. The hardness, fracture toughness and anti-wearability of these coatings are clearly compared. The results show that with the layers increasing, the fracture toughness and anti-wearbility are getting larger.

Enhancement of Heat-Resistance of Carbonyl Iron Particles by Coating with Silica and Consequent Changes in Electromagnetic Properties

Silica-coated carbonyl iron particles （CIPs） are fabricated with the Stober method to improve their heat-resistance and wave-aSsorption properties. The morphology, heat-resistance, electromagnetic properties and microwave absorption of raw-CIPs and silica-coated CIPs are investigated using a scanning electron microscope, an energy dispersive spectrometer, a thermal-gravimetric analyzer, and a network analyzer. The results show that the heat-resistance of silica-coated CIPs is better than that of raw CIFs. The reflection losses exceeding -lOdB of silica-coated CIPs are obtained in the frequency range 9.5-12.4 GHz for the absorber thickness of 2.3 mm, and the same reflection losses of uncoated CIPs reach the data in the lower frequency range for the same thickness. The enhanced microwave absorption of silica-coated CIPs can be ascribed to the combination of proper electromagnetic impedance match and the decrease of dielectric permittivity.

Microstructure and Properties of Plasma Spraying Boron Carbide Coating

Microstructure of plasma spray boron carbide coating was studied by SEM and TEM. Its physical, mechanical and electrical properties were measured. The results showed that high microhardness, modulus and low porosity of B4C coating were manufactured by plasma spray. It was lamellar packing and dense. The B4C coating examined here contained two principal structures and two impurity phase besides major phase. The relatively small value of Young's modulus, comparing with that of the bulk materials, is explained by porosity . The Fe impurity phase could account for the relatively high electrical conductivity of boron carbide coating by comparing with the general boron carbide materials.

Effect of microstructure on the mechanical, thermal, and electronic property measurement of ceramic coatings

Ceramic materials were investigated as thermal barrier coatings and electrolytes. Electrophoretic deposition（EPD） and physical vapor deposition（PVD） were employed to fabricate samples, and the mechanical properties and microstructure were examined by nanoindentation and microscopy, respectively. Yttria-stabilized zirconia/alumina（YSZ/Al2O3） composite coatings, a candidate for thermal barrier coatings, yield a kinky, rather than smooth, load–displacement curve. Scanning electron microscope（SEM） examination reveals that the kinky curve is because of the porous microstructure and cracks are caused by the compression of the indenter. Li0.34La0.51 Ti O2.94（LLTO） on Si/Sr Ru O3（Si/SRO） substrates, an ionic conductor in nature, demonstrates electronic performance. Although SEM images show a continuous and smooth microstructure, a close examination of the microstructure by transmission electron microscopy（TEM） reveals that the observed spikes indicate electronic performance. Therefore, we can conclude that ceramic coatings could serve multiple purposes but their properties are microstructure-dependent.

Wave-absorbing Properties of a Cement-based Coating with MnO2/Activated Carbon Composite

MnO_2/activated carbon composite（Mn-ACC） wave absorber was prepared by the reaction between Mn（CH_3COO）_2 and KMnO_4 on activated carbon. Then, a novel cement based composite absorbing coating（CB-CAC） was prepared by adding the Mn-ACC, manganese zinc ferrite and rubber particles into cement. XRD method was used to analyze the reaction products of the Mn-ACC. The tensile bond strength and the wave absorbing properties of the CB-CACs were also tested. The results showed that the crystallinity of MnO_2 formed in the Mn-ACC was poor. Adding Mn-ACC into the CB-CAC led to first increase and then decrease of the tensile bond strength. The tensile bond strength reached 1.89 MPa with 8.51% of the Mn-ACC. The CB-CACs obtained the optimal absorbing properties with the cement, manganese zinc ferrite, Mn-ACC, rubber particles and H_2O mass ratio of 7.5？7.5？1？1？5.5, respectively. The band width of the reflection below-10 dB was up to 8.8 GHz, which accounted for 57.14% of the test band.

Comparative Study on Optical Properties and Scratch Resistance of Nanocomposite Coatings Incorporated with Flame Spray Pyrolyzed Silica Modified via in-situ Route and ex-situ Route

A new type of transparent scratch resistant coatings including in-situ modified SiO2 （g-SiO2） in flame spray pyrolysis （FSP） process was prepared. The maximum content of g-SiO2 in the coating was 15 wt%, which is higher than that of SiO2 modified by traditional wet chemical route （I-SiO2, only 10 wt%）. The results of transmission electron microscopy have demonstrated that in-situ surface modified g-SiO2 particles dispersed well with smaller agglomerates in the final coating, which was much better than the particles modified via wet chemical route. Visible light transmittance and haze tests were introduced to characterize the optical quality of the films. All coatings were highly transparent with the visible light transmittance of above 80%, especially for coatings containing g-SiO2, which exhibited slightly higher visible light transmittance than l-SiO2 embedded one. The haze value of coatings incorporated with 15 wt% g-SiO2 was 1.85%, even lower than the coating with 5 wt% I-SiO2 （haze value of 2.09%）, indicating much better clarity of g-SiO2. The excellent optical property of g-SiO2 filled coatings was attributed to the good dispersion and distribution of particles. Nano-indention and nano-scratch tests were con- ducted to investigate the scratch resistance of coatings on nano-scale. The surface hardness of the coatings rose by 18% and 14%, and the average friction coefficient decreased by 15% and 11%, respectively, compared to the neat coat due to the addition of 10 wt% g-SiO2 and I-SiO2. The pencil hardness of the coating with 15 wt% g-SiO2 increased from 2B for the neat coating to 2H. However, the pencil hardness of coating with 10 wt% I-SiO2 was only H. The results showed that the g-SiO2 embedded coatings exhibited higher scratch resistance and better optical properties.

Preparation and Performance of Fluorescein Isothiocyanate⁃Labeled Fluorescent Starch and Polyvinyl Alcohol for Warp Sizing

In order to solve the problems of low accuracy and poor variety adaptability of the current measurement method of the permeability and coating property of sizing paste in textile industry, taking starch and polyvinyl alcohol(PVA) as the representatives of the most commonly used textile sizes, various concentrations of fluorescent molecules fluorescein isothiocyanate(FITC) were used to label starch and PVA to prepare fluorescein(F)-starch and F-PVA fluorescent sizes with different degrees of labeling(DLs) for the first time, respectively. Then the starch and PVA derivatives were employed to size pure cotton warp yarns. After preparing the sections of the sized yarns, the permeability and coating percentage of starch and PVA paste to the yarns were calculated by using a fluorescence microscope and the Photoshop software, respectively. The results demonstrate that F-starch and F-PVA with appropriate DL of 0.791% and 0.161%, respectively, exhibit good fluorescence property and similar sizing performance to the sizing performance of unlabeled starch and PVA. It is considered that fluorescence labeling of sizing agents with fluorescein units can provide an innovative way for the accurate determination of the permeability and coating property of sizing paste to warp yarns.

A New Type Anticorrosion Coating for Ocean Reinforced Concrete Structures

Corrosion of reinforced concrete structures is a serious problem in ocean engineering. As an orientation of study, anticorrosion coating technique is developed and widely applied, but many problems need to be solved. LSW-2 type anticorrosion coating for maritime reinforced concrete structures is characterized by sea water resistance, salt fog resistance, moisture and heal resistance as well as impermeability to chlorions. The new type coating can be applied to wet concrete surface by conventional construction technique. It is a breakthrough in solving the above mentioned problem. The paper mainly introduces the test results, the property indices, coating procedure, construction technique and economic benefit of Ihe coating.

Preparation and properties of Al-Mn alloy coatings in NaCl-KCl-AlCl_3-CeCl_3 molten salts

Al-Mn alloy coatings were electrodeposited on an iron substrate from AlCl3-NaCl-KCl molten salts with anhydrous MnCl2 enhanced by the addition of CeCl3. The microstructure and properties of the Al-Mn alloy coatings were investigated, and scanning electron microscopy, X-ray diffraction, and polarization curves were used to determine the composition, surface morphology, phase structure, and corrosion resistance of the obtained deposits. The results showed that the surface coatings were smooth, and that the crystallites were dense and uniform when 0.22 wt.% CeCl3 was added to the molten salt. An amorphous mixture of Al and Al6Mn was obtained. CeCl3 enhanced the corrosion resistance and increased the hardness of the single amorphous phase alloys. The pitting potential of the coating was approximately -1.1239 V, and its hardness was 390 kgf/mm2.

Microstructure and Performance Analysis of Organic Coating under High Temperature and High CO_2 Partial Pressure

To evaluate the property of the organic coatings in oil and gas plants, the aging process was studied in high temperature and high CO_2 partial pressure environment. Correlations were developed between the macroscopic properties and microstructure of the organic coatings. The surface appearance, mechanical properties, and permeability of the organic coatings were measured. Furthermore, the crystal structure of the organic coatings was investigated through synchrotron radiation grazing incidence X-ray diffraction（GIXRD） on the BL14B1 beam line in Shanghai Synchrotron Radiation Facility. Combined with the Fourier transform infrared spectroscopy, the molecular structure of the organic coatings was investigated. The experimental results indicate that the thickness variation and weight loss of the organic coatings increase with the immersion time, and the penetration resistance of the coating obviously decreases as the temperature rises. Moreover, the degradation of the organic coatings with immersion time in high temperature and high CO_2 partial pressure environment is caused by the amorphization of the organic coatings as the groups and bonds of the organic coatings were not damaged.

Tribological properties of FeCoCrNiAlB_x high-entropy alloys coating prepared by laser cladding

FeCoCrNiA1Bx（x=0, 0.25, 0.50, 0.75） coatings were prepared by laser cladding to study the effects of boron on the structure and properties of high-entropy alloys coatings. The microstructure, microhardness, and wear resistance properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, metallographic micro-hardness test, and friction wear test, respectively, and the mechanism of the wear behavior was also analyzed. The results showed that the high-entropy alloys consisted of BCC phase and eutectic structure, which contained FCC phase and M2B. With boron addition, the content of BCC phase increased while that of eutectic structure decreased. The wear resistance of the high-entropy coatings was considerably improved with increasing addition of horon, and accordingly, the FeCoCrNiAlB0.75 coating showed the best wear resistance.

Flow properties of fine powders in powder coating

Three types of nanoparticles and their combinations were blended into a fine powder, which has been used in the powder coating industry. To study their effects on flow properties, the modified powder samples were characterized using a variety of techniques that tested the powder under different powder states ranging from dynamic to static. It was found that all three nanoparticles improved the flow properties of the powder to some degree, though the amounts of the nanoparticles needed were different depending on their physical properties. Secondly, inconsistency among these powder characterization techniques was also found. This is attributed to the different states of the powder samples during a measurement including dynamic, dynamic-static and static states. It was confirmed that characterization techniques which test the flow properties of a powder under all three states are needed to fully describe the flow properties of the powder. Finally, the effects of combinations of nanoparticles were explored, and it was found that combinations of nanoparticles can intensify, weaken or combine the effects of their component nanoparticles. The effects of nanoparticle combinations are not a simple summation of the effects of their comnonent nanoparticles.

Effect of activators on the properties of nickel coated diamond composite powders

Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding wheels were then prepared from Ni-coated diamond composite powders with different activators. The microstructural characterizations of this composite powders were finally conducted by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, and the mechanical and tribological properties of as-prepared diamond grinding wheels were also measured. There are changes in microstructures and properties of the composite powders with activators. The activator concentration also has an influence on the morphologies and phase structures of the Ni coating on diamond particles.The composite powders with more compact coating of nickel can be prepared by adding 1 g dm^（-3） or more AgNO_3 as an activator to electrodeposit nickel on diamond. The mechanical and tribological properties of diamond grinding wheels were significantly improved when the coating phase structure of Ni crystal grew with（111） plane orientation on the surface of diamond particles. The wheels made from nickel coated diamond composite powders possessed the advantages of easy preparation and outstanding tribological properties. Therefore, Ni coated diamond composite powders exhibit a great potential to be extensively applied in diamond cutting and grinding tools.

Research methods and influencing factors of interfacial heat transfer during sub-rapid solidification process of strip casting

Interfacial heat transfer behavior between the molten steel and twin-rolls is a key issue in the strip casting process,and it has already attracted wide attention from industrial and academic communities of steel.The research methods and influencing factors on the interfacial heat transfer were summarized.Numerical simulation models,semi-industrial scale,and laboratory equipment have been developed in this field,and these methods were also improved by worldwide researchers based on the development of computer,automatic,and visual technologies.Coating properties,naturally deposited film,and casting parameters are the main factors which affect the heat transfer significantly.Although lots of research has been carried out,the internal relations among these influencing factors,interfacial heat transfer,and the quality of the strip are still worth to be further explored.Keywords Strip casting Interfacial heat transfer Simulation method Coating property Naturally deposited film Casting parameter.

Perylene-Based Fluorescent Sizing Agent for Precise Evaluation of Permeability and Coating Property of Sizing Paste

Warp sizing is considered as the most important process of weaving preparation in the textile field.The quality of sized warp yarns is directly determined by the permeation and coating of sizing paste into/on warp yarns.However,many significant flaws of the current method of permeability and coating property of sizing paste,such as low accuracy and narrow variety adaptability for sizing agents and warp yarns,have emerged in the evaluation process.In order to eliminate the inherent flaws in the current method,the investigation chose chitosan(CS)as a representative of common sizing agents,introduced various amounts of perylene units onto molecular chains of the CS,and prepared a new functional sizing agent-fluorescent CS with different labeling degrees of perylene.Furthermore,PVA-perylene was synthesized to evaluate the permeability and coating property of PVA sizing paste.Then,three indexes to indicate the permeability and coating property of sizing paste,i.e.permeation percentage,coating percentage and integrity percentage of sizing film,were evaluated using the CS-perylene and PVA-perylene derivatives prepared.Due to the fluorescence emitted by the perylene units,the three indexes can be determined accurately and conveniently depending on only fluorescent microscope and common image processing software.The investigation efficiently solves the difficult problem of evaluating permeation and coating property of the pastes of both bio-based and petroleum-based sizing agents with appropriate degrees of labeling and has a significant guiding function on accurate determination of the quality of sized yarns.

Preparation of FeCo-, FeNi- and NiCo-alloy coated cenosphere composites by heterogeneous precipitation

Precursors of binary alloy （Fe112C0112, Fel/2Ni1/2, Ni1/2Co1/2, hereinafter referred to as FeCo, FeNi, NiCo） coated cenospheres were prepared by heterogeneous precipitation under optimized conditions. Magnetic binary alloy coated cenosphere composites with core-shell structure were subsequently obtained by thermal reduction of the as-prepared precursors at 700℃ for 2 h under H2/N2 atmosphere. The results showed that the alloy coatings were uniform and the binary alloy coated cenosphere composites basically retained the spherical morphology, suggesting that the thickness of the alloy coating could be adjusted to fabricate core-shell composites with multilayer structures. The composites exhibited higher coercivity than the pure alloy powders, and could therefore be used for high-performance functional materials and devices.

Self-Lubricating PEO Coating on an Al Alloy Produced by Vacuum Impregnation Post-treatment

The objective of this research was to develop a novel self-lubricating coating on an AA6061 aluminum alloy.Three coatings were prepared by the plasma electrolytic oxidation（PEO） process using 50-, 500-, and 1000-Hz pulsed direct current, respectively. The as-deposited coatings were then post-treated using two different methods, viz., ultrasonic vibration-aided vacuum oil impregnation（UVOI） and oil impregnation under ambient pressure（OIAP）. After posttreatment, an oil-containing, self-lubricating top layer was formed on the coatings. The effects of the coatings＇ surface morphologies and structures on their oil-holding capabilities were discussed. The results revealed that coatings prepared with higher frequency had a greater oil-holding capacity using OIAP post-treatment, while those prepared with lower frequency had a greater oil-containing capability using UVOI post-treatment. These phenomena are related to the morphologies of the coatings produced with various current modes. The tribological properties of the coatings before and after post-treatments were investigated by pin-on-disc sliding wear tests. Due to the formation of a lubricant-containing top layer, the post-treatment coatings had a lower friction coefficient and improved wear resistance compared with the asdeposited coatings. In addition, the coatings after UVOI treatment had better wear performance than those post-treated using the OIAP process. Among all coatings, the coating produced with a 50-Hz pulsed current followed by UVOI posttreatment achieved the lowest friction coefficient（0.03） and best wear resistance when sliding against a Si3N4 ceramic counterface. This study indicates that a novel self-lubricating coating can be prepared by a PEO process combined with vacuum oil impregnation post-treatment.