Preparation of Melamine/Rice Husk Powder Coated Shellac Microcapsules and Effect of Different Rice Husk Powder Content in Wall Material on Properties of Wood Waterborne Primer

The melamine/rice husk powder-coated shellac microcapsules were prepared by in-situ polymerization with melamine resin mixed with rice husk powder as microcapsule wall material and shellac as microcapsule core material. The effect of the addition amount of microcapsules with different wall material ratios on the performance of wood waterborne primer coating was investigated. The results show that the most important factor affecting the performance of microcapsules is the content of rice husk powder. Through the preparation and analysis of shellac microcapsule primer coating coated with melamine/rice husk powder, when the content of microcapsule powder is 0–6%, it has little effect on the optical properties of wood waterborne primer coating, and the microcapsule with 5.5% rice husk powder has little effect on the color difference of primer coating. The coating hardness increases with the increase of rice husk powder content in wall material. When the rice husk powder content in wall material is more than 5.5%, the coating hardness reaches the best. When the content of microcapsule powder is 3.0–9.0%, the adhesion of the coating is better, and the coating with rice husk powder content of 5.5% in microcapsule wall material has better impact resistance. When the content of rice husk powder was 5.5% and the content of microcapsule powder was 6%, the elongation at break of the primer coating was the highest and the tensile resistance was the best. The composition of wood waterborne primer did not change after adding microcapsule. The water-based primer with microcapsule has better aging resistance. The water-based primer coating with rice husk powder content of 5.5% and the addition amount of 6% had the best comprehensive performance, which lays the technical reference for the toughness and self-repairing of the waterborne wood coatings.

Implementation of the Chicot–Lesage Composite Hardness Model in a Determination of Absolute Hardness of Copper Coatings Obtained by the Electrodeposition Processes

The influence of various electrolysis parameters, such as the type of cathode, composition of the electrolyte and electrolysis time, on the morphology, structure and hardness of copper coatings has been investigated. Morphology and structure of the coatings were analyzed by scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD), while coating hardness was examined by Vickers microindentation test applying the Chicot–Lesage (C–L) composite hardness model. Depending on the conditions of electrolysis, two types of Cu coatings were obtained: fine-grained mat coatings with a strong (220) preferred orientation from the sulfate electrolyte and smooth mirror bright coatings with a strong (200) preferred orientation from the electrolyte with added leveling/brightening additives. The mat coatings showed larger both measured composite and calculated coating hardness than the mirror bright coatings, that can be explained by the phenomena on boundary among grains. Independent of electrolysis conditions, the critical relative indentation depth (RID) of 0.14 was established for all types of the Cu coatings, separating the zone in which the composite hardness can be equaled with the coating hardness and the zone requiring an application of the C–L model for a determination of the absolute hardness of the Cu coatings.

Cr-Based Sputtered Decorative Coatings for Automotive Industry

The present work aims to study the impact of O and N addition on Cr-sputtered coatings on plastic (polycarbonate, PC) used in automobile parts, as a promisor alternative for auto part metallization, while eliminating the usage of toxic hexavalent chromium. The coatings were deposited using DC magnetron sputtering from a single pure Cr target in a reactive atmosphere (N2 and/or O2). The deposition of the coatings was performed maintaining the total pressure constant and close to 1 Pa by tuning Ar pressure while reactive gases were added. The target current density was kept at JW = 20 mA·cm−2. Structural characterization revealed a mixture of α-Cr, δ-Cr, β-Cr2N, and CrN crystalline structures as well as amorphous oxides. The coating hardness ranged from 9 GPa for the CrON coating to 15 GPa for the CrN coating. All deposited coatings showed a particularly good interface adhesion; adjusting the amount of O and N made it possible to tune the optical properties of the Cr-based coatings as desired. The promising results open future industrialization of sputtered Cr-based coatings for automotive industries.

The Relationship between Coating Property and Solid Particle Erosion Resistance of AIP-Deposited TiAlN Coatings with Different Al Contents

TiAlN coatings with different Al ratios were deposited by the cathodic arc ion plating (AIP) method, and the relationship between solid particle erosion resistance and structural, mechanical properties was investigated by a micro slurry-jet erosion (MSE) test. The crystal structure of TiAlN coating changes depending on the Al ratio. The coating shows a B1 single cubic phase between the Al ratio of 0 and 0.58; above this ratio, formation of a B4 hexagonal phase is observed. The mechanical properties such as hardness and Young’s modulus of the TiAlN coating also depend on the Al ratio and the crystal structure. The erosion rate decreases by increasing the Al ratio up to 0.58, as the coating is a cubic single phase. The TiAlN coating shows the lowest erosion rate at an Al ratio of 0.58. The erosion rate increases drastically as the crystalline phase changes from the B1 cubic to B4 hexagonal phase at the Al ratio of more than 0.58. The change in erosion rate is also discussed in connection with mechanical properties such as erodent particle hardness to coating hardness ratio and coating hardness to Young’s modulus ratio.

Research on Chrome Plating Quality of the Internal Surfaces in the Hydraulic Drives with Hydrostatic Guideways

The article presents a study of the characteristics of experimental samples with a chrome coating: the straightness and ovality of the inner surface of the cylinder, as well as the hardness and thickness of the chrome coating. The chrome coating is obtained on a previously developed installation for applying chrome coating on the inner surfaces of hydraulic cylinders of hydraulic drives with hydrostatic guides. The measurement of the geometric characteristics of the internal surface of the samples was carried out, the values ​​of deviations from roundness and deviations from straightness were obtained. A study of the chrome coating was carried out, for this we cut out sectors from the samples, carried out their sample preparation, measured the hardness and took pictures under a microscope, measured the hardness and thickness of the chrome coating. The obtained measurement results: deviation from roundness, deviation from straightness, coating hardness, coating thickness - correspond to the specified technical requirements, the proposed construction of the installation for applying chrome coating to the inner surfaces and the electrolyte composition, selected earlier, are applicable for chrome plating of the inner surfaces.

The influence of pulse-plasma treatment on the phase composition and hardness of Fe-TiB2-CrB2 coatings

This work are presented the research results of pulse plasma treatment influence on the phase composition, hardness, roughness and element composition of coatings on the bases of Fe-TiB2-CrB2. The Fe-TiB2-CrB2 coating was deposited by detonation method. The following pulse-plasma treatment was used to modify the structure and properties of the surface layers of the sprayed coating. The results of mechanical experiments showed that the hardness of Fe-TiB2-CrB2 coating increased after the treatment. On the basis of the X-ray analysis, it has been established that the increase of coating hardness is connected with phase transformations in a surface layer, in particular, with formation of oxide phases and increase of carbide particles quantity.

Influence of Fuel/Oxygen Ratio on Coating Properties and Cavitation Resistance of WC and Cr3C2 Cermet Coatings Deposited by HVOF

Hydroelectric turbines are strongly affected by cavitation and the damage it can cause to critical part surfaces and profiles. The study of thermal spray processes and materials is thus relevant to improving turbine performance. The main objective of this work is to evaluate the influence of fuel-oxygen ratio on tungsten- and chromium-carbide cermet coatings deposited by HVOF. Particle velocity and temperature were measured as were coating hardness, porosity, and cavitation resistance. Higher particle velocities were obtained at higher fuel ratios, producing harder, denser coatings with better cavitation resistance. Based on test results, the wear mechanism starts with the nucleation of the cavitation that occurs in the pores, resulting in the formation of craters and the eventual detachment of lamellae as indicated by the smoothness of the surface.

The effect of spray angle on the microstructural and mechanical properties of plasma sprayed8YSZ thermal barrier coatings

Thermal barrier coatings (TBCs) are favorable for better protection of gas turbines and aero engines at high temperatures. The TBCs were fabricated using NiCrAlY bond coat and 8% wt. yttria-stabilized zirconia (YSZ) topcoat onto the nickel-based superalloy Inconel 800 by atmospheric plasma spray. In this article, the investigation of microstructural and mechanical properties of 8YSZ TBCs with the effect of spray angle has been discussed. The microstructural and elemental analyses were conducted by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The porosity analysis was conducted based on SEM image analysis using a gray scale threshold. Mechanical properties such as coating hardness, surface roughness, and thickness are measured by indentation, surface profilometer, and optical microscopy. The result shows the effect of the spray angle over the coating surface in terms of pores and microcracks. The influence of the spray angle leads to different grain growth resulting in the shadow region. A large number of defects and a decrease in coating hardness were observed for 60 degrees pray angle compared to the 90 degrees pray angle. A large number of defects led to developing rough surfaces, resulting in low hardness and increased porosity. The experimental results showed that the plasma sprayed 8YSZ TBC with a 90 degree spray angle can improve the durability and performance of the TBCs, as it has better microstructural and mechanical properties.

Influence of Spray Parameters on the Thickness, Hardness and Porosity of low-pressure Cold Sprayed WC-Ni Coatings

In this study, a 33 full factorial design methodology was used ­­to analyze the effects of spray parameters on the thickness, hardness, and surface porosity of low-pressure cold-sprayed WC-17Ni coatings. Three levels were selected for the spray parameters included in the design which were the powder feed rate (17.1 g/min, 21.1 g/min, and 23.7 g/min), gas temperature (475℃, 500℃, and 525℃), and the nozzle to substrate stand-off distance (3 mm, 5 mm, and 10 mm). It was found that the feed rate was the most significant parameter that affected the coating thickness. The surface porosity was most significantly affected by stand-off distance. The coating hardness was most influenced by the interaction between the feed rate and stand-off distance. An optimization study was then performed to maximize the coating thickness and hardness while minimizing the surface porosity. The optimal spray parameters (OSP) were found to be at a feed rate of 23.7 g/min, 500℃ for the carrier gas temperature, and 10 mm for the stand-off distance. The OSP yielded a coating that was 1.22 ± 0.06 mm thick, with a hardness of 364.5 ± 8.5 HV and porosity of 6.8 ± 0.6%. With a multi-parameter process, the system response is affected by both the variation in the individual parameters and the interaction of the parameters with each other. It was also concluded that the interaction between the parameters significantly affected the coating hardness. These results suggest that variation of the selected parameters produce statistically significant effects on the coating quality of WC-17Ni coatings using a low-pressure cold spray system.

The Impact of Heat Treatment on the Behavior of a Hot-Dip Zinc Coating Applied to Steel During Dry Friction

The analyzed topic refers to the wear resistance and friction coefficient changes resulting from heat treatment (HT) of a hot-dip zinc coating deposited on steel. The aim of research was to evaluate the coating behavior during dry friction after HT as a result of microstructure changes and increase the coating hardness. The HT parameters should be determined by taking into consideration, on the one hand, coating wear resistance and, on the other hand, its anticorrosion properties. A hot-dip zinc coating was deposited in industrial conditions (according EN ISO 10684) on disc-shaped samples and the chosen bolts. The achieved results were assessed on the basis of tribological tests (T11 pin-on-disc tester, Schatz®Analyse device, Sindelfingen, Germany), microscopic observations (with the use of optical and scanning microscopy), EDS (point and linear) analysis, and microhardness measurements. It is proved that properly applied HT of a hot-dip zinc coating results in changes in the coating’s microstructure, hardness, friction coefficient, and wear resistance.