Papers by Keyword: Coating Properties

Abstract: In modern engineering the great attention is paid to the creation and implementation of new electroplating coating to ensure the durability, hardness and corrosion resistance. One of the effective methods for improving the properties of composite coatings is the method of galvanic deposition. The principle of obtaining of the composite electroplating was based on the fact that together with the metals ion some disperse particles of different sizes and nature are co-deposited. By including into metal matrix the particles are improve the performance coatings and increase the reliability and durability of products. The chloride electrolyte for application of the wear-resistant composite galvanic coating of nickel-cobalt-silicon oxide system was designed. The influences of the electrolysis modes and the electrolyte composition to a physical mechanical properties of the coating (wear resistance, firmness to corrosion, micro-hardness, internal stress, porosity, adhesion) were investigated. The possibility of the usage of received coating as the firmness to corrosion material with anti-frictional properties was showed.

Abstract: The receiving method and some properties of the composite nickel containing galvanic coating on base nickel-cobalt-oxide silicon-carbide silicon system were discussed. Chloride electrolyte for the application of the composite electroplating coating with firmness to wear and corrosion properties of nickel-cobalt-oxide silicon-carbide silicon system was elaborated. Influence of electrolysis and electrolyte composition on physico-mechanical properties (firmness to wear, corrosion resistance, hardness, internal tensions, porosity, adhesion) of the composite electrolytic coating of nickel-cobalt-silicon oxide system, electroplated from chloride electrolyte, and on the properties of electrolyte (diffusing ability, output current draught) were investigated. The possibility of using for composite electroplating of nickel-cobalt-silicon oxide-carbide silicon system as a firmness to wear coating in instead of chrome was showed.

Abstract: In the cold spray process, solid particles impact on a surface with high kinetic energy, deform plastically and form a coating. This enables the formation of pure and dense coating structures. Even more, coating performance and deposition efficiency can be improved by assisting the process with a laser. Laser-assisted cold spraying (LACS) has shown its potential to improve coating properties compared with traditional cold spraying. In this study, coating quality improvement was obtained by using a co-axial laser spray (COLA) process which offers a new, cost-effective laser-assisted cold spray technique, for high-quality deposition and repair. In the COLA process, the sprayed surface is laser heated while particles hit the surface. This assists the better bonding between particles and substrate and leads to the formation of tight coating structures. This study focuses on the evaluation of the microstructural characteristics and mechanical properties (e.g., hardness and bond strength) of LACS metallic coatings.

Abstract: Thermal spraying influences several physical and chemical properties of the coating surface. The most important of them are hardness, density, porosity, corrosion resistance and adhesion. This technology of surface treatment of material is often used for its high degree of hardness. Hardness and erosion resistance are the parameters that need to be achieved particularly in working conditions where there is excessive component wear. In this paper, we deal with the impact of purifying on the quality of molybdenum layer. Insufficient cleaning may result in a poor quality of the sprayed layer. Our aim is to measure and analyse the quality of molybdenum layer thickness applied by thermal spraying after insufficient cleaning.

Abstract: WS₂ soft coatings were deposited by medium-frequency magnetron sputtering, multi-arc ion plating and ion beam assisted deposition technique on the YT15 cemented carbide substrates. The influence of the substrate bias voltage on the coating properties has been studied. The coatings exhibited a dense and fine grained structure. WS₂ soft coatings with substrate bias voltage of -100 V revealed a better coating properties than other four samples, as the best crystallization of (002) preferred crystal orientation of Ⅱ texture, the most smooth and uniform microstructure of the coating, the largest critical load of 43.25 N and the largest coating thickness of 1.5 μm. But the microhardness of sample S1 was only 515.4 Hv. The critical load and the thickness of WS₂ coatings decreased firstly, then increased, and finally reduced with the increasement of substrate bias voltage. And the microhardness of the coatings decreased firstly, then increased, and decreased, finally increased with the increasement of substrate bias voltage.

Abstract: The effects of internal spraying environment on the microstructures and mechanical properties of plasma spraying NiCrBSi+15%Mo coatings were investigated. For experimental analysis of spraying environment, a specialized internal plasma device and its test unit were developed. Firstly, microstructures of spraying coatings and powders were analyzed by scanning electron microscopy (SEM). Furthermore, the boding strength, porosity and micro-hardness of the coatings were investigated and determined separately. According to these properties of plasma spraying coating, the influence of spraying environment on the coating properties and specimen temperature could be investigated. The results show that that the coating performances decreased because of the dust, smog and high temperature of the internal spraying environment. The high-performance internal coatings can be obtained by properly designing spraying process and using the special spraying device.

Abstract: Pure nickel powder was low pressure plasma sprayed onto a steel substrate held at different temperatures during spraying. The as-sprayed coatings consist of columnar grains whose axes are nearly perpendicular to the lamellae composing the coatings. As the coating temperature becomes higher, the length of the columnar grains increases and is longer than the thickness of the lamellae, indicating the growth of the grains across the lamellar interfaces during spraying. On the other hand, the coatings that were heat treated after spraying consist of coarse equiaxed grains. The coatings that experienced high temperatures during spraying or the heat treated coatings have large porosity and contain large globular pores. The hardness, apparent density and the tensile strength of the coating itself were the highest for the coating prepared at a low temperature and became low on heat treatment. The thermal conductivity in the direction perpendicular to the coating was the largest for the coating that consisted of long columnar grains.