Properties Of Plasma Coatings Research Articles

IMPROVING THE EFFICIENCY OF RESTORATION AND HARDENING OF THE WORKING BODIES OF TILLAGE MACHINES BY PLASMA-POWDER SURFACING OF CARBIDE ELECTROEROSIVE MATERIALS

The use of powders obtained from solid alloy waste as a highly solid dispersed component of the composition for plasma-powder surfacing will improve the quality, reliability and durability of plasma coatings of working bodies of tillage machines with a minimum of costs for powder materials. However, the properties of these plasma coatings have not been studied enough, so it is necessary to conduct comprehensive studies. (Research purpose) The research purpose is improving the technology of restoration and hardening of the working bodies of tillage machines by plasma-powder surfacing of powder materials obtained by electroerosive dispersion of solid alloy waste T30K4. (Materials and methods) Carbide powders made by electrodispersing solid alloy waste T30K4 in kerosene were used to obtain plasma coatings. We chose for the renovation object a pointed cultivator paw made of 40XC rolled steel. The obtained plasma coatings were studied using modern equipment and complementary methods of physical materials science. (Results and discussion) We have developed, tested and investigated a new technology for restoring and strengthening the working bodies of tillage machines using the example of a pointed cultivator paw by plasma-powder surfacing of carbide electroerosive powder materials. The effectiveness of the development was confirmed by the properties of plasma coatings: the microstructure of the coating has a fine-grained structure, without inclusions, uniform phase distribution and the absence of pores, cracks and discontinuities; elements W, Ti and Co in the coating are evenly distributed; phases of carbides WC and TiC are present; the grain size of the coatings is about 0.3 micrometers; the microhardness of the coatings is about 14245 megapascals. (Conclusions) The results of field tests showed that the resource of the working bodies of tillage machines, restored and strengthened with carbide electroerosion materials, is 1.25 times higher than the resource of new parts.

Multi-Layers Composite Plasma Coatings Based on Oxide Ceramics and M-Croll

The paper considers the influence of the parameters of the plasma spraying process on the technological characteristics of multilayer coatings based on nickel-chromium, nickel-chromium-aluminum-yttrium materials, oxide ceramics, intended for operation at high temperature and additional dynamic loads. The design of plasma coatings during their application (with subsequent high-energy processing) under such conditions requires a comprehensive solution – both the use of high-quality powder ingredients and the optimization of technological parameters. The plasma process of applying powder materials has been improved to obtain the maximum values of their utilization factors. The technological characteristics that affect the properties of plasma coatings are optimized, namely: the flow rates of the plasma-forming and materials-transporting gases, the flow rate of supplied powder materials, the current and voltage of the electric arc of the plasma torch, the distance from the plasma torch nozzle exit to the substrate. The paper presents the results of studies of the structure of coatings, performed using scanning electron microscopy. Their analysis has made it possible to form general regularities obtained by the action of radiation of compression plasma flows on coatings formed by air plasma. The considered structures are created using the processes of melting, compaction and high-speed cooling of plasma coatings. The main optimization indicators are the maximum local compaction and spillage of the obtained compositions with the absence of defects and destruction from the impact of compression plasma flows. The main effect during the action of radiation of a compression plasma flow on previously formed coatings is thermal. It contributes heating of the near-surface layer. When the coating is exposed to radiation of compression plasma flows, a remelted layer of oxides with a thickness of about 12–15 µm is created, smoothing the relief of the formed surface and creating a network of cracks on the surface, diverging into the depth of the coating. The liquid-phase processes occurring in the molten phase of the near-surface layers after exposure to compression plasma radiation change the structure of the layers and contribute to the modification of their mechanical properties. By smoothing the surface, increasing the density of the surface crystallized layer and minimizing macro-defects – pores or macrocracks – the mechanical characteristics of the coatings increase.

Влияние нанодисперсных ингредиентов на свойства плазменных покрытий

Влияние нанодисперсных ингредиентов на свойства плазменных покрытий

Activation of structure formation and control of properties of chromium-nickel-plasma coatings with nanocomponents

The issues of plasma spraying activating and controlling the formation of coating structure with enhanced functional characteristics by imposition external magnetic field in the field of the arc discharge, as well as modifying the sprayed mixture by nanodispersed components, are considered. The possibilities of controlling the spatial distribution and energy characteristics of heterogeneous plasma stream under the influence of external magnetic field are shown. The wear resistance and physicomechanical properties of plasma coatings made from powder mixtures of macro- and microparticles in the presence of the optimal amount of nanophases in the formed coating are studied.

Microstructural analysis, evaluation of the adhesion and utilization properties of plasma coatings on alloy steel substrate

Abstract Once with the technological development, many variants of improving surface behavior through coating with various materials have emerged. In this paper are studied the microstructure, adhesion to the substrate and the utilization properties of thermal plasma coatings on alloy steel substrate (100Cr6). The samples were obtained by plasma spray from three types of powder, both with the bonding and non-bonding versions: Sample 1 - topcoat of Eutalloy 10112 (Ni-Cr-B-Si-Fe-WC), Sample 2 - bonding layer from NiAlSi and Eutalloy 10112 as topcoat; Sample 3 - NiCrFe topcoat (M42); Sample 4 - bonding layer of NiAlSi and NiCrFe topcoat (M42). The samples were analyzed for microstructural changes both longitudinal and in the cross section (for evaluation of the modifications produced at the substrate - coating interface). The adhesion to the substrate was evaluated by the scratch method, applied both longitudinally and in the cross section of the coatings. The results revealed that all the coatings have a good adherence at the substrate and are suitable for applications where wear resistance is needed

Experience of high-nitrogenous steel powder application in repairs and surface hardening of responsible parts for power equipment by plasma spraying

The questions of the application of novel diffusion-alloying high-nitrogenous steel powders for repair and surface hardening of responsible parts of power equipment by plasma spraying are considered. The appropriateness of the method for operative repair of equipment and increasing its service life is justified. General data on the structure, properties, and manufacture of nitrogen-, aluminum-, and chromium-containing steel powders that are economically alloyed using diffusion are described. It is noted that the nitrogen release during the decomposition of iron nitrides, when heating, protects the powder particles from oxidation in the plasma jet. It is shown that the coating retains 50% of nitrogen that is contained in the powder. Plasma spraying modes for diffusion-alloying high-nitrogenous steel powders are given. The service properties of plasma coatings based on these powders are analyzed. It is shown that the high-nitrogenous steel powders to a nitrogen content of 8.9 wt % provide the necessary wear resistance and hardness of the coating and the strength of its adhesion to the substrate and corrosion resistance to typical aggressive media. It is noted that increasing the coating porosity promotes stress relaxation and increases its thickness being limited with respect to delamination conditions in comparison with dense coatings on retention of the low defectiveness of the interface and high adhesion to the substrate. The examples of the application of high-nitrogenous steel powders in power engineering during equipment repairs by service companies and overhaul subdivisions of heat power plants are given. It is noted that the plasma spraying of diffusion-alloyed high-nitrogenous steel powders is a unique opportunity to restore nitrided steel products.

Influence of electropulse impact on mechanical properties of plasma coatings

Influence of electropulse impact on mechanical properties of plasma coatings

Properties of plasma-sprayed coatings treated by laser radiation

The effect of laser treatment on the properties of plasma coatings made from the self-fluxing alloy PGSR-3 with additions of titanium carbide, heat-resistant Ni−Cr−Al−Y alloy, and clad Ni−Al powders was investigated. Laser treatment increased the adherence of the coating to the substrate, density of the surface layers, and promoted the formation of structures with a uniform distribution of alloying elements.

Reconditioning crankshafts of car engines by air‐plasma spraying

At present, there are a large number of methods available for reconditioning worn crankshafts of car engines in car repair plants. The authors believe that the most efficient methods are those which enable the surface of crankshafts to be built up without melting the base. One of these methods is air-plasma spraying. The use of plasma torches with magnetic arc stabilisation and the application of powder feeders with built-in pneumatic vibrators (Authors cert No. 1799230, USSR) has made it possible to increase greatly the service properties of plasma coatings. The service life of shafts is increased mainly by ensuring a high strength of bonding the coating with a parent metal, which should be uniform over the entire surface of sprayed pins and should equal 30-40 MPa. One of the factors reducing the strength of crankshafts is the stress concentration formed at the fillet and edges of holes in pins of oil channels. This leads to failure of components of the crank of journals in these areas. When reconditioning crankshafts by spraying, it is recommended to displace the fillet into the journal to reduce the stress concentration and prevent damage of the coating in these zones (Fig. 1). In the presence of an unloading groove in the journal, the stresses in the fillet zone are distributed more uniformly. The tests show that the depth of the fillet should be (0.01—0.015) df, but for single-row carburettor engines

Coating of titanium carbide powders with an Ni-Fe-P layer and the properties of plasma coatings of them I. Coating of titanium carbide powders with a nickel-iron-phosphorus alloy

Coating of titanium carbide powders with an Ni-Fe-P layer and the properties of plasma coatings of them I. Coating of titanium carbide powders with a nickel-iron-phosphorus alloy

Microstructure, composition and property relationships of plasma-sprayed thermal barrier coatings

The benefits deriving from the use of thermal barrier coatings are briefly reviewed. Properties important for a thermal barrier coating are discussed and reasons for the selection of ZrO2-based alloys highlighted. Candidate zirconia alloys are critically evaluated in terms of their thermal and mechanical properties. Since coatings currently applied consist of a tetragonal phase, the long-term stability of the phase structure and the avoidance of the monoclinic phase is addressed, as is the effect of long-term ageing on the thermal properties. The relationship between microstructure and properties of plasma coatings is reviewed. Future trends, such as extending areas of application in jet engines, use of alternative alloys, and methods of application and optimization of plasma sprayed coatings by modelling the plasma spray process, are also briefly discussed.

Properties of plasma coatings from complex alumina-titania powders

Powdered materials based on alumina with TiO 2 additions [i] have found the widest application for strengthening textile machine components using plasma spraying; these additions enhance the ceramic coating quality by increasing the density and adhesion strength relative to the substrate. Mechanical powder mixtures containing aluminum and titanium oxides tend to separate as they are carried to the plasma stream; therefore, it is better to use sintered or fused compositions from this system. The Swiss company Plasma-Technik AG produces powders based on alumina (Piasmatex-OT3 and Piasmatex-OTi3 with 3 and 13% TiO 2 respectively) [2]. Powders of this type are not produced in this country. The authors have suggested a method for producing alumina powders that are alloyed with titania, and which is based on sprayed firing of suspensions of the original compounds. The droplets are suspended in the hot zone for 1-3 sec, which induces uniform heating over the whole volume and the formation of mainly spherical particles. However, irregularly shaped particles measuring 10-20 ~m are present in the powder, it is likely that the most coarse particles are trapped in closed pores by the high vapor pressure effect, and that these pores rupture on severe heating.

Properties of plasma coatings made of heattreated chromium oxide powders

Properties of plasma coatings made of heattreated chromium oxide powders

Physicochemical properties of plasma coatings

The author test several sprayed metal coatings -including titanium, copper, nickel, molybdenum, tungsten, and alsifer alloy - against a variety of substrates for their adhesion, permeability to hydrogen, thermal expansion, porosity, electron work function, and gas desorption and diffusion behavior. Effects of various plasma arc process parameters are assessed.