Papers by Keyword: Flame Spraying

Abstract: Tungsten Carbide (WC) hard coating is widely used to coat the surface of the steel tools which provide tribological properties. In this paper, 0.25 wt% & 0.35 wt% of Carbon Nanotubes (CNT) were mixed with tungsten carbide (WC) powders as the feedstock powders. Method of solution dispersion in ethanol media using an ultrasonic device was used for coating the surface of WC powders with CNT powder. The mixed powders were then used as the feedstock powder to coat onto the surface of tool steel using the flame spraying process. The coated surface microstructures were observed under a scanning electron microscope (SEM), x-ray diffraction (XRD), and the energy dispersive spectroscopy (EDS) was used for the phase characterization and identification. The wear rate of coated steels was determined using the Ogoshi machine, and the Vickers hardness method used to measure their microhardness. The effects of CNT on the microstructure of the coated material and the surface mechanical properties were investigated. The results showed that the mixture powder preparation using an ultrasonic method in SDS solution and the ball-milling process was suitable to disperse the CNT on the surface of WC feed powders due to produce an adequate relationship between CNT' and WC powders increasing the surface mechanical properties of coatings. The wear resistance of the coated material produce using the mixture of WC powder with 0.35 wt% CNT increased around 50% higher than the WC coated steel without CNT addition. Also, the hardness of coating reinforced CNT increased significantly compared with the hardness of WC coated and the steel substrates. Microhardness value from the base metal to the WC-CNT coated steel increased from 550 HV to 1717 HV and also the wear rate from the base metal to the WC-CNT coated steel decreased from 0.86 mm³/min to 0.017 mm³/min. These results indicate that CNT is an excellent alternative to improve the surface mechanical properties of WC coatings.

Abstract: The article presents the results of the influence of the kinematic and geometric parameters of the thermos-sprayer location on the adhesion strength of the anti-friction coating. A mathematical apparatus for calculating the inertia forces acting on an anti-friction coating particle is proposed. The results of a number of experimental studies confirming the convergence of theoretical positions are presented. As a result, dependencies have been revealed that make it possible to predict the bond strength of the anti-friction coating with the steel base during gas-flame spraying.

Abstract: The article presents the results of experimental studies of the micro-hardness of anti-friction surfaces of bimetallic sliding bearings. As a result, the nature and features of the process of distribution of the micro-hardness of the coating along the height of the anti-friction coating were revealed. A method of manufacturing a bimetallic sliding bearing is proposed, which will allow an increase in the micro-hardness of the anti-friction coating and its uniform height distribution. This method allows to reduce the porosity of the anti-friction coating and to achieve the specified processing parameters of the anti-friction surface.

Abstract: The paper considers the application of wear resistant coatings by methods of gas thermal and flame spraying. It demonstrates the relationship between adhesion strength of the sprayed coating and surface roughness after abrasive jet machining using piston rings with steel-molybdenum coating as an example. The authors consider the results of studies aimed defining the relationship between surface roughness and of jet-abrasive machining conditions: the distance between the nozzle exit and the workpiece, the number of passages, the operating air pressure and frequency of the shot swapping.

Abstract: TThe present study is an attempt to observe and evaluate the dry rolling wear behavior [1] of three types of Ni-base coatings on an Amsler type wear machine, against low-alloyed steel discs. The tested coatings were obtained by flame spraying (on the same low-alloyed steel substrate as the discs) using commercial Ni-base self-fluxing powders: 1060-00 and 1355-20 type (manufactured by Hoganas) and JK 586 type (manufactured by Deloro Stelite Co). In order to increase the strength of the layers, the deposition was followed by fusing [2]. The tests were conducted on pairs of coated – uncoated discs at the same load and the same speed in all three cases. In order to evaluate the wear behavior, there were observed and measured the surface roughness and the rolling path profiles. A severe wear regime with adhesion as the main phenomenon was observed in case of the low-alloyed steel discs.

Abstract: The article deals with problems of high temperature strain gauge measurements. A preliminary experimental work for purpose of mastery of this technique after a longer break has been kicked off in VZLÚ. Initially, possibilities of usage of commercial products and two means of strain gauge attachment were verified.

Abstract: Carbon nanotubes (CNTs) was introduced into Ni60/Al₂O₃ coating by flame spraying. The effect of adding CNTs on the tribological properties of the coating was studied by varying the CNTs content as 0.0, 1.5, 3.0 and 4.5 wt% in the Ni60/Al₂O₃ powders. The microhardness tester was used to measure the microhardness of the coating. Wear tests were performed on a pin-on-disk tribometer, to evaluate the tribological properties of the Ni60/Al₂O₃/CNTs coatings. Microstructural characterization was performed using scanning and transmission electron microscopy. Ni60/Al₂O₃/CNTs coatings revealed a lower wear rate and friction coefficient compared with the original coating, and their wear rates and friction coefficients showed a decreasing trend with increasing mass fraction of CNTs within the range from 0 to 3.0 wt% due to the effects of the reinforcement and reduced friction of CNTs. The results showed that the CNTs played dual roles in improving the tribological performance of the coating, indirectly by influencing the microstructure and mechanical properties of the coating and directly by acting as a lubricating medium.

Abstract: Lifetime of details directly influences lifetime of machines and equipments. Details in most cases wear out, instead of collapse. Raise of their wear resistance is a perspective problem. The most economic way is drawing hard-wearing coverings on a surface of the details made of steel. In our work coverings from oxide ceramics (Al₂O₃ and Al₂O₃+TiO₂) coatings, covered by gas-flame spraying on a surface of the specimens made from tool steels 105WCr6 were investigated. Before a conversion coating specimens were hardened and tempered, the surface was exposed to sandblasting, and the special sub layer for raise of an adhesion of a covering with a basis was put. After drawing a ceramic covering micro hardness of a covering and a basis was measured. Then it was tested contact and abrasive wear resistance of surfaces on original installations. It is resulted and circuits a technique of research of wear resistance. Agency on wear resistance of an aspect oxide ceramics, type of wear contact and abrasive, heating of the superficial layer arising because of a friction of two surfaces is investigated. At the end of work leading-outs and are presented to the recommendation on application oxide ceramics to increase of wear resistance of steel details.

Abstract: Coatings were turned by two tools: a) ISO 2R 2525K10, geometry and cutting parameters recommended by Messner Eutectic Castolin Company (tool angle β = 90^o, approach angle κ_r = 45^o, nose radius r_ε =0,8 mm, clearance angle α = 6^o, rake angle γ = -5^o) b) bit tool with CBN WNGA080408S01030A insert mounted in DWLNRL-2525M08 holder (cutting inserts β = 80^o, approach angle κ_r = 95^o, nose radius 0,8 mm, clearance angle α = 6^o, rake angle γ = -6^o). The influence of cutting speed, feed rate, depth of turning on the coating surface roughness was estimated. The following cutting parameters: cutting speed V_c = 45 214 m/min, feed rate f = 0,04 0,196 mm/rev, depth of cut a_p = 0,05 0,3 mm. The lowest value of the roughness R_a = 0,5μm of the coatings were obtained by using cutting tools and parameters and bit tool: V_c = 214 m/min, f = 0,06 mm/rev, a_p = 0,3 mm.

Abstract: Barium ferrites hollow microspheres were prepared by self-propagating high-temperature synthesis self-reactive flame spraying method. The droplets enter in the cooling medium and solidified rapidly so that the gas can not escape to remain holes inside the products. The powder samples were used for characterization. The microstructure and crystal structure were studied by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres. They are spherical or ellipsoidal shapes from nanometer dimension to several micrometers. The phase structure of composite powders is the mixtures of barium ferrite and Fe₂O₃.