Application Of Wear-resistant Coatings Research Articles

A New Two-Step Method for Laser Cladding of Silicon Carbide in Wc-Co Substrates

WC-Co cutting tools are widely used by the metalworking industry. In order to improve the properties of these tools, research on the application of wear-resistant coatings, such as polycrystalline diamond, are of great importance to several applications. It is known that the occurrence of high-stress levels between the coating and the substrate can lead to adhesion failures. One strategy to minimize these failures is applying an intermediate layer of SiC. In this work, the deposition of a SiC layer was carried out by a novel two-step laser cladding approach. Instead of cladding directly the pre-synthesized SiC on the substrates, a 200 µm silicon powder layer was pre-deposited on the WC-Co substrates and then irradiated with a 30 W CO2 laser. To improve metallurgical bonding between the tungsten and the Si layer, all substrates were chemically attacked. This attack allows cobalt removal from the surface and increases surface roughness, improving the laser cladding process. After the SiC laser cladding, samples were coated with a 200 µm graphite powder layer and irradiated again by a CO2 laser. The samples were characterized by SEM, EDS, and XRD analysis. The results showed that in the first step, an irradiation energy of about 0.27 J was enough to fuse the silicon powder to the substrate and in the second step, 0.13 J was enough to promote the reaction between silicon, carbon and the WC substrate, resulting in the in-situ synthesis of SiC. Finally, a new method was proposed for the deposition of SiC on WC-Co based substrates and the observed results allowed the proposal of an empirical equation to describe the chemical reactions of the process.

Results of tests for abrasive wear on a VIM LTDS installation

A number of well-known methods of accelerated testing for relative wear resistance are considered including a procedure based on the Brinell-Howarth method for laboratory studies and implemented on a IM-01 facility (designed at WISHOM) in which a powder abrasive is used. The shortcomings of those methods are discussed. A new VIM LTDP installation is developed in which an abrasive tape (320 mm and 15 mm in length and width, respectively) with a grain size of P60 is used as an abrasive material. The degree of wear was determined by a decrease of the sample mass using weighing on a balance before and after testing with an accuracy of 0.0001 g. The test results were obtained as a relative wear resistance e equal to the ratio of the values of the wear resistance of the test and standard samples. Consideration of the relative wear resistance makes it possible to increase the accuracy of the results due to the exclusion of the effect of changes in external parameters which determine the wear rate during testing. The installation ensures accelerated testing of the samples, i.e., the time for testing one sample is about 5 min. The structure and the grain size of the working body, the load value in the contact zone and the speed of interaction between the sample and tool are preserved. The use of an abrasive tape with different grain size provides for application of the unit to a wide range of tasks using samples without any preliminary grinding, but with the obligatory preliminary cleaning of the samples from slags and large particles after application of wear-resistant coatings.

RELIABILITY OF VEHICLE VEHICLES AT THE STAGE OF PREPARATION

The reduction of the duration of running-in is most strongly influenced by the speed-power and technological factors. It was experimentally established that at specific loads of 0.15 – 3 MPa and tribopair velocities of 6 – 40 m/min (0.1 - 0.66 m/sec) and methods of surface hardening and surface hardening, nitrocementation and ion-plasma thermocyclic nitriding, a combination of speed, power and technological factors can reduce the running-in process by 1.5 - 2 times.A mathematical model has been developed that combines the components of these factors for the running-in process in relation to the reduction of the latter.The stand for experimental research of the tribotechnical system, which consists of an automatic gearbox with a magnetic brake, a power supply, a control panel and a PC, has been upgraded. The firmware is written in the Python programming language.For further research in the chosen direction, the application of wear-resistant coatings with a thickness of 3 … 10 μm by PVD methods containing nitrides and carbides is promising.

Thermal Plasma Spray to Protect Large-Size Parts of Friction Joints against Wear

The authors thereof have developed a technology for application of wear-resistant coatings to protect against wear. The research team tested how efficiently powdered material could be heated in a plasma jet. They studied the physical and mechanical properties of coatings by kinetic micro-indentation and tested the plasma sprays for wear resistance. Tribological laboratory tests used the roller-on-roller method. Thus, WC/Co/Cr coatings had the most stable tribological properties and were more wear-resistant, compared to other tested coatings. Cylinder liners of heavy-duty diesel engines were enhanced by this technology. The pilot batch showed promise, as it might triple effectively the service life of diesel engines.

Insight into high temperature performance of magnetron sputtered Si-Ta-C-(N) coatings with an ion-implanted interlayer

Challenges related to the application of wear resistant coatings at high temperatures require the development of novel materials with an exceptional combination of mechanical, chemical and tribological properties. The present paper is focused on understanding of relationships between structure, composition and high-temperature performance of the Si-Ta-C-(N) coatings. The coatings were produced using combined magnetron sputtering (MS) and ion implantation (CMSII) technique. It was found that ion implanted coatings demonstrated better thermal shock resistance compared to MS Si-Ta-C-(N) coatings. The Si-Ta-C-(N) coatings revealed a nanocomposite structure consisting of 2–3 nm fcc TaC(N) grains and amorphous a-Si and a-SiC(N) phases. The composition and structure of amorphous matrix and nanocrystallites strongly affected tribological performance of the Si-Ta-C-(N) coatings. The N-doped coatings exhibited exceptionally good tribological performance due to a higher ductility of N-rich amorphous a-SiCN and a-SiNx matrix, and fcc Ta(C,N)-based crystallites compared with the a-Si + a-SiC, and fcc TaC-based phases in N-free coating. The Si-Ta-C-(N) coatings easily withstood oxidation annealing at 800 °C due to the formation of a 200 nm protective TaSiOx amorphous layer. Oxidation annealings revealed that under thin protective TaSiOx layer crystalline components of coatings did not change when Si and C from the amorphous matrix started to diffuse towards the substrate at 800 °C but even after redistribution of elements and formation of oxide scale the coatings demonstrated reasonably high hardness – 13–16 GPa. Triboactivated formation of TaSiOx fibers which could slide/roll against the same TaSiOx tribolayer during high-temperature tribotests resulted in low coefficient of friction values (0.23 at 800 °C) and absence of wear.

Application of wear-resistant coatings by plasma-spraying on the surface of parts of a complex shape

The article describes the features of plasma spray coating of parts of a complex shape, an effective trajectory of the plasma torch relative to the surface is developed, enabling to avoid overheating of the part and provide uniform coating thickness. An example of using this development for treating the surface of a screw by applying a wear-resistant coating by plasma spraying is given.

Application of hot hydrocarbons for a plasma installation in the application of wear-resistant coatings

The results of comprehensive research in the field of using exhaust gases from an internal combustion engine (ICE) as a source of hot hydrocarbons instead of propane-butane or natural gas to reduce oxidative processes are presented. It is shown that the introduction of hot hydrocarbons from the exhaust gases of a diesel engine significantly reduces the redox potential of the plasma jet of the plasmatron with respect to the sprayed material. An experimental mobile multifunctional plasma installation has been developed, which makes it possible to perform air-plasma spraying and melting of applied wear-resistant coatings. In this case, the exhaust gases of the internal combustion engine are used as the plasma-forming gas.

Optimisation of electro-spark coating method

Application of wear resistant coatings on cutting tools in a technological process requires taking into account multiple factors. Optimisation of the hardening process presents one of the main steps that needs to be addressed. This paper describes a method of optimisation of the electro-spark coating (ESC) process. The performance of the process was chosen as the target function. A parametric function was defined based on the previously developed mathematical model of the process whereby the condition of the strong connection of coating material with the foundation was used. Another parametric function is a prerequisite for a suitable coating thickness. Additional limitations are the characteristics of the equipment for the reinforcement

Investigations on TaC Localized Dispersed X38CrMoV5-3 Surfaces with Regard to the Manufacturing of Wear Resistant Protruded Surface Textures

The potential of lowered surface features as well as the application of wear resistant coatings have been known for many years to improve the tribological behavior of forming tools. More recent studies also discuss the capability of protruded microfeatures for adjusting the tribological behavior between contacting surfaces. The demand for a high wear resistance of such structures as well as their economical and reliable production, however, often limits the industrial application. The laser implantation process can overcome these limitations. In contrast to conventional cw-laser dispersing processes, where the formation of uniform metal matrix composite layers is intended, this surface engineering technique aims to improve the tribological behavior of contacting surfaces by a localized dispersing of pre-placed hard ceramic particles. This enables the formation of deterministic textures composed of separated wear resistant dome- or ring-shaped microstructures (implants). Since TaC shows very promising material properties for improving the wear resistance of tools exposed to severe operating conditions, this paper analyzes its suitability for pulsed laser implantation on X38CrMoV5-3 tool steel for the first time. In the experiments, the influence of the particles and the laser parameters (pulse power, pulse duration and focal diameter) on the material properties of the localized dispersed zones was studied by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The composite’s (micro-) hardness was measured and calculated by using a rule of mixture. Additionally, the influence of the laser parameters and the TaC particles on the geometrical properties of the implants was studied by optical microscopy and white light interferometry. The results showed that defect-free implants with hardness values of ~900 HV1 can be obtained at the focal spot, since a localized dispersing of the TaC particles is possible using a pulsed millisecond laser. However, in dependence of the laser intensity, also a partial dissolution of the initial particles occurs. This leads to the precipitation of new dendritic TaC nanoparticles and to varying contents of retained austenite in the matrix. Both effects have a strong influence on the implant hardness and must be considert by the rule of mixture. Regarding the geometrical response it was pointed out that protruded microfeatures with heights up to 10 μm can be created. In comparison to laser remelted zones, the implanted zones showed significantly altered weld pool profiles due to the influence of the particles on the melt convection. A transition of the implant shape from predominantly dome-shaped to predominantly ring-shaped was observed for intensities >1.7∙106 W/cm2 due to the onset of the keyhole effect. In conclusion, TaC particles seem to be very suitable for laser implantation on hot-work tool steels. The implants can be used for textures, where flat structures are needed. Since the TaC particles can be dispersed in the LIZ, it may be possible to reduce abrasive and adhesive wear due to the promising material properties of this hard phase and the improved hardness of the implants.

Frictional Properties of Laser-Applied Coatings

Laser application of wear-resistant coatings is considered. The conditions of coating application are outlined, and the results of wear tests on the coatings are presented.

Modeling of Tribological Characteristics of Specimens with Wear-Resistant Coating Using Dummy Variables

In the process of machining, one of the main factors affecting machining tool wear is friction. A decrease in the coefficient of friction between the machining tool and a machined part is a key challenge for researchers. One of the methods to decrease the coefficient of friction and, consequently, to improve the endurance of the tool is the application of wear-resistant coatings. In the current study, modelling of triboprocesses using dummy variables is proposed. Since a peculiarity of modelling of manufacturing processes is a presence of a large number of quality parameters, the influence of all key parameters on the value of the coefficient of friction has been analysed. Also, an adequate model of the dependence of the conditions of the manufacturing process on the coefficient of friction has been developed. The results of the model are important not only for analysis of friction between contact surfaces itself, but also as supplementary and qualitative estimation of different manufacturing processes.

Magnetically Ordered Electrolytic Coatings in Hydraulic Systems

The application of wear-resistant coatings in the presence of a magnetic field is proposed for components of hydraulic systems. A method is developed for controlling the residual stress and mechanical properties by means of crystallographic anisotropy.

Development of technology for manufacture of bimetal camps of ship diesels

The results of the development of the technology for the manufacture of bimetallic fuselage washers of marine ICE, which assumes the basis of the washer to be made from low-cost steels with the application of a high-hardness surface layer on the cams instead of cementation.
 To implement the idea, a number of mechanisms and devices have been developed and manufactured that have enabled the application of wear-resistant coatings and mechanical treatment of paddles.

The Formation of Surface Roughness of Piston Rings for the Purpose of Improving the Adhesion of Wear-Resistant Coatings

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.

Evaluation of arc sprayed coatings for erosion protection of tubes in atmospheric fluidised bed combustion (AFBC) boilers

Improvement in cored wire composition and fabrication has made possible the application of wear resistant coatings using the attractive twin wire arc thermal spray technique. In the present work, different wear resistant coatings named Alpha 1800, Armacor M and Ducor were deposited using TAFA 9000 wire arc spray equipment for their application in atmospheric fluidized bed combustion boilers. The erosion behaviour of these coatings was evaluated in a test rig and compared with that of carbon steel. Evaluation of coatings up to 600 °C indicated that the lowest erosion rates were observed for Alpha 1800 coating, the erosion rate of this coating being 5–10 times lesser than steel base depending upon the test temperature and erodent impact angle. Therefore, Alpha 1800 coating was sprayed on the superheater coils of an AFBC power plant.

Praxair, Inc.

AbstractChemicals (MIC: 11.1 SIC: 2813 NAIC: 325120)Praxair produces oxygen, nitrogen and argon through several air separation processes of which cryogenic air separation is prevalent. Co.'s Surface technologies segment supplies wear‐resistant and high‐temperature corrosion‐resistant metallic and ceramic coatings and powders to the aircraft, printing, textile, plastics, primary metals, petrochemical, and other industries. It also manufactures electric arc, plasma, and high velocity oxygen fuel spray equipment as well as arc and flame wire equipment for the application of wear resistant coatings. The coatings extend wear life and are applied at Co.'s facilities using a variety of thermal spray coatings processes.

Increasing the life of high-speed steel cutting tools

The paper describes work on determining the rational area of use, mastering of production operations, and introduction into the plants of the industry of various methods of increasing the life of high-speed tools. Among these methods are carbonitriding, treatment of the tool by shock cooling and by application of a magnetic field, and the application of wear resistant coatings by the method of cathodic-ionic bombardment. The article briefly characterizes each method. Experience in the introduction of the carbonitriding process has shown that the greatest increase in life is obtained for relatively large cutting tools such as hubs and large diameter drills. The effectiveness of shock cooling depends to a great degree upon the original structure of the tool material and upon the requirements imposed on it in service (for stability). Experience in the magnetic treatment of drills and end mills up to 30mm in diameter has shown that the life of a magnetically treated tool with subsequent demagnetization increases by 1.2-1.4 times and without demagnetization by 1.7-2 times. The effectiveness of magnetic hardening depends not only upon the correctly selected strength of the magnetic field and time of application, but also upon the time of postmagnetic aging. Wear resistant coatingsmore » applied by the cathodic-ionic bombardment method increases by 2-5 times the life of a cutting tool. However, careful preparation of the tool surface is required as well as careful control of the temperature and thickness of the coating.« less

Application of wear-resistant coatings on machine parts and tools by electric spark alloying

Application of wear-resistant coatings on machine parts and tools by electric spark alloying

Application of wear resistant coatings to the journals of cast iron crankshafts

1. Worn cast iron crankshafts of automobile and tractor engines can in principle be reclaimed using the processes of electric arc and plasma weld deposition. 2. Plasma weld-faced crankshafts slightly surpass crankshafts reclaimed by electric arc deposition in operating performance.