Examination of tribological properties of oxide-polymer and carbide-polymer coatings formed by flame, plasma and HVOF spray processes (original) (raw)
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Wear behavior of plasma and HVOF sprayed WC-12Co+6% ETFE coatings on AA2024-T6 aluminum alloy
Surface and Coatings Technology, 2010
In this study, WC-12Co + 6% ethylene trifluoroethylene (ETFE) coatings were formed on the surface of an AA2024-T6 aluminum alloy using both plasma spray and high velocity oxygen fuel (HVOF) processes. The characterization of the coatings was made by microscopic examinations, thickness, porosity, contact angle and hardness measurements and X-ray diffraction (XRD) analysis. The coefficient of friction and wear resistance of coatings were obtained using a reciprocating wear tester by rubbing a 10 mm diameter Al 2 O 3 ball on the coatings in dry and acid environments. It was observed that the WC-12Co + 6% ETFE coating sprayed using HVOF method exhibited higher hardness and contact angle, better tribological performance and higher amount of retained WC when compared to the plasma sprayed WC-12Co + 6% ETFE coating. The wear resistance of the HVOF sprayed WC-12Co + 6% ETFE coating tested in acid environment was almost one and a half times bigger than that of dry sliding condition, but the plasma sprayed WC-12Co + 6% ETFE coating tested in acid environment showed a lower wear resistance when compared to the result of the experiment performed on dry sliding condition.
Tribological Properties of Hard Metal Coatings Sprayed by High-Velocity Air Fuel Process
Journal of Thermal Spray Technology, 2015
Lowering the thermal energy and increasing the kinetic energy of hard metal particles sprayed by the newly developed HVAF systems can significantly reduce their decarburization, and increases the sliding wear and corrosion resistance of the resulting coatings, making the HVAF technique attractive, both economically and environmentally, over its HVOF predecessors. Two agglomerated and sintered feedstock powder chemistries, WC-Co (88/12) and WC-CoCr (86/10/4), respectively, with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Their dry sliding wear behaviors and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al 2 O 3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with the formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviors were evaluated via standard Neutral Salt Spray, Acetic Acid Salt Spray, accelerated corrosion test, and electrochemical polarization test at room temperature. The optimization of the tribological properties of the coatings is discussed, focusing on the suitable selection of primary carbide size for different working load applications.
2010
Tribological behavior of plasma sprayed carbon nanotube (CNT) reinforced aluminum oxide (Al 2 O 3 ) composite coatings was examined at room temperature, 573 K and 873 K using tungsten carbide (WC) ballon-disk tribometer. The weight loss due to wear of Al 2 O 3 coating was found to be increasing with the temperature while Al 2 O 3 -CNT coating showed a decreasing trend in the weight loss with the temperature. Relative improvement in the wear resistance of Al 2 O 3 -CNT coating compared to Al 2 O 3 coating was found to be 12% at room temperature which gradually increased to ∼ 56% at 573 K and ∼ 82% at 873 K. Protective layer as a result of tribo-chemical reaction was observed on the wear track of both of the coatings. The improvement in the wear resistance of Al 2 O 3 -CNT coating was attributed to three phenomena viz. (i) higher hardness at the elevated temperature as compared to Al 2 O 3 coating, (ii) larger area coverage by protective film on the wear surface at the elevated temperature and (iii) CNT bridging between splats. The coefficient of friction (COF) of Al 2 O 3 coating was nearly constant at room and elevated temperature whereas COF for Al 2 O 3 -CNT coating decreased at the elevated temperature (873 K).
Materials Today: Proceedings, 2021
The present work deals with tribological investigation of Al 2 O 3-40% TiO 2 coating deposited using plasma spraying. The structural characterization of coating was done using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). The micro hardness was measured by vickers micro hardness tester whereas fracture toughness was determined by Indentation Fracture Toughness Test (IFT) method. The sliding wear tests were carried out at different test conditions involving simultaneous variation of load (P) ranging from 5 to 30 N and sliding velocity (V) ranging from 0.1 m/sec to 0.6 m/sec. The sliding wear rate increased with increasing parameter P Â V and friction coefficient displayed minima at a load of 20 N and sliding velocity of 0.4 m/sec. The flash temperature showed the increasing trend with P Â V parameter. The variation in coefficient of friction and wear rate with varying test conditions was associated with change in wear mechanism from plastic grooving to delamination of splats & splat fracture and formation & removal of tribo layer of Ti 2 O 3 and Ti 3 O 5 on worn surface.
Tribology of FeVCrC coatings deposited by HVOF and HVAF thermal spray processes
Wear, 2018
This work studies FeVCrC-based coatings as potential alternatives to conventional Ni-and Co-based alloys for wear protection. Specifically, the microstructure and tribological properties of the coatings are characterized as a function of the particle size distribution of the feedstock powder, of the deposition technique-High Velocity Oxygen-Fuel (HVOF) or High Velocity Air-Fuel (HVAF) sprayingand of specific processing parameters. HVOF-sprayed coatings obtained from fine feedstock powder exhibit numerous oxide inclusions, which provide high hardness (≈ 900 HV 0.3) but do not excessively impair fracture toughness, as determined through scratch testing techniques. HVAF-sprayed coatings obtained from the same feedstock powder contain much fewer oxide inclusions, and some of them possess simultaneously high hardness and high toughness. Defects (e.g. speckles) are instead formed in case unsuitable HVAF torch hardware is employed. A coarse feedstock powder always results in unmelted inclusions, which impair the cohesion of the coatings, particularly of the HVAFsprayed ones. Most coatings anyway exhibit very low sliding wear rates < 3 × 10 −6 mm 3 /(N m); abrasive grooving and surface fatigue-induced pitting are the main wear mechanisms. Oxide inclusions do not affect negatively the response of HVOF coatings, whereas too many unmolten particles increase pitting under severe test conditions. Rubber-wheel abrasion testing produces comparatively more severe grooving.
Materials
An usual material, EN-GJL-250 cast iron, used for automotive braking systems, was covered with a ceramic material (105NS-1 aluminium oxide) using an industrial deposition system (Sulzer Metco). The main reason was to improve the corrosion and wear (friction) resistance properties of the cast-iron. Samples were prepared by mechanical grinding and sandblasting before the deposition. We applied two and four passes (around 12–15 µm by layer) each at 90° obtaining ceramic coatings of 30 respectively 60 µm. The surface of the samples (with ceramic coatings) was investigated using scanning electron microscopy (SEM), dispersive energy spectroscopy (EDS) and X-ray diffraction (XRD). Scratch and micro-hardness tests were performed using CETR-UMT-2 micro-tribometer equipment. The better corrosion resistance of the base material was obtained by applying the ceramic coating. The results present a better corrosion resistance and a higher coefficient of friction of the coated samples.
Tribological Behaviour of Thermally Sprayed Coatings: A Review
SSRN Electronic Journal, 2018
Coatings are used for modifying the surface properties of critical components subjected to mechanisms such as corrosion, oxidation, wear, or under an excessive heat load failure. Selection of the coating material and method of depositions are very important for any application. Coatings are effectively and economically used to guard the substrate surface from wear also to reduce friction. The tribological response of a coating system depends on many factors like coating properties, counterpart, substrate, interface, and running conditions. Hence, selection of the appropriate coating for a given tribological application is difficult. Thermally sprayed WC and CrC based cermet coatings are extensively used in the hydro turbine for resistance to wear like abrasive, erosive and cavitation. The NiCrAlY coating showe d better resistance to high-temperature oxidation and corrosion due to the formation of protective oxides. At high temperature working environment and chemically aggressive condition NiCrSiBC alloy reveals a good balance between corrosion and wear resistance. The NiCrBSi coating showed a good surface finish as well as the bonding interface. This paper presented the review related to the selection of coating powder and process of protective wear resistance coating by thermal spray techniques. The effect of spraying techniques and spraying parameters on the performance of the coating is different for every coating. The wear types, powders, Plasma spray and HVOF spray methods are discussed to identify the coating for a specific application.
Surface and Coatings Technology, 2006
In this paper the porosity, phases, mechanical properties and abrasive wear resistance of ceramic layers of Al 2 O 3 /TiO 2 deposited by flame spray process were evaluated. The percentage of titania has a strong influence on the coatings porosity, as shown by the fact that with increasing titania content porosity will be reduced. The crystalline phases of the deposited layers changed according to the characteristics of the powder and the thermal process employed. While hardness depends only on the percentage of titania content, in the studied range, toughness depends on several factors, such as hardness, porosity and intergranular precipitation. The resistance to abrasive wear depends almost exclusively on the hardness of the coating.
Tribological behavior of HVOF- and HVAF-sprayed composite coatings based on Fe-Alloy+WC–12% Co
Surface and Coatings Technology, 2014
Fe-based coatings are promising alternatives to Ni-based ones, because of lower cost and lower toxicity. Following a previous research, where the sliding wear resistance of HVOF-sprayed Fe-Cr-Ni-Si-B-C alloy coatings was found to compare favorably with that of a Ni-Cr-B-Si-C alloy and of electroplated chromium, the present study investigates the wear resistance of Fe-Cr-Ni-Si-B-C + WC-Co composite coatings. The Fe-alloy feedstock powder was therefore blended with 0, 20 and 40 wt.% of a WC-12 wt.% Co powder and sprayed by HVOF and HVAF processes. HVAF-sprayed coatings exhibit less structural alteration than HVOF-sprayed ones, which results in lower intrinsic nanohardness of both Fe-alloy and WC-Co splats; however, HVOF-and HVAF-sprayed coatings exhibit similar Vickers microhardness. Somewhat poorer interlamellar bonding in HVAF-sprayed coatings results in a greater tendency to microcracking during dry sliding wear testing at room temperature; however, dry sliding wear rates of HVOF-and HVAF-sprayed samples never differ significantly. The reinforcing effect of WC-Co decreases the wear rate of composite coatings (≈10 −6 mm 3 /(Nm)) by more than order of magnitude, compared to unreinforced ones (≈1-2 * 10 −5 mm 3 /(Nm)). As the test temperature is increased to 400°C and 700°C, the dry sliding wear rates of all samples increase (up to 10 −4 mm 3 /(Nm) or greater). The greatest changes are observed when the WC-Co content is larger, as it suffers from oxidation and thermal alteration more than the Fe-alloy matrix. The abrasive wear resistance of the Fe-based coatings, evaluated by rubber-wheel testing, is also significantly improved by the addition of WC-Co.
Tribological Properties of Alumina-Zirconia Composite Coatings Prepared by Plasma Spraying
Proceedings on Engineering Sciences, 2019
The intent of this research was to determine the tribological trends of zirconia as an additive to a plasma-sprayed alumina coating matrix. For the deposition process, pure alumina and alumina-withzirconia (5%, 10%) weight percentages were employed to be coated on steel substrates using an airhydrogen plasma. The torch power was set to ~40 kW. The surface roughness for the alumina coatings were in the range from 2.6-3.2 µm and with additive percentages of zirconia, it was found to vary between 3.0-3.7 µm. XRD measurements indicated that the predominant phase in the alumina-zirconia coatings was tetragonal-ZrO 2 (t-ZrO 2) and with alumina, it was α-Al 2 O 3 and γ-Al 2 O 3. The tribological properties such as the friction coefficient and the wear-rate of the alumina-composite coatings had been inspected to evaluate its dependence on the type and concentration of the additive powders. An increase in friction-coefficient was observed with the addition of zirconia. The normalized wear rates were in the range of ~10-5 mm 3 /Nm for the composite coatings with certain exceptions.