Steel Counterbody Research Articles

Tribology of WC reinforced SiC ceramics: Influence of counterbody

Hot pressed silicon carbide (SiC) composites prepared with 0, 10, 30 or 50 wt% tungsten carbide (WC) are subjected to dry sliding wear against WC-Co and steel ball. In particular an attempt has been made to answer the following important questions: (i) How does the load (from 5 to 20 N) effect sliding wear behaviour of SiC-ceramics against WC-Co and steel counterbodies? (ii) Is there any effect of WC content on friction and wear characteristics of SiC ceramics? (iii) Does the dominant material removal mechanism of SiC ceramics change with the addition of WC or counterbody? (iv) What is the influence of mechanical properties on the sliding wear? Experimental results indicated that coefficient of friction (COF) for the SiC ceramics varied between 0.66 and 0.33 with change in load and counterbodies. Wear volume for SiC ceramics found approximately 6−10 times more against WC-Co as compared against steel. Wear volume changes from 2.0 × 10–3 mm3 to 1.2 × 10–2 mm3 with change in counterbodies for SiC-(10, 30 or 50 wt%) WC composite at 20 N. SiC ceramics indicated abrasion and composites reveal tribochemical wear as major material removal mechanisms. Wear is influenced by the hardness of counterbody and fracture toughness of SiC-WC composites.

Friction and wear of PEEK in continuous sliding and unidirectional scratch tests

Abstract Friction and wear of a commercially available polyetheretherketone were investigated by two different testing approaches, namely the standard pin-on-disc (POD) configuration and an unidirectional pin-on-flat (POF) scratch test, in a wide range of pv-products from 0.001 to 8 MPa m/s under dry sliding condition. It was found that the steady state friction coefficient gained from POD tests slightly decreases with increasing sliding velocity from 0.1 to 1 m/s, further increase in the velocity to 4 m/s results in an obvious raise of the friction coefficient. It is assumed that this increase can be attributed to the high interfacial temperature induced strong adhesion between PEEK surface and steel counterbody. No obvious difference of the friction coefficients between POD and POF tests is noted in the studied range. With respect to the wear rate, the wear rate measured from POD increases with monotonously increasing velocity. Possible reasons for these observations are discussed based on the analysis of the worn surfaces of polymer samples and transfer films formed on the steel counterface as well as the investigations on the thermal characteristics of different tribo-systems.

The roles of rigid particles on the friction and wear behavior of short carbon fiber reinforced PBT hybrid materials in the absence of solid lubricants

Abstract Polymeric materials filled with micro-sized short carbon fiber (SCF) and various internal lubricants, i.e. graphite and PTFE etc., have been proved as a beneficial tribomaterial formulation in contact with a steel counterbody. The SCFs carry the most load applied on the tribosystem, while the internal lubricants improve the friction behavior of the polymer matrix. In the present study, the roles of rigid particles on the friction and wear performance of SCF filled Polybutylenterephthalate (PBT) with and without graphite were investigated by using a pin-on-disc (PoD) tribometer under dry sliding condition. The experimental results show that the tribocomposite filled with nanoparticles without graphite particles presents outstanding friction and wear performance especially under moderate and severe load conditions in combination with superior mechanical properties compared with graphite-filled tribocomposite. The friction coefficient and wear rate under a pv-condition of 3 MPa and 2 m/s are 0.18 and 0.8*10−6 mm3/Nm, respectively. Based-on the optical analysis of the worn surfaces of the polymer samples and the transfer layers formed on the steel disc, the possible friction and wear mechanisms were discussed.

The influence of centrifugal forces on friction and wear in rotational sliding

To investigate the influence of centrifugal forces on the oil film stability and the lubrication regime, mirror polished steel surfaces (AISI 304) were tested using a ball-on-disc tribometer in rotational sliding mode with a steel counter body (AISI 52100). Different sliding radii (1.5 and 6 mm) were used to vary the angular velocity. The tests were conducted under fully-flooded conditions using Poly-alpha-olefin oils. The measured coefficients of friction were complemented by the measurement of solid-solid contact ratios and the analysis of the respective wear tracks. It could be shown that the centrifugal forces have a great influence on the oil film lifetime. Thereby, the oil film lifetime is longer for larger sliding radii and higher viscosities.

Fatigue failure of 45# steel in dry sliding against Kevlar/PTFE hybrid composite under elevated load

Frictional failure is inevitable for friction pairs. A common sense about the frictional failure of steel-polymer composite friction pair is that the polymer composites are the primary failure part rather than the steel counterpart. However, an opposite case was newly found in the case of fabric self-lubricating liner (Kevlar/PTFE hybrid composite) spherical plain-bearing under elevated load: the steel counterbody suffered a fatigue failure before the fabric composite fails, which resulted in the final failure of the bearing. This paper investigated such fatigue failure of surface chrome plated 45# steel by systematically studying the wear characteristics of 45# steel and fabric composite, the stress distribution of the 45# steel and fatigue features within cross section of the 45# steel. Results showed that wear characteristics of both fabric composite and 45# steel exhibited regional characters. Failure mechanism of the 45# steel was found to be fatigue failure (mainly fatigue pitting), which was revealed by mathematical analysis of the stress distribution of the 45# steel and the fatigue cracks found within subsurface of the cross section of the 45# steel.

Examining a mechanism of generating the fragments of protective film in the trybological system "epoxycomposite–steel"

The influence of multifunctional fillers on wear resistance of epoxycomposites, operated under conditions of friction without lubrication at elevated slip velocity and loadings was explored. Introduction of these fillers in the optimum amount provides high cohesive strength and gives epoxycomposites tribotechnical properties. The developed composition of materials allows the implementation of the effect of selective transfer during friction interaction. Wear intensity of epoxycomposites under different loading and velocity modes was determined, which made it possible to establish favourable mode of formation of a protective film. The analysis of structural elements of tribosurfaces of materials and a counter was carried out and chemical composition of fragments of the protective film on tribosufraces was defined. It proved a hypothesis on the formation of a copper protective film at tribosurfaces as a result of selective transfer. The reasons for initiation of the process of generation of protective film fragments on surfaces of tribobodies was established and the sequence of stages of its formation in highly filled epoxycomposites was defined. The shape, dimensions and the area of fragments of a protective film, formed at tribosurfaces of the system epoxycomposite – a steel counter body system, were determined. The formed film in the form of fragments of elongated shape in direction of the friction process stabilizes the process of tribointeraction due to the capability of self-restoring. Using the developed epoxycomposites, which operate under the mode of selective transfer, decreases friction coefficient and wear intensity due to the formation of laminar and porous structure of a film. Accordingly, it will allow controlling the process of friction, reducing material and economic costs in the process of maintenance and repair of equipment, which solves topical scientific and practical tasks of modern tribomaterials science. Feasibility of using the protective copper films in tribonodes was established, which will make it possible to expand the area of using the triboproducts in machine building, instrument engineering, chemical and light industries.

Effect of debris size on the reciprocating sliding wear of aluminium

The literature is controversial in relation to the influence of wear debris on tribological behaviour. Some works have shown that the presence of debris is fundamental to the formation of a protective tribolayer, thus reducing friction, whereas others showed that the presence of wear debris could contribute to increase friction coefficient due to the energy spent dragging them into the contact. This work aims to study the influence of the presence of wear debris, simulated by Al2O3 particles, on the tribological behaviour of an aluminium-steel pair under reciprocating sliding contact. Special emphasis is given to the particle size (0.05 µm, 0.1 µm, 1 µm and 10 µm). The particles were dispersed in distilled water (2 wt.%) as the source of debris. Reference tests were carried out solely in the presence of distilled water. The addition of alumina particles contributed to a significant reduction in friction coefficient, in particular for the largest particles (diameter ϕ=10 µm). When the larger particles were added, it was possible to observe the formation of a tribolayer on the sample surface leading to a gain of mass. In opposition, the wear rate of the counter body increased when large particles were added and the wear tracks showed strong evidence of abrasive wear. This suggests that hard and large wear debris, incorporated in the tribolayer formed on the samples, can act as hard protuberances, leading to abrasive wear of the counterbodies. When small particles were added, friction was still reduced when compared with the reference test, but the reduction of the friction coefficient was less significant. Small particles reduced the steel counter body wear rate and did not affect significantly the wear rate of the aluminium samples. It is proposed that small debris can get entrapped in the surface irregularities of the specimens and therefore participate less in the formation of the tribolayers.

Analysis of structure and tribotechnical properties of plasma carbide-silicon coatings under conditions of elevated temperatures

In a fundamentally new way we obtained a composite metal-ceramic coating of the SiC–Al2O3 system, which contains metallic component based on iron. The metallic component was not introduced into the original charge in the powder form but was obtained as a result of grinding the charge components in steel drums with steel grinding bodies. We studied the possibility of obtaining plasma coatings applied from this composition to steel parts with the intermediate sublayer from intermetallic compound Ni3Al for restoring and reinforcing their surfaces. The optimum modes of the application of coating from this material by the plasma method were established. Using the method of scanning electron microscopy and X-ray phase analysis, the structure of coating applied from this material on medium-carbon steel was investigated. Obtaining coatings from these inexpensive components with high performance properties presents economic and technological interest. As a result, tribotechnical properties of coatings under friction conditions with heating of friction contact to 500 оС with the steel counterbody were explored. The regularities of their wear were established. Using the methods of scanning electron microscopy and X-ray phase analysis, the friction surfaces of the obtained coatings were studied and special features and laws governing the mechanisms of their wear under conditions of elevated temperatures were determined. The possibility of applying these coatings for protecting and reinforcing parts of aviation ground-based equipment, working at elevated temperatures, was shown.

Effects of laser peening on fretting wear behaviour of alloy 718 fretted against two different counterbody materials

This paper deals with the effects of laser peening on fretting wear behaviour of a nickel-based superalloy, alloy 718, fretted against two different counterbody materials (alumina and SAE 52100 steel). Laser peening was carried out on alloy 718. Microstructural characterization of laser peened surface was done by electron back-scattered diffraction and transmission electron microscopy. Surface roughness, nanoindentation hardness, and residual stress of both laser peened and unpeened samples were determined. Fretting wear tests were conducted on unpeened and laser peened samples using two different counterbody materials (alumina and SAE 52100 steel balls). The results show that nanocrystallites formed in the surface and near-surface regions and compressive residual stress were induced after laser peening. Hardness increased due to grain refinement at the surface and near-surface regions. There was no significant change in the surface roughness. The laser peened sample exhibited lower tangential force coefficient values compared to unpeened samples at all loads, which may be attributed to higher hardness. Samples fretted against alumina counterbody exhibited higher tangential force coefficient compared to samples fretted against steel counterbody. Owing to increased surface hardness and higher compressive residual stress, laser peened samples exhibited lower fretting wear damage compared to unpeened samples. Due to tribochemical reactions, the wear volume of unpeened and laser peened samples fretted against alumina counterbody was higher than that of the samples fretted against steel counterbody.

On Design and Tribological Behaviour of Laser Textured Surfaces

The paper reports an investigation into the functional response of textured surfaces with different designs that incorporated arrays of micro-dimples and grooves (40μm diameter/width and 15μm depth for both patterns) produced on tungsten carbide (WC) blocks by employing nanosecond (ns) and femtosecond (fs) lasers. In particular, the tribological performance of the textured WC blocks against stainless steel (SS316L) counterbody was evaluated in terms of friction and wear under dry condition compared to an untextured specimen. Friction tests were carried out on a reciprocating sliding tester while unidirectional ball-on-disc method was utilised to assess wear on the mating surfaces. The untextured surface exhibited a continuous rise in the friction coefficient from 0.15 to 0.5 from the start of the cycle to the end while the specimens textured with ns and fs lasers reached steady-state condition after 100 and 200 cycles with values between 0.35-0.45 and 0.3-0.4, respectively. Energy dispersive spectroscopy following wear tests showed a pronounced material transfer from the balls to the textured surfaces with stainless steel filling up some of the dimple and groove cavities; however, the reverse phenomenon was not apparent. Additionally, texturing with the fs laser exhibited formation of nano-ripples/structures in the produced dimples and grooves that can be further studied for creating nano-textured cutting tools or surfaces with super-hydrophobic/anti-ice properties.

Comparative analysis of the tribological characteristics of canine joint cartilage and UHMWPE-based biomimetic materials

We report the results of pin-on-disc friction and wear testing for canine shoulder and knee joint cartilages and UHMWPE-based biomimetic composites against stainless steel counter-body. The values of the friction coefficient for natural cartilage against carbon steel were found to lie around 0.01 for shoulder and 0.015 for knee joints. The orientation treatment and the incorporation of fluorinated carbon nanotubes applied to isotropic bulk UHMWPE caused both the reduction of the friction coefficient from ∼0.09 to ∼0.05, and as well as the decrease of wear rate down to 3 times.

Numerical modelling and experimental validation of debonding and heat transfer of carbon fiber reinforced composite under reciprocating sliding

Abstract Compressive and shear stresses as well as the generation of heat are critical issues in the failure mechanism of carbon fiber reinforced epoxy composites under reciprocating sliding. In this work, the mechanical stress distribution and maximum surface temperature generated on the wear track by reciprocating sliding against stainless steel counter body are modelled numerically. The computational results are used to directly compare them to experimental data to discuss the contact status and failure mechanism during the sliding process applying different sliding frequency and external environment. The debonding between the carbon fibers and the epoxy is modelled considering a cohesive interface modelling. We demonstrate numerically that the sliding frequency has a significant effect on heat generation. Experimentally, at higher frequencies, a more pronounced debonding and crack formation take place in the sub-surface region which is not the case at lower sliding frequencies. Water acts as a cooling agent and decreases the debonding because it functions as a plasticizer agent for the epoxy matrix.

Influence of phase composition on the sliding wear of composites in the system CaZrO3–MgO–ZrO2 against ZrO2 and steel

An attractive way to obtain low cost calcium zirconate (CaZrO3) composites is mixing natural limestone or dolomite with zirconia. These CaZrO3 based ceramic composites were often investigated as a promising high refractory for casting metal alloys, cements, thermal and environmental barrier coating.In this study the sliding wear, fracture mechanism and friction properties of a CaZrO3-MgO-ZrO2 ceramic against ZrO2 and steel counter bodies was carried out. Wear and fracture surface mechanisms, influence of its impurities and individual phases are discussed.The composite presents a coefficient of friction higher in ceramic/metal than in ceramic/ceramic pair, but the specific wear it is significantly higher when tested with the ZrO2 ball. The fracture surfaces present a dominant transgranular fracture when tested with steel and intergranular fracture against ZrO2.

Surface modification of diamond-like carbon coatings to control over run-in processes in friction pair

The effect of the nanostructure and chemical composition of thin Mo–Se–C films on the run-in of the diamond-like carbon coating (a-C) and the steel counterbody during ball-on-disk sliding test is studied. At the final stage of the deposition of the a-C coating on the steel substrate, a flow of atoms from the MoSe2 target was added to the flow of atoms being deposited. The influence of the air humidity on the selection of optimum structure and chemical composition of the film, which provide a fairly low (<0.07) coefficient of friction during the entire period of the run-in stage, is considered. In order to explain the effect of the modifying films, analysis of the specific features of the friction-induced changes in the composition of the films during wear debris formation has been carried out using Raman spectroscopy.

Self-Organization during Friction of Slide Bearing Antifriction Materials

This article discusses the peculiarities of self-organization behavior and formation of dissipative structures during friction of antifriction alloys for slide bearings against a steel counterbody. It shows that during self-organization, the moment of friction in a tribosystem may be decreasing with the load growth and in the bifurcations of the coefficient of friction with respect to load. Self-organization and the formation of dissipative structures lead to an increase in the seizure load.

Effect of relative humidity and full immersion in water on friction, wear and debonding of unidirectional carbon fiber reinforced epoxy under reciprocating sliding

Unidirectional carbon fiber reinforced epoxy was tested in ambient air at three different levels of relative humidity and under full immersion in demineralized water. Reciprocating sliding tests were performed at 23 °C against either stainless steel or alumina balls moving in parallel or anti-parallel direction to the fibers. We demonstrate in this work that humidity and water immersion affect significantly the fiber debonding. Under sliding against stainless steel or alumina at low relative humidity, fiber debonding is more pronounced than at high relative humidity and at water immersion. The wear depth increases with increasing relative humidity when sliding against stainless steel, whereas it remains practically constant against alumina. For all test conditions, the wear depth is larger when tested against stainless steel than against alumina. It was found that the thin moisture film formed at the surface of the stainless steel counter body leads to a higher corrosive risk than water immersion. More precisely, we demonstrate that high humidity leads to the production of oxide debris originated from the stainless steel ball which increases markedly the wear by abrasion. These debris lead to a high fluctuation of the coefficient of friction measured on carbon fiber reinforced epoxy composite sliding against stainless steel at 85% RH, whereas a steady state coefficient of friction is noticed against alumina.

Implementation of a wear model of rigid bodies for identifying the wear law based on the results of tribological tests

By comparing the calculation results with the experimental data, the wear law of bronze against steel counterbody under dry sliding friction is identified. The bronze sample was a block in three configurations, i.e., block–bar and block–pad with and without clearance. The calculation of wear of the sample was carried out based on a wear model of rigid bodies. Quite close values of the power wear law parameters were obtained for the different configurations of the sample. This demonstrates the effectiveness of using the rigid body wear model to identify the wear law of friction units in case of developed wear.

Understanding the hydrogen and oxygen gas pressure dependence of the tribological properties of silicon oxide–doped hydrogenated amorphous carbon coatings

Silicon oxide-doped hydrogenated amorphous carbons (a–C:H:Si:O) are amorphous thin films used as solid lubricants in a range of commercial applications, thanks to its increased stability in extreme environments, relative to amorphous hydrogenated carbons (a–C:H). This work aims to develop a fundamental understanding of the environmental impact on the tribology of a–C:H:Si:O. Upon sliding an a–C:H:Si:O film against a steel counterbody, two friction regimes develop: high friction in high vacuum and low gas pressure (oxygen pressure<10mbar; hydrogen pressure<50mbar), and a low friction regime at higher gas pressures (10mbar<oxygen pressure<500mbar; 50mbar<hydrogen pressure<1000mbar). Scanning electron microscopy (SEM) revealed that the tribological behavior of a–C:H:Si:O is governed by adhesive junctions at the sliding interface. At low gas pressures, material transfer from the steel pin to the a–C:H:Si:O flat occurs. At higher gas pressures, a tribofilm forms on the steel countersurface. Raman and near edge X-ray absorption spectroscopy (NEXAFS) spectroscopies demonstrate that upon sliding under the higher gas pressure, low friction regime, a surface layer with an elevated fraction of sp2-bonded carbon atoms forms. These changes indicate that these gases favor the release of the adhesive junctions by dissociatively reacting with the mechanically-stressed sp2 carbon-rich surface layer.

Wear behaviour of hydrogenated DLC in a pin-on-disc model test under lubrication with different diesel fuel types

The wear behaviour of hydrogenated diamond like-carbon (DLC) coating in DLC/steel tribological contact in a pin-on-disc model test under lubrication with two diesel fuels is presented in this work. The first diesel fuel was standard EN590 that contained ester-based antiwear additives. In contrast to EN590, the second diesel fuel, called GDK650, did not contain antiwear additives. It was experimentally observed that the antiwear additives are detrimental to the DLC. The effects of load, speed and temperature on the DLC and steel counterbody wear were investigated. Steel counterbody wear volume was found to be not affected by pressure, temperature, speed and lubricant, whereas the DLC-coating revealed correlation between the parameters and wear rate. Regarding the results of the tribological tests under both diesel lubrications, new mathematical wear laws were developed.

Peculiarities of the wear mechanism of polymers reinforced with unidirectional carbon fibers

The paper presents the results of experimental studies of the friction pairs composed of a carbon fiber-reinforced polymer rubbing against a steel counterbody in the dry friction conditions. Changes in the structure of the worn surface of the composites were analyzed using the atomic-force microscopy as dependent on the varying specific load in the friction contact and geometry of the carbon fibers subjected to destruction.