Steel Tribopair Research Articles

Tribological behavior and mechanism of Ti3SiC2/Cu composites in a wide temperature range under lubrication condition

Preparation of Ti3SiC2/Cu composites using Spark Plasma Sintering (SPS) process. The friction and wear behavior of Ti3SiC2/Cu-45# steel tribo-pair under lubrication conditions was investigated in a wide temperatures range. The results demonstrated that the influence of temperature on the tribological properties of the Ti3SiC2/Cu-45# steel tribo-pair under lubrication condition was characterized by a continuous transition from a lubricant to an oxide film. At 200 ℃, mobility of the lubricant increased and the friction interface was in the boundary lubrication state. As the temperature increased, the base oil in the lubricant rapidly evaporated, causing to solidification of the lubricant, and the friction interface formed the friction oxide film. The mechanisms of friction and wear were primarily abrasive wear and tribo-oxidation wear.

Friction and Wear Mechanisms of Ti3SiC2/Cu Composites under the Synergistic Effect of Velocity–Load Field at 800 °C

Ti3SiC2/Cu composites were prepared using spark plasma sintering technology, and the effect of the velocity–load bivariate on the tribological behaviors of the Ti3SiC2/Cu-45# steel tribo-pair at 800 °C was investigated. The physical change and frictional chemical reaction during the friction process were analyzed based on the morphology characterization and frictional interface phases. The related friction and wear mechanism model was established. The results showed that the influence of velocity and load on the tribological performance of the Ti3SiC2/Cu-45# steel tribo-pair was not monotonically linear. When both the velocity and load were large, the coordinated effect of the two led to a low friction coefficient (0.52). At 800 °C, the velocity mainly affected the exfoliation and re-formation of the oxide film on the wear surface of the Ti3SiC2/Cu-45# steel tribo-pair, while the load affected the extrusion and fragmentation of the oxide film on the wear surface of the tribo-pair. In the friction process, frictional oxidation was the main influencing factor for the formation of the oxide film. When the velocity and load were small, the main frictional oxide consisted of SiO2−x and a small amount of CuO. When the velocity reached 1 m/s and the load reached 3 N, the oxide film was partially broken down and flaked off, and the matrix of the Ti3SiC2/Cu composite was exposed and oxidized, at which time the oxide film was composed of SiO2−x, TiO2, CuO, and Fe2O3. Under the synergistic effect of the velocity–load–temperature field, the friction and wear mechanism of the Ti3SiC2/Cu-45# steel tribo-pair changed from abrasive wear to frictional oxidation wear with the increase in velocity and load.

Modelling and fatigue reliability investigation on wear prediction of piston/cylinder pair based on friction fatigue mechanism

This paper aims to assess the wear reliability characteristics of the piston/cylinder pair based on the wear failure prediction using numerical and experimental techniques for the water hydraulic state. This is due to the complex forces and contact states acting in the piston, hence, making it difficult to establish a numerical model for wear failure prediction. The Hertzian contact and Elastic-Plastic mechanical equivalence are proposed in numerically modelling the friction fatigue mechanism based on asperity damage for piston/cylinder pair. An experimental analysis is conducted for the reciprocating ceramic peek-2507 steel tribopair to validate the effectiveness of the prediction model. The error between the numerical and experimental models is assessed to be less than 10% with a coefficient of determinant R2 of 0.99. The numerical wear data were scattered within the 10% confidence interval, indicating the high survivability of the predicted data. In addition, the reliability characteristics based on the volume of wear predicting in risk monitoring using the Weibull probability distribution function are proposed to model the reliability and probability of failure for the piston/cylinder pair. From the volume of wear prediction from the computed Mean-Volume-To-Failure (MVTF) = 17.8 mm3, the probability of failure based on the numerical modelling is estimated to be at 0.52. Hence, the proposed numerical model is suitable for predicting the wear volume in the water hydraulic state for various conditions.

Effect of DLC film on the mitigation of white etching areas (WEAs) under dynamic loading

The premature failures in wind turbine gearbox bearings are primarily caused by the decay of subsurface microstructure called white etching areas and white etching cracks. Severe operating conditions of wind turbine gearbox bearings necessitated for tribological coatings to enhance the system performance. The current study investigated the performance of hydrogenated diamond-like‑carbon (DLC) coating against white etching areas formation under sliding-dynamic conditions. The dynamic loading experiments were carried out in the dynamic pin-on-disc tribometer with Polyalphaolefin base stock oil under a boundary lubrication regime. Prior to the dynamic load tests, detailed tribological characterisation of the deposited DLC coating was carried out. The post-test analysis results were compared with the uncoated AISI 52100 bearing steel tribopair to evaluate the performance of DLC-coated bearing steel against white etching areas formation under given conditions. The results obtained show the capability of the proposed coating to delay the formation of white etching areas in the bearing steel.

Tribological properties of MoSx/rGO nanohybrids as additives in deep eutectic solvent

Environment-friendly and sustainable deep eutectic solvents (DESs) are considered as a new type of lubricant. Here, MoSx/rGO nanohybrids were prepared as lubricant additive to improve the tribological performance of DES. The nanohybrids exhibited excellent dispersibility in DES. Tribological tests indicated that the DES with 1.5 wt% of MoSx/rGO additive exhibited the best lubrication performance for steel tribopair by reducing friction (∼31.2%) and wear (∼88.2%) due to the synergistic effect between the MoSx/rGO nanohybrid and DES. The superior lubricating properties of DES containing nanohybrids are primarily due to the attachment of nanohybrids to the friction interface, which triggers the formation of a robust tribofilm. These findings provide new insights into enhancing the tribological performance of DES by incorporating effective additives.

Oleic acid modified oxide graphene/triazine-based covalent-organic frameworks composite: Cooperation between heterostructure and electrical double layer to enhance tribological performances

Designing novel additives to construct the lubrication film integrating multi-configuration provides a promising solution for developing the lubricants with the excellent tribological performances. Present work prepared the oleic acid-modified graphene oxide/triazine-based covalent-organic frameworks composite (o-GTC) via a two-step solvothermal reaction as a dispersible additive to PAO 10 oil. The XRD, FTIR, Raman and SEM analyses characterized the heterostructure of the o-GTC. Tribological tests reveal that an optimum dose of o-GTC (0.05 wt%) dramatically decreased friction and wear by 50.9% and 92.9% for steel tribopair. The investigation of worn scar uncovered that the firm and tenacious lubrication film integrating the electrical double layer and the heterostructure is formed on the sliding surface, which is responsible for the outstanding tribological performances.

Reliability assessment of PEEK/17-4PH stainless steel tribopair under seawater lubrication

The high reliability and extended life of seawater hydraulic components depends on the tribological properties of the key tribopairs. The main reason that restricts their life is the wear of the tribopairs in relative motion. Therefore, the performance degradation of the tribopair should be investigated. Due to the limitation of the test sample size and test time, a large number of tests cannot be performed in a short period of time. Therefore, with the development of the sensor and monitoring technologies, the Accelerated Degradation Testing (ADT) has become an accelerated test method that can efficiently select and analyze the reliability of tribopairs. In this paper, the friction and wear characteristics of polyether ether ketone (PEEK)/17-4PH stainless steel are investigated, and the acceleration stress related to its performance is analyzed. Taking into account the random characteristics of the degradation process, an ADT model based on the Wiener stochastic process is constructed, while using the MLE solver. Finally, the model is estimated and verified using PEEK/17-4PH stainless steel experimental data. The results show that the proposed model helps the reliable assessment and further research of tribopair material.

Surface Functionalization of WS2 Nanosheets with Alkyl Chains for Enhancement of Dispersion Stability and Tribological Properties.

Tungsten disulfide (WS2) exhibits intriguing tribological properties and has been explored as an excellent lubricious material in thin-film and solid lubricants. However, the poor dispersibility of WS2 has been a major challenge for its utilization in liquid lubricant applications. Herein, a top-down integrated approach is presented to synthesize oxygenated WS2 (WS2-O) nanosheets via strong acid-mediated oxidation and ultrasound-assisted exfoliation. The ultrathin sheets of WS2-O, comprising 4-7 molecular lamellae, exhibit oxygen/hydroxyl functionalities. The organosilanes having variable surface-active leaving groups (chloro and ethoxy) are covalently grafted, targeting the hydroxyl/oxygen functionalities on the surface of WS2-O nanosheets. The grafting of organosilanes is governed by the reactivity of chloro and ethoxy leaving groups. The DFT calculations further support the covalent interaction between the WS2-O nanosheets and organosilanes. The alkyl chain-functionalized WS2-O nanosheets displayed excellent dispersibility in mineral lube base oil. A minute dose of chemically functionalized-WS2 (0.2 mg.mL-1) notably enhanced the tribological properties of mineral lube oil by reducing the friction coefficient (52%) and wear volume (79%) for a steel tribopair. Raman analysis of worn surfaces revealed WS2-derived lubricious thin film formation. The improved tribological properties are attributed to ultralow thickness, stable dispersion, and low shear strength of chemically functionalized WS2 nanosheets, along with protective thin film formation over the contact interfaces of a steel tribopair. The present work opens a new avenue toward exploiting low-dimensional nanosheets for minimizing energy losses due to high friction.

Chemically functionalized 2D/2D hexagonal boron Nitride/Molybdenum disulfide heterostructure for enhancement of lubrication properties

Ultralow friction arising from interfaces of incommensurately stacked 2D/2D heterostructure of two different crystal lattices provides a promising solution for designing a new generation lubricants of superior tribological properties. Present work addressed the chemically functionalized 2D/2D heterostructure of h-BN and MoS2 nanosheets as a dispersible additive to engine oil for reducing friction and material losses. The h-BN nanosheets prepared by alkali-assisted hydrothermal exfoliation are used for growing the MoS2 lamellae via a chemical reduction in the presence of cetyltrimethylammonium bromide (CTAB). The XPS, FTIR, Raman, XRD, and HRTEM analyses confirmed the synthesis of the h-BN-MoS2-CTAB heterostructure. The grafting of CTA furnished excellent dispersibility of h-BN-MoS2-CTAB heterostructure in fully formulated engine oil, which ensured their uninterrupted supply to contact interfaces of steel tribopair. A minute dose of h-BN-MoS2-CTAB (30 ppm) to engine oil decreased the friction and wear by 44% and 96% for steel tribopair. The improved lubrication properties are ascribed to the excellent dispersibility of h-BN-MoS2-CTAB heterostructure in engine oil, low shear strength of incommensurately stacked h-BN and MoS2 lamellae, and the formation of protective thin film on steel tribo-interfaces. These findings suggest that 2D/2D heterostructure can be revolutionary materials for developing new generation lubricants.

Tribological behaviors of Mo2BC ceramics against various counterpart materials

In this study, the tribological behaviors of Mo2BC ceramics against four different counterpart materials were studied. It was established that the tribological properties of Mo2BC were sensitive to the counterpart material. For the Mo2BC/SiC and Mo2BC/Al2O3 tribo-pairs, a layer of tribofilm, mainly consisting of MoO3, was generated owing to the tribo-oxidation reaction. However, the tribofilm did not provide lubrication under ambient conditions. Tribo-oxidation and adhesion wear were the main wear mechanisms. For the Mo2BC/Si3N4 tribo-pair, only minor MoO3 tribo-oxides were generated, and the tribo-pair showed better tribological properties; the friction coefficient was as low as 0.42. The dominant wear mechanism was two-body abrasion. The Mo2BC/GCr15 steel tribo-pair showed a high friction coefficient, owing to the adhesion effect of Fe.

Aminoguanidine-based deep eutectic solvents as environmentally-friendly and high-performance lubricant additives

Halogen-free, environmentally-friendly, and economically viable lubricant additives, which can furnish excellent miscibility with mineral lube base oils and enhance the tribological properties, are gaining increasing interest for the formulation of new generation lubricants. Herein, aminoguanidine salt-based deep eutectic solvents (DESs) having variable mole ratios of fatty acid (as a hydrogen bond donor; HBD) are synthesized through a single-step facile approach. The detailed chemical characterizations based on FTIR and NMR (1H and 13C) confirmed the synthesis of DESs via a hydrogen-bonding network. A linear correlation between the shear stress and shear rate implied Newtonian fluidic behaviour of these DESs. An increasing mole ratio of octanoic acid decreased the viscosity and thermal stability of resultant DESs. The long alkyl chain of HBD furnished good compatibility of these DESs with SN 150 mineral lube base oil. The DESs as additives to SN 150 mineral lube oil improved the viscosity index by 12% and enhanced the tribological properties for steel tribopair by decreasing the wear volume (94%) and coefficient of friction (30%). The detailed analyses of worn scars revealed the formation of DESs-derived tribochemical thin film. The low shear strength of DESs-derived lubricious and protective thin film between steel tribopair facilitated the sliding and avoided the direct contact between the steel tribopair, consequently, significant enhancement of tribological properties.

Graphene-Based Aqueous Lubricants: Dispersion Stability to the Enhancement of Tribological Properties.

The present investigation demonstrates a green and scalable chemical approach to prepare aminoborate-functionalized reduced graphene oxide (rGO-AmB) for aqueous lubricants. The chemical, structural, crystalline, and morphological features of rGO-AmB are probed by XPS, FTIR, Raman, XRD, and HRTEM measurements. The spectroscopic analyses revealed the multiple interaction pathways between rGO and AmB. rGO-AmB exhibited long-term dispersion stability and improved the thermal conductivity of water by 68%. The thermal conductivity increased with increasing concentration of rGO-AmB and temperature. rGO-AmB as an additive to water (0.2%) enhanced the tribological properties of a steel tribopair under the boundary lubrication regime by the significant reduction in friction (70%) and wear (68%). The tribo-induced gradual deposition of an rGO-AmB-based thin film facilitated the interfacial sliding between the steel tribopair and protected it from the wear. The ultralow thickness, excellent dispersibility in water, high thermal conductivity, intrinsic low frictional properties, and good affinity toward the tribo-interfaces make rGO-AmB a potential candidate for aqueous lubricants.

Pristine, Reduced, and Alkylated Graphene Oxide as Additives to Paraffin Grease for Enhancement of Tribological Properties

Abstract Pristine, reduced, and alkylated graphene oxides are applied as lubricating additives in paraffin grease. It has revealed that their crystalline structure governs the tribological properties of grease for steel tribo-pair. The microstructural analyses of grease samples showed that a loose fiber network of soap in the presence of graphene-based additive allows their facile release for efficient lubrication. The surface analyses based on the microscopic and elemental mapping show the development of a graphene-derived protective film on the worn scars, which protected the tribo-surfaces and subsided the wear. The reduced graphene oxide (rGO) with the interlamellar distance of 0.35 nm in the (002) plane provided minimum resistance to shear and exhibited maximum reduction in coefficient of friction (COF) for the paraffin grease. The presence of oxygen functionalities in the basal of pristine and alkylated graphene oxide (GO) compromised the interlamellar shearing under tribo-stress; consequently, higher COF than that of rGO.

Tribological Performance of Steel With Multi-Layer Graphene Grown by Low-Pressure Chemical Vapor Deposition

Abstract To explore the potential of directly grown multi-layer graphene as an agent in reducing friction and wear of steel on steel tribo-pair, multi-layer graphene films were synthesized on GCr15 steel in a low-pressure chemical vapor deposition (LPCVD) setup using a gaseous mixture of acetylene and hydrogen onto a bearing steel substrate. An interlayer of electroplated nickel was deposited on steel to assist and accelerate the graphene deposition. The tribological performance was evaluated using a ball-on-disc tribometer with an average Hertzian pressure of 0.2, 0.28, 0.34, and 0.42 GPa over a stroke length of 5 mm against GCr15 steel ball and compared with bare steel and nickel-plated steel. The results indicate that the friction coefficient is dependent on the applied load and decrease with increasing load, and the minimum friction coefficient of ∼0.13 was obtained for an applied normal load of 1 N; however, the coating failed after 250 cycles. The decrease in friction coefficient has been attributed to the homogenization of the deposited multi-layer graphene along the sliding direction and transfer of graphene to counter-face ball leading to inhibition of metal-metal contact. The investigation suggests that this kind of coating has the potential of improving the tribological performance of metal-metal tribo-pairs.

Tribological behaviour of nano additive based PAO lubricant for eutectic Al-Si alloy-chromium plated chrome steel tribopair

Abstract Energy sources are depleting at the very fast rate and the major reason behind energy depletion is the friction and wear of material. These mechanism cumulatively share 45% energy losses in mechanical components. This problem strives to find out new innovation lubrication mechanisms. In this concern, new innovation i.e. the use of nano additive based lubricant is being implemented to reduce friction and wear of materials. The scope and focus of this study is to determine the tribological behaviour of nano particles alone or in combination for minimizing the friction and wear. Nano-Aluminium Oxide (n-Al2O3), Graphene Nano Platelets (GNP) are used in this study with PAO-4 lubricant for the eutectic Al-Si alloy-chromium plated chrome steel tribopair. Various characterization techniques are used to study the wear mechanism offered during the tribological testing. The tribological test are conducted on a ball-on-disc reciprocating tribometer with 10 N load 120 m sliding distance, 2 mm stroke and 30 Hz frequency. From the results, it is reported that 0.5 wt% GNP (optimum concentration) as the nano-additive exhibit excellent tribological performance to reduce the friction and wear by 35.89% and 20.86% for the tribopair in comparison to the 1 wt% n-Al2O3 (optimum concentration) nano additive based lubricating oil. n-Al2O3 also provides good lubrication effect with optimum concentration of 1 wt% but, the results are not so effective compared to GNP based lubricant. 1 wt% n-Al2O3 + 0.5 wt% GNP i.e. Optimum hybrid Lubricant report minimum COF of 0.035 and minimum wear volume of 0.009 mm3 in comparison to other hybrid composition. Overall enhanced anti-wear and anti-friction behaviour is reported by using nano-additives based lubricants, which offers different nano lubrication mechanisms (ball bearing, mending and tribo oxide layer) to enhance the lubricity of the base lubricant.

Effect of Graphene-Based Nanoadditives on the Tribological and Rheological Performance of Paraffin Grease

The present study deals with tribological and rheological evaluations of paraffin grease having variable dosages (0.01-0.05 wt.%) of graphene oxide (GO), reduced graphene oxide (rGO), and octadecylamine-functionalized GO (GO-ODA). The microstructural and chemical characteristics of GO, rGO, and GO-ODA were analyzed by HRTEM, XRD, and FTIR. The graphene-based nanoadditives significantly improved the tribological properties between the steel tribo-pair by decreasing the wear and friction. The optimized dose of GO, rGO, and GO-ODA decreased the coefficient of friction (COF) by ~ 34.3, ~ 50.3, and ~ 34.3%, and wear volume by ~ 86.6, ~ 85.4, and ~ 80.9%, respectively. The friction reduction by GO, rGO, and GO-ODA nanoadditives conserved the energy by ~ 34.3, ~ 50.3, and ~ 34.4%, respectively. The spectroscopic and microscopic analyses of worn surfaces suggested the formation of graphene-based tribo-film, which facilitated the shearing under tribo-stress and protected the tribo-interfaces against the wear. The rheological results corroborate the roles of graphene-based nanoadditives and lube oil of grease under the tribo-stress, which is vital for the sustainability of tribo-film on the interacting surfaces. The graphene-based tribo-film reduced the friction, subsidized the wear, and conserved energy consumption.

Tribological characteristics of as-cast A356/10wt.% SiCp functionally graded composite dry sliding against EN-31 steel under unidirectional and oscillatory modes

A comparison in tribological response characteristics of as-cast Al-SiCp functionally graded composite material (FGM) dry sliding against hardened EN-31 steel under unidirectional and oscillatory sliding modes was investigated for a sliding/oscillating velocity of 0.4m/s slid through 500m utilizing a pin-on-disc configuration. The A356/10 wt.% SiCp FGM was prepared using vertical centrifugal casting technique. The microstructure characterization was done by Leica optical microscope, and the microstructural analysis revealed the presence of different zones due to the radial gradient distribution of SiCp reinforcement. The hardness variation was found to have a good correlation with its microstructural features at different zones of FGM. Wear loss against load curve indicated an increase in trend for both sliding modes, whereas the coefficient of friction versus load plot showed a decreasing trend for both cases under an identical set of operating parameters. Further, oscillatory wear loss of FGM/EN-31 steel tribopair was observed to be higher in comparison with unidirectional sliding mode for the entire load range, (30-150N) investigated. At the same time, the coefficient of friction of tribopair in oscillatory sliding mode was found to lower than the unidirectional mode.

Effect of load on the friction and wear properties of aluminum hybrid composite/chromium plated chrome steel tribopair under boundary lubrication conditions

Friction and wear loss are the main reason that contribute to the failure in the IC engine components. This emerges the demand for the light weight, low friction and wear resistant material to enhance the efficiency and to reduce the emission problem in the IC engine components. In this concern, tribological test are performed on the hybrid aluminium matrix composites (Al–Si/Al2O3/GNP) composite fabricated using non-conventional rapid Spark Plasma Sintering (SPS) against chromium plated chrome steel ball under boundary lubrication conditions at room temperature using Ball-on-disc tribometer configuration. Friction & wear studies are conducted under high loading conditions ranging 100 N–300 N with 120 m sliding distance, 30 Hz frequency, 2 mm stroke length. From the study, it is reported that coefficient of friction (COF) as well as the wear significantly reduces; attributed to SAE20W50 engine oil lubricant with GNP Nano particles used as the secondary reinforcement (solid lubricant) in the hybrid composite. Ultra-mild adhesion and abrasion are the dominating wear mechanisms for the hybrid composite samples.

Friction and wear characteristics of PA 66 polymer composite/316L stainless steel tribopair in aqueous solution with different salt levels

Abstract Friction and wear behaviour of a PA 66 composite with 25% glass fibre reinforcement sliding against a 316L stainless steel have been investigated using different aqueous solutions under mixed/boundary lubrication. The aqueous solutions used are deionized water, seawater, seawater without group II metal salts, solution of dissolved Group II metal salts and solution of group II metal salts and NaHCO3. Lower friction and wear was obtained when lubricated with seawater. However, when deionized water or salt solutions without group II metal salts is used, increased wear was observed. The lower friction and wear in seawater solution is due to group II metal ions and bicarbonate ions that facilitate formation of the sparingly soluble carbonates that act as a lubricating tribofilm.

Pristine and Alkylated MoS2 Nanosheets for Enhancement of Tribological Performance of Paraffin Grease Under Boundary Lubrication Regime

In the present study, lubricating grease was developed with paraffin oil and 12-lithium hydroxy stearate metal soap as a thickening agent. MoS2 nanosheets were synthesized by hydrothermal method and functionalized with 1-octadecanethiol (i.e., MoS2-ODT). The MoS2 and MoS2-ODT nanosheets were dispersed in the grease with different concentrations to evaluate its tribological performance. Tribological results unveiled that the addition of MoS2 nanosheets in grease appreciably reduced the coefficient of friction and mean wear volume of tribo-interfaces as compared with pure grease. Energy dispersive spectroscopy (EDS) spectrum revealed the deposition of MoS2 on the worn surface and confirmed a thin tribo-film which protects steel tribo-pair against wear.