Effect of Load on the Tribological Properties of Eutectic Al-Si Reinforced n-Al2O3 under Dry Sliding ConditionsRead the full article
Advances in Tribology publishes papers on the science of friction, wear, and lubrication. Topics covered include investigations into contact mechanics, wear and damage processes, surface and coating engineering, and lubrication technology.
Advances in Tribology maintains an Editorial Board of practicing researchers from around the world, to ensure manuscripts are handled by editors who are experts in the field of study.
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Estimation of the Oxidative Deterioration of Turbine Oil Using Membrane Patch Color
Lubricating oils degrade into two main products: oxidation products and solid particles. Oxidation products, called varnish, of turbine oils for power generation have become a particularly serious problem in recent years. The first step in determining the potential to produce varnish is to determine the remaining life of the antioxidant in the oil, but even though turbine oil may have antioxidants of sufficient longevity, varnish problems still occur frequently. Accordingly, to prevent varnish, it is necessary to diagnose oil oxidation products. Thus, the authors have developed a diagnostic method using membrane patch color, but the relationship between membrane patch color and the remaining life of turbine oils has yet to be clarified. This paper investigates a new method for estimating the oxidative degradation of turbine oils that uses membrane patch color and the dry turbine oxidation stability test (dry TOST) based on oxidation products and the remaining life of the turbine oils. Sample oils were prepared and degraded by oxidation in the laboratory using a dry TOST apparatus, and the membrane patch color was measured using a colorimetric patch analyzer (CPA). The relationship between membrane patch color and the rotating pressure vessel oxidation test (RPVOT) residual rate was then investigated. The results show that the new estimation method using the CPA and dry TOST is able to monitor the decrease of the RPVOT residual rate from the early stages of oxidative deterioration.
The Performance of Squeeze Film between Parallel Triangular Plates with a Ferro-Fluid Couple Stress Lubricant
The present study aims at investigating a couple stress ferrofluid lubricant effects on the performance of the squeezed film when a uniform external magnetic field is applied. For this purpose, Shliomis ferrohydrodynamic and couple stress fluid models are employed. The considered geometry is parallel triangular plates. The effects of couple stress, volume concentration, and Langevin parameters on squeeze film characteristics including time vs. height relationship and load-carrying capacity are investigated. According to the results, employing couple stress ferrofluid lubricant in the presence of the magnetic field leads to an increased performance of the squeeze film.
Tribological Behaviour of Neem Oil with and without Graphene Nanoplatelets Using Four-Ball Tester
The present work was aimed to study the friction and wear behaviour of graphene nanoplatelets (GNPs) under extreme pressure conditions as an anti-weld additive for neem oil. The effect of neem oil, blended with various loading of GNPs on the friction and wear characteristics has been investigated. From the experimental results, it was found that 1 wt.% of GNPs in neem oil showed the least coefficient of friction and smoother wear scar diameter. The extreme pressure test was performed on neem oil with and without GNPs as per ASTM standards. The extreme pressure test results indicated the improvement in seizure load of neem oil by 27.8% at 0.5 wt.% of GNPs as compared to pure neem oil. Optical microscopy of worn steel ball surface revealed the pit formation and the formation of wedge cutting edge in GNPs modified neem oil.
High Temperature Friction and Wear Performance of PVD Coatings under Press Hardening Contact Conditions
Press hardening is widely employed to produce automotive structural and safety components from advanced high-strength steels. This process depends on friction between the forming tools and the work piece. Wear of the forming tools affects the dimensional accuracy of produced components and reduces their service life. It is therefore desirable to reduce wear of forming tools for press hardening applications. One way to achieve this is by applying hard physical vapour deposited (PVD) coatings on the tool. In this work, the tribological behaviour of PVD coated tool-work piece material pairs has been studied at elevated temperatures in an experimental set-up simulating the tribological conditions in press hardening. Four different PVD coatings deposited on tool steel and uncoated tools as reference were studied during sliding against uncoated and Al-Si coated 22MnB5 steel. Results show that uncoated tools exhibited the lowest coefficient of friction when sliding against uncoated 22MnB5 steel. A CrWN coating initially showed low coefficient of friction but it increased with increasing sliding distance. A TiAlN coating and one of two AlCrN coatings showed similar frictional behaviour when sliding against uncoated 22MnB5 steel. During sliding against uncoated 22MnB5 steel, adhesive wear has been found to be the dominant wear mechanism. Adhesive wear was considerably reduced in the case of hard PVD coated tools in comparison to that of uncoated tools. During sliding against Al-Si coated 22MnB5 steel, no clear advantage in terms of friction behaviour of uncoated or PVD coated tools was observed. However, the transfer of Al-Si coating material from the work piece to the tools was significantly reduced for PVD coated tools. Frictional instabilities in all cases involving Al-Si coated work piece material further confirmed the occurrence of adhesive material transfer.
Wear Resistance of (Diamond-Ni)-Ti6Al4V Gradient Materials Prepared by Combined Selective Laser Melting and Spark Plasma Sintering Techniques
An approach of sintering 3D metal printed lattices and diamond nickel-coated particles is proposed which can be used for the production of tunnel boring machine (TBM) cutters and mining equipment blades. Nickel-coated diamond particles are mixed with titanium powder and incorporated into a lightweight Ti6Al4V (3D printed) lattice with the help of spark plasma sintering (SPS) method. Effect of Ti6Al4V lattices size, diamond particles size, and nickel coating layer thickness on wear resistance of composites is discussed. Functionally graded lattice (FGL) structures were produced by selective laser melting (SLM) method, representing an increasingly growing additive manufacturing engineering area introduced in material engineering. Impact-abrasive tribo-device (IATD), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and optical surface profiler (OSP) were used to characterize samples. An ab initio design of diamond-metal composite is based on the improvement of impact and abrasive wear resistance of Ti6Al4V by adding diamond particles and by applying of gradient lattice structure. The specimen with larger size of the diamond particle and thicker Ni coating has better wear resistance. In addition, ANSYS software simulations were done to analyze the effect of the presence of 3D printed lattice via nonlinear finite element AUTODYN solver under impact test. Diamond-based gradient composite material produced by combined SLM-SPS methods can be applied in applications where resistance against impact-abrasive wear is important.
Comparative Experimental Study of Tribo-Mechanical Performance of Low-Temperature PVD Based TiN Coated PRCL Systems for Diesel Engine
Piston ring and cylinder liner (PRCL) interface is a major contributor to the overall frictional and wear losses in an IC engine. Physical vapor deposition (PVD) based ceramic coatings on liners and rings are being investigated to address these issues. High temperature requirements for applications of conventional coating systems compromise the mechanical properties of the substrate materials. In the current study, experimental investigation of tribo-mechanical properties is conducted for various titanium nitride (TiN) coated PRCL interfaces in comparison with a commercial PRCL system. Low-temperature PVD based TiN coating is successfully achieved on the grey cast iron cylinder liner samples. Surface roughness of the grey cast iron cylinder liner substrates and the thickness of TiN coating are varied. A comprehensive comparative analysis of various PRCL interfaces is presented and all the trade-offs between various mechanical and tribological performance parameters are summarized. Coating thickness between 5 and 6 micrometres reports best tribo-mechanical behaviour. Adhesion and hardness are found to be superior for the TiN coatings deposited on cylinder liner samples with higher roughness, i.e., ~ 5-micron Ra. Maximum 62 % savings on the COF is reported for a particular PRCL system. Maximum 97% saving in cylinder liner wear rate is reported for another PRCL system.