Pure Base Oil Research Articles

Rolling contact fatigue life of AISI 52100 steel balls with mineral and synthetic polyester lubricants with PTFE nanoparticle powder as an additive

This work evaluates the rolling contact fatigue life of AISI 52100 steel bearing balls with mineral and synthetic oil, with and without additive, using a four-ball tester. IP 300/87 was applied with a total load of 600 kg (corresponding to a maximum Hertz stress of 8.709 MPa). SN-350 (a neutral mineral solvent) and TMP-05 (an environment friendly synthetic polyester) of the same viscosity were additivated with PTFE nanoparticle powder in different percentages. The total test time for each specimen was recorded and processed on Weibull probability plots. L 10 and L 50 are given for pure base oils and oils additivated with 1, 3 and 5 wt.% of PTFE powder. The results point to an increase in the fatigue life when additive-containing oils were used. In order to provide some understanding of the protection mechanism of the additive, the contact angle and the influence of the surface wettability on the lubricant unctuosity were analysed. Scanning electron microscopy and LINK techniques were used to study pitting, crack propagation, the chemical influence of additive and fluorine content.

High Temperature Tribological Behavior of Nano-Al<sub>2</sub>O<sub>3</sub> in Different Base Oils

High temperature tribological behavior of nano-Al2O3 in different base oils were tested by a SRV multifunctional test system. The results show that the nano-Al2O3 particles can obviously improve the antiwear and friction reducing properties of the base oil under high temperature and high load. The friction coefficients of the base oil with added nano-Al2O3 are reduced about 35%, and abrasion loss reduces about 60%. When temperature is 500°C and load is 500N the pure base oil has lost lubricative function, but the base oil with added nano-Al2O3 can still remain the lower friction coefficients. Tribological behavior should be similar to the “ball bearing” lubrication action of the nano-Al2O3 particles, so the movement between the two tribological pairs becomes sliding/rolling.

Influence of slide-to-roll ratio on tribofilm generation

Rolling contact fatigue has become a surface initiated problem. This phenomenon is due to the initiation and propagation of cracks from the surface to the volume of mechanical pieces. A great amount of research has been done since the 1970s to understand its origin, but many aspects remain unclear. Many authors found that the lubricant composition and especially certain additives can either improve or reduce fatigue life, depending on the operating conditions. It is now admitted that additives form a tribofilm in the rubbing track, especially under pure sliding conditions, but no direct relation to rolling contact fatigue has been drawn to this moment. The knowledge of the reaction pathways of lubricant additives under various sliding conditions as well as the tribofilm properties and morphology has become an important issue. In this work, the mini traction machine has been used to study friction under different sliding conditions of a pure mineral base oil and a formulated oil containing five selected additives. The results suggest that friction is likely to mimic tribofilm formation. The slide-to-roll ratio influences the rate of direct asperity contacts and hence tribofilm growth.

Tribological behaviour of DLC coatings in combination with biodegradable lubricants

The tribological behaviour of coated components lubricated with a biodegradable saturated ester and unsaturated ester has been studied. Different diamond-like carbon (DLC)-based coatings were selected as low friction coatings: pure DLC, Si-doped, Ti-doped and W-doped DLC. The performance of the studied ester oils has been compared with sunflower oil and mineral oil lubrication as reference. The oils were all formulated in the same way with conventional anti-wear (AW) and extreme-pressure (EP) additives. Ball-on-disc tests were performed for friction and wear analyses. It was found that DLC/steel contacts lubricated with biodegradable lubricants show similar friction as steel/steel contacts. AW additive activity which was clear in steel/steel contacts was not found in DLC/steel contacts. The wear was low in the DLC/steel contact both for the coating as for the steel surface even when pure base oil was used as lubricant.

Charging Ability of Pure Hydrocarbons and Lubricating Oils

An experiment using a purpose-built test rig to examine the effect of oil chemistry on the charging ability of various oils revealed that the charge produced depends on two extrinsic properties; the electric field (used to charge the droplet) and the droplet radius. A normalization parameter was developed from these dependencies and used to compare the results from the tests described herein. Four classes of liquids were tested. These were pure hydrocarbon liquids (hexadecane, decane, and squalane), base oils (both mineral and synthetic stocks), formulated oils (mineral base oil with additives), and commercial oils (fully formulated mineral and synthetic oils, available over-the-counter). The charging for both pure hydrocarbons and base oils indicates that the charged species have a low mobility and thus are likely to be large, bulky molecules. For this reason, the charging of the base oils is noticeably time dependent and the charge imparted on the oil did not always reach saturation. The charging (rate) of base oils appears to follow the level of impurities (particularly sulfur). Generally, both pure hydrocarbons and base oils tend to charge more when a positive field is applied. Conductivity values help to explain the measured charge levels. This would be expected as conductivity is related to the ionic species (charge carriers) present. The majority of the formulated and commercial oils tested reached charge saturation for all conditions tested, resulting in a normalized value of around 0.1 pC mm− 1 V− 1 , comparable with a theoretical calculated value. The formulated and commercial oils that did not reach saturation have conductivities comparable with base oils and therefore behave in a fashion similar to the base oils.

Experimental investigation of porous bearings under different lubricant and lubricating conditions

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (OS) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 20W50), two fully formulated commercial engine oils (SAE20W50) and lubricating oils with commercial additive concentration ratio of3% were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coefficient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without OS lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.

The Tribological Properties of Oils Added with Diamond Nano-Particles

A technique of relative optical interference intensity (ROII) and a high-precision force measuring system were used to measure film thickness and friction force of the oils added with ultra-fine diamond powder (UDP) in the nano-scale. The results show that the oil containing UDP nano-particles forms a thicker film than does the pure base oil. In the rubbing process, the hard spherical UDP nano-particles plow the two surfaces and produce many smooth micro-grooves. The friction force decreases with sliding distance. The possible mechanisms for such reduction and physical model of diamond nano-particles as additives in oils are discussed.

Application of a new concept to detergency

The purpose of this paper is to describe a new concept in the detergency phenomenon for engines. It is well known that oil detergency is associated with additive adsorption, neutralisation of the acid formed, and insoluble encapsulation. However, the literature is poor in relation to the mechanical properties of oxidised oil film created during the coking process. Basic experiments taking a pure base oil and an overbased additivated oil show clearly two different types of mechanical behaviour in the burned oil film. The base oil creates a ductile film very adherent to the substrate. Conversely, the additivated film can be very brittle and shows clearly cohesive cracks followed by adhesive film-substrate cracks. A physico-mechanical model is proposed to explain the role played by the internal stress developed in the film during its gel state. This analysis leads to a simple thermooxidation laboratory test, where mechanical behaviour is evaluated by peeling and is correlated with engine detergency.

Investigation of rolling oils and oil emulsions in the cold rolling test. I. Rolling tests with lubricants composed of pure base oils and additives: de|Werner Lueg, Paul Funke, and Winfrid Dahl. Stahl und Eisen, v. 77, no. 25, Dec. 12, 1957, p. 1817–1830

Investigation of rolling oils and oil emulsions in the cold rolling test. I. Rolling tests with lubricants composed of pure base oils and additives: de|Werner Lueg, Paul Funke, and Winfrid Dahl. Stahl und Eisen, v. 77, no. 25, Dec. 12, 1957, p. 1817–1830