Raimondas Kreivaitis

Tribologic behaviour and suspension stability of iron and copper nanoparticles in rapeseed and mineral oils

Abstract Metal particles, suspended as wear debris or as additives, have a major influence on lubrication technology. They are known mostly for negative roles, but even iron nanoparticles, which are likely to pass through most filters, have not yet been quantitatively evaluated for their effects on friction and wear. In this study iron and copper nanoparticle suspensions were formulated in high sulphur paraffinic mineral oils and food grade rapeseed oil. The suspension stabilisation mechanism based on steric repulsion appeared more effective than ionic repulsion principle. Iron nanoparticle suspensions were investigated using four ball antiwear tribotester. Iron nanoparticles did not show statistically significant effects on wear or friction in mineral oil suspension. However, addition of surfactants improved the tribological performance. Wear, friction and sample temperature data along with microscopy evaluation suggested that formation of protective films in the friction zone was the most likely reason for reduction of wear, average friction and the duration of break-in regime.

Influence of manufacturing methods on the tribological properties of rapeseed oil lubricants

Tribological properties of rapeseed oils manufactured and processed by different methods and modified by the anti-wear additives were analysed. Tribological tests presented that unrefined rapeseed oil has better wear resistance compared to refined oil. Modification of rapeseed oil with 2% of special biological anti-wear additives has the greatest influence on refined rapeseed oil. Chemical analysis shows that refinement removes acids from oil. Refinement and lower acidity allows more efficient operation of special biological anti-wear additives.

The influence of Oxidation on Tribological Properties of Rapeseed Oil

Abstract Approximately a half of all consumed lubricants, in one or another way, end up in the environment. Some countries put forward recommendations or even requirements for the use of environmentally friendly bio-lubricants the purpose of which is to reduce a negative influence of lubricants. The priority areas of using environmentally friendly lubricants cover water transport, hydraulic systems in forestry machinery, railway applications, road building machines etc. Particularly it is the case when an increased possibility of putting a lubricant in the environment occurs. Regarding good lubricity and excellent biodegradability, vegetable oils are widely used as environmentally friendly lubricants. The biggest disadvantage of vegetable oils as base stock for lubricants is pure oxidation stability. This article deals with the influence of thermal oxidation on tribological properties of rapeseed oil. The obtained results show that oxidation decreases lubrication ability due to structural changes in oil. ...

Effect of ethanol on performance and durability of a diesel common rail high pressure fuel pump

AbstractThis paper presents a comparative experimental study for determining the effect of ethanol on functionality of a high pressure pump of the common rail fuel injection system. For experimental durability tests were prepared two identical fuel injection systems, which were mounted on a test bed for a fuel injection pump. One of the fuel injection systems was feed with diesel fuel; other fuel injection system was fuelled with ethanol–diesel fuel blend. A blend with 12% v/v ethanol and 88% v/v diesel fuel and low sulphur diesel fuel as a reference fuel were used in this study. To determine the effect of ethanol on the durability of the high pressure pump total fuel delivery performance and surface roughness of pump element were measured prior and after the test. Results show that the use of the ethanol–diesel blend tested produced a negative effect on the durability of the high pressure fuel pump. The wear of plungers and barrels when using ethanol–diesel fuel blend caused a decrease in fuel delivery u...

Development and modification of Fe and FeCu nanoparticles and tribological analysis of the lubricants with nano‐suspensions

Purpose – The purpose of this paper is to investigate the possibility of using the iron nanoparticles and iron nanoparticles coated with copper layer as additives to base oils.Design/methodology/approach – Fe and Fe+Cu nanoparticles were synthesized by a reduction modification method and added to mineral oil. The size and structure of prepared nanoparticles were characterized by SEM, TEM, XRF, AAS and XRD analysis. Tribological properties of modified lubricants were evaluated on a four‐ball machine in a model of sliding friction pairs.Findings – Spectral and microscopy analysis evidently displayed the formation of Fe and Fe+Cu nanoparticles in suspensions of colloidal solutions and oil. The size of formed nanoparticles was in 15‐50u2009nm range. Tribological experiments show good lubricating properties of oils modified with Fe and Fe+Cu nanoparticles: higher wear resistance (55 per cent and 46 per cent accordingly) and lower friction coefficient (30 per cent and 26 per cent accordingly). The tests show that n...

Tribological properties of combined molybdenum coatings formed by electric-spark alloying on stainless steel

To improve the operational properties of the parts of machines made of quenched stainless steel 30X13, the surface were hardened by electric-spark alloying (ESA) with combined coatings (molybdenum + chromium and molybdenum + bronze). The results of investigations showed the correlation between the wear resistance of coatings and their hardness. It has been noted that the roughness of all alloyed coatings after tribological tests lowered, while the roughness of unalloyed surface of steel 30X13 increased. The smallest coefficient of friction has been established for samples alloyed with the molybdenum + bronze combined coating.

Effect of fatty-acid composition and structure of alkyl radicals of plant oil triglycerides on their tribotechnical characteristics

Sunflower, corn, rapeseed, olive, and linseed oils have been tested on a four-ball friction machine. The fatty-acid composition of oils has been determined. It has been shown that the similarity of their antiwear characteristics and the holding range of surface-active substances is related to the equivalence of the chain lengths of alkyl radicals. It has been determined that the activation of unsaturated bonds as a result of the oxidation and thermomechanical exposure upon friction has a positive influence on the friction interaction due to tribopolymerization and film formation on the abrasive surfaces. It has been stated that, with change in the average chain length of alkyl radicals and the number of unsaturated bonds by the addition of corresponding triglycerides, one can control the tribotechnical characteristics of plant oils.

Lubrication properties of modified lard and rapeseed oil greases with sodium and lithium thickeners

Purpose – The purpose of this paper is to conduct research on the possibility of improving the tribological and utilization properties of lard and rapeseed oil bio-based greases by mixing it with ethanol and selection of thickener and modification with special biological additives. Design/methodology/approach – Rapeseed oil- and lard-based greases with sodium and lithium soap thickeners were mixed with either water or ethanol and modified with a special biological anti-wear additive. Tribological properties of modified lubricants evaluated on a four-ball machine. Findings – Rapeseed oil- and lard-based greases suspended in ethanol and modified with bio-additive have the same wear resistance as the industrial non-biological lubrication grease and much higher wear resistance as bio-based reference grease. The tribological efficiency of the additives is higher in greases of rapeseed oil and less efficient in lard-based greases. Oxidation and wear tests show that investigated bio-based greases have comparativ...

Tribotechnical Properties of Edible Vegetable Oils

The basic mechanical and tribotechnical properties of olive, corn, sunflower, rapeseed oils and mineral oil I-20 were determined. It is found that mechanical properties of oils are comparable or better to properties of I-20, as well as their load-carrying capacity meet or exceed up to 60 %, antiwear properties are more effective of 1.3-2.3 times, load wear index is higher by 2.3 times. According to tribological characteristics, the oils are ranked from best to worst as follows: olive, corn, rapeseed and sunflower. DOI: https://doi.org/10.15544/balttrib.2015.02