Juozas Padgurskas

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. ...

New tribotechnical materials for the friction pair radial lip seal/shaft

The possibilities increasing the wear resistance of friction pair radial lip seal/shaft were tested using fluoroligomeric materials and selective transfer technologies. Measurements of friction moment, temperature in contact spot and wear of friction surfaces show that fluoroligomeric coat and selective transfer technologies (metallpolymeric oil additives and NABA‐coat on shaft) can considerably decrease the friction losses and increase the wear resistance of friction pair. The microscopic analysis of surfaces shows that using tribotechnical materials in contact spot of friction surfaces forms virtually different structures which can explain the different efficiency mechanisms of the mentioned materials. These tests show that in friction pair radial lip seal/shaft the tribomaterials could be used which create selective transfer effect and have regenerating properties.

Investigation of tribological properties in piezoelectric contact

The aim of the paper is to describe the ways to increase the reliability of the piezoelectric motors, related to tribological processes of the contact zones piezoelectric transducer—rotor or slider, in which both static forces and ultrasonic two dimensional vibrations are taking place. The problems of frictional wear are dealt with introducing and realizing the concept of adaptive tribological pair with optimal rheological parameters of components, enabling to effect self-diagnostics of the pair by exploiting direct piezoelectric effect of already existing piezoelectric transducers. This will allow for the forecast of durability and its significant increase when using new advanced materials (including nano-particles). Some results of experiments are given, including correlation of diagnostic signals with the parameters of wear.

The effect of fluorine oligomer coatings on the tribocontacts of a piezoelectric actuator

The tribological study of the parameters of piezoactuator when switching over contacts a trib- ocouple deals with of rotation of piezoactuator steady during 500 m when the rotor from polished steel C45 (HRC 50, Ra = 2 μm) is used. Often the rotation speed leaps up to 16-18 min-1. The coating with fluoroli- gomeric material stabilizes the rotation and continuous operation of piezoactuator. The steady rotation speed starts from a 50-m run (350 rotor revolutions, i.e., cycles of repeating impacts on the surface). The lower dam- age of the friction surface takes place after a 500-m run when the rotor is coated with fluoroligomeric mate- rial. Scratch tests show that steel surface with the fluoroligomeric layer has a lower hardness and 20% higher elasticity compared to a noncoated surface.

Investigation of tribological properties of carbide coatings deposited by electrospark at piezoelectric tribocontact

Investigations presented in this paper were carried out using an originally designed rotary piezoelectric motor of a standing wave tribotester. Test conditions, such as the normal force value in the friction pair, the rotor stop torque value, and the test duration can be programmed and changed in a desirable mode. The rotation speed, covered distance and loading torque of a piezo actuator were measured. Two different coatings (WC-Co8 and TiC15-Co6) were tested as the rotor friction surface and the wear of friction pairs (rotor, counter body) was evaluated after the tests. Investigations reveal an incidental advantage of output parameters of the piezo actuator with the TiC15-Co6 coating on the friction pair. Besides, high hardness of carbide surfaces requires paying more attention to the wear resistance of the frictional material of the counter body.

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 15‐50 nm 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.

Research into nanoparticles obtained by electric explosion of conductive materials

One of the primary nanoparticles production methods is electric explosion of wire (further — EEW) which is known as a physical phenomenon since 1771. Limitation of EEW as a method of nanoparticles production lies in a great dispersion of particle diameters — a spectrum of nano- and micrometric diameters (103 and higher differences in diameters are likely). Due to great differences in nanoparticles diameters formed by explosion (in aerosol conditioned by explosion), a continuous separation of nanoparticles from aerosol flows is essential. Dispersion of conductor explosion products is mostly affected by a diameter of wire, density of comparative energy, duration of the energy input. Objective of this research is to investigate the vista of producing nanoparticles by EEW at low voltage and high energy surplus using the wire of an enlarged diameter. Analyses have been made by exploding the iron wire of 60 mm length and 0.31 and 0.45 mm diameter and the copper wire of 0.375 and 0.49 mm diameter. Purity of the wire material was 99.5% of iron and 99.9% of copper. To separate nanoparticles from aerosol a separation device was used which consists of a precipitator and three stages centrifugal cyclone. SEM analysis of Fe nanoparticles using SEM showed the mean diameter of particles about 69 nm (for wire Ø0.45 mm). Cu nanoparticles was 97 nm in diameter (for wire Ø0.49 mm). XRD spectra of iron and copper nanoparticles indicated a high oxidation level of Fe and Cu (oxides of different crystollagraphic axes are formed such as Fe3O4, Fe2O3, CuO, Cu2O). A moderate quantity of pure Fe and Cu metals (Fe(110), Fe(211), C(l 11), Cu(200)).