Influence of Contamination of Gear Oils in Relation to Time of Operation on Their Lubricity

The quality and reliability of consumables, including gear oils, results in the failure-free operation of the transmission components in heavy trucks. It is known that oil viscosity is essential for all lubricated tribopairs for wear and friction reduction in all vehicles with a gearbox. Viscosity may be influenced by the contamination that wear products can impart on the oil. Oil contamination can also affect lubrication efficiency in the boundary friction conditions in gearboxes where slips occur (including bevel and hypoid gearboxes). The present research focused on this issue. An obvious hypothesis was adopted, where it was theorized that exploiting the contaminants that are present in gear oil may affect how the lubricating properties of gear oils deteriorate. Laboratory tests were performed on contaminants that are commonly found in gear oil using the Parker Laser CM20. The study was designed to identify a number of different solid particles that are present in oil. At the second stage, friction tests were conducted for a friction couple “ball-on-disc” in an oil bath at 90 °C on a CSM microtribometer. The quantitative contamination of the gear oils that contained solid particles and the curves representing the friction coefficients of fresh oils with a history of exploitation were compared. The test results were statistically analysed. Exploitation was shown to have a significant impact on the contamination of gear oils. It was revealed that the contamination and the mileage had no effect on the tested oils.

Arctic transmission oil

The tasks of the development of the Far North, the Arctic and the Antarctic require ensuring the operability of equipment units in low temperatures. To solve this problem, it is necessary to develop lubricants using new synthetic oils, a distinctive feature of which are low pour points. On the basis of polyethylsiloxane fluid and petroleum oil, we have developed a gear oil for the Arctic latitudes, which is efficient at temperatures down to -75 ° C (TMarktic). It is shown TMarktic’s antifriction properties are better than those of TSgip helicopter tail gear oil. The combined use of XPS and IR-Fourier methods for the analysis of the friction surface made it possible to conclude that the formation of the boundary film involves both antiwear additive molecules, which are part of the modified oil, due to the P-O, P=O, S=O bonds, so and molecules of polyethylsiloxane liquid due to C-O and Si-O bonds. Secondary surface structures are formed by TMarctic oil on the surface of iron oxide and include hydrocarbon and siloxane fragments. The high antiwear and extreme pressure properties of TMarktic are due to free sulfur and bound in iron sulfide.

Abrasive Wear, Scuffing and Rolling Contact Fatigue of DLC-Coated 18CrNiMo7-6 Steel Lubricated by a Pure and Contaminated Gear Oil

Due to extreme working conditions of mining conveyors, which contaminate gear oil with solid particles, their transmissions are exposed to intensive abrasion, scuffing, and even rolling contact fatigue (pitting). These effects shorten gear life. To prevent their occurrence, a wear-resistant coating can be deposited on gear teeth. The resistance to abrasive wear, scuffing, and pitting was investigated and reported in the article. Simple, model specimens were used. Abrasive wear and scuffing were tested using a pin-and-vee-block tribosystem in sliding contact. A cone–three-ball rolling tribosystem was employed to test pitting. The material of the test specimens (pins, vee blocks, cones) was 18CrNiMo7-6 case-hardened steel. Two types of DLC (Diamond-like Coatings) coatings were tested, W-DLC and W-DLC/CrN. The vee blocks and cones were coated. Two industrial gear oils were selected to lubricate the specimens: one with a mineral and one with a synthetic PAO (polyalphaolephine) base, as pure oil or contaminated with solid particles from a coal mine. The results show that, to minimize the tendency to abrasion, scuffing, and pitting of specimens made of 18CrNiMo7-6 steel, the W-DLC/CrN coating should be deposited. This coating also gives very good protection when the lubricating oil is contaminated.

Influence of Lubricant Supply on Thermal and Efficient Performances of a Gear Reducer for Electric Vehicles

The amount of lubricating oil in a gear reducer greatly influences components' temperature and efficiency of the reducer. A thermal network simulation model of a gear reducer for electric vehicles based on AMESim software was built for thermal and efficiency analysis of the reducer, where heat production and transfer processes of each component in the reducer are considered. Moreover, secondary development sub-models were developed to real timely calculate the convection coefficients based on different lubricating oil temperatures and working conditions. Next, the experiments were conducted to verify the developed model regarding transmission efficiency and lubricating oil equilibrium temperature in the reducer. The deviation between the numerical and experimental results is below 5%, which indicates high accuracy of the developed thermal network model. Thereafter, efficiency and heat balance simulation tests under different working conditions were performed to determine an optimal lubricating oil supply which is 14 mm gear-oil-immersion oil supply in this study. Finally, a comparison between the reducer with the optimal oil supply and that with normally used 22 mm gear-oil-immersion supply in the NEDC cycle in low temperature was conducted. The reducer with the optimal oil supply shows 1.032% energy saving. The method presented in this paper provides a good guide to design and optimization of the gear reducer for electrical vehicles.

EFFECT OF THE ESTER ON THE RESISTANCE OF ISOPARAFFIN OILS THICKENED WITH ESTER THICKENERS TO MECHANICAL DEGRADATION

This article examines the effect of esters on the resistance to mechanical degradation of ester thickeners as viscosity modifiers in thickened isoparaffin oils. The main reason for triggering such engine oils is the destruction of the thickener. The introduction of the ester should increase the polymer's resistance to rupture when passing through mechanisms with small gaps – gear oil pumps, in the lubrication system of an internal combustion engine. Also, esters with long alkyl chains should increase the solubility of polar thickeners in low-polar base oils, which can expand the application ranges of such thickeners and increase the resistance of thickened oils to low temperature-to eliminate the precipitation of the thickener at low temperatures. Depending on the thickening capacity of the viscosity modifier, its application may allow the production of motor oils with an extended service life in the entire range of viscosities of commercial oils according to SAE J300.

A New Benzotriazole Phosphite Ammonium Salt Derivative (PN) Extreme Pressure Additive to Improve Gear Oil Tribological Properties

In this paper, a new benzotriazole phosphite ammonium salt derivative extreme pressure additive called PN was synthesized. Four-ball experiments and SRV experiments were used to test the high temperature and extreme pressure performance of PN additive, and comparisons were made with the commonly used additives including ZDDP and T304. The results show that the COF and wear amount of the PN additive in the four-ball experiment were much smaller than that of the ZDDP and T304 additives. The COF of the PN additive in the RSV experiment changed slightly with temperature, and it had better high temperature extreme pressure performance in friction reduction than the traditional ZDDP and T304 additives. When the temperature was 120oC, the COF of PN was about 30% lower than that of traditional additives. Thermogravimetric analysis showed that the failure temperature of PN additives was within 180-200oC, and the thermal stability was better than that of ZDDP and T304. After the four-ball test, SEM was used to observe the morphology of wear spots on the ball surface. It was found that the wear spots containing PN additive had slight adhesive wear, while those containing ZDDP and T304 showed serious adhesion and ploughing wear, and the surface appeared peeling and tearing. XPS was used to detect the chemical composition of friction surface containing PN additive, and thus the formation process of film on frictional surface was analyzed.

Finite Element Analysis-Based Thermo-Mechanical Performance Study of Heavy Vehicle Medium Duty Transmission Gearbox

The main objective of this chapter is to investigate the performance of automobile transmission gearbox under the influence of load, rotational speed, and lubrication on multi speed gearbox gear surface. Gear oil SAE 80W-90 was used as gearbox lubricant, for cooling of transmission gearbox for high performance. An assumption has been made at the air-gear oil mist within transmission is under steady state condition, in isothermal equilibrium with the transmission gear oil bath of lubricant. The lubrication in multi speed transmission is subjected to thermo-elastohydrodynamic lubrication. The present chapter deals with the thermo-mechanical performance study of multi speed transmission (4 speed, excluding reverse gear) system, which combines transient structure analysis of the gear train assembly. The engaged gear teeth pairs transmit torque subjected to thermo-elastohydrodynamic arrangements of lubrication. The study here analyzed transmission in second gear pair.