Evaluation of tribological properties of selected engine oils during operation of the friction pairs of steel-on-steel

¹ Lublin University of Technology, Fundamentals of Technology Faculty, Department of Fundamental of Technology, 38 Nadbystrzycka Street, 20-618 Lublin, Poland
² Lublin University of Technology, Mechanical Engineering Faculty, Department of Production Engineering, 36 Nadbystrzycka Street, 20-618 Lublin, Poland
³ Lublin University of Technology, Electrical Engineering and Computer Science Faculty, Institute of Computer Science, 36B Nadbystrzycka Street, 20-618 Lublin, Poland

^⁎ Corresponding author: jjozwik@pwsz.chelm.pl

Abstract

The paper includes an assessment of the tribological properties of mineral and synthetic Lotos oil marked SAE 15W/40 and SAE 5W/40 at ambient temperature and 100 ̊C. The evaluation was based on the analysis of the tribological properties of friction couple consumables. Tribological tests were performed using the Anton Paar THT 1000 high temperature tribotester according to ASTM G133. Tribological properties were investigated using the “ball on disc” method. The change of friction coefficient, friction couple temperature, volume wear of samples and counter-samples and Hertz stresses were evaluated. In addition, hardness tests of the friction couple materials as well as surface roughness before and after friction were performed. On the basis of tribological studies, it was noted that Lotos Synthetic 5W/40 oil has better cooling properties compared. For both oils the coefficient of friction was lower at ambient temperature than at 100 ̊C. The highest value of volume wear of the sample was noted for the combination lubricated with Mineral Oil 15W/40 at 100 ̊C (0.0143 mm³) while for counter-sample lubricated with synthetic oil at ambient temperature (0.0039 mm³). The highest sample wear coefficient was recorded for the mineral oil lubricated at temperature of 100 ̊C (3.585*10^-7 mm³/N/m) while for counter-sample lubricated with synthetic oil at ambient temperature (9.8768*10^-8 mm³/N/m). The Hertz stress for each test couple had a value of 1.787 GPa.