STUDY OF THE INFLUENCE OF SURFACE IRREGULARITIES OF STEEL BALLS ON LUBRICATION

Abstract

The surface quality of bearing steel balls is one of the factors that can have a significant impact on friction and wear processes in the friction pairs of lubricated mechanical systems. Bearing steel balls from different production series often have uneven surface microgeometry, ranging from smooth and polished to rough, scratched, or having other defects. The influence of these differences on tribological behavior remains insufficiently studied. This work presents a comparative tribological analysis of steel balls from four different production series. The initial surface condition was assessed using an optical microscope, and the hardness of the material was determined using the Vickers method. Tribological tests were performed on a four-ball machine in accordance with DIN 51350 using SAE 5W-30 engine oil. During the test, the torque and coefficient of friction were recorded, and after the tests, the sizes of the wear spots were measured. The results of the study revealed a relationship between material hardness, initial surface quality, and tribological characteristics: the higher hardness series had a lower coefficient of friction and smaller wear spots. The series with the visually smoothest surface showed the highest wear due to lower hardness, indicating that hardness is a more important factor for durability than surface appearance. The conclusions can be useful for engineers making decisions about bearing selection and quality assessment.