The ball-burnishing process is a particular finishing treatment that can improve selected properties of different materials. In the present study, the ball-burnishing technique was used to investigate the effect of input parameters of processes on selected surface layer features like surface roughness and residual stresses of the 42CrMo4 steel surfaces. The burnishing process was conducted on Haas CNC Vertical Mill Center VF-3 using a tool with tungsten carbide tip. A further objective of our research was to improve tribological properties of the aforementioned steel by the ball-burnishing process. The results of the investigations showed that it was possible to reduce the root mean square height of the surface Sq from 0.522 μm to 0.051 μm and to increase wear resistance compared to ground samples.

The results of experimental investigations on the effect of the oil pockets existence on seizure resistance of sliding elements are presented. Seizure tests were conducted with block-on-ring apparatus at increasing pressure. The stationary block (counter specimen) contacted the rotating steel ring (specimen). The tested assemblies were lubricated by oil L-AN 46, which was heated to 30°C before each experiment. The sliding was unidirectional. The block was a part of a bearing sleeve-hardened EN-GJS 400-15 cast iron with a hardness value of 50 HRC. The ring samples, 35 mm in diameter, were made from hardened 42CrMo4 steel of hardness 32 HRC. The friction force and temperature near the contact zone were measured during the tests. Some variants of specimen surfaces were created by burnishing technique. They were characterised by the oil pocket density, the holes depth, length, and width. The oil pockets existence of area density of 10% on the ring surface improved seizure resistance of the sliding pair steel-cast iron for speed of 0.27 m/s. The pit shape and orientation are very important, too.

Wear tests were conducted using a pin-on-disc tester. In the experiment, a steel disc of hardness 40 HRC was put in contact with a steel pin of hardness 64 HRC with spherical end. Disc samples were prepared in order to obtain very similar values of the Sq parameter of one-process and two-process isotropic surfaces. Height of one–process disc surfaces, characterized by the Sq parameter was in the range 0.5 – 6 µm, but of two-process textures 1- 4.5 µm. Dry and lubricated tests, using different contact conditions were carried out. During testing, the friction force was monitored as a function of time. Wear of disc was measured after the test using white light interferometer. Tests under boundary lubrication condition were done using L-AN 46 oil.

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