Search

The constant development of environmental protection causes the necessity to increase the efficiency of machines. By increasing the efficiency of machines, energy losses can be limited, leading to lower energy consumption. Friction reduction leads to an increase in efficiency and a decrease in wear. In this paper, selected surface texturing methods, such as burnishing and abrasive jet machining, with their limitations are presented. Thanks to those processes, various surface textures can be obtained. Examples of applications of these methods for friction and wear reduction are shown.

Surface texturing is an option of surface engineering resulting in reduction of friction due to the creation of isolated dimples or grooves on sliding surfaces. The purpose of this work is to find the effect of the groove bottom profiles on the reduction of the friction force. Investigations were conducted using an Optimol SRV5 tribotester equipped with a pin-on-disc module. A disc made of 42CrMo4 steel, with a 100 mm diameter acted as a sample. A counter-sample was made of the same material, however, its diameter was 20 mm. The sliding conditions were selected to be similar to those of a sliding crankpin bearing pad operating in a high-performance internal combustion engine. Surface texturing was found to be beneficial for a reduction in the friction coefficient up to 55% in comparison to the untextured disc. Tribological performances of discs with spiral groove patterns were better than those with a radial layout. In most cases the convergent profile of the groove bottom was superior to the dam shape.

This paper presents the results of the tribological experiments conducted using an oscillating wear tester under lubricated conditions. Specimen from piston ring slid against counter-specimen from cylinder liner. Various surface textures of cylinder liners resulted from honing and/or plateau honing. Tests were carried out for two normal loads of 100 and 300 N at a temperature of 80 °C, the stroke was 3 mm, the frequency was 10 Hz. Each experiment was divided into four time intervals. During breaks between the particular parts of the test, the surface topography of cylinder liners was measured by a white light interferometer. It was found that an increase in the normal load led to an increase in changes of the liner surface textures.

Tests were carried out using a pin-on-disc tester under starved lubrication conditions. To achieve a conformal contact, a special construction was used with an adjustable counter sample. Textured surfaces with two dimple patterns (spiral an radial) and four shapes (circle, oval, triangle, and chevron) were tested. The contact area was lubricated with L-AN-46 oil. Before the tests, surface topographies of the discs were measured by a white light interferometer Talysurf CCI Lite. Tests showed that, in starved lubrication conditions, oil pocket shape and pattern affected the friction force.

The experiments were carried out using an Optimol SRV5 oscillating wear tester under lubrication. Specimens were cut from gray cast iron cylinder liners honed and/or plateau honed with diamond or ceramic stones. Counter-specimens were cut from chromium-coated compression ring. Short time tests of 30 min duration were conducted at a temperature of −20 °C, with a stroke of 3 mm. In addition, for a few sliding assemblies, durations of tests at the low temperature were extended to 24 h. For comparison, similar tests for a smaller number of sliding pairs were carried out at a temperature of 80 °C. Before and after tests cylinder liner surface topographies were measured by a white light interferometer Talysurf CCI Lite. It was found that the changes of liner height and frictional resistance at the low temperature were smaller from those tested at the elevated temperature. Two-process textures tested at the low temperature led to a smaller final coefficient of friction, compared to one-process surfaces; opposed results were obtained at the high temperature.

Tribological tests were conducted using a pin-on-disc tester in unidirectional sliding under starved lubrication. A specimen of 25.4 mm diameter with a hardness of 50 HRC and a counter-specimen of 5 mm diameter with a hardness of 40 HRC were made from 42CrMo4 steel. Specimens were textured by abrasive jet machining. An average depth of oil pockets was 10 μm, a mean diameter was 0.5 mm and a pit-area ratio was 17%. Tribological behavior of sliding pairs with textured and untextured (polished) discs were compared. Friction tests were conducted at normal loads of 10, 20, 30, 40, 50 and 60 N increased in a stepwise manner, a sliding speed was set to 0.6 m/s. Friction behaviors were evaluated at room temperature and at elevated temperature (80 °C). The tested assemblies were lubricated by different oils. Surface texturing always led to beneficial performance of sliding pairs. However the best effect of surface texturing was observed at smaller loads and elevated temperature. Under these conditions, the effect of kind of oil on tribological behavior was negligible.

Experiments were carried out using a pin-on-disc tester in conformal contact starved lubrication and unidirectional sliding with constant normal load of 20 N and sliding speed of 0.8 m/s. Different combinations of co-acted samples were studied: textured specimen and untextured counter-specimen, both samples textured and untextured. Samples with the following densities of dimples were tested: 2.25%, 5%, 9%, 14% and 20.25%. The best tribological performance was achieved for both surfaces textured with the smallest pit-area ratio. For large area densities tribological behaviors of sliding pairs with one sample textured were better than those with both samples textured.

Experiments were carried out using pin-on-disc tester in conformal lubricated contact conditions for different normal loads. Surface texturing was done using abrasive jet machining with the application of laser cut mask. In order to eliminate the effect of different input variables in all the experiments, pit-area ratio and sizes of oil pockets were very similar. Five types of oil pocket arrays were tested: radial, concentric, spiral, of a square arrangement, and of a random arrangement for 5% and 17% of pit-area ratio. Different dimple diameters caused various oil pocket densities. The experiments were also made for untextured polished discs. During tests, the friction force was monitored as a function of time. Before and after tests, disc surface topography was measured using a white light interferometer Talysurf CCI Lite. The beneficial effect of surface texturing was obtained for spiral arrays of dimples on disc surface. The presence of a radial array of oil pockets resulted in the worst tribological properties of tribological assemblies containing textured discs.

Investigations were performed to study the effect of graphite surface texturing on the friction coefficient reduction of graphite-steel sliding pair in dry flat contact. Friction tests were carried out using an Optimol SRV 5 tester, equipped with a rotation pin-on-disc module. Graphite discs of 100 mm diameter and 10 mm thickness were tested. Surface texturing was made with abrasive jet machining. Counter samples made of 42CrMo4 steel were polished. Four types of textured surfaces were tested. The tests revealed that a direction of the converging bottom texture had a substantial effect on the scatter of the friction coefficient. High stability and low value of the coefficient of friction were achieved for the disc texture with bottom steps parallel to the arm of the chevron. Low friction forces were obtained for the angle between arms of 120°.