Abstract
The aim of the research was to evaluate the influence of the initial roughness of a steel pin cooperating with a graphite ring—dry and wet—on the mechanism of sliding layer formation. A ring–pin friction pair was used for the study, where the rings were made of expanded graphite, while the pins were made of acid-resistant steel. In the first case, the steel pin interacted with a dry graphite ring, and in the second case, the graphite rings were moist. To determine the effect of initial surface roughness, the pins were divided into three roughness groups. To determine changes in surface geometry due to material transfer, the Ra and Rz parameters were measured. This project investigated how the initial roughness value of the steel surface pin cooperating with expanded graphite influences the formation of the sliding layer. Increasing the initial roughness of the steel surface interacting with the graphite contributes to faster layer formation and reduced roughness. The state of the expanded graphite—dry and wet—influences the formation of the sliding layer of graphite—a wet graphite component causes a faster smoothing of the steel surface. The running time of the wear apparatus has an effect on the resulting layer. The highest roughness group is the most favorable from the viewpoint of sliding layer formation.
Highlights
The material transfer phenomenon in a graphite–metal pair consists of the transfer of the graphite to the metal surface, so that, with time, the pair can work in graphite–graphite configuration
Performed in dry conditions, (b) tests performed with moist graphite rings
The results obtained allow us to formulate the following conclusions: The initial roughness value of the steel surface working with expanded graphite affects the formation of the sliding layer and the roughness of the steel surface after testing
Summary
The material transfer phenomenon in a graphite–metal pair consists of the transfer of the graphite to the metal surface, so that, with time, the pair can work in graphite–graphite configuration. The literature data on this phenomenon mainly refer to the material transfer of plastics containing graphite as filler [1,2]. The study shows that graphitemodified materials form a sliding layer on the metal surface, which is a factor retarding the destruction process on friction surfaces and increases the product value of pressures and speeds at which the exploitation of the tested materials is possible [3,4,5,6]. The nature and course of the layer formation depend on many factors. These include, but are not limited to, the operating environment, the temperature, the material and the roughness of the mating surfaces [8,9]
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