Abstract
In the study, the friction stir processing (FSP) method was used to modify the surface layer of a tin-based bearing alloy. The modification was aimed at extending the service life of bearings by improving their tribological properties. The results of investigations of the microstructure, hardness and tribological properties of the SnSbCu bearing alloy after FSP using various rotational speeds of the tool—280, 355, 450 and 560 RPM—and the constant traverse speed of 355 mm/min are presented. Particular attention was paid to the possibility of changing the morphology of the precipitates present in the alloy, and to the impact of this parameter on improvement of the tribological properties. The research carried out in this paper covered investigations of the microstructure using light and scanning electron microscopy (SEM) along with analysis of the chemical composition in micro-areas and Brinell hardness tests. Additionally, the sizes of the SnSb and CuSn precipitates present in the microstructure before and after the modification process were determined, as were the tribological properties under technically dry friction conditions and lubrication with TU 32 oil. It was proven that using friction stir processing favors refinement of the microstructure and improves the tribological properties of the analyzed alloy.
Highlights
Two of the most important properties which sliding bearings should have are wear resistance and a low coefficient of friction
The investigated alloy is characterized by a multiphase microstructure, consisting of large diamond-shaped hard SnSb phases and numerous needle-shaped and nearly globular-shaped CuSn phase precipitates (Figure 3)
The results indicate a change in the morphology of the phases present in the investigated alloy
Summary
Two of the most important properties which sliding bearings should have are wear resistance and a low coefficient of friction. The increasing demands on the operational properties of manufactured elements present even more challenges for surface engineering. One of the promising methods of microstructure modification in surface layers is a new method—FSP—friction stir processing. This method was developed by Mishra et al [1] based on the basic principles of friction stir welding technology (FSW) [2]. The FSP method, unlike FSW, is used to modify the microstructure of the materials, and not to join metal elements. The process consists of heating and plasticizing the material as a result of the friction of a tool equipped with a shoulder and a pin plunged into the material and moving along the modified surface of the element. Sharma et al [4] shows that the microstructure in the process zone
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