Investigation of effect of colemanite addition on the wear performance of an aluminum silicon alloy journal bearing material

Journal bearings are machine elements that are used in support of moving parts and selection of materials for their manufacture is very important. In the beginning, some materials such as wood, iron and leather had opportunities being used as plain bearings materials. However, because of reasons such as not to satisfy desired properties; bronze, brass and white metal has taken place of them. Aluminum based alloys have been developed in recent years to replace the mentioned materials used as journal bearings materials due to some disadvantages such as being expensive and insufficient tribological properties for most applications. Pure aluminum like other pure elements is used as the matrix material by adding various alloying elements especially silicon, copper, manganese, zinc and magnesium for reasons such as poor castability and inadequate mechanical properties. Aluminum and its alloys are suitable for casting and they have a low density, a low melting point and their mechanical properties are quite good. They adapt well with metallic compounds such as silicon carbide and alumina. Therefore, aluminum and its alloys are often preferred material for manufacturing MMC (metal matrix composite). In this study, firstly, a reference material of AlSi6ZnCuFe alloy has been produced. In the next step, 6 different content experimental materials have been designed with the casting method by adding ppm level colemanite to the reference material. Then, these specimens have been provided with ready to use by making the necessary cleanup for use in experimental studies. In order to determine the effects of colemanite ingredients on the microstructure and mechanical properties of test specimens; OM, SEM with EDX, DTA, DTG, TG/TGA thermal analysis tests, hardness measurements, wearing out, corrosion and compression experiments have been carried out. As a result of the experimental studies, it was determined that the insertion of ppm level colemanite made a considerable percentage of increase in the microstructure and mechanical properties of bearing material. In contrast, it was not observed any significant changes in other thermal properties including material phase transition temperature. However, it was determined that the insertion of colemanite caused sudden oxidation in some specimens at certain colemanite adding ratio. Keywords: Sliding bearing, Colemanite, Wear, SEM, EDX