Significant research has been done to improve the wear properties of the components used in internal combustion engines. Excessive wear is observed in components such as cylinder liners and rings, which can lead to lower volumetric efficiency of the engine, increase oil consumption, polluting emissions, and scuffing related issues. Since tribological systems in internal combustion engines are complex, the different wear mechanisms involved need to be investigated to improve the life of components. Cast irons are commonly used for engine components, especially compacted graphite irons (CGI) for piston rings and gray cast irons (GCI) for cylinder liners. This work aims to evaluate the tribological behavior of two different microstructures of CGI (pearlitic and ausferritic), sliding on pearlitic GCI. The samples of CGI with different microstructures and hardness were evaluated in a short-stroke reciprocating sliding tester, using Petronas Urania SAE 30 API CF lubricant oil at 100 °C for four hours. The characterization of worn surfaces was made using a scanning electron microscope (SEM) and 3D roughness measurements. The coefficient of friction (COF) comparison between the two CGI microstructures showed very similar results with COF = 0.11. The pearlitic CGI showed more severe wear than the austempered one, confirmed by SEM images and the difference in topography parameters before and after the tests. Phosphorus, sulfur, and zinc were detected by EDS analyses in the samples' worn-out regions, indicating the formation of tribo-films, which was further confirmed by the friction tests.
This work presents a comprehensive tribological analysis comparing the performance of two types of lubricants-a synthetic and a natural ester-used in industrial reciprocating air compressors. A comprehensive tribological analysis comparing the performance of two types of lubricants-synthetic and natural esters-used in industrial reciprocating air compressors were carried out using surface characterisation methods and lubricant analyses. The formed and detected tribo-films were not efficient to avoid the wear observed on the cylinders, although they may have been to avoid the wear on the rings. Regarding the lubricant analyses, particle analysis showed that none of the lubricants favoured solid particle leaching to a greater extent. A biolubricant such as the one employed in this study would be suitable for replacing a mineral lubricant in situations like the ones observed in this work.
Compacted graphite iron (CGI) has been considered an excellent option for heavy-duty engine blocks due to its superior mechanical properties, which allow reduction of weight, enhancing engine performance. Abrasion is a recognized wear mechanism in engine blocks, meaning it deserves to be evaluated for CGI. This study analyzed two grades of high-strength CGI (GJV450 and GJV500) submitted to microscale abrasion tests in free ball configuration using two different slurries: diamond and silica. There was more wear to the surfaces tested with silica due to the particle size, which was one order of magnitude larger than the diamond. The data obtained showed that both materials presented similar resistance when tests were performed with the diamond slurry. On the other hand, when silica was used, GJV500 presented 2.5 times greater wear resistance than GJV450, even though its global hardness was only 17% greater.
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