Metal matrix composites are undoubtedly a group of advanced engineering materials. Compared to unreinforced matrix material, they are characterized by increased strength, greater stiffness, increased wear resistance, better mechanical properties and dimensional stability at elevated temperatures as well as lower density. Due to its very favorable tribological properties for many years research has been conducted on the application of MMC in friction node. The article presents important technological aspects related to the production and properties of composite pistons. Under industrial conditions, a composite suspension (AlSi7Mg2Sr0.03/SiCp 10 vol %) was prepared to allow casting of the semi-finished pistons series. Machining parameters of the working surfaces of the piston were selected on the basis of the turning test made on PCD, PCNM and uncoated carbide tools. The tribological properties of the composite pistons were determined on the basis of the pin-on-disc and the abrasion wear. The scuffing tests carried out under real operating conditions have confirmed the possibility of using composite pistons in air compressors.
When designing the composition and structure of a composite material intended for tribological cooperation, many external and structural factors must be considered. The aim of this research was to compare the tribological properties (wear resistance and friction coefficient) of AlSi7Mg1Sr0.03/SiCp and AlSi7Mg1Sr0.03/GCsf single-reinforced composite layers with AlSi7Mg1Sr0.03/SiCp + GCsf hybrid composite layer formed in sleeves via vertical centrifugal casting. Profilometry enabled quantitative and qualitative analyses to be performed on the wear traces formed on investigated surfaces. The results show that a hybrid composite layer containing spherical glassy carbon particles had a significantly lower and more stable coefficient of friction (μ) and a higher wear resistance compared with single composite layers. The obtained effect was related to the mechanism of vitreous carbon consumption, which was crushed during operation, and then introduced between the cooperating friction surfaces. In this way, it acted as a solid lubricant, which stabilized the coefficient of friction and reduced the wear process.
The article presents the results of the first phase of research on the development of manufacturing composites by pilot-scale technology. Producing of composite suspension in sufficient quantity to obtain approximately 50 casting pistons in one production cycle was the aim of this study. This allowed to assess the stability of the composite suspension manufacturing process and above all stability the casting process. Composite suspension (AlSi7Mg/SiCp and heterophase SiCp+Cg ) were prepared in one technological cycle including refining and modification of the alloy matrix, the introduction of ceramic particles and the homogenization of the suspension under reduced pressure. Objective of this study was to determine the basic parameters of the suspension of the manufacturing process, such as metal refining period, the rate of particles introduction and time of homogenization. In addition, as a evaluation criterion of quality the manufactured composite material accepted the possibility of pre-cast piston machining.
The main purpose of the investigations was to develop the phase composition of the composite assuming that the component selection criterion will be the formability of piston work surfaces during the machining. wear resistance under the friction conditions was assumed as the additional parameter for the assessment of composite material. in the study were used AlSi7Mg/SiC+Cg and AlSi7Mg/SiC+Gr hybrid composites prepared by the stir casting method.
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