Abstract
Oxidation of Al-Sn bearing alloy occurs during production, processing and use, which reduces both alloy performance and performance of coatings applied to the alloy surface. Therefore, the oxidation mechanism of Al-Sn bearing alloy is studied at 25, 180, 300, and 500 °C. The oxidation morphologies of the alloy were observed by scanning electron microscopy (SEM), and the oxidation products were determined by X-ray diffraction (XRD). The oxidation weight gain curves were obtained by thermogravimetric analysis. The experimental results show that: Al-Sn bearing alloy is oxidized quickly to form Al2O3. As the oxidation temperature increases, Sn phase start to precipitate along the grain boundary and form networked spheroids of Sn on the alloy surface. The amount of precipitation increases with further increase of the oxidation temperature. Cracks and holes are left in the alloy. The oxide layer is mainly composed of Sn, SnO2, and Al2O3. At 25 °C, oxidation rate of Al-Sn alloy approach zero. At 180, 300, and 500 °C, the oxidation rate increases quickly conforming to a power function, and eventually remains stable at about 3 × 10−6 mg·mm−2·s−1.
Highlights
IntroductionEngine is the key component of automobiles, tanks, armored vehicles [1], ship, and other equipment, in which the bearing bush is a very important part in the engine to protect the spindle and connecting rod [2–4]
The workpiece needs to be pretreated by removing surface impurities and oxide layer
Si is added to improve the hardness of Al-Sn bearing alloy, which leads to improvements in the tribological properties [27]
Summary
Engine is the key component of automobiles, tanks, armored vehicles [1], ship, and other equipment, in which the bearing bush is a very important part in the engine to protect the spindle and connecting rod [2–4]. In order to obtain Al-Sn bearing alloy with better performance, Cruz et al [9], studied the effect of Al-Sn bearing alloy casting microstructure on the final mechanical properties and wear resistance. They concluded that increasing the primary dendrite arm spacing improved wear resistance. The alternating stress increases greatly, especially when the engine starts or accelerates instantaneously Under such conditions the lubricating oil film cannot be formed in time, and the crankshaft and bearing bush are in dry grinding state, which can lead to the easy damage of the bearing bush and crankshaft, resulting in engine scrap [12,13]. Non-equilibrium magnetron sputtering ion plating technology has been widely used to prepare coatings with fine grain size, uniform structure, and good friction resistance [17,18]. The oxidation film constitutes a barrier between the anti-friction film and the Al-Sn alloy, leading to poor adhesion, coating failure, and subsequently, failure of the bearing shell [19,20]
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