Akademik Veri Yönetim Sistemi
JOURNAL OF ALLOYS AND COMPOUNDS, cilt.977, 2024 (SCI-Expanded)
The oxidation behavior of novel xSiNb cast irons designed for use as exhaust manifold material is studied by computational alloy thermodynamics and oxidation tests. Computational alloy thermodynamics is applied to determine the oxidation behavior of novel xSiNb cast irons (x: 4, 5, 6 and 7 wt%) designed as alternative exhaust materials to commercial SiMo ductile cast iron. In the modelling studies, the types and amounts of the oxides formed on the surface, depending on the oxygen partial pressure, are investigated at 750 and 850 degrees C and the findings reveal that as the silicon content increases the amount of Si-rich Fe2SiO4 phase increases that acts as a protective barrier. Oxidation tests are carried out in two stages to verify the modelling studies. Initially, thermogravimetric analyses are carried out at 800 degrees C to determine the oxidation kinetics of xSiNb cast irons and the results indicate that oxidation kinetics are reduced as silicon content increases. Then, oxidation tests are carried out at 750, 800 and 850 degrees C for 24 h in dry air atmosphere to characterize the oxides formed on the surfaces and cross-sections of cast irons. Characterization studies show that (i) a thinner oxide layer is formed on the surface as silicon content increases, (ii) the oxide layer consists of an outer and an inner layer, (iii) the inner layer has more silicon content compared to the outer layer. All findings indicate that xSiNb cast irons have potential for high temperature applications and can be preferred to SiMo ductile cast iron.