ABSTRACT: The cast iron that comes with a ferritic matrix is mainly used for the application that requires higher temperature working conditions, such as exhaust manifold. However, the higher demand for obtaining material shows higher efficiency led the material production companies and manufacturers to use Ni-resist austenitic ductile cast irons and stainless steels, which are relatively more expensive than cast iron and are considered as the main challenge for them. This challenge motivated the manufacturer to develop new alloys that show high-temperature resistance, higher resistance for oxidation, and lower cost. In this study, works postulates the resistance of the phases formed due to oxidation of the cast iron alloy with the ratio of (0 to 4 wt% Al) based on the oxidation, X-ray diffraction, and optical microscopy. The oxidation mechanisms of the referred alloy were presented at the range of high temperature (700-900 ?). The results showed the temperature of oxidation and Al content are linearly proportional. Low resistance for oxidation was noticed at a lower value of oxidation temperature. The oxidation resistance was characterized by the formation of FeO, Fe2O3, and Fe3O4. The performance of the alloyed cast-irons was significantly enhanced as the content of Al increased. As the content of Al increased, the scale thickness reduced gradually. The behavior of the alloyed cast-irons oxidation kinetic for all conditions of the test was parabolic in its nature at various constants of parabolic rates.
CONCLUSIONS
1. Addition of aluminum to the molten (cast-iron) with attention being taken into consideration compensating the value of the lost aluminum by about 15% due to the difference between the melting temperature of the two materials as the aluminum is largely lost due to oxidation at high temperatures and burning large amounts of it.
2. The resulting slag increases significantly after adding aluminum to the molten, which in turn plays the role of slag insulation due to the high affinity of oxygen.
3. Aluminum acted as a strong graphitizing material and at the same time enriched with the formation of graphite slices, which was similar to the role of silicon in addition to the phases consisting of graphite and ferritic matrix.
4. The specific weight gain increased with an increase in oxidation temperature when stabilizing the proportion of aluminum (at the ratio of one aluminum). Thus, the resistance to oxidation decreased by forming a non-protective flak layer that was not adherent to the surface, as oxygen absorption increases, and the alloy fails. Thus, the sample weight increased, and with the increase in the amount of graphite, the peeling ratio increased, and its highest value reached a temperature of 900?
5. The specific weight gain decreased with an increase in the percentage of aluminum in alloy cast iron with stabilization of the temperature (at one temperature) due to the formation of a surface layer adhering to the surface and its best value was obtained at a temperature of 900? and the percentage of aluminum is 4.7%.
6. Aluminum played an important role in changing the condition of the microstructure. The composition of the matrix included different ratios of perlite, ferrite, and graphite.
7. There was no sign of spalling at temperatures ranging from 700 to 900 °C in aluminum-alloyed cast-irons. The rate of oxidation in the aluminum-alloyed cast-iron decreased with increasing the content of aluminum.