STUDY OF ISOTHERMAL OXIDATION RESISTANCE OF ODS FERRITIC STEEL (Fe-16Cr-4Al-1Ni-0,4Y2O3) AT TEMPERATURES OF 700, 800, AND 900ᴼC

• Main Author: SYAFIQ (NIM : 12514028), AHMAD
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/25205
• Institution: Institut Teknologi Bandung

Substantial energy demand in the future encourages the development of a green power plant that has a high efficiency, one of which is a fission and fusion reactor plant that is currently entering Generation IV. The operating temperatures and pressures targeted at gen IV are 625oC, 25 MPa and will continue to increase annually. However, the malfunction of generating equipment may cause overheating, so the actual temperature is higher than the operating temperature. Prevention of malfunctions and high temperatures requires good material in terms of oxidation susceptibility. Oxide-Dispersion-Strengthened (ODS) materials are capable to occupy the desired criteria as well as other properties such as ductility, fracture toughness, and neutron radiation resistance. This research studied the effect of temperature and exposure time of isothermal oxidation of ODS Fe-16Cr-4Al-1Ni-0,4Y2O3 (weight%) at high temperature. <br /> <br /> Series of experiments began with manufacturing ODS alloys through mechanical alloying using a Planetary Ball Mill. The ratio of powder and ball used was 1:10 with 1290 rpm for 2 hours. The compounded powder was compacted at 499 MPa pressure for 4 minutes. The green sample was then sintered at 1000 oC for 6 hours under inert condition. As sintered sample was first analyzed to identify formed phases, porosity, and hardness using optical microscopy (OM), SEM-EDS, and Vicker Hardness Test, respectively. Isothermal oxidation tests for as sintered samples were performed at temperature of 700, 800, and 900oC in 5, 20, 50, and 100 hours. Oxide product formed on the surface was analyzed by XRD and SEM/EDS, whereas the oxidation kinetics rate was analyzed by observing changes in oxide thickness over exposure time by using OM and SEM/EDS. <br /> <br /> Based on research results, the sintered sample has relatively same composition as starting composition but there is an 8,5% oxygen inclusion which is concentrated in grain boundary. The porosity and hardness of the sintered sample were 5,865% and 321,13 HV. The result of the oxidation test shows that the most protective sample obtained at temperature of 700oC for 100 hours with oxide thickness of 263,99 &#956;m. The analysis of correlation value tests show that the kinetic rate of oxidation related to the parabolic kinetic equation. While the oxidation rate constant at temperatures of 700, 800, and 900oC are 681,21; 3.009,8; and 12.179 &#956;m2/hour, respectively. Activated energy that required for oxidation reaction of this alloy is 136,5 kJ mol-1The oxide products formed are mostly Fe2O3, Fe3O4, AlFe2O4, and (Fe,Cr)2O3.