OXIDATION RESISTANCE BEHAVIOR OF ALUMINA-FORMING AUSTENITIC STAINLESS-STEEL FE-20NI-14CR-6AL-1.2TI-1NB-0.2C-0.1Y WITH ADDITION VARIATION OF SILICON AT 900°C

• Main Author: INTAN FATMAWATI, LULU
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/62533
• Institution: Institut Teknologi Bandung

The demand for electricity in Indonesia is predicted to increase every year as the utilization of electricity in various applications increases massively. Based on RUPTL PT. PLN 2021-2030, electricity demand growth in 2030 will reach 390 TWh. The production of more clean energy is one of the things that is currently being considered. Increasing the efficiency of heat conversion power plants can be done by increasing the operating temperature. Alumina-forming austenitic stainless steel (AFA SS) alloy is one of the candidate materials for those applications. In this study, AFA SS oxidation behavior with the addition variation of silicon was investigated by the isothermal semi-cyclic oxidation method. A series of isothermal oxidation experiments have been carried out to study the effect of silicon addition on the oxidation resistance of Fe-20Ni-14Cr-6Al-1.2Ti-0.2C-1Nb-0.1Y-xSi with x of 0, 0.25, 0.5, and 0.75 (%wt.). Hereinafter, the AFAm term will be used. The experiment was started with AFA-m fabrication. To produce homogeneous alloy buttons, repeated melting was carried out four times. Further homogenization was done by heating the alloy button at 1100°C for 6h in a tube furnace with high purity argon. The button was then prepared to become sample coupons. Isothermal semi-cyclic oxidation experiments were performed at 900°C in air for 25h in the tube furnace. After oxidation testing, the weight gain of samples was calculated. Several samples were then characterized using Optical Microscope, XRD, SEM-EDS, and Vicker Hardness Machine. From characterization results, alloy microstructures, formed oxide compounds, elemental distribution in the oxide and alloy, and hardness of alloys were obtained. Based on research results, AFA-m has Fe-???? matrix, B2-NiAl, carbides phase, and Laves phase. Silicon addition to alloy is likely to produce ????+ ????. The hardness of AFA-m has an increasing trend with the addition of silicon. The increase of hardness was caused by an increase in the volume fraction of the B2-NiAl. The hardness of the alloy decreased after oxidation. The oxide compounds formed on the metal surface are FeO/Fe0,945O, Fe3O4, Fe2O3, FeAl2O4, Cr2O3, NiO, dan Al2O3. The oxidation behavior of AFA-m underwent a change in mechanism from the formation of a continuous and exclusive Al2O3 on AFA-m alloy without silicon addition to discontinuous Al2O3 and a mixture of other oxides (Fe oxides, Cr2O3, NiO) in the alloy with the addition of silicon. Logarithmic oxidation behavior is confirmed for all AFA-m alloys.