CYCLIC OXIDATION BEHAVIOUR STUDY OF 69.5Fe-14Ni-9Al-7.5Cr ALLOY AT 800, 900 AND 1000˚C

• Main Author: KENANGA (NIM : 12514008), ALMA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/25396
• Institution: Institut Teknologi Bandung

The effort to improve efficiency in power plants is still in progress, knowing that the amount of fuel reserve will decrease from time to time. This condition leads to the need of high-temperature materials able to withstand high operating parameters such as temperature and pressure, not only by its strength but also its resistance to high-temperature oxidation. Fe-base ferritic alloy with B2-ordered (Ni,Fe)Al phase strengthening is being developed to replace Ni-base austenitic alloy because of its cheaper price. Since the operating parameters will not always be in a stable condition, a set of experiment was conducted to study the behaviour of 69.5Fe-14Ni-9Al-7.5Cr alloy under cyclic oxidation at 800, 900 and 1000&#730;C. <br /> <br /> <br /> The cyclic oxidation test was conducted at 800, 900 and 1000&#730;C for 35 cycles, each consisted of an hour of furnace heating and 15 minutes of air cooling. Weight change per initial area was recorded for each cycle to give quantitative data regarding the cyclic oxidation behaviour. Then, the samples were characterized using X-ray Diffraction (XRD) to analyze the oxide compound/phase and Scanning Electron Microscope – Energy Dispersive Spectroscopy (SEM-EDS) with x-ray mapping to know the morphology, spot elemental analysis and element mapping of the oxide at the surface and cross-section area of the sample. All the data were used to analyze oxide behaviour during thermal cycle. <br /> <br /> <br /> The average value of dW/A0 at 800, 900 and 1000&#730;C was 0.1199, 0.1458 and 0.2806 mg/cm2 respectively. The main component of the existing oxide was Al2O3. Cr, Fe and Ni elements were incorporated in Al-oxide with the tendency of Cr to concentrate near the outer layer whereas Fe and Ni near the substrate at 800&#730;C and early cycle of 900 and 1000&#730;C. However, Cr, Fe and Ni content decreased at the end of the cycle. Ni content at the oxide was found very low compared to others. Nodules were found at the surface of the sample at 800&#730;C. The remaining of Fe-oxide was found at 900 and 1000&#730;C. Also, convoluted morphology existed at the lowermost layer and observed to be larger at 1000&#730;C. In general, the oxide layers at the surface of the sample was uneven due to spalling.