STUDY OF ISOTHERMAL OXIDATION BEHAVIOR OF 68,5Fe-14Ni-9Al-7,5Cr-1Mo ALLOY AT 800, 900 AND 1000 oC

• Main Author: JONATHAN (NIM : 12514037), ANDREW
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/25542
• Institution: Institut Teknologi Bandung

Electricity demand in Indonesia grows averagely 8,6% per year. In order to fulfil the demand, Indonesian government has made 80,5 GW power plant construction project which are dominated by steam power plant. Now, the implementation of steam temperature in steam power plant has reached up to 700oC. One of developing materials used in steam power plant is ferritic steel. One research has shown that ferritic steel which composed of 69,5Fe-14Ni-9Al-7,5Cr (wt%) has a good oxidation resistance. In this research, molybdenum is added 1wt% so the alloy now composed of 68,5Fe-14Ni-9Al-7,5Cr-1Mo (wt%). This alloy is then oxidized at 800, 900 and 1000oC in order to examine its oxidation behavior. <br /> <br /> This research procedure is started by melting metals used in the alloy based on the composition of 68,5Fe-14Ni-9Al-7,5Cr-1Mo (wt%). Melting product, button, is then homogenized in inert condition for 24 hours at 1100oC. Button is then cut into 12 pieces of thin beam with thickness ±1 and min. diagonal 5 mm. Every side of thin beam is then ground (grit 400, 600, 800, 1000, 1200, 1500, 2000), washed with soap and rinsed with distilled water. Every sample is then oxidized in temperature variation: 800, 900 dan 1000oC and time variation: 1, 10, 50, 150 hours. Several characterization is done to oxidized sample: XRD, SEM-EDS-X-ray Mapping of surface and surface cross-section. Scale thickness of every sample is also measured by optical microscope. <br /> <br /> The results of XRD show that all 150hr samples in every temperature variation contain Al2O3. SEM images of 150hr sample at 800oC shows grain cluster morphology, at 900oC shows whisker morphology and at 1000oC shows wrinkling morphology. X-ray Mapping result of surface cross-section shows that all scale of 150hr sample in every temperature are dominated by Al oxide where EDS result of this surface cross-section shows that as the scale gets deeper, other elements oxide tends to decrease. Scale thickness data shows that scale thickness increases significantly at earlier oxidation time until 10hr oxidation and then the thickness grows slowly as time increases.