Microstructure Evolution Study of Ferritic Fe-14Ni-9Al-7,5Cr-5Mo Steels at Temperatures 800, 900, 1000oC

• Main Author: SETYA UTAMA (NIM : 12514049), IKRA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/27962
• Institution: Institut Teknologi Bandung

The needs for steam power plants using coal will dominate the 35,000 MW program with a share of 56.97% of the planned total power plant. The amount of electricity production generated depends on the efficiency of the plant which is also affected by the operating temperature and pressure. Therefore, it is necessary material capable of operating in such extreme conditions. The advanced ferritic steel can be a substitute alternative to nickel-based super alloys for specific uses. Various studies say that the addition of elements of molybdenum can inhibit coarsening of precipitate. In this study, we studied the effect of temperature and aging duration on Fe-14Ni-9Al-7.5Cr-5Mo alloys. <br /> <br /> A series of experiments have been conducted to study the effect of temperature variation and time of heat treatment on the evolution of microstructure, precipitate particle size and volume fraction of B2 precipitate and the value of hardness of advanced ferritic steel alloys. Alloys with composition 64,5Fe-14Ni-9Al-7,5Cr-5Mo (% weight) are melted on Mini Arc Furnace using retort to form button. The alloy is then cut and subjected to heat treatment under atmospheric conditions at temperatures of 800, 900, and 1000oC for 6.20 and 48 hours. The observation of microstructure was done by using optical microscope and scanning electron microscope (SEM). Furthermore, alloy hardness values were tested using a vicker hardness tester. <br /> <br /> The experimental results show aging at a temperature of 800oC, resulting in a square-shaped hierarchical precipitate. While aging at a temperature of 1000oC produces a spherical precipitate with the presence of nano precipitates dispersed in the Fe matrix. The addition of aging time duration, from 6 hours to 48 hours, does not change the shape of precipitates. The Fe-Ni-Al-Cr-Mo alloy with aging at 800oC has a relatively low volume fraction, which is 20.56% at 6 hours, then rises slightly in 48 hours to 20.97%. Meanwhile, aging at 1000oC for 6 hours has a volume fraction of 27.85% and rose to 33.27% during aging for 48 hours. Fe-Ni-Al-Cr-Mo alloys with aging at 1000oC have a larger precipitate size than a temperature of 800oC. The longer the aging of precipitate size is also greater. Increased aging time and temperature increases the hardness value of the alloy.