STUDY ON THE HOT CORROSION RESISTANCE OF FE-20NI-14CR-6AL-1,5TI-0,3SI-0,2C ALUMINA FORMING AUSTENITIC STAINLESS STEEL AT TEMPERATURES OF 700, 800, AND 900°C

• Main Author: Jeremy Geraldo, Matthew
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69137
• Institution: Institut Teknologi Bandung

The use of electricity increases along with the development of technology around the world. Indonesia’s electricity consumption increased by 5.78% from 2020 to 2021 and is predicted to continue to increase in the future. Electric Steam Power Plants (PLTU) contribute to about 50% of all electricity generation in Indonesia. PLTU is a type of power plant that uses hot steam to turn a turbine. The hot steam comes from the process of evaporation of air through a boiler, this plant uses coal or fuel oil to heat the air. In industrial gas turbines, sulfur reacts with NaCl to form Na2SO4 at high temperatures which causes accelerated oxidation or hot corrosion of components. High temperature operations require materials which have a good combination of corrosion resistance, mechanical properties, and microstructural stability. In this study, hot corrosion testing of Fe-20Ni-14Cr-6Al-1,5Ti-0.3Si-0.2C alumina forming austenitic stainless steel alloy was carried out at temperatures of 700, 800, and 900°C for 5, 20, and 50 hours. A series of experiments were carried out to study the hot corrosion resistance of Fe-20Ni-14Cr-6Al-1,5Ti-0.3Si-0.2C alloy. The experiment was started by melting all the elements with a mini DC electric arc furnace. The samples were then homogenized using a horizontal tube furnace at a temperature of 1100°C for 6 hours. Samples were cut and polished with 60-2000 grit. Then, the samples were tested for hot corrosion using a horizontal tube furnace at temperatures of 700, 800, and 900°C for 5, 20, and 50 hours, respectively. The test result is the final weight of each sample. The samples tested at temperatures of 700 and 900°C with a time of 5 and 50 hours were characterized using x-ray diffraction (XRD) and scanning electron microscope (SEM) - energy dispersive spectroscopy (EDS). The results showed that the Fe-20Ni-14Cr-6Al-1,5Ti-0.3Si-0.2C alloy had a Fe-? matrix with B2-NiAl, TiC carbides, and Laves phase precipitates. The value of change in sample weight increases with increasing test temperature. The average values of dW/A0 at temperatures of 700, 800, and 900°C are -0.2301 mg/cm2, 1.4832 mg/cm2, and 2.594 mg/cm2, respectively. The hot corrosion mechanism begins with the formation of protective Cr2O3 and Al2O3 oxides. Furthermore, the salt mixture destroys the protective oxide layer and the sulfur reaches the alloy matrix causing internal sulfidation. The oxide compounds formed on the surface of the alloy are Al2O3, Cr2O3, FeO, Fe2O3, Fe3O4, TiO2, NiO, NiCrO4, and NiCr2O4.