STUDY ON THE EFFECT OF HEATING ON THE MICROSTRUCTURE EVOLUTION AND HARDNESS OF AISI 430 FERRITIC STAINLESS STEEL

• Main Author: Christian, Albert
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/65996
• Institution: Institut Teknologi Bandung

Stainless steel is one of the alloys which can be used for high-temperature and corrosion resistance applications. Ferritic stainless steel is one of the classes of stainless steel. Recently, ferritic stainless steel has been used for the automotive exhaust system. Several reasons support the development of this application such as reducing gas pollution, increasing the engine's performance leading to higher temperature operation, and light material with longevity. In order to operate well as a material for an automotive exhaust system, ferritic stainless steel has to withstand at least the temperature of 900 oC. Therefore, mechanical properties and corrosion resistance are important for material operation. In this research, the effect of heating on both microstructure and hardness of the AISI 430 ferritic stainless steel was studied. Grain growth and precipitation kinetics were also analyzed. A series of heating experiments under atmospheric conditions had been done in order to study the effect of temperature and heating duration on microstructural evolution, grain size, carbide precipitate size, the volume fraction of carbide, and the hardness of AISI 430 ferritic stainless steel. The sample was prepared with the size of 1.5 cm x 1.5 cm with 2 mm thickness, heated in the muffle furnace at the temperature of 750, 800, dan 850 oC for 10, 15, and 20 hours. The microstructural observation was done with an optical microscope and scanning electron microscope. Vickers hardness tester was used to obtain the sample hardness. The result shows that there was a change in average grain size because of heating. The grain size grew as both the temperature and heating duration increased. Abnormal grain growth occurred with the presence of the precipitate. The intermetallic phase, and sigma phase was not found due to element mapping of carbon giving the uniform distribution. Heating also affected the average radius of carbide precipitate. At a temperature of 850 oC, the average radius of carbide precipitate was 390, 499, dan 556 nm with a heating duration of 10, 15, dan 20 hours, respectively. Volume fraction increased with longer heating duration. At temperature of 850 oC, the volume fraction was 12.397, 16.44, and 23.04 % with a heating duration of 10, 15, dan 20 hours, respectively. The hardness decreases with a longer heating duration. The decrease in hardness was mainly because of the average grain size and average radius of precipitate which increased.