HOT CORROSION RESISTANCE STUDY OF HIGH ENTROPY ALLOY AL0,75COCRCUFENI IN NA2SO4 AND V2O5 MOLTEN SALT THROUGH CYCLIC HEATING AT 1100 ?C

• Main Author: Abraham Talabessy, Joshua
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86345
• Institution: Institut Teknologi Bandung

The development of alloy in present days is highly sought due to the increasing demand for metals. Various sectors within the transportation industry require alloys with superior mechanical properties, such as within the aviation industry. The presence of high entropy alloy Al0.75CoCrCuFeNi can be utilized for high temperature applications due to its ability to maintain the form of the alloy through its intrinsic properties. The frequent occurrence of salts as residues from fossil fuels can pose a threat to the integrity of the alloy by inducing hot corrosion. Experiments were conducted to test the resistance of the alloy to Na2SO4 and V2O5 cyclic exposure to simulate the performance of turbine blades in aircraft engines, and these experiments were conducted at 1100 ?C. A cyclic hot corrosion test was performed, lasting one hour per cycle, to study the microstructural stability and the degradation tendency of the Al0.75CoCrCuFeNi alloy in this environment. The experiment began with the melting of the alloy elements using direct current – electric arc furnace (DC-EAF) and continued with homogenization at 1100 ?C in an inert tube furnace. Subsequently, button metal was cut to produce coupons, some of which were characterized, and then subjected to hot corrosion testing at 1100 ?C with variations of 4, 8, 12, and 16 cycles on the remaining coupons. The alloy that underwent hot corrosion testing was characterized using X-ray diffractometer (XRD), scanning electron microscope – energy dispersive spectrography (SEM-EDS), and optical microscope. Based on the experiments conducted, it was found that the homogenized Al0.75CoCrCuFeNi alloy consists of three constituent phases which are FCC or facecentered cubic in dendritic form, FCC rich in Cu in interdendritic form, and FCC + BCC or body-centered cubic in interdendritic form. The values of the initial and subsequent reaction coefficients as a function of time respectively for the variations of 4, 8, 12, and 16 cycles were found to be -3,2408×10-3 and -1,1138×10-5, -1,1321×10-3 and -7,8611×10-6, -1,0277×10-3 and -8,6111×10-6, -7,3141×10-4 and -7,4889×10-6. The changes caused by hot corrosion occurred was visible in the morphology and the distribution of the alloying elements. The mechanism of hot corrosion was predominantly influenced by oxidation and salt fluxing.