MICROSTRUCTURE AND HIGH TEMPERATURE OXIDATION PROPERTIES OF Fe-Cr-Ni HK30 ALLOY MANUFACTURED BY METAL INJECTION MOLDING

초록

This study investigated the microstructure and high temperature oxidation properties of Fe-25Cr-20Ni-1.5Nb, HK30 alloy manufactured by metal injection molding (MIM) process. The powder used in MIM had a bi-modal size distribution of 0.11 and 9.19 mu m and had a spherical shape. The initial powder consisted of gamma-Fe and Cr23C6 phases. Microstructural observation of the manufactured (MIMed) HK30 alloy confirmed Cr23C6 along the grain boundary of the gamma-Fe matrix, and NbC was distributed evenly on the grain boundary and in the grain. After a 24-hour high temperature oxidation test at air atmospheres of 1000, 1100 and 1200 degrees C, the oxidation weight measured 0.72, 1.11 and 2.29 mg/cm,(2) respectively. Cross-sectional observation of the oxidation specimen identified a dense Cr2O3 oxide layer at 1000 degrees C condition, and the thickness of the oxide layer increased as the oxidation temperature increased. At 1100 degrees C and 1200 degrees C oxidation temperatures, Fe-rich oxide was also formed on the dense Cr2O3 oxide layer. Based on the above findings, this study identified the high-temperature oxidation mechanism of HK30 alloy manufactured by MIM.

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