HIGH TEMPERATURE OXIDATION PROPERTY OF Ni BASED SUPERALLOY CM247LC PRODUCED VIA SELECTIVE LASER MELTING PROCESS

초록

CM247LC alloy was manufactured by using selective laser melting (SLM) process, one of the laser powder bed fusion (L-PBF) methods. The hot isostatic pressing (HIP) process was additionally conducted on the SLM-built CM247LC to control its microstructures and defects. The high temperature oxidation property was investigated, and it was compared with conventional DS247LC sample (reference) prepared via the directional solidification process. The L-PBF HIP sample showed blocky-type MC carbides generated along the grain boundary with average size of about 200 nm. A semi-spherical primary gamma' phase of size 0.4-1.0 mu m was also observed inside the grains. Moreover, the DS247LC sample displayed a coarse eutectic gamma' phase and many script-type MC carbides. Furthermore, cuboidal-type gamma' with an average size of about 0.5 mu m was detected. High-temperature oxidation tests were conducted at 1000 degrees C and 1100 degrees C for 24 hours. The results at 1100 degrees C oxidation temperature showed that the measured oxidation weight gains for HIP and DS247LC were 1.96 mg/cm2 and 2.26 mg/cm2, respectively, indicating the superior high-temperature oxidation resistance of the L-PBF HIP sample. Based on the above results, a high-temperature oxidation mechanism of the CM247LC alloys manufactured by the SLM process and the directional solidification process has been proposed.

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