In Situ Observation of the Grain Growth Behavior and Martensitic Transformation of Supercooled Austenite in NM500 Wear-Resistant Steel at Different Quenching Temperatures

作者：Li, Zhongbo; Yuan, Qing^*; Xu, Shaopu; Zhou, Yang; Liu, Sheng; Xu, Guang

来源：Materials, 2023, 16(10): 3840.

DOI：10.3390/ma16103840

• in situ observation
• austenite
• martensite
• twins
• quenching temperature

In situ observations of the austenite grain growth and martensite transformations in developed NM500 wear-resistant steel were conducted via confocal laser scanning high-temperature microscopy. The results indicated that the size of the austenite grains increased with the quenching temperature (37.41 mu m at 860 degrees C -> 119.46 mu m at 1160 degrees C) and austenite grains coarsened at similar to 3 min at a higher quenching temperature of 1160 degrees C. Furthermore, a large amount of finely dispersed (Fe, Cr, Mn)(3)C particles redissolved and broke apart at 1160 degrees C, resulting in many large and visible carbonitrides. The transformation kinetics of martensite were accelerated at a higher quenching temperature (13 s at 860 degrees C -> 2.25 s at 1160 degrees C). In addition, selective prenucleation dominated, which divided untransformed austenite into several regions and resulted in larger-sized fresh martensite. Martensite can not only nucleate at the parent austenite grain boundaries, but also nucleate in the preformed lath martensite and twins. Moreover, the martensitic laths presented as parallel laths (0 similar to 2 degrees) based on the preformed laths or were distributed in triangles, parallelograms, or hexagons with angles of 60 degrees or 120 degrees.