Influence of Carbon on the Microstructure of Carbon Steels produced by L-PBF

Paper in proceeding, 2022

The recent development of carbon steel for laser powder bed fusion (L-PBF) has shown that these alloys can be produced using the process. However, knowledge regarding their as-built microstructure remains limited. This work explores the microstructure of carbon steels (0.06-1.1 wt.% C) produced by L-PBF to examine the effect of carbon on phase formation and grain structure. Analysis found that the microstructure of these alloys was primarily composed of tempered martensite that contained nanosized carbides. Retained austenite was also observed at elevated carbon contents (≥0.75 wt.%) due to the suppression of the martensite transformation temperature. With increasing carbon content noticeable changes in the parent austenite grains was not observed, however, the fineness of individual martensite grains did increase. Additionally, a transition from lath to plate martensite was observed at 1.1 wt.% C. These findings establish an understanding of carbon steels that can further their development for L-PBF.