Austenite Formation during Laser Surface Hardening of Fully Pearlitic Steel

Despite the widespread use of laser heat treatment, a fundamental understanding of austenite formation kinetics at high heating rates remains a challenge. This gap is addressed by developing a novel model that uniquely accounts for the initial pearlite colony size and interlamellar spacing as critical input parameters. The model s predictions are validated against experimental observations, where the spatial variation of hardness reveals a distinct two-zone microstructure: a fully austenitized region and a partially transformed intercritical layer. The results show that the relative size of these zones is directly controlled by the initial microstructure. This research provides a crucial insight that austenite formation under rapid heating conditions occurs with negligible superheating, which is essential for optimizing laser processing parameters to achieve a desired microstructure. © 2025 Wiley-VCH GmbH.