Abstract
A new method was developed to determine the eutectoid temperature, A c1, of carbon steel during laser surface hardening. In the method a three-dimensional heat flow model with temperature-dependent physical properties was set up and solved for the temperature distribution employing a finite element method (FEM). Workpieces were heat-treated to produce a melted and hardened zone by a single pass of a continuous-wave TEM00 CO2 laser beam. The depth profile of the melted zone was used as a calibrator to solve the uncertainty imposed by the unknown surface absorptivity. Obtained was an A c1 of, on average, 770 °C, a superheat of 47 °C compared to the equilibrium A c1 of 723 °C. Furthermore, the numerical model was also employed to predict the hardened depth, and the results show that, for a depth of more than 100 μm, the eutectoid temperature 770 °C leads to a depth about 10% smaller than that predicted at 723 °C. The use of the temperature-dependent physical properties is critical; an error up to 80% could result if constant physical properties are used.
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Chen, CC., Tao, CJ. & Shyu, LT. Eutectoid temperature of carbon steel during laser surface hardening. Journal of Materials Research 11, 458–468 (1996). https://doi.org/10.1557/JMR.1996.0055
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DOI: https://doi.org/10.1557/JMR.1996.0055