Thermal analysis of a laser pulse for discrete spot surface transformation hardening

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Abstract
Conventional laser transformation hardening is achieved by scanning a laser beam over a surface to raise the temperature above the austenitizing temperature and allowing self quenching to form martensite. A new approach, developed at the National Research Council of Canada’s Integrated Manufacturing Technologies Institute, uses discrete pulses to create a series of hardened “spots.” Unfortunately, existing transformation hardening models do not apply to this case due to the traditional assumption of a scanning velocity. For this reason, new predictive tools must be developed. An analytical solution to the axisymmetric heat conduction under a Gaussian energy distribution is presented which can be used to calculate the temperature distribution from a short laser pulse. The method is also used to calculate the size of a transformation hardened spot under the incident energy of a stationary laser.