Laser hardening:
In this process as the name implies a laser beam is used to heat the work. Since the intensity of the laser beam is high the work may tend to melt if the high intensity beam is directly used. To avoid this a lens id used to reduce intensity by producing a defocused spot or scans of 1-25mm width. A 1kW laser produces a circular spot whose diameter may vary from 0.5 mm to 0.25mm. Industrial lasers are available up to 20kW. A case depth of 0.75mm can be achieved. The case depth is controlled by time and energy density. It takes lesser amount of time compared with induction and flame hardening methods. No separate quenching is required in laser beam hardening. Self-quenching takes place by the effect of surrounding unheated portion. The effect of heat in the surrounding surface is less and hence lesser is the chances of distortion.
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Image from;- http://www.laserline.de/tl_files/Laserline/img/en/laser-hardening.jpg
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