Heat Treating


Heat Treating with the HPDDL system


Through laser transformation hardening a material can be case hardened with negligible distortion. A comparison with flame and induction surface transformation hardening techniques clearly show that laser surface hardening is the most advantageous process. Flame hardening has poor reproducibility, poor quench and environmental issues. In induction hardening a quench is required, distortion of the part occurs and there is large thermal penetration. With laser beam hardening the applied light radiation instantaneously heats the surface, there is no radiation spillage outside the optically defined area. The bulk of the material acts as a heat sink for the extraction of heat from the surface. The major advantage of laser surface treatment is high processing speeds with precise case depths. Laser surface transformation hardening not only increases the wear resistance, but also under certain conditions the fatigue strength is also increased due to the compressive stresses induced on the surface of the component5.


The HPDDL is an ideal source for laser transformation hardening. The line of light, when moved across the work piece along the short axis [Figure 1] has high edge definition without the need for special cylindrical lenses [Nd:YAG] or water cooled integrators [CO2]. The wavelength is 800nm, which is highly absorptive, requires no pre-coating of the work piece to get absorption. The ISL-4000L has a modulation bandwidth of 20KHz, making ideal for in-situ temperature control.