When laser-hardening – also referred to as marginalized layer hardening – the laser beam with its adjustable focal spot size is guided over the welded surfaces by a robot. The energy of the laser is applied directly to the workpiece surface. This marginalized layer is then heated in a very short period of time and locally limited to the required hardening temperature. The integrated temperature measurement in the beam geometry ensures that the heat input is uniform. The laser beam's interaction time with the surface determines the hardness penetration depth.
Using a focused laser beam, the area to be hardened is very quickly heated to the critical temperature and subsequently quenched by the cold component volume. The material distortion is considerably reduced because of how quickly heat is applied with almost simultaneous self-quenching. This is thus considered a low-distortion or even distortion-free heat treatment. The carbon atoms change their position in the metal grid due to the high temperature. This behavior is desirable and called austenitization. Quick cooling keeps the metal grid from returning to its original shape. The result is martensite (a very tough metal structure that looks very fine under the microscope), which increases the hardness of the material. | Even for large tools from forming technology, laser hardening is a very cost-efficient, extremely fast process for marginalized layer hardening, because it enables partial hardening of selected stressed functional areas on the workpiece surface. This results in a zonally hard surface with a tough core, and the areas in the immediate vicinity are unaffected. The toughness of the basic material remains unchanged. Track widths from 1 to approx. 100 mm are possible depending on the laser power and system. The achievable hardness penetration depth is about 0.6 mm to 0.8 mm, and with many materials it can be up to 2 mm. |
The advantages of laser hardening can be summarized as follows:
Removing the workpiece is not necessary when using a mobile laser hardening robot.
Processing can take place on site, which saves an enormous amount of time.
Further advantages of mobile and flexible laser hardening:
