Scansonic, a producer of laser optics for welding, brazing and hardening, is showcasing two new innvovations in laser hardening at the Laser World of Photonics this year: its RLH-A laser processing optics and a new laser hardening process called CoHard.
RLH-A laser processing optics
Lasers for hardening steel surfaces can be used for high-precision hardening of the smallest structures. The new Scansonic RLH-A Rel. III laser optics offer increased precision compared to the earlier version.
Scansonic RLH-A laser processing optics were originally developed in cooperation with the automotive industry. Typical applications include laser hardening of camshafts or other rotating engine parts. Precisely defined heat treatment of highly-stressed surfaces is the key to lightweight construction. The reduction of weight and moving mass is an important factor in lowering fuel consumption and CO2 emissions. A major advantage of laser hardening is that the parts can be specifically heated. This minimizes distortion, which is often inevitable during flame or induction hardening. It also eliminates the need for post-processing. Users benefit from significantly higher efficiency and lower costs.
Innovative control technology ensures perfect results
Continuous advancements in engine design technology lead to increasingly complex components with intricate structures in the 0.1-millimeter range. The challenge in hardening these geometries is to regulate the laser power input so that the temperature in the areas to be hardened and the hardening depth remains constant – regardless of the metal thickness. Excessively high temperatures can lead to distortion of the components or melting at the edges.
The surface temperature of the component is measured during the hardening process with a pyrometer integrated into the optics. The control technology in the new RLH-A Rel. III uses two different methods for this. One is to control the scanner, which changes the speed of the laser beam on the surface. On thinner structures that heat up faster, the laser beam moves faster than on thicker pieces. The second control option regulates laser intensity. Using these two methods together ensures a precisely maintained temperature on the surface of the component for perfect hardness results.
Variable spot geometry and size
Along with the innovative control technology, Scansonic has integrated more features into its new laser optics. Spot geometry and size can now be adjusted separately to make the RLH-A Rel. III even more flexible in operation. In the past, the optics had to be changed for different components. Now, various applications can be used with the same optics. This increases efficiency and lowers user costs.
CoHard
Hardening of small surfaces, like the inside of a drill hole or the inner surface of a small workpiece, has in the past been subject to strict technical limitations. Standard methods for hardening the surfaces and edges of steel, including flame, induction, laser beam and electron beam hardening, require auxiliary means that are accompanied by specific disadvantages. Other processes use bake hardening, but this hardens the entire workpiece and can easily cause warping.
Innovative coaxial laser hardening
Scansonic has developed a new process called CoHard. This technology uses a laser beam to harden components which, due to their geometry, were not previously suitable for laser hardening. At the heart of the new coaxial laser hardening process is an optic that focuses the laser beam annularly using cone-shaped lenses known as axicons. The diverging laser beam strikes the inner wall of the hole behind the focal plane at a low angle of 5° to 15°. Axial shifting of the optic makes it possible to harden the entire surface. The area in which the laser energy is absorbed is extremely narrow, which minimizes or eliminates warping of the workpiece. And there is no need to rotate the workpiece during hardening because the profile of the laser beam is rotationally symmetric.
In the past, inductors capable of delivering sufficient power did not fit into holes smaller than 15 mm. In order to use laser beam hardening, deflection mirrors had to be placed in the drill hole. However, these mirrors are exposed to extremely high temperatures and can hardly be protected from contamination.
Initial testing shows positive results
The high efficiency of the new CoHard process was demonstrated in the first practical tests. Using a Yb:YAG laser as a beam source with a beam parameter product of 24 mm x mrad and a power of 3 kW, a drill hole with a diameter of 8 mm and a depth of 25 mm was hardened at a feed rate of 2.5 mm per second. Measurements on the workpiece verified the uniform hardening of the surface over the entire length of the drill hole. With the current configuration, the process can be easily used to harden holes with a diameter of 3 to 10 mm and a depth of 5 to 40 mm.
‘Our new CoHard process opens up new possibilities for a wide range of applications – from hardening of guides and sealing surfaces used in high-pressure pumps and valves, to the hardening of bolts with extremely precise surface hardness specifications,’ explains Peter Fixemer, Product Manager for Laser Hardening at Scansonic. The product is currently in a very promising prototype phase. Series-production optics will be developed by working together with customers and their individual requirements.
Like many other Scansonic optics, the entire RLH-A is based on a modular system and can be easily adapted to any specifications. Modern bus systems for communication within the laser optics and connection to a higher-level control ensure added flexibility.
Scansonic will also be presenting a simplified version of the laser optics at the trade show. The RLH-A Basic is available without the components required for laser beam scanning and adjusting spot geometry. This makes the lower-priced laser optics suitable for surface hardening of tools used in metal-forming presses and other applications.
