Compared to conventional processes, only an area close to the surface of the metal part is heated by the diode laser, while the rest of the material remains at ambient temperature.
Due to heat conduction, the surface will cool down as soon as the laser beam moves to another spot. This "self-quenching" creates a particularly fine-grained microstructure of great hardness without causing the base material to become brittle.
Contrary to conventional processes, laser-beam hardening works localized and the beam follows the contours precisely. This results in notably lower distortion of parts avoiding the extra-effort of having to rework them.
ADAPTED BEAM PROFILE
Diode lasers cover a wide range of typical and well-established applications: from the harde-ning of stressed zones at injection molding, cutting or forming tools, to the hardening of components in mass production.
- Local surface hardening exactly where required
- Low distortion and no rework
- Short wavelength enabling superior absorption
- Close-loop temperature control
- Highest process efficiency of all laser types
- Extremely reliable for production processes
In hardening, diode lasers are regarded as a well-established technology with short wavelength enabling superior absorption.
Direct diode lasers, and more and more frequently fiber-coupled diode lasers, are utilized in the power range of up to 8,000 W. The lasers come with pyrometer for temperature feedback control, as well as with specially developed homogenizing optics. These optics generate a line or rectangular spot optimized to the specific application, and result in a constant hardening depth across the entire width.
AVOIDING SURFACE MELTING
The use of a pyrometer enables precise control of the hardening temperature. This completely eliminates the risk of surface melting also near edges, avoiding the costs resulting from dama-ged parts. The combination of their short wavelength, good absorption and adapted beam profile guarantee highly efficient processing.
Dafferent techniqus of surface hardening allow for the use of cost-effective materials, also in components that are subject to high mechanical stress. In diode laser hardening, only the particularly stressed zones are hardened locally, for example, in steel and cast iron for tool manufacture.
A unique advantage of the diode laser over other processes is the possibility to adjust its spot ideally to the hardness contour and, therefore, to achieve extremely high processing speeds.
Its simple mode of operation allows the diode laser to be integrated easily into production processes and, if desired, to be used with an industrial robot.
LOCAL AND SELECTIVE HEATING
Compared to other lasers used for hardening, diode lasers distinguish themselves by very short wavelengths that are well absorbed and by their superior process stability. Special absorption layers that would prevent temperature control by a pyrometer and that may result in the contamination of surfaces are not required.
The advantage of diode lasers over conventional technologies can be summarized in two words: better quality.