Uses of Laser material processing for modification of surface properties

 

Laser Material Processing uses laser energy to modify the shape or appearance of a material. This method of material modification provides several advantages such as the ability to quickly change designs, produce products without the need for retooling, and improve the quality of finished products.

Another advantage of laser material processing is compatibility with a multitude of materials. Compatible materials range from non-metals such as ceramics, composites, plastics/polymers and adhesives to metals, including aluminium, iron, stainless steel, and titanium.

The effects produced by laser energy interacting with a material strongly depend upon the wavelength and power level of the laser and the absorption characteristics and chemical composition of the material.

A range of power levels is available for each laser type to optimize the laser energy-material interaction. However, the absorption characteristics and chemical composition of the material and the desired results greatly influence the selection of the laser type and power level.

The terms laser cutting, laser engraving, and laser marking are commonly referred to as laser processes. Depending upon material compatibility, a single laser process or multiple processes in combination can be applied to a material.  

The effects of the laser energy-material interaction are material ablation and/or material modification.

Material Ablation removes material completely from the top to the bottom surface or partially from the top of the material down to a specified depth. Material ablation is used for laser cutting, laser engraving, and laser drilling.

Surface Material Modification is a very different process which alters the properties and/or appearance of a material. Material modification is used for laser marking on the surface of a material by changing the appearance or properties of the material.

Figure 1: Example of the sub-micron scale surface texturing that can be achieved by laser treatment. 

Figure 1: Example of the sub-micron scale surface texturing which can be achieved by laser treatment.

TRESCLEAN Laser Surface Modification

The TRESCLEAN consortium have developed a range of new high-power ultra-short pulsed lasers for advanced surface treatment and texturing applications. The overall concept of laser treatment is illustrated in Figure 2.

Exploiting the breakthrough new laser sources developed at average powers of up to 1kW, together with new options to deliver high-power beams at various wavelengths including green and ultra-violet the results offer endless new possibilities for accurate and controllable laser surface texturing.

Direct Laser Interference Patterning (DLIP) and Laser Induced Periodic Surface Structuring (LIPSS) have been exploited with these new sources these techniques allow nanometre scale textures to be realised on surface structures as shown in Figures 2 and 3.

To enable the rapid treatment of large area surfaces, TRESCLEAN also developed an ultra-high-speed scanning unit which can scan the laser across the surface at speeds of 200m/s with laser pulses delivered at rates of 5-20MHz.

Together these technologies can provide unparalleled speed and precision for a multitude of surface treatment needs.

If you have a surface treatment challenge which laser treatment might address the DLIP technology is available from the University of Stuttgart spin out Light-Pulse Laser Precision (https://www.light-pulse.de) and LIPSS technology is available from ALPHANOV Optica and Laser technology centre (https://www.alphanov.com/en).

Figure 2: Simplified concept of laser treatment with SEM images illustrating sub-micron features that are achievable.

Figure 3: SEM images of the unique surface texturing achieved in TresClean. 

Figure 4: Injection mold textured with the DLIP process 

Figure 5: Injection mold structured with the LIPSS process

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The TresClean project is an initiative of the Photonics Public Private Partnership and has received funding from the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 687613