High-Speed Laser Surface Structuring for Thermal Spray Coating Preparation

The preparation of surfaces for coating processes is indispensable for maximal adhesion and good coating results. These technical surfaces can be treated by chemical, mechanical, or physical procedures. In thermal spray coating, grit blasting is a standard process for surface preparation. This mechanical roughening and activation of the surfaces is fast and easy to handle. On the negative side, the grit gets wasted and the generated pattern is inflexible. Therefore, attempts to substitute grit blasting with a laser application is discussed in this article. Herein, a theoretical evaluation of high-speed laser surface texturing (LST) is performed to find limits and points for the optimization of these processes. To estimate the surface processing rates, continuous wave, nanosecond, and ultrashort pulse laser machined dimples and grooves are investigated, and results of the spray coatings are presented afterward. The steel substrates are coated with Stellite 6 and tungsten. Adhesion tests and coating structures are analyzed. In terms of the optimization of the laser texturing, in situ temperature measurements show the influence of the laser process speed on the thermal load of the substrate. The influence of the number of scanning repetitions on heat accumulation during LST is also analyzed.

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