Development of laser dimpling strategies on TiN coatings for tribological applications with a highly energetic Q-switched fibre laser

Laser micromachining and structuring of thin ceramic surface coatings is an appealing process, especially for tribological applications. Studies show increased wear resistance and friction properties of dimpled surface coatings. The nature of the material and the delicacy of the coating integrity raise the problem of tight processing conditions, especially in terms of the ablated depth. However, for the industrial scale of the application, processing strategies with industrial grade laser systems are required. For this purpose, the present work reports the use of a highly energetic Q-switched fibre laser for the laser dimpling of TiN coatings applied in very limited micrometric thickness. The processing strategy that involves ramped pulse trains and controlled defocusing of the laser beam was demonstrated to be effective for controlling the dimple radius and depth without excessive machining to cause substrate contamination. The dimples were characterised for the amount of damage done by contaminating the coating material with the substrate. Results confirm that in non-contaminated conditions chemical composition of the TiN coating was also maintained.