Laser surface texturing (LST) treatment before thermal spraying: A new process to improve the substrate-coating adherence

There are a number of widely used texturing techniques, as etching, electrical discharge and abrasive blasting (sandblasting) which combine quality and optimised processing time. The process allows the ablation, fusion and/or vaporization, and finally substrate texturing in only one step by means of a concentrated energy bean in a focused spot.A pulsed Nd:YAG laser (1.064 μm radiation, 120 ns) with repetitive scans has been used to texture aluminium AL 2017 substrates. During the process, several laser parameters as scanning rate, distance between the laser impacts, frequency of the impulses and incident power have been studied to achieve NiAl coatings.Optical and scanning electron microscopy, and optical 3D profilometry were used to characterize the surface texture. Mechanical testing allowed evaluating the toughness and adhesion of the deposit.Surface texturing inducing holes on the substrate surface, coating adherence produced by thermal spraying mainly depends on the geometry of the texture (depth and diameter of holes) as well as on the distribution throughout the treated surface.