Study of surface topography parameters during shot peening process and their influence on the paint coating of adhesion

The surface state quality depends closely on the finishing process and regime parameters used, allowing the desired surfaces to be obtained according to their applications. The surface characterization has a large wingspan because the measurements of the different roughness parameters allow quantify the surface behavior; however, some parameters are more relevant than others depending on the surface operation. In this experimental work, XC52 steel surfaces were prepared by shot peening using an experimental protocol based on Taguchi L8 design of experiments methodology, where three factors at two levels each are considered, namely, the pressure "P," the impact angle "theta," and the projection time "t." A relationship between the "Std" texture direction and the processing regime parameters was established by means of a mathematical model, which allowed optimizing the adequate parameters which favor a good adherence. Moreover, the surfaces were characterized by the fractal dimension; the latter was calculated by two methods (box counting and correlation). The results show that the best surface condition offering good paint adhesion was characterized by DC = 1.916, Std = 179.95 degrees, Sdr = 0.23, and Sdq = 0.813 obtained by the following regime: a pressure of 5 bars and an impact angle of 90 degrees for a time of 1 min. In addition, the hybrid parameters and the texture direction seem to be the most relevant to describe the surfaces behavior to the coating adhesion of this steel.