Local improvement of structural steels high-friction properties by friction stir texturing

The microstructural, mechanical and tribological properties of textured structural steel surfaces, produced using a friction stir processing (FSP) related technique, called in current work friction stir texturing (FST), are analyzed in this paper. The textured/processed surfaces were produced using a WC-Co pinless tool and varying tool rotation and traverse speeds. Microstructural analysis of the textured/processed surfaces revealed an important grain refinement relative to the initial substrate microstructure. The mechanical strength of the refined structures, evaluated through hardness tests, was found to drastically increase, relative to the non-processed substrate. In the same way, the roughness measurements and friction tests revealed an important enhancement in roughness, as well as in static friction coefficient, of the textured/processed surfaces relative to non-treated and blasted surfaces. A linear relation between surface roughness, stiffness, friction coefficients and processing parameters was found, proving that the proposed texturing technique is suitable to be used in the production of friction tailored surfaces.