Influência do teor de carbono sobre a integridade superficial de aços submetidos à operação de roleteamento

Abstract

Surface integrity refers to a set of characteristics of the surface and subsurface layer that have great influence on the functional performance of mechanical components under conditions of wear, corrosion and fatigue, and is determined by the manufacturing processes employed. Thus, surface treatments are used together with these processes to produce a surface integrity suited to the desired function. Deep rolling is one of the surface treatments that involve cold working of the surface and subsurface layer and the present work addresses the study of the influence of some of its parameters (pressure, speed, feed and number of passes) on certain characteristics of the surface integrity (roughness, surface and subsurface microhardness and microstructure) of AISI 1020, 1065 and 1080 carbon steels. A significant improvement on surface finish was observed after deep rolling, however, an increase in pressure (especially with the reduction of the carbon content) and feed (especially with the increase of the carbon content) caused an increase in roughness. An increase in the number of passes, on the other hand, improved the surface finish in some cases. Regarding the surface microhardness, its increase after deep rolling was only observed in AISI 1080 steel. In addition, under all conditions tested deep rolling promoted an increase in the microhardness of the subsurface layer and in the affected depth in comparison to the specimens subjected to turning alone. However, an increase in pressure further increased the microhardness and the affected depth; an increase in speed reduced or did not change the microhardness and the affected depth and clear trends were not observed with different feed and number of passes. Finally, the microstructural analysis showed that the increase of the carbon content promoted a reduction in the deformation of the subsurface layer caused by deep rolling. Deformation was found to increase in AISI 1020 and 1065 steels with increasing pressure and to reduce with the elevation of speed and feed. The number of passes, on the other hand, affected only the subsurface layer of AISI 1020 steel.