Deformation by light Impacts to Create a Near-Surface Nano- and Microstructured Layer in AISI 316L Stainless Steel

A nano- and microstructured surface layer (NMSSL) was created on an AISI 316L stainless steel sample by impact loading. As a result of the impacts, a change in the microstructure of the test sample was observed: a decrease in the size of the grains, an increase in their misorientation, the appearance of slip bands inside the grains, the appearance of rounded shapes of different sizes (0,1–15 μm) and with different densities on the surface of the sample. Moreover, these nanomicrocrystalline grains had random crystallographic orientation. The microhardness of the deformed surface was assessed using the Vickers and Berkovich methods. The hardness imprints had an approximately equiaxial shape, but the sides of the imprints were often distorted. The microhardness on the impact-deformed surface ranged as Н = 2.7–4.2 GPa depending on the number of impacts, increasing with their growth and decreasing with the distance from the impact surface. The microhardness of the undeformed sample was 2.0 GPa. The main patterns of formation of the deformed layer depending on the number of impacts have been revealed.