AISI 316L steel was subjected to nitrocarburizing under glow discharge conditions, which was followed by DLC (diamond-like carbon) coatings deposition using the same device. The coatings were applied under conditions of direct current and pulsed glow discharge. In order to determine the influence of the produced nitrocarbon austenite layer and the type of discharge on the microstructure and mechanical properties of the coatings, the following features were analysed: surface roughness, coating thickness, structure, chemical composition, adhesion and resistance to frictional wear. For comparison purposes, DLC coatings were also deposited on steel without a nitrocarburised layer. The obtained results indicate a significant influence of the type of glow discharge on the roughness, hardness, nitrogen content and of the nitrocarburised layer on the resistance to wear by friction and adhesion of the produced coatings.

Surface roughness is an important indicator in the evaluation of machining and product quality, as well as a direct factor affecting the performance of components. A rapidly developing filtering technology has become the main means of extracting surface roughness. The International Organization for Standardization (ISO) is constantly updating and improving the standard system for filtering technology in order to meet the requirements of technological development. Based on the filters already accepted by the international standard ISO 16610, this study briefly introduces the filtering principle of each filter, reviews the development of each filter in the application of surface roughness, and compares the advantages and limitations of their individual performances. The application range of each filter is summarized and, finally, the future direction of the digital filtering used in surface roughness is extrapolated.