INFLUENCE OF PLASMA NITRIDING OF STEEL SUBSTRATES ON THE PROPERTIES OF TiN AND (Ti, Al) N COATINGS

摘要

The properties of polycrystalline TiN and (Ti, Al)N coatings deposited on not nitrided, conventionally plasma nitrided and low pressure plasma nitrided AISI Hll and AISI M2 steel substrates were investigated. The plasma deposition and low pressure plasma nitriding were performed in a Z700-LH magnetron sputter unit, while separate unit MONO5 was used for conventional plasma nitriding. For the characterisation of the composite structures, the following methods were used: scratch test, X-ray diffract ion analysis, scanning electron microscopy, scanning tunneling microscopy and microhardness measurements. It was found that the plasma nitriding prior to coating deposition strongly affects the growth and properties of hard coatings, such as the microhardness, adhesion, preferred orientation, structure and morphology. Plasma nitriding at low pressure has a greater effect than does conventional plasma nitriding: the adhesion is even more enhanced, the microharness is increased, the preferred orientation is more pronounced and the structure is slill columnar but more compact. All the changes are more clear visible in the case of TiN coating. The influence of the base substrate material on the coating properties is also evident. After plasma nitriding, the structure. morphology and topography of the coatings are less dependent on the steel grade of the substrate.