The effects of gas atmosphere on the tribological performance of conventional industrial hard coatings and nanolayered CrN/CrAlN and CrN/CrVN was investigated. The three atmospheres, i.e. ambient air, nitrogen and oxygen, changed different friction and wear properties of the tribological system. SEM observation and EDS analysis showed following: • The friction and wear properties are severely influenced by the atmosphere. The use of nitrogen supresses the oxidation processes resulting in a reduced wear rate of the coatings. Accelerated oxidation in oxygen environment causes a higher friction coefficient. • Oxidised surface and tribological films were observed when using oxygen atmosphere. • Several different wear products were observed. The roll–like structures were detected in TiAlN coating in all environments but were most extensive in the nitrogen environment. Some roll–like debris in chromium-based coatings were noticed also in the air atmosphere but were not noticeable in nitrogen. In the oxygen atmosphere, fish–scale–like debris were observed in chromium-based coatings.
COBISS.SI-ID: 28214055
Reduction of wear and corrosion, along with increasing thermal stability of tools presents industrial challenges which demand continuous development of new coating materials and coating design concepts. Recently, the main attention has been placed on research and application of multilayer and nanocomposite coatings. In this study, TiAlN and TiSiN layers were alternatively deposited to produce a nanolayered nanocomposite TiAlSiN coating. Single-layer TiAlN and TiSiN coatings were deposited along with the nanolayered coating for better understanding of its properties. All coatings were prepared by sputtering in an industrial unit equipped with four magnetron sources (two Ti-Al and two Ti-Si). According to XRD and XPS measurements, nanolayered TiAlSiN coating consists of crystalline fcc-TiN like and amorphous Si3N4 phases. TEM analysis revealed that TiSiN layers block the growth of TiAlN crystallites which are equiaxed with a size of around 5 nm. As a result, TiAlSiN coating exhibits high hardness (H = 39 GPa) which is attributed to limited dislocation activity in small crystals and suppression of grain boundary sliding.
COBISS.SI-ID: 27291943
Deep cryogenic treatment in combination with classic heat treatment shows a significant improvement in wear resistance of high speed steel tools. The aim of this research was to investigate how the microstructure of the substrate tool steel material, which was altered by deep cryogenic treatment and plasma nitriding, influences the properties of TiAlN coating. The results show that both influence the adhesion of the TiAlN coating to the high speed steel substrate. Better wear resistance of deep cryogenic treated samples in comparison with conventionally heat treated ones was also found.
COBISS.SI-ID: 27922471