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In this study, TiCrAlCN/TiAlN multilayer coatings were deposited on M2 high speed steel substrates by the Closed-Field Unbalanced Magnetron Sputtering system. The chemical composition, microstructure, morphology, mechanical and high temperature wear resistance properties of the coatings were characterized, analyzed and compared to the substrate. The high temperature wear tests were carried out under a load of 2 N at the lap (wear test distance) of 50 m and in dry sliding condition at Room Temperature (RT), 150, 300, 450, and 600 °C on atmospheric conditions. It has been found that the TiCrAlCN/TiAlN multilayer coatings have a higher wear resistance than the M2 substrate. The stable friction behavior and low friction tendency was determined at 600 °C. When the test temperature increased, the wear rates decreased. Narrow and smooth wear tracks and also the lowest wear rate were obtained at 600 °C.

Boriding and nitriding lead to improved tribological and corrosive properties of M2 high speed steel. Boronising treatment was carried out in Ekabor-II powders at the process temperature of 950 degrees C for 4 h. Gas nitriding was performed at 570 degrees C for 5 h with a gas mixture of 50% N-2 and 50% H-2. Structural and mechanical properties of borided and nitrided layers were characterised using X-ray diffrac-tion (XRD), optical microscopy and microhardness testing. Corrosion behaviour of borided and nitrided samples was also studied by the Tafel extrapolation and linear polarisation methods in 0.5 M NaHCO3 and 0.6 M NaCl solutions at 25 degrees C. Wear behaviour studies were carried out with a ball-on-disk testing method at a sliding speed rate of 0.3 m/s under 10 N loads in dry medium. The existing phases on borided and nitrided M2 steels were FeB, Fe2B and Fe3N0.94, Fe4N, respectively. The present phases of nitride compounds in nitrided M2 steel were Fe3N and Fe4N. The lowest friction coefficient and the highest wear resistance values were measured in the borided specimens that were subjected to wear. Borided M2 samples show a lower corrosion current and higher corrosion resistance than the other samples. The lowest corrosion rate was obtained on borided samples in both solutions. As a result of boronising and nitriding, the low surface hardness, wear and corrosion performance of M2 steel was improved.