Tribological behavior of duplex-coating on Vanadis 10 cold work tool steel

Powder metallurgy Vanadis 10 has an extensive range of applications as dies for extrusion and cold drawing. The tool surface is exposed to different requests (mechanical, chemical and tribological) and demands surface treatments to prolong its life. Few studies investigate the surface modification to optimize the tribological behavior of Vanadis 10. In this study, the combination of cryogenic treatment, two conditions of pulsed plasma nitriding and multilayer TiCN/AlTiN/CrAlTiN/CrN film deposition were evaluated. Pin-on-disc sliding tests were carried out at 0.1 m/s sliding speed, applied load of 10 N and sliding distance of 1000 m. The average hardness of all experimental conditions with multilayer film (2000 HV0.1) was approximately 2 times greater than the hardness of sub-zero treated Vanadis 10 (964 HV0.1). Plasma nitriding promoted the formation of Fe3N-epsilon compound layer in both experimental conditions. Cracks were observed in this layer. Duplex treatment does not guarantee satisfactory substrate-coating adhesion, because it depends on plasma nitriding conditions. Cryogenic treatment samples followed by plasma nitriding at 5% N-2, 75% H-2 and 20% Ar, presented higher dry sliding wear resistance in all tested conditions. This treatment is recommended for applications where Vanadis 10 requires high resistance to dry sliding wear.