Effect of Pre-treatment and Duration of Pulse Plasma Nitriding on Duplex Plasma Treatment by Physical Vapor Deposition of TiN on AISI D2 Steel

Surface treatments have been vastly used in the manufacturing industry to improve the life of tool materials. Plasma nitriding (PN) is widely used because it allows controlling the surface microstructure mainly by the formation of a compound layer and N 2 diffusion layer. Duplex surface treatments are new solutions for tools, combining the advantages of PN and physical vapor deposition (PVD) coatings by magnetron sputtering, looking for still better performance while at service. This investigation is an attempt to study the surface properties of AISI D2 steel with two different substrate conditions (as-received and heat-treated), tailored by duplex plasma treatment with a variation of PN duration (6, 12 and 24 h) followed by PVD of TiN coating. Surface properties and phase identification of the duplex-treated samples have been made by SEM and XRD. Other properties such as surface roughness, microhardness and wear resistance were evaluated by a surface profilometer, a Vickers microhardness tester and a ball-on-disk setup, respectively. The results indicated higher microhardness and wear resistance values for every heat-treated surface compared with the as-received samples. PN 6 h duplex treated had the highest microhardness and wear resistance properties among all. It is remarkable that the initial surface condition, N 2 diffusion layer and compound layer play a decisive role in enhancing the load-carrying and wear resistance capability of duplex-treated samples. Graphical Abstract