Relation between mechanical and tribological properties of plasma nitrided and TiCrN coated YXR-7 tool steel

Abstract

This study aims to establish the relation between mechanical and tribological properties of nitrided and TiCrN coated YXR-7 tool steel. Nanoindentation and scratch tests were conducted to evaluate the mechanical properties of the substrate. Hardness of the tempered tool steel was enhanced by 20.31% and 167.48% after nitriding and TiCrN coating respectively due to lower crystalline grain size (0.0144 µm) of the coating than the tempered (2.61 µm) and nitrided (1.89 µm) substrate. Elemental diffusion (Fe, Cr, W) from the substrate to coating also facilitates improved mechanical properties. Strain hardening index (n) obtained for tempered, nitrided and coated tool steel was 0.1, 0.2 and 0.3 respectively indicating lower pile-up in the TiCrN coating during nanoindentation. Coated surface exhibited lower depth and narrow scratch track compared to the nitrided surface attributed to high scratch hardness.