TiN, CrN and TiCrN coating architectures on M2 steel: consequences for wear and micro-impact resistance

Cutting and forming tools operating under high load conditions often suffer from premature wear. Applying hard, wear-resistant coatings particularly multilayer coatings can significantly enhance their functional properties. In this study, three multilayered coatings were deposited on hardened M2 steel bars using arc-evaporation: (1) TiN/TiCrN/TiN, (2) TiN/TiCrN/(TiN/CrN)10/TiN system and (3) (Cr/CrN)25. Mechanical (nanoindentation), tribological (cylinder on cylinder reciprocating tests) behavior of the coatings was investigated along with micro-impact tests. SEM/TEM analysis of the coatings revealed dense and fine-grained columnar structure in the direction of growth. All multilayer coatings showed enhanced wear resistance compared to the TiN monolayer. The TiN/TiCrN/TiN system exhibited the highest hardness (30.6 GPa) and best wear resistance against Al₂O₃, with an 88 % reduction in volume loss compared to TiN. This performance is consistent with its high load-bearing capacity (H3/E2 = 0.107 GPa), moderate H/E (0.059) and the lowest friction coefficient (<0.2). On the other hand, the (Cr/CrN)₂₅ coating demonstrated the best impact performance — with no chipping at 500 mN over 500 cycles and minimal damage at 1500 mN. This is attributed to its high H/E (0.074) and H3/E2 (0.126 GPa) ratios, along with a relatively low modulus (310 GPa), much more closely matched (Ec/Es ∼ 1.5) to the substrate than the other coatings.