Comparison of three advanced hard coatings for stamping applications

Three advanced hard coatings, CrTiN alloy, TiN/NbN multilayer and a multilayered C-composite, were field-tested and compared for their stamping wear resistance. All coatings were deposited onto SKH51 steel punches using an unbalanced magnetron sputtering system. Parametric studies of substrate bias, deposition pressure, composition, and structure effects on the coatings’ performance were conducted to determine the optimum deposition conditions. A 25-ton open-frame stamping machine was used for the stamping test on cold rolled carbon steel. Wear characteristics of the coated and uncoated punches were analysed using shearing and stripping force diagrams and optical microscopy. The results showed that: (1) all three coatings significantly improved the wear resistance and stamping performance; and (2) CrTiN coating out-performed the other two, owing to its high hardness, good adhesion and moderate friction coefficient.