Properties and Performance of Hard Coatings on Tool Steels under Cyclic Indentation

In this paper cracking resistance and fatigue properties of five hard coatings - TiN, TiCN, TiAlN, AlTiN and nanocomposite nACo (nc-AlTiN/a-Si3N4) on tool steels - Weartec and Vanadis 6 are evaluated by means of the cyclic Vickers indentation method. The analytical part covers an evaluation of damage evolution of the coated system versus the number of cycles. The effect of mechanical response - Young's module/Hardness ratio (E/H ratio) on the crack propagation is described in the form of a diagram with various curves, each one associated with a certain number of indentation cycles. The comparative adhesion testing was conducted with the use of the Rockwell C technique. It was found that the type of cracks formed in the coated systems under cyclic loading is dependant on the E/H ratio values. The data obtained enable the cracking and fatigue resistance of the coated system to be compared and an optimal coating for metal forming tools applications to be selected.