Application of the indentation method for cracking resistance evaluation of hard coatings on tool steels

Abstract

In this paper cracking resistance and fatigue properties of five hard coatings-TiN, TiCN, TiAlN, AlTiN and nanocomposite nc-AlTiN/a-Si 3 N 4 (nACo®) on tool steels Weartec TM 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 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 depends on the Young modulus/hardness ratio. The data obtained permits to compare the cracking and fatigue resistance of the coated systems and to select the optimal coating for bulk and sheet metal forming tools.

Effect of substrate roughness on adhesion and tribological properties of nc-TiAlN/a-Si3N4 nanocomposite coatings deposited by cathodic arc PVD process

“…The fracture toughness value for TiN closely matches within the range 2 to 7 MPa.m 0·5 reported by others. 44 It is reported elsewhere 45 that the coatings with lower E/H ratios, as that of nc-TiAlN/a-Si 3 N 4 , are prone to more cracking due to brittle damage (tensile driven cracking), while coatings with higher E/H ratios such as TiN are prone to quasi-plastic damage (shear driven cracking). Hence, such fracture toughness values for two different coatings are quite reasonable.…”

Nano- and Micro-Scale Impact Testing of Hard Coatings: A Review

“…For example, surface radial cracks which grow gradually extend from the impact zone with an increasing number of cycles and/or load. In cyclic Vickers indentation of hard coatings on tool steels, the observed crack morphology around the indent was found to depend on the H/E ratio of the coatings [78]. A quasi-plastic damage mode with radial cracks that increased in length under continued cyclic loading was found in coatings with relatively lower H/E [78].…”

Influence of Si- and W- doping on micro-scale reciprocating wear and impact performance of DLC coatings on hardened steel

“…In cyclic loading of brittle ceramics with spherical tungsten carbide indenters radial cracks were observed that were absent in single loading [33]. In cyclic Vickers indentation of hard coatings on tool steels the type of cracking depended on the H/E ratio of the coatings [80]. A quasi-plastic damage mode with radial cracks that grew with number of cycles was typical in lower H/E coatings.…”