Enhancing mechanical properties and cutting performance of industrially sputtered AlCrN coatings by inducing cathodic arc glow discharge

Abstract

The average ion energy per deposited atom (E d ) is defined as the product of the ion energy (E i ) and ion-deposition flux ratio (J i /J d ) in magnetron sputtering deposition. E d captures both the geometrical, and plasma characteristics of the deposition system and hence is regarded as a fundamental parameter for describing the energy dependency of coating structure and properties. Nevertheless, E d is not a universal parameter since an independent variation of its components, i.e., E i and J i /J d , may result in the same E d but different coating structures and properties. While the controlling of J i /J d is not possible in most conventional magnetron sputtering systems, this study employed an industrially developed SCIL® (sputter coatings induced by lateral glow discharge) technology to independently control the ion flux (J i ) and investigate the dependence of structure, mechanical properties , and cutting performance of the AlCrN coatings on the E d and its components. The results revealed that the structure of the AlCrN coatings was mainly dependent on the J i /J d component of E d , where a transition from a cubic structure into a hexagonal structure took place beyond a critical level of J i /J d . The elastic modulus showed no E d dependency and was only affected by coating structure. However, the hardness was strongly dependent on the E d . Whether in E i or J i /J d , an increase led to a hardness enhancement through the synergic effect of the residual stress hardening, coating densification, and grain refining mechanisms. The cutting performance of deposited tools under real working conditions was also found to be dependent on the E d and, in particular, on J i /J d . Increasing E d from ~860 to ~1170 eV/atom led to a ~55% increase in tool lifetime, reaching 90% performance of the benchmark arc-deposited coating. • The structure of AlCrN coatings was dependent on the ion-deposition flux ratio. • The E eff was only structure-dependent without E d dependency. • Regardless of structure, a linear relationship between H and E d was established. • Increasing plasma ionization degree increased the lifetime of sputtered tools.