Indentation of Coatings at micro/nano scale: Crack formation and deflection

TL;DR

This paper investigates nano- and micro-scale indentation of hard coatings, revealing crack formation, deflection, and a novel stress-induced crystallization phenomenon affecting crack behavior.

Contribution

It introduces the observation of stress-induced crystallization causing crack deflection in CNx films during nanoindentation.

Findings

Radial and lateral cracks observed during nanoindentation.

Crack deflection due to stress-induced crystallization in CNx films.

Cracking phenomena analyzed at micro and nano scales.

Abstract

Nanoindentation is an effective way of finding mechanical properties at nanoscale. They are especially useful for thin films where elimination of the substrate effect is required. The mechanism is based upon depth sensing indentation based on Oliver and Pharr modeling. Nanoindentation was used to evaluate the nanomechanical and fractographic properties of hard coatings deposited by magnetron sputtering. Radial and lateral cracks accompanied by delamination of the coatings were observed during the indentation tests. A novel phenomenon of stress induced crystallization was observed in case of the CNx films which resulted in crack deflection. Indentations at micro scale using Vickers Indenter were also done and the cracking phenomena were analyzed.