Dynamic contact behavior of graphite-like carbon films on ductile substrate under nano/micro-scale impact

Abstract

Coated components are often subjected to high strain rate and repetitive contact damage in practical service, so how to quickly evaluate the dynamic contact behavior of the thin protective coating is particularly important. Highly resolved single nano-impact and novel multiple micro-scale impact tests were used to investigate the dynamic hardness and fatigue failure of 0.55–1.52 μm thick graphite-like carbon (GLC) films on 316L stainless steel with varied thickness, respectively. By analyzing the impact depth and velocity before and after the indenter first contact with the sample, the dynamic hardness of GLC film/substrate system was obtained reasonably based on the energy approach in single nano-impact tests. Possible reasons for the higher dynamic hardness than quasi-static hardness include overestimation of the plastic absorbed energy W p and the strain rate sensitivity of materials. The thickest film/substrate system studied had a higher dynamic hardness than the thinner films due to its higher load carrying capability. Results with the multiple micro-impact technique showed that a GLC film with intermediate thickness (1.1 μm) was more resistant to the impact fatigue, while the thinnest film, 0.55 μm, exhibited more pronounced radial cracks under the indent and the thickest film , 1.52 μm, showed more significant edge ring cracks, these differences resulting from the combined action of stress distribution, film microstructure and mechanical properties . • Provide an energy-based method to evaluate the dynamic mechanical properties of thin films or film/substrate system. • Improve the understanding of impact failure of hard coatings deposited on ductile substrates by the novel micro-impact. • Investigate the influence of acceleration force on the dynamic contact behavior of hard coatings on ductile substrates. • Discuss the influence of film thickness on their dynamic contact behavior.