Review of Fatigue of Coatings/Substrates

Abstract

A review of fatigue of coatings/substrates is presented. Fatigue damage is either local or general, depending on the range of cyclic loads. Local fatigue damage includes rolling contact fatigue (RCF), fretting fatigue, fatigue-wear and general wear. Applied loads are localized consisting of rolling contacts or sliding contacts, and the resulting damage is mostly surface related. Crack initiation, surface pitting, delamination, spalling, buckling and enhanced wear can result from local fatigue damage of coatings. General fatigue damage results when the loads are of longer range such as cyclic bending, torsion or uniaxial or biaxial tension/compression etc. The mechanics of fatigue, role of microstructure, micromechanics in terms of crack nucleation, growth and fracture are reviewed. Defects produced during processing form precursors for crack nucleation. It is shown that optimization of the processing conditions to minimize defect density is essential to enhance fatigue resistance of coatings/substrates.

Ceramics and ceramic coatings in orthopaedics

“…However, if the coating delaminates in vivo, it can have a dramatic opposite effect, leading to poorer fatigue of the underlying metal [133]. Comprehensive reviews on coating/substrate fatigue, and corrosive fatigue of implantable metals have been provided by Sadananda et al [386] and Antunes et al [387].…”

Stress relaxation through interfacial sliding in nanocrystalline films

“…Such films can be divided into nanocrystalline thin films and thicker ones, often called nanocrystalline coatings. Both the structure and the properties of nanocrystalline films are significantly influenced by internal stresses occurring at interphase boundaries (first of all, boundaries between substrates and films) due to crystal lattice parameter mismatch, elastic modulus mismatch, thermal coefficient of expansion mismatch, and plastic flow mismatch between adjacent phases [16]. Commonly it is desired that the level of internal stresses be decreased, because these stresses are capable of initiating cracks and/or causing the structural transformations responsible for degradation of the functional characteristics of films.…”