Cyclic delamination behavior of plasma-sprayed hydroxyapatite coating on Ti–6Al–4V substrates in simulated body fluid

• Published in: Materials Science & Engineering C Vol. 67; pp. 533 - 541
• Main Authors: Otsuka, Yuichi, Kawaguchi, Hayato, Mutoh, Yoshiharu
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.10.2016
• Subjects: Biomaterial; Body Fluids - chemistry; Coated Materials, Biocompatible - chemistry; Coating; Corrosion fatigue; Delaminating; Delamination; Dissolution; Durapatite - chemistry; Fracture mechanics; Humans; Hydroxyapatite; Interface fracture mechanics; Mathematical models; Plasma Gases - chemistry; Plasma-spray coating; Stress corrosion cracking; Surgical implants; Titanium - chemistry; Hydroxyapatite; Biomaterial; Stress corrosion cracking; Interface fracture mechanics; Corrosion fatigue; Plasma-spray coating
• ISSN: 0928-4931; 1873-0191
• DOI: 10.1016/j.msec.2016.05.058

This study aimed to clarify the effect of a simulated body fluid (SBF) on the cyclic delamination behavior of a plasma-sprayed hydroxapatite (HAp) coating. A HAp coating is deposited on the surfaces of surgical metallic materials in order to enhance the bond between human bone and such surfaces. However, the HAp coating is susceptible to delamination by cyclic loading from the patient's gait. Although hip joints are subjected to both positive and negative moments, only the effects of tensile bending stresses on vertical crack propagation behavior have been investigated. Thus, the cyclic delamination behavior of a HAp coating was observed at the stress ratio R=−1 in order to determine the effects of tensile/compressive loading on the delamination behavior. The delamination growth rate increased with SBF immersion, which decreased the delamination life. Raman spectroscopy analysis revealed that the selective phase dissolution in the HAp coating was promoted at interfaces. Finite element analysis revealed that the energy release rate Gmax showed a positive value even in cases with compressive loading, which is a driving force for the delamination of a HAp coating. A prediction model for the delamination growth life was developed that combines a fracture mechanics parameter with the assumed stress-dependent dissolution rate. The predicted delamination life matched the experimental data well in cases of lower stress amplitudes with SBF. •Delamination growth rates are higher at edge of interfaces.•Delamination propagation rates of HAp coating became higher in SBF.•Delamination curves can be arranged by Paris law.•Localized dissolution of HAP coating occurred at interfaces.•Prediction model of delamination lives can provide good result.