Mechanical properties and Young's modulus of plasma‐sprayed hydroxyapatite coating on Ti substrate in simulated body fluid

Abstract

This study evaluated the Young's modulus, residual stress and strain, bonding strength, and microstructure of the plasma-sprayed hydroxyapatite coating (HAC) on Ti6Al4V substrate with and without immersion in Hank's balanced salt solution (HBSS). The purpose was to explore the possible correlation of HAC durability and mechanical properties of the coating. The results show that the residual stress and strain, Young's modulus, and bonding strength of the HAC after immersion in HBSS are substantially decreased. The decayed Young's modulus and mechanical properties of HACs are accounted for by the degraded interlamellar or cohesive bonding in the coating due to the increased porosity after immersion that weakens the bonding strength of coating and substrate system. The biologic implications of the research are discussed in detail. This study contributes to the arguments that the method to alleviate the dissolution of HAC will increase the bonding strength of the coating system after immersion, which together with the controlled residual stress and strain in the coating might promote the long-term stability of the HA-coated implant.

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

“…Since the thermal expansion coefficients A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 14 of metals exceed those of CaPO 4 , the compressive residual stresses were observed for metallic substrates covered by CaPO 4 . Depending on the experimental conditions and the application or non-application of pre-or post-deposition techniques, the numerical values appeared to vary from -140 to -10 MPa [88,173,[188][189][190][191][192]. Furthermore, immersion in simulated body fluid (SBF) was found to reduce the compressive residual stress until zero and even redistribute it from compressive to tensile [88].…”

Calcium orthophosphate coatings, films and layers

“…This happened because metals had a higher rate of thermal diffusivity than calcium orthophosphates and, thus, the cooling rate of the first layer was faster (Gross et al 1998b). Besides, residual stresses in the plasma sprayed coatings, films and layers were found and measured (Valter et al 1997; Tsui et al 1998; Yang et al 2000; 2003c; Yang and Chang 2005; Carradó 2010; Yang 2011). …”

Surface engineering of titanium thin films with silk fibroin via layer‐by‐layer technique and its effects on osteoblast growth behavior

“…10 Another surface modification approach is coating with hydroxyapatite to enhance the biocompatibility of orthopedic and dental titanium-based materials. 11,12 Alkaline treatment 13 and thermal oxidization 14 on titanium and its alloy were reported to be efficient approach to improve osteoblast growth behavior, respectively.…”