Microstructural properties and Adhesive Strength of 316L Stainless Steel Coated with Hydroxyapatite Derived from Mussel Shell Wastes via Flame Spray Deposition

Abstract

316L stainless steel (316L SS) is an excellent implant material because of its durability, low modulus, superior corrosion resistance, and biocompatibility. However, 316L SS was bioinert and cannot be combined with living tissue. To cover this weakness, 316L SS needs to be coated with a material that has high bioactivity, such as hydroxyapatite (HA) bioceramic. Flame spray deposition (FSD) is a promising method for applying hydroxyapatite to 316L SS, but the deposition product’s low interfacial adhesion makes it brittle. This study recommends preheating the substrate (300, 600, and 900) C to improve the adhesive bond before coating it with hydroxyapatite. The coated 316L SS product was then subjected to mechanical testing and analytical techniques (XRD and SEM/EDX) to evaluate its osseointegration, microstructures, and adhesive strength. After preheating to 900oC, the resulting coated steel showed a significant increase in adhesion strength. The crystallinity index also increased to 99.35%. However, the porosity and layer thickness decreased. The current work can shed light on the coating procedure for stainless steel, which is a promising material for implants, and it can also guide future investigations into the potential uses of HA made from mussel wastes.