BIOCOMPATIBLE & BIOACTIVE COATING OF HYDROXY APATITE ON 316L STAIN LESS STEEL FOR ORTHOPAEDIC IMPLANTS

Abstract

Surface treatment of the metallic implants by depositing coatings of biomaterials is an important method for imparting new properties and applications into these implants. The coatings of hydroxyapatite (HA) were deposited over 316-L stainless steel (SS) substrate samples by using two different coating techniques. First, electrophoretic deposition (EPD) technique was used for depositing HA on 316-L SS substrate plates. The sintering process after the EPD to enhance the attachment between the substrate material and coating was avoided. Instead a polymer binder poly vinyl alcohol (PVA) was incorporated in HA before the deposition for this purpose. Deposition rate was controlled by varying 3 process variables including: voltage, time and pH of the suspension. Second coating technique used was spray pyrolysis. Sintering was used during this technique after deposition (to give strength to the coating) at 900 °C for 2 hours and temperature above that was avoided, so that both substrate sample and coatings can be saved from any high temperature damage. The deposition rate here was also controlled by varying 3 process variables including: substrate surface temperature, duration of the spray and nozzle-tosubstrate distance. Structural properties of these coatings were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Surface roughness and dimensional analysis of coatings was studied by atomic force microscopy (AFM). Purity of the obtained coatings was confirmed by using Raman spectroscopy. Such HA coatings in combination with metallic biomaterials can be used for biomedical applications where properties like biocompatibility and bioactivity are required, such as orthopaedic implants and dental implants