LAUSR

Abstract Calcium phosphate coatings (CaP) (i.e., brushite and hydroxyapatite) were grown by pulsed current electrodeposition on FeMnSiPd alloys, a newly developed material proposed for biomedical implants. The electrolytic baths contained Ca(NO3)2·4H2O and NH4H2PO4 as precursors. Bath additives, such as H2O2 and NaOH, were used to promote hydroxyapatite (HAp) coating formation directly from the bath. The effect of the electrodeposition parameters on the structure, morphology and mechanical performance of the coatings was investigated. Increasing the electrodeposition time from 900s to 3600s resulted in an increase of HAp over the dominant brushite structure. Addition of 2000 ppm of NaOH or 3000 ppm of H2O2 also promoted an increase of HAp fraction when compared to the coatings obtained from the additive-free bath. Nonetheless, pure HAp was only achieved with the addition of 4000 ppm of NaOH to the electrolyte. The morphologies of the CaP particles in the coatings ranged from needle- to plate-like structures depending on the electrodeposition parameters and the resulting phases. The mechanical behaviour of the coatings was studied by scratch testing and nanoindentation. As a general trend, the Young's modulus and hardness values of the electrodeposited coatings were lower than those reported for fully-dense HAp, independently of the deposition conditions, because of the porous morphology of the coatings. No signs of cracking or delamination were observed during nanoindentation or scratch tests except for the coating prepared form the electrolyte containing 3000 ppm of H2O2.