Hydroxyapatite, (HA), is a calcium phosphate bioceramic that has been widely used in orthopaedics and dentistry due to its biocompatibility and osteoconductivity. However, its poor bulk mechanical properties have limited its use to coating on metallic surfaces.  The plasma spraying technique is the most commonly used method for the production of HA coatings. Specifically, low energy versions of it have been appointed as most suitable techniques to spray HA without major phase decomposition and crystallinity decrease. However, HA coatings have small non-interconnected porosity which would hinder the posterior cellular ingrowth.

The present work aims to produce thick coatings as a step further towards the bone scaffolds. Aiming to produce bone scaffolds will require addition of second phases to the matrix material (HA) to improve both the final mechanical properties and porous structure of the components.

A reference HA series was produced. Statistically designed experiments (DoE) were used to determine the effect of three process parameters on four HA coating properties (layer thickness, roughness, crystallinity and phase purity). Models describing the effects of the variables on these coating properties were developed and the optimal parameters were selected to produce the biocomposite coatings. Three mechanical properties (Vicker’s microhardness (H_v), Young’s modulus (E) and fracture toughness (K_IC)) and porosity were measured as reference on the sample produced with the selected parameter set.

In order to improve the structure, a bioreabsorbable polymer (Polycaprolactone (PCL)) was selected. The reinforcement material selected was a bioinert ceramic, Titanium Oxide (TiO₂). The addition of these materials was also optimised using DoE. Early results suggest an improvement in both structure and mechanical properties.

Further research will involve the characterization of the dissolution behaviour of the components and determination of cell behaviour.

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1. Selective laser sintering of hydroxyapatite/poly-ε-caprolactone scaffolds