Advanced Structured Materials

Abstract

Hydroxyapatite (HA) is one of the most significant calcium phosphate bio-ceramic which is used commercially in biomedical application due to its similar structure with natural bone, bioactivity, and stability in body fluid. HA has excellent biological properties, while plasma sprayed HA coatings have poor bond strength which makes it difficult to use HA coated implants under mechanical stress. Wollastonite (CS) is a calcium silicate based bioactive ceramic which is used in thermal spraying due to its higher bond strength than HA coatings, however it dissolves quicker than HA in simulated body fluid (SBF). The aim of this work is to produce HA-CS composite powder in order to increase bond strength of the coating. In this study, commercial CS and precipitated HA mixture suspension which involved wt. 20% CS was prepared for spray drying (SD) application. HA-CS composite microspheres were granulated by spray drying to supply homogeneity of coating and carry powders to the plasma easily. Afterwards, HA and HA-CS composite microspheres were coated by plasma spraying on carbon steel. Results showed that HA-CS composite coatings have higher adhesion strength, while it decomposes easier to other calcium phosphates than pure HA coating. Additionally, HA-CS coating has higher rate of porosity and un-melted particles.