Optimisation of plasma spray conditions for production of bioceramics

Coated implants have, in recent years, been actively researched and put to use in many biomedical engineering applications. The coating is hydroxyapatite(HA), a calcium phosphate compound with attractive bioactive and biocompatible properties that can enhance the fixation process of biomedical implants. Thermal spraying provides a potent means for depositing the HA coatings on implants. Amongst the popular thermal spray techniques are combustion flame spray, plasma spray and high velocity oxy-fuel spray (HVOF). Past research has shown that plasma spraying normally induce undesirable phase changes to the HA feedstock. Hence, the coatings usually contain many bioinert or bioresorbable phases. These deleterious effects can be effectively curtailed through proper process settings, powder modification, and powder sizing. This report investigates the versatility of thermal spray techniques to perform: (i) spheroidisation of HA powders (ii) preparation of HA-based biocomposite powders and coatings and, (iii) depostion of HA coatings. The combustion flame was utilized to produce fine spheroidised HA powders and HA-based composite powders while plasma spray and HVOF spray deposit the spheroidised HA powders to form dense coatings