Influence of gas flow rate on the microstructure and mechanical properties of hydroxyapatite coatings fabricated by gas tunnel type plasma spraying

Gas tunnel type plasma torch was used to spray hydroxyapatite (HA) coatings on 304 stainless steel substrate at different plasma gas (Ar) flow rates (100-170 l/min). Microstructure was observed by scanning electron microscope and phase analysis by X-ray diffraction. The mechanical properties such as hardness and abrasive wear resistance of HA coatings sprayed at different gas flow rates were investigated. The results showed that the gas flow rates affect greatly the microstructure and mechanical properties of HA coatings. Crystallinity increased and porosity decreased as the gas flow rate increased. Hardness and abrasion resistance increased as the gas flow rates increased.