Understanding cold spray technology for hydroxyapatite deposition

The standard method for applying hydroxyapatite (HAP) coatings to biomedical implants is plasma spraying. However, due to the high temperature of the plasma, these coatings frequently experience negative effects like evaporation, phase change, de-bonding, gas release, and residual stresses. This paper summarizes a revolutionary technique known as a cold spray (CS), which allows HAP coatings to be applied at temperatures well below their melting point. CS has several advantages over conventional high-temperature technologies, and it seems to be approaching parity with other older methods. When applied using the CS approach, the HAP coatings enhance bioactivity, increase corrosion resistance, and maintain the characteristics of calcium phosphate ceramics. This study aims to give a concise and comprehensive overview of HAP-based materials, including substituted-HAP and HAP/polymer composites, and their applications in bone tissue engineering. To better understand the advantages of CS technology, a comparison of CS, high-velocity oxy-fuel (HVOF), and plasma spray is given at the end. The perspective and difficulties were also highlighted.