The mechanical and microstructural properties of VPS-Ti porous coating deposited on titanium alloy substrates for osseointegration

Abstract

The topography of the surface of the deposited VPS-Ti coatings on substrate surfaces of implants relating to the roughness and porous structure plays a decisive role in the process of on growth of the implants to the bones i.e.osseointegration. Direct bone on growth has been successfully achieved by using micro rough coating surfaces, such as the use of vacuum plasma spraying VPS -Ti coatings. The aim of this study was to make a comprehensive review of the characterization of porous VPS-Ti coatings deposited on substrates of titanium alloy that will find application in orthopedics.One of the preferred features of the VPS process is the ability to achieve optimum macro and micro structure of the surface of implants by optimizing the spray parameters of the powder deposition and by the range of the powder granulation. In order to achieve an optimum surface roughness, open porosity and structure of VPS-Ti coatings conducted was the optimization of deposition of powder with a change in plasma current and powder carrier gas flow rate of (700 A, 35 l/min and 800A, 20 l/min). Lower intensity plasma current with a greater flow of powder heats and melts the powder particles less forming micro pores of a larger size and a higher proportion of open pores and vice versa higher plasma currents and reduced flow provide better melted particles forming a smaller share of micro pores and open porosity in the deposited layers. Image analysis showed that by optimization of parameters in the coatings open porosity can be formed ranging from 45% to 57%. By examining the properties of the deposited layers it was determined that the most optimal roughness and share of open pores for osseointegration have the Ti layers which have been deposited with the lowest amperage and highest flow of powder carrier gas.