Powder bed laser sintering of copper-doped hydroxyapatite: Numerical and experimental parametric analysis

Abstract

Additive manufacturing (AM), especially powder bed laser sintering (PBLS), has been an increasingly popular field since the 1980s. Direct SLS is particularly challenging with ceramic materials due to their low thermal conductivity, high melting point, and brittle mechanical behaviour. In addition, they require longer processing times for a reliable sintering degree. In this work, the impact of some crucial parameters in SLS applied to a copper-doped hydroxyapatite bioceramic was studied. Incorporating copper ions into the hydroxyapatite matrix by thermal treatment can stimulate blood vessel formation, simultaneously improving the material's mechanical integrity and antibacterial properties. Moreover, it facilitates laser power absorption by the material at the laser wavelength. Thin films were prepared with controlled thicknesses using dip-coating on glass substrates, and they were irradiated by an ytterbium laser (1.070 µm wavelength). Experimental laser irradiation was systematically compared to numerical models to predict the maximum temperature produced on the film surface by laser irradiation. The evaluated parameters are the absorptivity from the copper concentration, the film thickness, and the laser source (scanning velocity and power). Combining low laser scanning speeds with low film thickness and optimised absorption tuned by the copper concentration has made possible the development of well-sintered ceramics by the PBLS technique. • SLS on Cu-doped HAP films has been experimentally and numerically investigated. • The injected power density controls the local processing temperature. • Key parameters are copper concentration, film thickness, laser scan rate, and power. • The temperatures predicted from numerical models corroborate the film morphologies. • Optimal conditions for SLS processing can be obtained from this approach.