Powder bed selective laser process (sintering/melting) applied to tailored calcium phosphate-based powders

• Published in: Additive manufacturing 2022-02, Vol.50, p.102542, Article 102542
• Main Authors: Navarrete-Segado, P., Frances, C., Tourbin, M., Tenailleau, C., Duployer, B., Grossin, D.
• Format: Article
• Language: English
• Subjects: Chemical and Process Engineering; Chemical Sciences; Chlorapatite; Engineering Sciences; Hydroxyapatite; Material chemistry; Powder bed fusion; Selective laser melting; Selective laser sintering
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2021.102542

This paper focuses on the tailoring of calcium phosphate powders for their use as powder bed selective laser process feedstock. Hydroxyapatite and chlorapatite were used as starting powders for the preparation of different blends through the addition of graphite as a laser absorptance additive. A methodical study was conducted to compare the processing windows of the blends containing different amounts of graphite through the laser patterning of circular samples. It was found that the addition of graphite increases the process window of the powder blends being the powder without additive non processable. Hydroxyapatite showed a clear phase transition (decreased when using higher volumetric energy density) into other calcium phosphate phases while chlorapatite was demonstrated to be thermally stable during the whole process (examined through X-ray diffraction and vibrational spectroscopies). In parallel, the study evaluating the powder blend composed of hydroxyapatite and graphite for the production of solid and complex parts was carried out although it required long printing times. The productivity of the process was improved by modification of printing parameters. Then, a series of solid samples were produced for the analysis of the microstructure and mechanical properties. High interconnected porosity was observed in the samples which could improve the bioactivity of the bioceramic scaffolds. A post-treatment of the parts increased their proportion in the hydroxyapatite phase and their mechanical properties. These results are expected to contribute to the application of powder bed selective laser processing of calcium phosphates powders toward bone tissue engineering. [Display omitted] •Graphite as absorption additive improves the laser-material interaction enlarging the process window.•Laser parameters directly influence the hydroxyapatite phase transition into other calcium phosphate phases.•Chlorapatite did not undergo phase transition during the process due to its inherent higher thermal stability.•Solid parts containing a majority of HA phase in the structure were obtained although with low mechanical properties.