The influence of laser processing parameters on the densification and surface morphology of pure Fe and Fe-35Mn scaffolds produced by selective laser melting

Highly customisable implants with lattice structures can be achieved using selective laser melting (SLM) paving the way for tailored biodegradable Fe-based implants. For the first time, a systematic analysis is presented in terms of laser processing conditions required for scaffolds of pure Fe and a binary Fe-35 Mn alloy. The processability of the two materials were compared in terms of densification behaviour, surface roughness and geometrical error. Both materials were successfully processed into high quality scaffolds with excellent strut morphology and low processing porosity. The differences in the laser processing conditions between the pure metal and the binary alloy were discussed. The lower melting temperature of the Fe-35 Mn alloy required lower energy density for reaching the fully dense condition. Surface roughness and geometrical errors were found to be similar for the two materials. The microstructure of pure Fe was characterized by equiaxed α-ferrite grains, whereas the Fe-35 Mn had a microstructure consisting of columnar γ grains, with each γ-grain comprising of a network of individual cells.