Modeling of interstitials diffusion during debinding/sintering of 3D printed metallic filaments: Application to titanium alloy and its embrittlement

Parts made by metal additive manufacturing processes assisted by sintering suffer from embrittlement due to binder/powders interactions. Using a core-shell approach, we modelled the diffusion of carbon and oxygen from the binder into the metallic powders. The model was assessed by measuring the interstitials content upon various debinding/sintering steps. The diffusion/precipitation phenomena during these non-isothermal treatments lead to either a saturated solid solution or the precipitation of titanium carbides. The consequences on the mechanical behavior of single 3D printed filaments were quantified by bending tests, highlighting a transition from brittle to ductile fracture depending on the debinding parameters. This approach can be applied to understand the role of fast diffusing interstitial elements into various powders systems in order to optimise the chemical composition and the mechanical properties of 3D printed metallic parts.