Oxygen boost diffusion of additively manufactured Ti-6Al-4V for improved oxide layer adhesion

Abstract

The advancement of additive manufacturing (AM) for Ti-6Al-4V has broadened its application, particularly in the biomedical field, where patient-specific implants with complex geometries, previously unattainable via traditional manufacturing, are now feasible. However, untreated Ti-6Al-4V is known to exhibit poor wear performance. To address this, post-processing treatments such as boost diffusion, which involves oxygen diffusion to induce gradual case hardening, followed by thermal oxidation to form a hard, wear-resistant oxide layer, have shown promise in enhancing the wear properties of AM Ti-6Al-4V. This study investigates boost diffusion treatment to optimise the formation of an adherent oxide layer on AM Ti-6Al-4V, while also examining the impact of the starting microstructure on treatment efficacy. The optimised boost diffusion process resulted in an oxygen diffusion depth of 215 μm and hardness values up to three times higher than the bulk material, particularly at the oxide layer/metal substrate interface. The adhesion of the oxide layer was rated as class one.