Structure-property relationships of differently heat-treated binder jet printed Co-Cr-Mo biomaterial

Abstract

This investigation systematically examines the influence of sintering temperature and aging treatment on the density, microstructure evolution, phase formation, and mechanical properties of a binder jet printed Co-Cr-Mo biomedical alloy. Sintering at 1380 °C for 2 h yielded a near-fully dense part (99.1%) with favorable mechanical properties (up to 325 HV0.1 hardness and up to 693 MPa ultimate tensile strength). The grain size remained unchanged after aging at 800 °C for 24 h (89 ± 21 µm). Aging resulted in increased microhardness and tensile strength due to phase formation (Cr23C6, CrMo, and ε phase), but a significant decrease in ductility. Consequently, the sintered and aged specimen exhibited higher hardness (522 HV0.1), yield strength (641 MPa), and ultimate tensile strength (854 MPa) compared to cast Co-Cr-Mo alloy. Biocompatibility testing with fibroblasts showed a cell viability of 95 ± 2%, indicating that binder jet printing did not affect the biocompatibility of the Co-Cr-Mo alloy. Exemplary printed parts including hip-joint, partial denture, and small-scale knee joint were successfully demonstrated. This study highlights the comparable properties of binder jet Co-Cr-Mo alloy to the cast alloy, affirming its potential for biomedical applications.