Selective laser melting of CoCrMo-Ti6Al4V bimetallic composites: fabrication, characterization, and cytocompatibility

Bimetallic structures integrating Ti6Al4V and CoCrMo alloys present a promising solution for advanced orthopedic implants by combining high fracture toughness with excellent wear resistance. However, the direct fabrication of these dissimilar metals via Selective Laser Melting (SLM) is significantly hindered by metallurgical incompatibility and high residual stress, which typically lead to interfacial delamination and curling deformation. In this study, a Ti6Al4V-CoCrMo bimetallic composite was successfully developed using SLM. To overcome manufacturing defects, a loose CoCrMo transition layer was employed as a mechanical buffer to accommodate residual stresses, while optimized external support structures provided physical anchoring to suppress geometric distortion and edge curling.The microstructural evolution, elemental distribution, and phase composition were systematically characterized using electron microscopy and diffraction techniques. The mechanical performance was evaluated through hardness and sliding wear tests, while the biological response was assessed using bone marrow mesenchymal stem cells (BMSCs). The results indicated that the three-layer architecture effectively eliminated macro-defects and ensured structural integrity. The composite exhibited a substantial enhancement in surface hardness and wear resistance, achieving performance levels comparable to monolithic CoCrMo alloy.Fracture analysis revealed a cohesive failure mode within the transition layer, demonstrating robust metallurgical bonding between the dissimilar components.Furthermore, in vitro assessments confirmed excellent cytocompatibility and healthy cell proliferation on the composite surfaces. This research establishes a reliable fabrication methodology for complex bimetallic components, offering broad application prospects in personalized medical devices, joint replacements, and tissue engineering.