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

Bimetallic structures integrating Ti6Al4V and CoCrMo alloys present a promising strategy for advanced orthopedic implants by synergistically 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 frequently lead to interfacial delamination and edge warping. In this study, a CoCrMo-Ti6Al4V bimetallic composite was successfully fabricated using SLM. To overcome manufacturing defects, a CoCrMo transition layer printed with low laser energy density was employed as a mechanical buffer to mitigate residual stresses, while optimized external support structures provided physical anchoring to suppress geometric distortion. The microstructural evolution, elemental distribution, and phase composition were systematically characterized using field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. Mechanical performance was evaluated through hardness and sliding wear tests, while the biological response was assessed using human bone marrow mesenchymal stem cells (BMSCs). The results demonstrated that the three-layer architecture effectively eliminated macroscopic defects and ensured structural integrity. Furthermore, the composite exhibited a substantial enhancement in surface hardness and wear resistance, achieving an interfacial bonding strength of 43.21 ± 1.07 MPa. Fracture analysis revealed a cohesive failure mode within the transition layer, indicating robust metallurgical bonding between the dissimilar components.In vitroassessments confirmed excellent cytocompatibility, exhibiting high cell viability (>95%) and proliferation on the composite surfaces. Ultimately, this research establishes a reliable fabrication methodology for complex bimetallic components, offering broad application prospects in personalized medical devices, joint replacements, and tissue engineering.