Abstract:

Binder jet additive manufacturing (BJ-AM) offers a scalable approach for producing Co–Cr–Mo components with complex geometries; however, the combined effects of printing parameters, sintering conditions, and post-processing heat treatments on mechanical and electrochemical performance remain insufficiently understood. In this study, ASTM F75 Co–Cr–Mo alloy was fabricated via BJ-AM while systematically varying printing parameters, including powder particle size distribution, binder saturation, and recoat speed. The printed parts were subsequently sintered at elevated temperatures under different atmospheres (vacuum, N₂–5%H₂, and Ar–5%H₂) to evaluate their influence on densification behavior and microstructural evolution.
Following sintering, two material conditions were investigated: the as-sintered state and a post-processed condition involving solutionizing and ageing heat treatments. Densification was quantified using Archimedes measurements, and microstructural characterization was performed using scanning electron microscopy, electron backscatter diffraction, and X-ray diffraction texture analysis to assess pore morphology, grain structure, crystallographic texture, and phase constitution, with particular emphasis on the FCC γ-Co to HCP ε-Co transformation and the formation of secondary phases such as σ-phase and carbides.
Mechanical performance was evaluated through microhardness measurements and room-temperature tensile testing conducted in accordance with ASTM standards. Functional surface performance was assessed through electrochemical polarization measurements, and tribocorrosion experiments performed on both the as-sintered and solutionized + aged conditions in 1%NaCl solution. The evolution of wear coefficient, coefficient of friction, corrosion current density, and material degradation under combined mechanical and electrochemical loading was correlated with processing history, phase balance, and microstructural features.
The results demonstrate that printing parameters, sintering atmosphere and temperature, and post-processing heat treatment collectively govern densification, phase stability, and defect populations, which in turn control tensile behavior, wear resistance, and corrosion response. While solutionizing and ageing enhance hardness and wear resistance, their influence on corrosion and tribocorrosion behavior is strongly dependent on the resulting microstructure and secondary phase distribution. This work establishes an integrated process–microstructure–property–performance framework for BJ-AM Co–Cr–Mo alloys and provides practical guidance for optimizing their mechanical integrity and surface durability for biomedical applications.

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Dr. Waris Khan