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Metallurgical and Materials Transactions A

, Volume 41, Issue 12, pp 3216–3227 | Cite as

Comparison of Microstructures and Mechanical Properties for Solid and Mesh Cobalt-Base Alloy Prototypes Fabricated by Electron Beam Melting

  • S.M. Gaytan
  • L.E. MurrEmail author
  • E. Martinez
  • J.L. Martinez
  • B.I. Machado
  • D.A. Ramirez
  • F. Medina
  • S. Collins
  • R.B. Wicker
Article

Abstract

The microstructures and mechanical behavior of simple, as-fabricated, solid geometries (with a density of 8.4 g/cm3), as-fabricated and fabricated and annealed femoral (knee) prototypes, and reticulated mesh components (with a density of 1.5 g/cm3) all produced by additive manufacturing (AM) using electron beam melting (EBM) of Co-26Cr-6Mo-0.2C powder are examined and compared in this study. Microstructures and microstructural issues are examined by optical metallography (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD), while mechanical properties included selective specimen tensile testing and Vickers microindentation hardness (HV) and Rockwell C-scale hardness (HRC) measurements. Orthogonal (X-Y) melt scanning of the electron beam during AM produced unique, orthogonal and related Cr23C6 carbide (precipitate) arrays (a controlled microstructural architecture) with dimensions of ~2 μm in the build plane perpendicular to the build direction, while connected carbide columns were formed in the vertical plane, parallel to the build direction, with microindentation hardnesses ranging from 4.4 to 5.9 GPa, corresponding to a yield stress and ultimate tensile strength (UTS) of 0.51 and 1.45 GPa with elongations ranging from 1.9 to 5.3 pct. Annealing produced an equiaxed fcc grain structure with some grain boundary carbides, frequent annealing twins, and often a high density of intrinsic {111} stacking faults within the grains. The reticulated mesh strut microstructure consisted of dense carbide arrays producing an average microindentation hardness of 6.2 GPa or roughly 25 pct higher than the fully dense components.

Keywords

Carbide Additive Manufacturing Electron Beam Melting Cr23C6 Carbide Microindentation Hardness 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

This research was supported by Mr. and Mrs. MacIntosh Murchison, Endowed Chairs at the University of Texas at El Paso. A Graduate Assistantship through the Materials Science and Engineering Ph.D. Program at the University of Texas at El Paso also supported part of this research. We are grateful to Mylin Cumberland of DePuy (a Johnson & Johnson Company) for providing the Arcam, as-built femoral knee component used in this research as well Arcam built rectangular block and cylinder components from Ryan Kircher of Medical Modeling, Inc. (Golden, CO). We are also grateful to ARCAM-AB, Sweden for their support and the provision of the reticulated mesh sample.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2010

Authors and Affiliations

  • S.M. Gaytan
    • 1
  • L.E. Murr
    • 1
    Email author
  • E. Martinez
    • 1
  • J.L. Martinez
    • 1
  • B.I. Machado
    • 1
  • D.A. Ramirez
    • 1
  • F. Medina
    • 2
  • S. Collins
    • 3
  • R.B. Wicker
    • 2
  1. 1.Department of Metallurgical and Materials EngineeringThe University of Texas at El PasoEl PasoUSA
  2. 2.Keck Center for 3D InnovationThe University of Texas at El PasoEl PasoUSA
  3. 3.Additive Manufacturing ProcessesCamarilloUSA

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