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Metals 2016, 6(8), 188; doi:10.3390/met6080188

Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications

1
Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Av. Universidad 3000, Circuito Exterior S/N, Cd. Universitaria, Mexico D.F. 04510, Mexico
2
Materials Science and Engineering Department, CEAS University of Wisconsin-Milwaukee, 3200 N. Cramer Street, Milwaukee, WI 53211, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Harrie Weinans and Amir A. Zadpoor
Received: 15 April 2016 / Revised: 3 August 2016 / Accepted: 11 August 2016 / Published: 16 August 2016
(This article belongs to the Special Issue Metallic Biomaterials)
View Full-Text   |   Download PDF [6388 KB, uploaded 16 August 2016]   |  

Abstract

Binary Co-Cr alloys containing various Cr contents were vacuum induction melted and cast into wedge-shaped copper molds. It was intended to develop a microstructure (1) free from interdendritic segregation and porosity; (2) having minimal intermetallic precipitates; and (3) suitable for biomedical applications. The resultant microstructures were evaluated from sections obtained longitudinally and centrally in the plane normal to the diverging wedge faces. All ingots showed a dendritic microstructure with some characteristic features. For instance, in Co-20–30 wt. % Cr alloys, the chilled cast microstructures consisted of columnar dendrites without interdendritic segregation, a minimum of intermetallic precipitates, and the presence of a predominantly athermal HCP ε-martensite (>80 vol. %). In addition, the metastable FCC γ-Co phase was identified by X-ray diffraction and scanning electron microscopy. In the case of 35–44 wt. % Cr cobalt alloys, a eutectic constituent including the σ-phase were found to develop in the interdendritic regions. From this work, a Co-20 wt. % Cr alloy was chosen for further investigation after heat treating below the γ/ε transition temperature. The resultant tensile strength and ductility were further improved after applying a heat treatment at 730 °C for 30 min, obtaining values of elongation of 26% as compared with 2.55 < 5 of elongation in the as cast condition. Also, the alloy corrosion resistance in artificial saliva was investigated. It was found that the exhibited corrosion rates for the as-cast and heat-treated conditions are between those reported for other similar systems. View Full-Text
Keywords: cobalt alloys; rapid solidification; athermal martensite; heat treatment; mechanical properties; biomedical alloys cobalt alloys; rapid solidification; athermal martensite; heat treatment; mechanical properties; biomedical alloys
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Ramirez-Ledesma, A.L.; Lopez, H.F.; Juarez-Islas, J.A. Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications. Metals 2016, 6, 188.

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