Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications
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 a...
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MDPI AG
2016-08-01
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| Series: | Metals |
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| Online Access: | http://www.mdpi.com/2075-4701/6/8/188 |
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| author | Ana Laura Ramirez-Ledesma Hugo F. Lopez Julio Alberto Juarez-Islas |
| author_facet | Ana Laura Ramirez-Ledesma Hugo F. Lopez Julio Alberto Juarez-Islas |
| author_sort | Ana Laura Ramirez-Ledesma |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-04-13T15:03:46Z |
| format | Article |
| id | doaj.art-cfebca1f25494e46bbe73a9c36b623da |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-04-13T15:03:46Z |
| publishDate | 2016-08-01 |
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| spelling | doaj.art-cfebca1f25494e46bbe73a9c36b623da2022-12-22T02:42:13ZengMDPI AGMetals2075-47012016-08-016818810.3390/met6080188met6080188Evaluation of Chill Cast Co-Cr Alloys for Biomedical ApplicationsAna Laura Ramirez-Ledesma0Hugo F. Lopez1Julio Alberto Juarez-Islas2Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Av. Universidad 3000, Circuito Exterior S/N, Cd. Universitaria, Mexico D.F. 04510, MexicoMaterials Science and Engineering Department, CEAS University of Wisconsin-Milwaukee, 3200 N. Cramer Street, Milwaukee, WI 53211, USAInstituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Av. Universidad 3000, Circuito Exterior S/N, Cd. Universitaria, Mexico D.F. 04510, MexicoBinary 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.http://www.mdpi.com/2075-4701/6/8/188cobalt alloysrapid solidificationathermal martensiteheat treatmentmechanical propertiesbiomedical alloys |
| spellingShingle | Ana Laura Ramirez-Ledesma Hugo F. Lopez Julio Alberto Juarez-Islas Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications Metals cobalt alloys rapid solidification athermal martensite heat treatment mechanical properties biomedical alloys |
| title | Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications |
| title_full | Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications |
| title_fullStr | Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications |
| title_full_unstemmed | Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications |
| title_short | Evaluation of Chill Cast Co-Cr Alloys for Biomedical Applications |
| title_sort | evaluation of chill cast co cr alloys for biomedical applications |
| topic | cobalt alloys rapid solidification athermal martensite heat treatment mechanical properties biomedical alloys |
| url | http://www.mdpi.com/2075-4701/6/8/188 |
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