title: Assessment of precipitation behavior in dental castings of a Co-Cr-Mo alloy.
abstract: This study investigated solute portioning and precipitation in dental castings of a Co-Cr-Mo alloy and discussed their effects on alloy performance, in particular, the mechanical properties. Samples of a commercial Co-29Cr-6Mo (mass%) alloy were prepared using a dental-casting machine. The precipitates formed owing to the partitioning behaviors of the alloying elements were investigated using scanning electron microscopy, electron backscatter diffraction analysis, electron probe microanalysis, and transmission electron microscopy. The prepared samples exhibited a very coarse face-centered-cubic γ-phase dendritic structure with an average grain size of a few millimeters. A large number of precipitates, which decomposed further into complex interdendritic constituents (σ- and M23C6 carbide phases) were observed in the interdendritic regions rich in Cr, Mo, Si, and C. A reaction between the σ-phase and carbon is probably responsible for the carbide M23C6; however, this reaction did not occur to completion in the current case in spite of slow cooling (i.e., long exposure to elevated temperatures) in dental casting. While these precipitates result in high strength (hardness) and/or brittleness, the properties can be improved further by optimizing the alloy composition and the manufacturing process. The results of this study shed light on the significance of precipitation control in dental castings of Co-Cr-Mo alloys and should aid in the design of novel biomedical Co-Cr-based dental alloys that exhibit better performances.
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan. Electronic address: k_yamanaka@imr.tohoku.ac.jp.
authors.forename: Kenta
authors.initials: K
authors.lastname: Yamanaka
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan; Department of Materials and Environmental Engineering, Sendai National College of Technology, 48 Nodayama, Medeshima-Shiote, Natori 981-1239, Japan.
authors.forename: Manami
authors.initials: M
authors.lastname: Mori
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Chiba
mesh_terms: D002857:Chromium / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry*; D008422:Materials Testing; D055595:Mechanical Phenomena; D008982:Molybdenum / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D003722:Dental Alloys; D002857:Chromium; D003035:Cobalt; D008982:Molybdenum
keywords: Co–Cr–Mo alloys; Dental casting; Mechanical properties; Microstructure; Precipitate; Solidification segregation