Microstructural Characterization of Co-Cr-Mo-W Alloy as Casting for Odontological Application (original) (raw)
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Microstructural Characterisation of Co-Cr-Mo Casting Dental Alloys
Advances in Science and Technology Research Journal
Metal biomaterials, including casting alloys, are the largest group of biomaterials used in den-tal prosthetics and maxillofacial surgery. Despite the scientific reports on the harmful effects of certain metals on living organisms, and due to the absence of non-metallic substitute materials ex-
Microstructural characterization of as-cast biocompatible Co–Cr–Mo alloys
Materials Characterization, 2011
The microstructure of a cobalt-base alloy (Co-Cr-Mo) obtained by the investment casting process was studied. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. This work focuses on the resulting microstructures arising from samples poured under industrial environment conditions, of three different Co-Cr-Mo alloys. For this purpose, we used: 1) an alloy built up from commercial purity constituents, 2) a remelted alloy and 3) a certified alloy for comparison.
2011
Dedication: This research project is dedicated to all who have supported the development of dentaltechnology in Ghana. il ABSTRACT ln this age of technological advancement in dentistry, the traditional method of manufacturing removable partial denture frameworks could be supplemented with rapid manufactured (RM) denture frameworks when the technology is fully developed. The RM technology has the potential to provide a better corrosion resistance, accuracy, high strength and density, reduce time and labour and eventually provide low cost restorations compared to the traditional 'lost wax technique' which is considered laborious and time consuming. However, fundamental independent tests including tensile and corrosion tests must be completed to move current researches from a proof of concept stage towards rn vivo pertormance studies if patients' safety is to be guaranteed. At the time of the presenl in vitro study, no published literature was found to have made a comparison between cast and RM dental alloys to investigate their tensile and corrosion properties. Test specimens and procedures used in this project were in accordance with BS EN ISO 22674:2006 for dental metallic restorations' During the corrosion test, electrobrightened and highly polished samples of an RM cobalt-chromium alloy were compared with those manufactured with a cast cobalt-chromium alloy. An RM as-received heat and non-heat treated cobaltchromium samples were also compared. The samples were immersed in artificial saliva (0.1M saline lactic acid) with pH 2.3+0.1 at a temperature of 37+0.1'C for 1 , 4, 7, 14, 21, 28, 35 and 42 days. The analytes were verif ied qualitatively for cobalt, chromium and molybdenum and quantitatively for released metal ions using an atomic absorption spectrometer. Results from the tests showed that the RM alloy had better ductility, modulus of elasticity, resilience, toughness and corrosion resistant properties. ln addition, surprisingly, electrobrightened samples released fewer metal ions than polished samples. RM as-received heattreated specimens released more metal ions than the non-heat treated as-received samples. The pedormance of the RM alloy has been largely linked to the manufacturing technique. Futther studies are recommended.
Acta Biomaterialia, 2012
The microstructure and mechanical properties of as-cast Co-(20-33)Cr-5Mo-N alloys were investigated to develop ductile Co-Cr-Mo alloys without Ni addition for dental applications that satisfy the requirements of the type 5 criteria in ISO 22674. The effects of the Cr and N contents on the microstructure and mechanical properties are discussed. The microstructures were evaluated using scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), and electron back-scattered diffraction pattern analysis. The mechanical properties were evaluated using tensile testing. The proof strength and elongation of N-containing 33Cr satisfied the type 5 criteria in ISO 22674. e-phase with striations was formed in the N-free (20-29)Cr alloys, while there was slight formation of e-phase in the N-containing (20-29)Cr alloys, which disappeared in N-containing 33Cr. The lattice parameter of the c-phase increased with increasing Cr content (i.e. N content) in the N-containing alloys, although the lattice parameter remained almost the same in the N-free alloys because of the small atomic radius difference between Co and Cr. Compositional analyses by EDS and XRD revealed that in the N-containing alloys Cr and Mo were concentrated in the cell boundary, which became enriched in N, stabilizing the c-phase. The mechanical properties of the N-free alloys were independent of the Cr content and showed low strength and limited elongation. Strain-induced martensite was formed in all the N-free alloys after tensile testing. On the other hand, the proof strength, ultimate tensile strength, and elongation of the N-containing alloys increased with increasing Cr content (i.e. N content). Since formation of e-phase after tensile testing was confirmed in the N-containing alloys the deformation mechanism may change from strain-induced martensite transformation to another form, such as twinning or dislocation slip, as the N content increases. Thus the N-containing 33Cr alloy with large elongation is promising for use in dentures with adjustable clasps through one piece casting.
A R C H I V E S 10/3 Characteristic of intermetallic phases in cast dental CoCrMo alloy
Apart from chromium and molybdenum, casting alloys of cobalt usually contain also up to 0.35 % of carbon. With significant content of carbon, presence of carbide-forming alloying elements results in creating carbide phases. These alloys are characterised by dendritic structure of solid solution of chromium and molybdenum in cobalt with interdendritically precipitated carbides. Because of high chromium content, dominating are M23C6-type carbides, but chromium-rich carbides can be also of M7C3 and M3C2-types. The other elements in the alloy result in creating M6C and MC-type carbides. In the case of low carbon content, creating carbides and forming intermetallic phases based on the alloying elements and cobalt become limited. The presented research was aimed at characterising structure of the cobalt-based dental alloy containing trace quantity of carbon. Characterised were intermetallic phases hardening the alloy. Microscopic examinations using light microscopy, SEM and TEM were carri...
Materials
This study presents the correct processing of Co–Cr alloys as a method of preserving the properties of the materials as-cast, and therefore they can be safely placed in contact with the oral cavity tissues as resistance frameworks. The basic materials analyzed in this study were five commercial Co–Cr dental alloys with different components obtained in three processing steps. The analysis of the electrochemical behavior at the surface of the Co–Cr alloys was performed by electrochemical measurements: impedance spectroscopy (EIS), open circuit electrical potential (OCP), and linear polarization (LP). In terms of validation, all five alloys had a tendency to generate a stable oxide layer at the surface. After the measurements and the graphical representation, the alloy that had a higher percentage of tungsten (W) and iron (Fe) in composition showed a higher tendency of anodizing. After the application of the heat treatment, the disappearance of the hexagonal phase was observed, with th...
Assessment of precipitation behavior in dental castings of a Co-Cr-Mo alloy
Journal of the mechanical behavior of biomedical materials, 2015
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...
Microstructural effects on the wear resistance of wrought and as-cast Co-Cr-Mo-C implant alloys
Journal of Biomedical Materials Research Part A, 2005
The tribological behavior of two cobalt-base alloys-an as-cast high-carbon and a wrought low-carbon Co alloy-that are used as hip implant materials is examined in this work. This work discusses the experimental results of cobalt-cobalt wear pairs, in wrought and as-cast conditions, where the amount of hexagonal phase is systematically modified through an isothermal aging treatment. Fully FCC and HCP Co alloys are tested versus alloys with various volume fractions of HCP phase (0.05 to 1.0 vol-ume fractions). Preliminary results indicate that Co-Cr-Mo/Co-Cr-Mo alloy pairs both possessing an HCP matrix microstructure tend to exhibit outstanding wear properties.
2018
The limitations of investment casting of cobalt-based alloys are claimed to be less problematic with significant improvements in metal additive manufacturing by selective laser melting (SLM). Despite these advantages, the metallic devices are likely to display mechanical anisotropy in relation to build orientations, which could consequently affect their performance ‘in vivo’. In addition, there are inconclusive evidence concerning the requisite composition and post-processing steps (e.g. heat-treatment to relieve stress) that must be completed prior to the devices being used. In the current paper, we evaluate the microstructure of ternary cobalt-chromium-molybdenum (Co-Cr-Mo) and cobalt-chromium-tungsten (Co-Cr-W) alloys built with Direct Metal Printing and LaserCUSING SLM systems respectively at 0°, 30°, 60° and 90° inclinations (Φ) in as-built (AB) and heat-treated (HT) conditions. The study also examines the tensile properties (Young's modulus, E; yield strength, RP0.2; elong...
AIP Conference Proceedings, 2014
Cobalt-based alloys are widely used as total hip and knee replacements because of their excellent properties, such as corrosion resistance, fatigue strength and biocompatibility. In this work, cobalt alloys with variation of Cr (28.5; 30; 31.5; 33, and 34.5% wt) have been synthesized by smelting method began with the process of compaction, followed by smelting process using Tri Arc Melting Furnace at 200A. Continued by homogenization process at recrystallization temperature (1250º C) for 3 hours to allow the atoms diffuses and transform into γ phase. The next process is rolling process which is accompanied by heating at 1200º C for ± 15 minutes and followed by quenching. This process is repeated until the obtained thickness of ± 1 mm. The evaluated material properties included microstructure, surface morphology, and hardness value. It was shown that microstructure of cobalt alloys with variation of Cr is dominant by γ phase, thus making the entire cobalt alloys have high hardness. It was also shown from the surface morphology of entire cobalt alloys sample indicated the whole process of synthesis that had good solubility were at flat surface area. Hardness value test showed all of cobalt alloys sample had high hardness, just variation of 33% Cr be in the range of ASTMF75, it were 345,24 VHN which is potential to be applied as an implant prosthesis.