The Microstructure and the Electrochemical Behavior of Cobalt Chromium Molybdenum Alloys from Retrieved Hip Implants

Emerson, Christopher P.

doi:10.25148/etd.fidc000069

Cited by 3 publications

(3 citation statements)

References 83 publications

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“…The main phase in the samples produced from the studied composition is ε-phase, its share by volume was 53%. As it is known ε-phase is a solid solution on the base of cobalt with hexagonal lattice where atoms of chromium and molybdenum may be embedded [25]. The second phase in the studied samples has phase-centered cubic lattice.…”

Section: Resultsmentioning

confidence: 89%

Synthesis of Tree-Component Cobalt-Based Alloy by Selective Laser Melting

Сапрыкин

Sharkeev²,

Saprykina

et al. 2022

MSF

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The paper presents studies aimed at producing a three-component alloy from the powders of cobalt, chromium and molybdenum (66 wt % Co, 28 wt % Cr, 6 wt % Mo), with a stable phase structure by selective laser melting. At the beginning of the work, the initial powders were graded on sieves with mesh sizes of 20-70 µm. The powder mixtures were obtained by mechanical mixing of various fraction powders and mechanical alloying in a planetary ball mill. The samples were produced using the VARISCAF-100MVS selective laser melting unit. The melting process of powder materials was completed in a chamber filled with inert gas argon after preliminary vacuum degassing. The microhardness analysis of the samples before and after the thermal treatment was completed. The results of phase composition studies, X-ray diffraction analysis, scanning electron microscopy are presented. Examination of the X-ray profiles of the samples proves that the obtained alloy mainly contains the epsilon-phase which improves the hardness and the wear resistance of the product.

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Section: Resultsmentioning

confidence: 89%

Synthesis of Tree-Component Cobalt-Based Alloy by Selective Laser Melting

Сапрыкин

Sharkeev²,

Saprykina

et al. 2022

MSF

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show abstract

“…Samples characterization. As we described elsewhere [5] samples, produced from R powder, were represented by single ε-phase, which is a low-temperature solid solution of Cr and Mo in Co hcp lattice [18]. Refined lattice parameters were a = 0.2535±0.0001 nm and c = 0.4114±0.0002 nm, which exceeds the etalon values, which are a = 0.2507 nm and c = 0.40695 nm [19].…”

Section: Resultsmentioning

confidence: 99%

Comparison the Preparation Methods of Powder Feedstock for Laser Powder Bed Fusion

Химич

Ibragimov

Chebodaeva

et al. 2022

SSP

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Four various methods of powder feedstock preparation for laser powder bed fusion are compared. Application of commercial spherical powder leads to the formation of single-phased state. Powder mechanically alloyed during 14 minutes in air atmosphere provides conditions for the formation of double-phased state with nonuniform distribution of components in the samples. Mechanical alloying in Ar-atmosphere during 30 minutes leads to the formation of double-phased state with more uniform distribution of components and precipitations of Cr2O3. Preliminary mechanical sieving of the powder allows to produce double-phased samples with nonuniform distribution of components comparable with that in samples produced from powder mechanically alloyed during 14 minutes in air atmosphere. Microhardness of all the studied samples produced from all the studied powders was comparable. All the proposed methods of powder feedstock preparation are applicable in laser powder bed fusion depending on the required properties, elemental and phase composition of the final product.

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“…The lattice parameters of both phases did not correspond to the etalon. This was due to the formation of solid solutions on the basis of two possible Co lattices, corresponding to high-and low-temperature ε-and γ-phases [29,31]. It should be noted, that here and further ε, γ, σ and µ symbols are used to define the type of lattice, which are hcp, fcc, tetragonal and rhombohedral, respectively.…”

Section: Resultsmentioning

confidence: 99%

Influence of thermal treatment duration on structure and phase composition of additive Co-Cr-Mo alloy samples

et al. 2022

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Laser powder bed fusion (LPBF) requires application of powders with specific characteristics. These are near-spherical shape of particles, uniform elemental composition, typical particle size of 5 -70 µm, etc. Such powders are produced by spheroidization methods. They have such disadvantages as high cost and sale only in large quantities. There are publications describing application in LPBF powders, produced by the methods, alternative to spheroidization. In the current study, powders of pure raw Co, Cr and Mo were used for the production of Co-Cr-Mo powder mixture. Samples of Co-28 wt.% Cr-6 wt.% Mo alloy were produced by LPBF from this powder mixture. Due to the difference between melting temperatures of Co, Cr and Mo, inclusions of Cr and Mo were formed within the bulk of samples. Studies of phase and elemental composition, structure and microhardness of the as-produced samples and after post-treatment with varied duration are represented. As-produced samples have non-uniform elemental composition and are represented by the main Co-based phase. Increasing the annealing duration leads to the sequential dissolution of un-melted Cr and Mo inclusions. Complete dissolution of Cr particles was observed at 10 hours of treatment and complete dissolution of Mo particles was not observed after 20 hours of annealing. Microhardness non-linearly changes with the increasing duration of annealing. This is due to the phase transformations and diffusion processes occurring at such type of post-treatment. Complete dissolution of Mo-particles could be achieved by further increasing the annealing time or by varying the mode of laser powder bed fusion.

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The Microstructure and the Electrochemical Behavior of Cobalt Chromium Molybdenum Alloys from Retrieved Hip Implants

Cited by 3 publications

References 83 publications

Synthesis of Tree-Component Cobalt-Based Alloy by Selective Laser Melting

Synthesis of Tree-Component Cobalt-Based Alloy by Selective Laser Melting

Comparison the Preparation Methods of Powder Feedstock for Laser Powder Bed Fusion

Influence of thermal treatment duration on structure and phase composition of additive Co-Cr-Mo alloy samples

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