Journal articles: 'Co-base alloys'

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Podhorná, Božena, Irena Andršová, Jana Dobrovská, Vlastimil Vodárek, and Karel Hrbáček. "Structure Stability of Ni-Base and Co-Base Alloys." Materials Science Forum 782 (April 2014): 431–36. http://dx.doi.org/10.4028/www.scientific.net/msf.782.431.

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This article summarises results of structure stability investigation of cast Ni-base and Co-base alloys after prolonged high temperature exposure at 900-1100 °C. Cast Ni (Co)-Cr-W-C alloys are resistant to high-temperature corrosion, due to high chromium content. Their heat resistance is caused by presence of carbides, which are stable at very high temperatures. Carbides precipitate in shape of large plate-like particles or carbide eutectics at casting cell boundaries, thus forming carbide skeleton of the alloy. Carbide morphology and temperature stability depends on chemical composition of the alloy, e.g. carbide content, type and content of carbide-forming elements. Microstructure changes were evaluated by stereological analysis and X ray-spectral microanalysis.

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Sahay, S. K., and B. Goswami. "Recent Developments in Co-Base Alloys." Solid State Phenomena 150 (January 2009): 197–219. http://dx.doi.org/10.4028/www.scientific.net/ssp.150.197.

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Cobalt base alloys are being designed and developed to produce the best possible combinations of high temperature properties. Existence of martensite forms consisting of various intermetallic compounds has been described along with the variables associated with fcc-hcp transition at respective conditions of formation. Achievements of cobalt base alloys have been primarily due to various thermodynamic and kinetic parameters for most suitable combinations of alloying. The phase transformations in this review include the study of defect structure, martensite transformation, order-disorder kinetics, and recrystallization and grain growth mechanisms. The improvements in mechanical properties stem from the contribution of additional alloying elements to discontinuous precipitation, diffusion mechanism at grain boundaries and changes in compressive strength, yield strength, elongation and brittleness. L12-compound in cobalt base alloys possesses an important identity, which changes the characteristics of usable compositions.

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Makineni, Surendra Kumar, Mahander Pratap Singh, and Kamanio Chattopadhyay. "Low-Density, High-Temperature Co Base Superalloys." Annual Review of Materials Research 51, no. 1 (July 26, 2021): 187–208. http://dx.doi.org/10.1146/annurev-matsci-080619-014459.

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Co base superalloys strengthened by coherent L12 ordered γ′ precipitate in a disordered face-centered cubic γ matrix represent a new opportunity for high-temperature alloy development. The emergence of alloys with low density and high specific yield strength at elevated temperatures has further energized the research and development efforts in the last 5 years. Initially stabilized by the addition of small amounts of Nb and Ta, these new generations of alloys with multiple alloying additions to form basic quaternary and ternary alloys have steadily expanded the property envelopes to raise hope for a modern class of superalloys with higher-temperature capabilities. This article reviews the work of a vibrant set of researchers across the globe whose findings are constantly unlocking the potential of these alloys. These developments have achieved high-temperature strength (at 870°C) >0.6 GPa, γ′ solvus temperature exceeding 1,100°C, and densities between 7.8 and 8.6 g/cm3.

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Takezawa, Kazuhiro, Shigeharu Ukai, and Shigenari Hayashi. "Microstructure Control of Co-Base ODS Alloys." Advanced Materials Research 239-242 (May 2011): 864–67. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.864.

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As high-temperature metallic materials, Co-base ODS alloys were produced by means of mechanical alloying, spark plasma sintering and hot rolling. Co-3wt%Al-1.2wt%Hf-ODS alloy was found to be an attractive composite like material, which is formed by spinodal like decomposition. The metastable phases were traced by hard phase containing dense oxide particles and soft one containing less oxide particles. Their tensile stress at 1,000 °C was improved by Hf addition that forms Y2Hf2O7type oxide particles and shortens their space distance.

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Lopez, H. F. "Alloy Developments in Biomedical Co-Base Alloys for HIP Implant Applications." Materials Science Forum 736 (December 2012): 133–46. http://dx.doi.org/10.4028/www.scientific.net/msf.736.133.

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The development of cobalt alloys for the development of HIP implants has been evolving overtime. Accordingly, in this work an overview of the main microstructural factors that impact the mechanical properties, as well as the effect of interstitials such as carbon and nitrogen. In addition the role alloy pre-straining and heat treating on the amount of ε-martensite and on the exhibited mechanical properties is described. In general, it is shown that as the amount of ε-martensite exceeds 60 vol. percent, the alloy ductility is drastically reduced as the HCP phase becomes dominant in the matrix.

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Zhang, Lin, Xuanhui Qu, Xinbo He, Din Rafi-ud, Mingli Qin, and Hongmin Zhu. "Hot deformation behavior of Co-base ODS alloys." Journal of Alloys and Compounds 512, no. 1 (January 2012): 39–46. http://dx.doi.org/10.1016/j.jallcom.2011.08.097.

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Hu, Chun Lian, and Shang Lin Hou. "Study on Microstructure and Oxidation-Resistance of Superalloy Coating with Ni-Base Substituting for Co-Base." Advanced Materials Research 581-582 (October 2012): 586–89. http://dx.doi.org/10.4028/www.scientific.net/amr.581-582.586.

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Microstructures, morphologies and energy spectrums of oxidized films and their cross sections of plasma sprayed alloy coating Co-02 with Co-base, Co-04 whose matrix is nickel partially instead of cobalt and NDCo-02 with Ni-base substituting for Co-base were investigated. The result indicates that the coatings of these three kinds of alloys are white austenite base and Cr7C3 and Cr7(C, B)3 eutectic; Co-02 produces Cr2O3 oxidation protection film, and there were distinct areas with shortage of chromium in Co-04 and NDCo-02 coatings where CoCr2O4 and NiCr2O4 oxidation protection films were produced with spinel structure, these efficiently improved oxidation resistance; these three kinds of alloys have super oxidation resistance which increases according to NDCo-02,Co-04 and Co-02 orderly. The level of oxidation resistance was assessed.

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Gu, Yue Feng, C. Cui, D. Ping, Hiroshi Harada, Akihiro Sato, and J. Fujioka. "Development of New Generation Turbine Disk Superalloys in the HTM21 Project." Materials Science Forum 546-549 (May 2007): 1277–80. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.1277.

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A new kind of cast & wrought (C&W) Ni-Co base superalloys named as “TMW alloys” was developed recently for compressor and turbine disk of gas turbine engines in the High Temperature Materials 21 Project at the National Institute for Materials Science (NIMS) in Japan. These Ni-Co base superalloys combine the characters of two kinds of γ- γ’ two-phase alloys (Ni-base and Co-base superalloys) and can be fabricated by cheap cast and wrought processing route. The results showed that some of these TMW alloys have superior tensile strength at temperatures up to 750 °C and higher creep resistances up to 725 °C than commercial UDIMET 720 LI alloy.

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9

Schenk, Th, D. Holland-Moritz, W. Bender, and D. M. Herlach. "Statistical analysis of nucleation in undercooled Co-base alloys." Journal of Non-Crystalline Solids 250-252 (August 1999): 694–98. http://dx.doi.org/10.1016/s0022-3093(99)00162-3.

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10

Mukherji, Debashis, and Joachim Rösler. "Design Considerations and Strengthening Mechanisms in Developing Co-Re-Based Alloys for Applications at + 100°C above Ni-Superalloys." Advanced Materials Research 278 (July 2011): 539–44. http://dx.doi.org/10.4028/www.scientific.net/amr.278.539.

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Although Ni-base superalloys meet the gas turbine needs of today, they are used very close to their melting range. Demands for applications at higher temperatures are presently met partly through component cooling and application of thermal barrier coatings. However, this approach can not be sustained indefinitely unless the base metal melting temperature is also significantly increased. Rhenium addition can substantially increase the melting point in Co-base alloys and thereby provide a unique opportunity in the development of new alloys for very high temperatures – e.g. for applications at +100°C metal temperature above present day single crystal Ni-base superalloys. The design considerations behind the Co-Re alloy development are presented in this paper. Selected results from the alloy development studies are also presented.

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11

Zhang, Lin, Xin Bo He, Ming Li Qin, Ye Liu, and Xuan Hui Qu. "The Influence of Ni on the Microstructure of Co-Base ODS Alloys." Advanced Materials Research 535-537 (June 2012): 1011–14. http://dx.doi.org/10.4028/www.scientific.net/amr.535-537.1011.

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Co-based ODS alloys strengthened by γ΄ precipitates and nanosized oxides are promising high-temperature structural materials. Single solid solution of Al and W in the matrix can not be achieved after mechanical alloying, resulting in the formation of low volume fraction of γ΄ phase and several kinds of secondary phases. The addition of Ni promotes the precipitation of γ΄ phase and reduces the amount of secondary phases by the enlargement of the solid solution limit of Al and W within the matrix. In comparison with the lower fracture strength and cleavage fracture mode of the alloy without the addition of Ni, Ni-containing Co-base ODS alloys exhibit much higher fracture strength and obvious ductile facture mode.

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12

Carek, Andreja, Jasenka Zivko Babic, Zdravko Schauperl, and Tomislav Badel. "Mechanical Properties of Co-Cr Alloys for Metal Base Framework." International Journal of Prosthodontics and Restorative Dentistry 1, no. 1 (2011): 13–19. http://dx.doi.org/10.5005/jp-journals-10019-1003.

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ABSTRACT Purpose This study investigated the effect of two welding methods on the mechanical properties of a cobalt-chromium (Co-Cr) alloy for metal base framework. Materials and methods Fifty-four plates were cast for TIG and laser welding. Cobalt-chromium for plates were prepared and divided into three groups of 18 samples. Group 1 and 2 were cut at the center of the plate. Eighteen specimens were joint by using TIG (Primotec Phaser Mx1), and other 18 by laser (Nd:YAG laser). Specimens in the as-cast condition were used as control group (group 3). After joining, each specimen was microscopic analyzed and tested to flexural and dynamic failure. Failure loads were recorded and fracture strength calculated. Results The changes in microstructure and micro-hardness were studied in the heat-affected zones (HAZ) and unaffected zones. Micro- hardness values increased in the heat-affected zone (HAZ) and in welded material compared to the parent material. The ANOVA test showed a highly significant difference (α = 0.05) between the joint strengths of the as-cast control specimens and, TIG and laser-welded joints. The flexural and dynamic strength of the joints were higher than those for the TIG-welded joints, and both were higher than the laser-welded joint strengths for the tested Co-Cr alloy. Conclusions Although laser is more popular, in our research TIG showed better results for flexural and dynamic strength.

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13

Tsunekane, Masafumi, Akane Suzuki, and Tresa M. Pollock. "Single-crystal solidification of new Co–Al–W-base alloys." Intermetallics 19, no. 5 (May 2011): 636–43. http://dx.doi.org/10.1016/j.intermet.2010.12.018.

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14

Zhang, Lin, Shigeharu Ukai, Takeshi Hoshino, Shigenari Hayashi, and Xuanhui Qu. "Y2O3 evolution and dispersion refinement in Co-base ODS alloys." Acta Materialia 57, no. 12 (July 2009): 3671–82. http://dx.doi.org/10.1016/j.actamat.2009.04.033.

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15

Zhang, Hualei, Min Zhao, Xun Sun, Dandan Cai, Yunzhi Wang, and Xiangdong Ding. "Elastic properties of Co-base alloys: An ab initio study." Computational Materials Science 170 (December 2019): 109150. http://dx.doi.org/10.1016/j.commatsci.2019.109150.

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16

Xue, Fei, Mei Ling Wang, and Qiang Feng. "Phase Equilibria in Co-Rich Co-Al-W Alloys at 1300^°C and 900°C." Materials Science Forum 686 (June 2011): 388–91. http://dx.doi.org/10.4028/www.scientific.net/msf.686.388.

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The phase equilibria of Co-base trial alloys of Co-9Al-7.5W, Co-5.5Al-10W and Co-9Al-3W at 1300°C and 900°C were determined in the present investigation. The experimental alloys were γ single-phase alloys at 1300°C, although the existence of the γ' phase and the ε phase was identified due to cooling effect. The nearly cuboidal γ' phase and the plate-like DO19 phase in alloys 9Al-7.5W and 5.5Al-10W were coarsened after long-term annealing at 900°C. It is suggested that the alloy 9Al-7.5W was in γ+γ' two-phase region, while the alloys 5.5Al-10W and 9Al-3W were in γ+DO19 two-phase region and γ singe-phase region at 900°C, respectively.

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17

Arrieta-Gonzalez, Cinthya Dinorah, Roberto Ademar Rodriguez-Diaz, Jan Mayen, Rogel Fernando Retes-Mantilla, María Teresa Torres-Mancera, Lya Adlih Oros-Méndez, Héctor Cruz-Mejía, Nestor Starlin Flores-Garcia, and Jesús Porcayo-Calderon. "Electrochemical Performance of Fe40Al-X (X = Cr, Ti, Co, Ni) Alloys Exposed to Artificial Saliva." Materials 13, no. 5 (March 1, 2020): 1095. http://dx.doi.org/10.3390/ma13051095.

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Fe–Al intermetallic compounds have been considered excellent candidates as alternative alloys for various applications in corrosive environments compared to other Fe-based alloys. Their excellent corrosion resistance is due to the development of an Al-based passive layer. The performance of the passive layer can be improved by adding a third alloy element. Therefore, in this study the electrochemical performance of the Fe40Al intermetallic alloy modified by the addition of a third alloy element (Cr, Ti, Co, Ni) is evaluated. The corrosion resistance of intermetallic alloys has been evaluated by electrochemical tests (potentiodynamic polarization curves, and measurements of open circuit potential, linear polarization and electrochemical impedance) in artificial saliva. The performance of intermetallic alloys was compared with that of Ti. The results obtained showed that the addition of Ni and Ti substantially improves the corrosion resistance of the base intermetallic. The corrosion resistance shown is comparable or greater than that shown by Ti. However, the addition of Co reduces the corrosion resistance of the base intermetallic.

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18

Barnes, J. J., and G. Y. Lai. "Factors affecting the nitridation behavior of Fe-base, Ni-base, and Co-base alloys in pure nitrogen." Le Journal de Physique IV 03, no. C9 (December 1993): C9–167—C9–174. http://dx.doi.org/10.1051/jp4:1993915.

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19

Ghiban, Nicolae, Brandusa Ghiban, Nicolae Şerban, and Alexandru Ghiban. "Heat Treatments Influence on Corrosion Behaviour of Some Metallic Biomaterials Potentially Used in Metal-Ceramic Prosthesis." Key Engineering Materials 587 (November 2013): 293–96. http://dx.doi.org/10.4028/www.scientific.net/kem.587.293.

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The present paper put in evidence the influence of applying different heat treatments on some metallic materials such as cobalt and titanium alloys, usualy used for medical applications. The alloys were cobalt base alloy type CoCrMo (22%Cr, 6%Mo, rest Co), in nontreated state, quenching at 1100°C /1h/aer, quenching at 1100°C /1h/air+ sensiblizing at 550°/4h/ air, 600°/4h/air and/or 650°C/4h/air and titanium base alloys - alloy TiMo0.3Ni0,7 (0.23%Mo, 0.72%Ni, Ti rest), alloy TiAl5Fe2V2Mo1,5(1.52%Mo, 5.15%Al, 2.56%Fe, 2.35%V, Ti rest), each of them in non treated state, annealing at 1050°C/1h/air and annealing at 850°C/1h/air. Corrosion tests were made at potentiostat-galvanostat AUTOLAB, in Ringer solution (for both alloys) and NaCl infusion solution (only for cobalt base alloy) by drawing the polarization curves. Our conclusion is that by applying correct and proper heat treatments to both at cobalt alloys and in titanium alloys there is an improving of the corrosion resistance.

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Cui, C. Y., Y. F. Gu, D. H. Ping, T. Fukuda, and H. Harada. "Phase Constituents and Compressive Yield Stress of Ni-Co Base Alloys." MATERIALS TRANSACTIONS 49, no. 3 (2008): 424–27. http://dx.doi.org/10.2320/matertrans.mbw200703.

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Hayakawa, M., K. Hayashi, Y. Ochiai, H. Matsuda, Y. Ishikawa, and K. Aso. "Plastic flow and field induced anisotropy in Co-base amorphous alloys." Journal of the Magnetics Society of Japan 10, no. 2 (1986): 249–52. http://dx.doi.org/10.3379/jmsjmag.10.249.

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MU, Danning, Changlin YANG, Xiaowei WEI, and Feng LIU. "RESEARCH ON GRAIN REFINEMENT IN BULK UNDERCOOLED Fe-Co BASE ALLOYS." Acta Metallurgica Sinica 48, no. 12 (2012): 1409. http://dx.doi.org/10.3724/sp.j.1037.2012.00286.

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Yan, H. Y., V. A. Vorontsov, and D. Dye. "Alloying effects in polycrystalline γ′ strengthened Co–Al–W base alloys." Intermetallics 48 (May 2014): 44–53. http://dx.doi.org/10.1016/j.intermet.2013.10.022.

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Hayakawa, M., K. Hayashi, Y. Ochiai, W. Ishikawa, H. Matsuda, and K. Aso. "Plastic Flow and Field Induced Anisotropy In Co-base Amorphous Alloys." IEEE Translation Journal on Magnetics in Japan 2, no. 5 (May 1987): 473–74. http://dx.doi.org/10.1109/tjmj.1987.4549496.

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Hayakawa, M., K. Hayashi, Y. Ochiai, H. Matsuda, W. Ishikawa, and K. Aso. "Plastic Flow and Field Induced Anisotropy in Co-Base Amorphous Alloys." IEEE Translation Journal on Magnetics in Japan 2, no. 9 (September 1987): 809–14. http://dx.doi.org/10.1109/tjmj.1987.4549618.

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Mercieca, Sven, Malcolm Caligari Conti, Joseph Buhagiar, and Josette Camilleri. "Assessment of corrosion resistance of cast cobalt- and nickel-chromium dental alloys in acidic environments." Journal of Applied Biomaterials & Functional Materials 16, no. 1 (October 26, 2017): 47–54. http://dx.doi.org/10.5301/jabfm.5000383.

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Background: The aim of this study was to compare the degradation resistance of nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys used as a base material for partial dentures in contact with saliva. Methods: Wiron® 99 and Wironit Extra-Hard® were selected as representative casting alloys for Ni-Cr and Co-Cr alloys, respectively. The alloys were tested in contact with deionized water, artificial saliva and acidified artificial saliva. Material characterization was performed by X-ray diffractometry (XRD) and microhardness and nanohardness testing. The corrosion properties of the materials were then analyzed using open circuit potential analysis and potentiodynamic analysis. Alloy leaching in solution was assessed by inductively coupled plasma mass spectrometry techniques. Results: Co-Cr alloy was more stable than the Ni-Cr alloy in all solutions tested. Leaching of nickel and corrosion attack was higher in Ni-Cr alloy in artificial saliva compared with the acidified saliva. The corrosion resistance of the Co-Cr alloy was seen to be superior to that of the Ni-Cr alloy, with the former exhibiting a lower corrosion current in all test solutions. Microstructural topographical changes were observed for Ni-Cr alloy in contact with artificial saliva. The Ni-Cr alloy exhibited microstructural changes and lower corrosion resistance in artificial saliva. The acidic changes did not enhance the alloy degradation. Conclusions: Ni-Cr alloys are unstable in solution and leach nickel. Co-Cr alloys should be preferred for clinical use.

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Lopez-Heredia, Marco A., Dora A. Cortés-Hernández, José C. Escobedo-Bocardo, and A. Medina Ramírez. "Biomimetic Process in Metals." Materials Science Forum 509 (March 2006): 211–0. http://dx.doi.org/10.4028/www.scientific.net/msf.509.211.

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A titanium base alloy and a cobalt base alloy have been subjected to a biomimetic process. Samples of titanium and cobalt alloys have been immersed in 10M and 5M NaOH solutions, respectively, then the samples have been heat treated and finally, immersed in either a simulated body fluid (SBF) with ionic concentration close to human blood plasma or in a simulated body fluid with an ionic concentration 1.5 times that of the SBF (1.5SBF) for a period of 21 days. An apatite layer has been observed after the immersion of the samples in SBF for both Ti and Co base alloys. The apatite layer observed on the Ti alloy samples is more homogeneous and thicker than that observed on the Co alloy samples. However, the apatite layer on both samples is not continuous and homogeneous along the surface. The layer of apatite formed is thicker on samples immersed in 1.5SBF. This is attributed to the higher ion concentrations, mainly of calcium and phosphorus. The Ca/P ratios measured in the apatite layers are close to that of bone.

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Inoue, Akihisa, Bao Long Shen, and Akira Takeuchi. "Syntheses and Applications of Fe-, Co-, Ni- and Cu-Based Bulk Glassy Alloys." Materials Science Forum 539-543 (March 2007): 92–99. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.92.

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This paper reviews our recent results of the formation, fundamental properties, workability and applications of late transition metal (LTM) base bulk glassy alloys (BGAs) developed since 1995. The BGAs were obtained in Fe-(Al,Ga)-(P,C,B,Si), Fe-(Cr,Mo)-(C,B), Fe-(Zr,Hf,Nb,Ta)-B, Fe-Ln-B(Ln=lanthanide metal), Fe-B-Si-Nb and Fe-Nd-Al for Fe-based alloys, Co-(Ta,Mo)-B and Co-B-Si-Nb for Co-based alloys, Ni-Nb-(Ti,Zr)-(Co,Ni) for Ni-based alloys, and Cu-Ti-(Zr,Hf), Cu-Al-(Zr,Hf), Cu-Ti-(Zr,Hf)-(Ni,Co) and Cu-Al-(Zr,Hf)-(Ag,Pd) for Cu-based alloys. These BGAs exhibit useful properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based glassy alloys have good soft magnetic properties which cannot be obtained for amorphous and crystalline type magnetic alloys. The Feand Ni-based BGAs have already been used in some application fields. These LTM base BGAs are promising as new metallic engineering materials.

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Hussain, A., R. Akhter, W. A. Farooq, and M. Aslam. "Laser Surface Alloying of Ni-Co Electroplated Low Carbon Steel." Key Engineering Materials 442 (June 2010): 137–43. http://dx.doi.org/10.4028/www.scientific.net/kem.442.137.

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Laser surface alloying of Ni-Co electroplated steel using 900 W CW CO2 laser to develop Fe-Ni-Co alloy on the surface is reported. Fe-Ni-Co alloys of different compositions are produced by varying the working speed from 0.25 m/min to 3m/min and laser spot size from 0.6 mm to 5mm. The development of microstructure in the melted zone is analysed in terms of composition variation and cooling rate. The microhardness of newly formed alloys reported here are three times higher as compared to base metal. Martensite is observed in the laser modified zone.

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Alvarez-Perez, Marco Antonio, Manuel García-Hipolito, Octavio Alvarez-Fregoso, and Julio Alberto Juarez-Islas. "Biocompatibility Evaluation of Co-Ribbons Prepared by Melt-Spinning." Advanced Materials Research 976 (June 2014): 98–102. http://dx.doi.org/10.4028/www.scientific.net/amr.976.98.

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Ribbons of Co-base alloy were tested as biocompatible material at in vitro process to develop in the future an implant dental device. Regarding research on the effect of rapid solidification on Co-alloys, few or absent studies to date have been assessed for the evaluation of surfaces properties when the alloys are placed in contact with human mesenchyme stem cells (hMSC). The Co-based ribbons were prepared by rapid solidification process and its surface attached with human adipose-derived mesenchymal stem cells to determine it toxicity, cells viability, adhesive and proliferation of the cells. Experimental results showed that Co-based ribbons are non-toxic material with 80% of increased cellular adhesion and exhibited excellent biocompatibility.

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Lo´pez de Lacalle, L. N., J. A. Sa´nchez, A. Lamikiz, and A. Celaya. "Plasma Assisted Milling of Heat-Resistant Superalloys." Journal of Manufacturing Science and Engineering 126, no. 2 (May 1, 2004): 274–85. http://dx.doi.org/10.1115/1.1644548.

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The term Thermal Enhanced Machining refers to a conventional cutting process in which an external energy source is used to enhance the chip-generation mechanism. The work presented here analyzes the basic aspects and the experimental results obtained when applying an assisting plasma jet to the milling process. This process, known as PAM (Plasma Assisted Milling) has been applied to the machining of three very low machinability materials: a Ni-base alloy (Inconel 718), a Co-base alloy (Haynes 25), (both belonging to the group of the heat-resistant alloys) and the Ti-base alloy Ti6Al4V. The study focuses on two major topics. First, the efficiency of the milling operation in terms of cutting speed, feed, axial and radial depths of cut and the plasma operating parameters has been addressed. Second, a study on the alterations of the metallurgical structure and the properties of materials after the PAM has also been performed. The process conditions for the above-mentioned Ni-base and Co-base alloys are detailed. The study under these conditions has shown an excellent performance of the whisker reinforced ceramic tools. In fact, cutting speeds as high as 970 m/min and large radial and axial depths of cuts are possible, driving to a cost-effective machining process. The absence of changes in the metallurgical structure of the alloys after applying the PAM process is also addressed. Therefore, it can be stated that this is a feasible approach to the optimization of the machining process of heat-resistant alloys. Finally, the results obtained in the PAM of Ti6Al4V are detailed. In this experimentation, a certain level of degradation was observed in the microstructure of the alloy when undergoing the PAM process, therefore the use of this technique is not recommended for this material.

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Saito, Yoshiyuki, and Kazuaki Mino. "Elevated Temperature Wear Maps of X40 and Mar-M247 Alloys." Journal of Tribology 117, no. 3 (July 1, 1995): 524–28. http://dx.doi.org/10.1115/1.2831285.

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Self-mated wear tests of X40 (Cobalt-base alloy) and Mar-M247 (Nickel base alloy) were conducted under unlubricated sliding conditions using a pin-on-disk tester. Wear maps were constructed for both alloys over the temperature range of room temperature to 1173 K at relatively low sliding speed. Microstructural and chemical information has been obtained by using various microscopies, an X-ray diffractometer, and an X-ray photo-electron spectroscopy. They show that the wear resistance of X40 is superior to that of Mar-M247 at room temperature due to the lower concentration of metallic state elements and higher concentration of Cr2O3 and Co (OH)2 at the surface of X40. The degradation in the wear resistance of X40 at about 500 K was attributed to the decrease in Cr2O3 and Co(OH)2 concentrations at the surface.

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Zhang, Lin, Xin Bo He, Xuan Hui Qu, Rafi Ud Din, Heng San Liu, Dan Li, and Hong Min Zhu. "Microstructural Formation in Novel Co-Base ODS Alloys Produced by Mechanical Alloying." Advanced Materials Research 415-417 (December 2011): 1136–39. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.1136.

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The main focus of this work was to study the microstructural evolution during the sintering and the heat treatment processes. The results indicated that mechanical alloying had induced the formation of supersaturated solid solution in immiscible Co-Al-W alloys, originating mainly from extensive grain boundary region, high dislocation density, and ample point defect. Spinodal decomposition is found to be the dominant mechanism for phase formation. The extremely fine grains (0.5~3 μm) provide short-circuited diffusion paths for the atomic movement that leads to the spinodal decomposition behavior. γ´ precipitates were formed by the combination of spinodal decomposition mechanism and the chemical reaction between the decomposed products of CoAl and Co3W.

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Hall, E. L., and M. R. Jackson. "Microstructural Characterization of Rapidly Solidified Carbide-Containing Ni-Base Superalloys." Proceedings, annual meeting, Electron Microscopy Society of America 43 (August 1985): 48–49. http://dx.doi.org/10.1017/s0424820100117315.

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The temperature capability of nickel-base superalloys which are used in aircraft turbines may be able to be extended if novel microstructures can be produced in these materials by rapid solidification. The primary goal of these efforts is to achieve a fine dispersion of small precipitates which are stable at high temperature in the alloys. One class of alloys which seem particularly promising are the eutectic superalloys, which solidify via a eutectic reaction in which a γ- γ’ matrix containing MC carbides is formed. For this investigation, alloys which contained either Ta, Ti, or V as the primary carbide former were studied. In all cases, the base alloy consisted of Ni-4%Co-4%Cr-5.5%Al-2%Mo-3%W-1.5%Re-0.3%C in weight percent. The alloys additionally contained either 9% Ta, 5.5% Ti, or 4.5% V (subsequently referred to as alloys A, B, and C, respectively). The alloys were rapidly solidified by melt-spinning in vacuum.

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Hasuda, Yuichi, Asahi Handa, Yuki Kobori, Shinichi Kinebuchi, Toshiaki Furusawa, and Yasuo Harigaya. "Grinding of Super-Alloys Using Metal-Bonded CBN Wheel." Key Engineering Materials 523-524 (November 2012): 143–48. http://dx.doi.org/10.4028/www.scientific.net/kem.523-524.143.

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Superalloys, used for turbine blades and jet engines for airplanes, have low heat conduction and high strength at elevated temperature. These properties make it very difficult to obtain effective grinding processes with high accuracy. Superalloys with fine performance under high temperature circumstances attract great attention to be used as the material for turbine blades. It has been expected to establish reliable efficient grinding of superalloys at the final grinding process. In this study, the influence of wheel wear, grinding ratio, and surface roughness, with the grinding process of superalloys, using metal bonded CBN wheel were carefully observed. Since superalloys have lower heat conduction and they cause a severe wheel wear, which leads to low grinding ratio. However, the high grinding ratio of about 800 and the stable figure of surface roughness of Rz=2μm were obtained when Co-base PWA647 and X45 were ground by using metal-bonded CBN wheel. Consequently, the Co-base superalloys perform rather well producing finer grinding process than the intensive Ni-base or Fe-base superalloys.

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Ozcelik, Tuncer Burak, and Burak Yilmaz. "Galvanic gold plating for fixed dental prosthesis." European Journal of Dentistry 07, no. 03 (July 2013): 373–76. http://dx.doi.org/10.4103/1305-7456.115426.

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ABSTRACTMetal ceramic partial fixed dental prostheses have been commonly used for the replacement of missing teeth for many years. Because of an increase in the price of gold, base metal alloys have been the choice of alloy for the fabrication of metal ceramic restorations in many dental clinics. Some major disadvantages of base metals are their corrosion and the dark coloration they may cause at the crown margins. This article describes a galvanic gold-plating technique, which is used to minimize corrosion and improve the esthetics of metal ceramic restorations fabricated with Cr-Co base metal alloys. This technique involves the deposition of a 6 μm to 8 μm 24 K gold layer directly onto the Cr-Co cast prosthesis framework. The technique improves metal surface properties, making them more biocompatible and usable, however, requires additional equipment and experienced laboratory technicians. Clinical studies should be performed to corroborate the long term success of this technique.

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Gorr, Bronislava, and Hans Jürgen Christ. "High-Temperature Oxidation Behaviour of Co-Re-Cr-Based Alloys: Limitations and Ways to Improve." Advanced Materials Research 278 (July 2011): 545–50. http://dx.doi.org/10.4028/www.scientific.net/amr.278.545.

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Ni-based alloys are the most widely used alloy system in high-temperature applications. However, the use of Ni-based alloys is limited to temperatures below 1100°C. The experimental Co-Re-Cr-based alloys are promising for high-temperature applications for service temperatures beyond 1200°C. A complete miscibility in the Co-Re system allows to steadily elevate the melting point of the system with the rhenium content. In addition, rhenium takes the role as solid solution strengthening element. In the case of Co-based alloys, the oxidation resistance at high temperature is mainly based on the formation of a protective Cr2O3 scale. The purpose of the present investigations is to gain an insight into the oxidation mechanisms of the model Co-Re-Cr alloys and to find ways to improve oxidation resistance of this class of materials. Earlier investigations of the authors showed a rather poor oxidation resistance during exposure to laboratory air. Oxidation at 1000°C in air yielded an oxide scale that consists of a Co-oxide outer layer on a thick and porous Co-Cr oxide and a semicontinuous and therefore non-protective Cr-oxide film on the base metal substrate. As a consequence of the lacking protectiveness of the oxide layer the vaporization of rhenium oxide takes place and hence leads to a rapid loss of Re. The aim of recent investigations is to study the effect of Si on the high-temperature oxidation behaviour of Co-Re-Cr alloys by means of kinetic and microstructural examinations. It was found that Si stabilizes the Cr2O3 scale, enhancing the oxidation resistance significantly. Hence, the synergetic effect of chromium with silicon could be considered as an encouraging perspective to improve the oxidation resistance of Co-Re-Cr alloys. Apart from that, other concepts to enhance the oxidation resistance of this class of materials are discussed, such as the formation of a borosilicate layer or protective Al2O3 scale on the substrate surface.

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Kano, Stefania Carvalho, Gerson Bonfante, Raquel Hussne, and Aline F. Siqueira. "Use of base metal casting alloys for implant framework: marginal accuracy analysis." Journal of Applied Oral Science 12, no. 4 (December 2004): 337–43. http://dx.doi.org/10.1590/s1678-77572004000400016.

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The original protocol for implant prosthesis recommends the use of a gold framework for acrylic and ceramic prosthesis. However, due to its high cost, the use of alternative alloys is desired. This study compares the marginal accuracy of pre-made cylinders versus plastic cylinders cast with two different base metal casting alloys. Five samples each of (1) plastic cylinder cast in cobalt-chromium alloy, (2) plastic cylinder cast in nickel-chromium alloy, and (3) silver-palladium pre-made cylinder (control) were examined for marginal accuracy according to: (A) vertical gap; (B) horizontal gap and (C) horizontal gap depth at the abutment/cylinder interface. Data were submitted to statistical analysis (ANOVA and Student-Newman Keuls, p<0.05). Mean values for vertical, horizontal and gap depth were 4.13µm, 14.5µm and 6.93µm for pre-made cylinder, 23.18µm, 33.2µm and 88µm for Ni-Cr cast cylinder and 25.6µm, 51.8µm and 114.54µm for Co-Cr cast cylinder. No statistically significant differences were found between cast groups (1 and 2), but significant better fit was obtained with pre-made metal cylinders when compared to cast cylinders with Ni-Cr and Co-Cr alloys, for all analyses.

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Zagorodny, I. V., A. A. Ilyin, V. N. Karpov, A. M. Nadezhin, S. V. Skvortsova, S. V. Sergeev, A. A. Plushev, and N. S. Gavryushenko. "Titanium alloys in hip arthroplasty." N.N. Priorov Journal of Traumatology and Orthopedics 7, no. 2 (May 30, 2000): 73–76. http://dx.doi.org/10.17816/vto104258.

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Experimental study of thermal-hydrogenous processing influence on the structure, mechanical and tribologic properties of titanium-alloy ѴТ6 was performed. After processing the firmness of alloy was increased up to 40-42 un. HRC in comparison with 28 un. HRC in hot rolling condition. Friction coefficient of VT6 alloy head on extra high molecular polyethylene was similar to the friction coefficient of Co-Cr-Mo alloy head. Wear of extra high molecular polyethylene in couple with titanium-alloy was 5 times lower than in couple with Co-Cr-Mo alloy. Surface hardening of VT6 alloy by thermal-hydrogenous processing 10 times decreases the wear of bone cement at friction. On the base of experimental study the new cemented hip endoprosthesis SFEN was elaborated.

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Kang, Sung, Teppei Muramatsu, and Mahoto Takeda. "TEM Study and Magnetic Measurements of Nano–Scale Particles Formed in Cu–Base Alloys." Advanced Materials Research 89-91 (January 2010): 757–62. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.757.

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The precipitation behavior of nano–scale particles formed in Cu–base alloys was studied by means of transmission electron microscopy (TEM) and SQUID measurements. Linear arrangements of two or more nano–scale particles cubic in shape were observed in the <100> orientations of matrices in a Cu–Co alloy. Although the trend was less explicit in a Cu–Fe alloy, Fe precipitates accompanying twin–like lattice modulations were found in the decomposition, when no deformation was applied. The present SQUID measurements revealed several significant influences to magnetic properties were induced during the precipitation in Cu–base alloys. Lorentz electron microscopy confirmed that phase transformation from γ → α occurred at the stage that the Fe particles reach to 40~60nm in size.

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Berthod, Patrice, Pierric Lemoine, and Lionel Aranda. "Study of the Behavior in Oxidation at High Temperature of Ni, Co and Fe-Base Alloys Containing Very High Fractions of Carbides." Materials Science Forum 595-598 (September 2008): 871–80. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.871.

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Nine cast alloys reinforced by very high fractions of carbides, Ni-30Cr-xC, Co-30Cr-xC and Fe-30Cr-xC with x varying from 1.2 to 2.0, were tested in oxidation at high temperature between 1,000 and 1,200°C in air for 50 hours. After oxidation, their surfaces and sub-surfaces were characterized. Even for very high carbon contents, the chromia-forming behaviour of the nickel alloys is kept. The oxidation modes of the cobalt alloys and iron alloys are not changed compared to low carbon alloys of these families. The differences of diffusion easiness of chromium in matrix, between nickel alloys, cobalt alloys and iron alloys are the same as for alloys with lower carbon contents, as suggested by the lower chromium gradients in the nickel alloys compared to the two other alloy types. Sub-surface microstructure transformations due to oxidation were observed in some cases (coarsening of carbides due to an inwards diffusion of carbon, change of the sharing between BCC-FCC of iron matrix due to outwards diffusion of chromium). Catastrophic oxidation never occurred for these alloys during the 50 hours of exposition to air at high temperature.

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Alvarado-Orozco, J. M., J. E. Garcia-Herrera, B. Gleeson, F. S. Pettit, and G. H. Meier. "Reinterpretation of Type II Hot Corrosion of Co-Base Alloys Incorporating Synergistic Fluxing." Oxidation of Metals 90, no. 5-6 (June 1, 2018): 527–53. http://dx.doi.org/10.1007/s11085-018-9853-6.

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Suzuki, Akane, Garret C. DeNolf, and Tresa M. Pollock. "Flow stress anomalies in γ/γ′ two-phase Co–Al–W-base alloys." Scripta Materialia 56, no. 5 (March 2007): 385–88. http://dx.doi.org/10.1016/j.scriptamat.2006.10.039.

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Kimura, Yoshisato, Kiichi Sakai, Shinya Teramoto, and Yoshinao Mishima. "Microstructure Control of Co₃AlC-Base Heat Resistant Alloys Using Optical Floating Zone Melting." Materials Science Forum 475-479 (January 2005): 833–36. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.833.

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Aiming for further improvement of mechanical properties of Co3AlC-based heat resistant alloys, microstructure control was conducted using optical floating zone (OFZ) melting. Unidirectional solidification was performed to align Co3AlC/a(Co) two-phase eutectic microstructure. Co3AlC single phase poly-crystal alloys were successfully fabricated for the first time by taking advantage of OFZ. Mechanical properties were evaluated for selected alloys by compression tests at ambient temperature, 1073 K and 1273 K. Excellent elevated temperature strength is achieved in Co3AlC single phase alloys and ductility is sufficiently improved in Co3AlC/a(Co) two-phase alloys.

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McDevitt, Erin T. "Feasibility of Cast and Wrought Co-Al-W-X Gamma-Prime Superalloys." Materials Science Forum 783-786 (May 2014): 1159–64. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1159.

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In 2006, J. Sato et al. discovered the L12 gamma-prime phase in the Co-Al-W alloy system. Since that time there has been a significant academic effort to characterize and understand the thermodynamics, the structure, and properties of alloys in this system. That work has shown that such alloys have promise as next generation high temperature materials due to the ability to engineer a high gamma-prime content alloy with a higher gamma prime solvus and higher melting point than many Ni-base gamma-prime strengthened alloys. Furthermore, a relatively narrow range of solidification temperature and large range of temperature between the gamma-prime solvus and the solidus are two characteristics that suggest cast and wrought versions of the alloys should be able to be manufactured routinely. However, to date all published research has been on small, laboratory scale samples typically less than about 2 kg, cast and hot rolled or cast as single crystals. This paper describes ATI’s experience in assessing the feasibility of manufacturing a cast and wrought billet product in the Co-Al-W-X alloy system. Three 22 kg heats were produced to examine a small range of alloy compositions of potential commercial interest: Co-9Al-9W, Co-9Al-9W-2Ti, and Co-9Al-9W-2Ti-0.02B, respectively. Each heat was vacuum induction melted and vacuum arc remelted. The as-cast microstructure will be presented. Ingots were homogenized and hot worked. The microstructure at various stages of production are shown and hot working behavior is described.

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Czerwinski, Frank. "Exploring Thixoforming for Net Shape Manufacturing." AM&P Technical Articles 177, no. 4 (May 1, 2019): 14–19. http://dx.doi.org/10.31399/asm.amp.2019-04.p014.

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Suzuki, Aya S., Catherine M. F. Rae, R. A. Hobbs, and Hideyuki Murakami. "Secondary Reaction Zone Formations in Pt-Aluminised Fourth Generation Ni-Base Single Crystal Superalloys." Advanced Materials Research 278 (July 2011): 78–83. http://dx.doi.org/10.4028/www.scientific.net/amr.278.78.

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Fourth generation superalloys are characterised by the addition of Ru which contributes to improved creep resistance whilst improving the microstructural stability. However, Ru additions have a negative effect on coated Ni-base superalloys, promoting Secondary Reaction Zone (SRZ) formation. Formation of a layer of SRZ beneath an aluminised or Pt-aluminised coating has the potential to reduce the effective cross section of a blade by in excess of 100 μm or 10% of the wall thickness. In this paper the effects of alloy composition on the formation of the SRZ in Pt-Aluminised fourth generation alloys were investigated systematically. A series of experimental fourth generation alloys was used having two distinct compositions of Co, Mo, W and Ru and conforming to a four factorial 'Design of Experiments' model. These alloys showed significant and consistent changes in the SRZ depending on alloy composition. These were in distinct contrast to the effects of these elements on stability in the bulk. Mo was demonstrated to be by far the most effective element suppressing SRZ formation, followed by Co. In contrast, both W and Ru enhance SRZ formation.

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Tak�cs, J�nos, and L�szl� Mark�. "Lewis-base properties of the HFe3(CO)9S? and Fe3(CO)9S2? cluster anions." Transition Metal Chemistry 10, no. 1 (1985): 21–24. http://dx.doi.org/10.1007/bf00620626.

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Carreiro, Adriana da Fonte Porto, Ricardo Faria Ribeiro, Maria da Gloria Chiarello de Mattos, and Renata Cristina Silveira Rodrigues. "Evaluation of the castability of a Co-Cr-Mo-W alloy varying the investing technique." Brazilian Dental Journal 16, no. 1 (April 2005): 50–55. http://dx.doi.org/10.1590/s0103-64402005000100009.

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The purpose of this study was to compare the castability of Co-Cr-Mo-W (Remanium 2000), Ni-Cr (Durabond) and Co-Cr-Mo (Vera PDI) alloys invested with either conventional (phosphate- and silica-based) or mixed investing techniques. A 10 X 10 mm square-shaped nylon net containing 100 open squares served as a template for construction of wax patterns, which were invested with phosphate-based investment (Termocast), silica-based investment (Refrafil) and mixed investing technique (2-mm layer phosphate investment plus filling with silica investment). Forty-five cast specimens (5 per experimental condition) were obtained and sandblasted with aluminum oxide. The number of completely reproduced cast segments was counted to obtain a percentage designated "castability value", which indicated the accuracy of the alloy to reproduce mold details. Statistical analysis using two-way ANOVA and Tukey's test showed that, comparing the alloys, Remanium 2000 had statistically similar castability (p>0.05) to Vera PDI and lower than Durabond (p<0.05). Considering the mixed technique results, Remanium 2000 yielded lower castability value (p<0.05) than Durabond and Vera PDI alloys, which showed similar results to each other (p>0.05). In conclusion, the castability of the Co-Cr-Mo-W alloy (Remanium 2000) was comparable to that of the Co-Cr alloy (Vera PDI) and worse than that of the Ni-Cr alloy (Durabond). Except for Remanium 2000, the mixed investing technique considerably improved the accuracy of the alloys to reproduce cast details, compared to the phosphate-based investment. The mixed investing technique appears as a viable alternative to improve castability of base metal alloys without decreasing the surface quality of the metallic pieces.

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Karge, L., R. Gilles, D. Mukherji, P. Beran, P. Strunz, M. Hoelzel, and J. Rösler. "Beyond Ni-base superalloys: Influence of Cr addition on Co-Re base alloys strengthened by nano-sized TaC precipitates." Physica B: Condensed Matter 551 (December 2018): 1–5. http://dx.doi.org/10.1016/j.physb.2017.11.059.

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Journal articles on the topic 'Co-base alloys'

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