Tribological Performance of CoCrMo Alloys with Boron Additions in As-Cast and Heat-Treated Conditions

Hernández-Rodríguez, M.A.L.; Lozano, Diego; Martinez-Cazares, Gabriela M.; Bedolla-Gil, Yaneth

doi:10.3390/met11020355

Cited by 3 publications

(2 citation statements)

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“…As pointed out by Gomes et al [ 14 ], the microstructure of cobalt alloys allows for a higher concentration of carbon, with carbides dispersed inside the grains and around the margins, where their precipitation can provide the alloy with enhanced resistance and hardness. Typically, the microstructure of an as-cast cobalt-base alloy presents a dendritic α-FCC matrix that is metastable at ambient temperature, together with inter-dendritic precipitates composed mainly of M 23 C 6 carbides [ 15 ]. Co-Cr-Mo alloys are manufactured via casting processes, sometimes being subjected to solution-annealing heat treatments and forging, and adopting different microstructures that impart hardness, strength, and wear resistance [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

Scratch and Wear Behaviour of Co-Cr-Mo Alloy in Ringer’s Lactate Solution

et al. 2023

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Cobalt–chromium–molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, together with electromagnetic stirring, to reduce its grain size. The samples were subjected to wear and scratch tests in simulated body fluid (Ringer’s lactate solution). Since a reduction in grain size can influence the behaviour of the material, in terms of resistance and tribological response, four samples with different grain sizes were produced for use in our investigation of the behaviour of the alloy, in which we considered the friction coefficient, wear, and scratch resistance. The experiments were performed using a tribometer, with mean values for the friction coefficient, normal load, and tangential force acquired and recorded by the software. Spheres of Ti-6Al-4V and 316L steel were used as counterface materials. In addition, to elucidate the influence of grain size on the mechanical properties of the alloy, observations were conducted via scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The results showed changes in the structure, with a reduction in grain size from 5.51 to 0.79 mm. Using both spheres, the best results for the friction coefficient and wear volume corresponded to the sample with the smallest grain size of 0.79 mm. The friction coefficients obtained were 0.37 and 0.45, using the Ti-6Al-4V and 316L spheres, respectively. These results confirm that the best surface finish for Co-Cr-Mo alloy used as a biomedical implant is one with a smaller grain size, since this results in a lower friction coefficient and low wear.

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Section: Introductionmentioning

confidence: 99%

Scratch and Wear Behaviour of Co-Cr-Mo Alloy in Ringer’s Lactate Solution

et al. 2023

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“…The idea of HBCIs was to replace the cementite carbide (Fe 3 C) in wear-resistant Fe-C alloys with a harder boride (Fe 2 B) [ 20 ]. For this purpose, in the Fe-C alloy, carbon was partially replaced by boron: HBCIs initially contained 1.2–3.5 wt.% B and 0.2–0.5 wt.% C to create an Fe 2 B-based eutectic (plain Fe-B alloys) [ 21 , 22 ]. The superiority of Fe 2 B compared to Fe 3 C in terms of hardness is due to the stronger hybridisation of the “metal–boron” bond compared with the “metal–carbon” bond [ 23 ].…”

Section: Introductionmentioning

confidence: 99%

Investigations of Abrasive Wear Behaviour of Hybrid High-Boron Multi-Component Alloys: Effect of Boron and Carbon Contents by the Factorial Design Method

et al. 2023

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This paper is devoted to the evaluation of the “three-body-abrasion” wear behaviour of (wt.%) 5W–5Mo–5V–10Cr-2.5Ti-Fe (balance) multi-component (C + B)-added alloys in the as-cast condition. The carbon (0.3 wt.%, 0.7 wt.%, 1.1 wt.%) and boron (1.5 wt.%, 2.5 wt.%, 3.5 wt.%) contents were selected using a full factorial (32) design method. The alloys had a near-eutectic (at 1.5 wt.% B) or hyper-eutectic (at 2.5–3.5 wt.% B) structure. The structural micro-constituents were (in different combinations): (a) (W, Mo, and V)-rich borocarbide M2(B,C)5 as the coarse primary prismatoids or as the fibres of a “Chinese-script” eutectic, (b) Ti-rich carboboride M(C,B) with a dispersed equiaxed shape, (c) Cr-rich carboboride M7(C,B)3 as the plates of a “rosette”-like eutectic, and (d) Fe-rich boroncementite (M3(C,B)) as the plates of “coarse-net” and ledeburite eutectics. The metallic matrix was ferrite (at 0.3–1.1 wt.% C and 1.5 wt.% B) and “ferrite + pearlite” or martensite (at 0.7–1.1 wt.% C and 2.5–3.5 wt.% B). The bulk hardness varied from 29 HRC (0.3 wt.% C–1.5 wt.% B) to 53.5 HRC (1.1 wt.% C–3.5 wt.% B). The wear test results were mathematically processed and the regression equation of the wear rate as a function of the carbon and boron contents was derived and analysed. At any carbon content, the lowest wear rate was attributed to the alloy with 1.5 wt.% B. Adding 2.5 wt.% B led to an increase in the wear rate because of the appearance of coarse primary borocarbides (M2(B,C)5), which were prone to chipping and spalling-off under abrasion. At a higher boron content (3.5 wt.%), the wear rate decreased due to the increase in the volume fraction of the eutectic carboborides. The optimal chemical composition was found to be 1.1 wt.% C–1.5 wt.% B with a near-eutectic structure with about 35 vol.% of hard inclusions (M2(B,C)5, M(C,B), M3(C,B), and M7(C,B)3) in total. The effect of carbon and boron on the abrasive behaviour of the multi-component cast alloys with respect to the alloys’ structure is discussed, and the mechanism of wear for these alloys is proposed.

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