Berkovich nanoindentation and deformation mechanisms in a hardmetal binder-like cobalt alloy

Roa, J.J.; Jiménez‐Piqué, E.; Tarragó, J.M.; Zivcec, Maria; Broeckmann, Christoph; Llanes, L.

doi:10.1016/j.msea.2014.10.064

Cited by 25 publications

(15 citation statements)

References 38 publications

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“…This difference may be related to two different phenomena: (1) the unconstraint effect generated by the hard and stiff ceramic WC particles; and (2) the presence of C and W atoms dissolved as solid solution in the Co binder. On the other hand, the hardness value is also around 1.5 and 5 times higher than those previously reported by Roa et al [37] and Roebuck et al [2] in model-like alloys, respectively. The main reason for such a difference is the constraining effect exerted on the metallic binder by the surrounding carbides.…”

Section: Mechanical Property Mappingcontrasting

confidence: 53%

Mapping of mechanical properties at microstructural length scale in WC-Co cemented carbides: Assessment of hardness and elastic modulus by means of high speed massive nanoindentation and statistical analysis

Roa

Phani

Oliver

et al. 2018

International Journal of Refractory Metals and Hard Materials

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This paper studies the correlation between the microstructure and the mechanical properties at the nanometric length scale of individual WC grains as well as the metallic cobalt binder in cemented carbide systems. The local crystallographic orientation has been determined by electron backscattered diffraction and the microstructural analysis has been performed using field emission scanning electron microscopy. Small-scale hardness and elastic modulus have been assessed by means of high speed massive nanoindentation and subsequent statistical analysis. The attained mechanical property mappings present a clear correlation between local hardness and stiffness with chemical nature for each constitutive phase as well as with the crystallographic orientation for the WC particles. Besides expected findings associated with individual phases, such as clear anisotropy of the ceramic phase (basal plane being harder and stiffer than the prismatic one) and relatively high flow stress for constrained binder, the protocol implemented provides novel information on local mechanical response at interfaces between ceramic particles with different orientations as well as regions within the metallic cobalt binder close to the WC-Co interface.

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Section: Mechanical Property Mappingcontrasting

confidence: 53%

Mapping of mechanical properties at microstructural length scale in WC-Co cemented carbides: Assessment of hardness and elastic modulus by means of high speed massive nanoindentation and statistical analysis

Roa

Phani

Oliver

et al. 2018

International Journal of Refractory Metals and Hard Materials

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“…The presence of the different gray scale bands in the Co binder in the bulk material suggests that there exists Co with both fcc and hcp crystal configurations in the material before micropillar milling and uniaxial compression. Furthermore, deformation within the Co binder can occur through other mechanisms as planar slip, twinning or from deformation-induced phase transformation (from fcc to hcp structure), as they have been observed in previous works reported in the literature [37][38][39][40][41]. However, the extent of the deformation of the Co binder after uniaxial compression, must be evaluated by means of TEM, and it will be addressed in future research.…”

Section: Accepted Manuscriptmentioning

confidence: 87%

Scale effect in mechanical characterization of WC-Co composites

Sandoval

Rinaldi

Tarragó

et al. 2018

International Journal of Refractory Metals and Hard Materials

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© 2017 Elsevier LtdThe study of mechanical response of materials at small length scales has gained importance due to the recent advances in micro- and nano-fabrication as well as testing systems. However, most of the reported work has been dedicated to investigate single-crystals or boundary-containing metallic systems, while much less attention has been paid to composite materials, and in particular those combining soft and hard phases. In this work, a systematic procedure is followed for machining micropillars of diameters ranging from 1 to 4 µm in a WC-Co composite with a WC mean grain size around 1 µm, by means of focused ion beam milling. In-situ uniaxial compression of the micropillars and subsequent field emission scanning electron microscopy inspection were conducted. Clear size effects are evidenced. Smaller test specimens (probe size approaching the mean WC size) exhibit deformation/failure mechanisms observed for WC crystals; while for bigger sample sizes, the mechanical response involves several mechanisms directly linked with the microstructural characteristics of the bulk-like cemented carbide material. On the other hand, independent of micropillar size, carbide-carbide or carbide-binder interfaces are found to be preferential sites for nucleation of critical damage events.Peer ReviewedPostprint (author's final draft

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“…A value of 600 MPa may be taken for σ 0 , from the reference work by Roebuck and Almond [48]. This value of strength is significantly higher than that expected for bulk Co, as expected from the solid solution strengthening contribution associated with dissolved tungsten and carbon [48,49]. It may be assumed that the K t value is equal to the corresponding fatigue crack growth threshold (for a load ratio of 0.1), which in its turn is linearly dependent on the grain size [50] due to the action of crack-deflection as an additional toughening mechanism in cemented carbides [27,50].…”

Section: Analytical Assessment Of R-curve Behavior: Toughening Mechanicsmentioning

confidence: 99%

FIB/FESEM experimental and analytical assessment of R-curve behavior of WC–Co cemented carbides

Tarragó

Jiménez‐Piqué

Schneider

et al. 2015

Materials Science and Engineering: A

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Exceptional fracture toughness levels exhibited by WC-Co cemented carbides (hardmetals) are due mainly to toughening derived from plastic stretching of crack-bridging ductile enclaves. This takes place due to the development of a multiligament zone at the wake of cracks growing in a stable manner. As a result, hardmetals exhibit crack growth resistance (R-curve) behavior.In this work, the toughening mechanics and mechanisms of these materials are investigated by combining experimental and analytical approaches. Focused Ion Beam technique (FIB) and Field-Emission Scanning Electron Microscopy (FESEM) are implemented to obtain serial sectioning and imaging of crack-microstructure interaction in cracks arrested after stable extension under monotonic loading. The micrographs obtained provide experimental proof of the developing multiligament zone, including failure micromechanisms within individual bridging ligaments. Analytical assessment of the multiligament zone is then conducted on the basis of experimental information attained from FIB/FESEM images, and a model for the description of R-curve behavior of hardmetals is proposed. It was found that, due to the large stresses supported by the highly constrained and strongly bonded bridging ligaments, WC-Co cemented carbides exhibit quite steep but short R-curve behavior. Relevant strength and reliability attributes exhibited by hardmetals may then be rationalized on the basis of such toughening scenario.

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Berkovich nanoindentation and deformation mechanisms in a hardmetal binder-like cobalt alloy

Cited by 25 publications

References 38 publications

Mapping of mechanical properties at microstructural length scale in WC-Co cemented carbides: Assessment of hardness and elastic modulus by means of high speed massive nanoindentation and statistical analysis

Mapping of mechanical properties at microstructural length scale in WC-Co cemented carbides: Assessment of hardness and elastic modulus by means of high speed massive nanoindentation and statistical analysis

Scale effect in mechanical characterization of WC-Co composites

FIB/FESEM experimental and analytical assessment of R-curve behavior of WC–Co cemented carbides

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