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Fracture and fatigue of rock bit cemented carbides: Mechanics and mechanisms of crack growth resistance under monotonic and cyclic loading
Torres, Y.; Tarragó Cifre, Jose María; Coureaux Mustelier, David; Tarrés, E.; Roebuck, C.; Chan, P.; James, M.; Liang, B.; Tillman, M.; Viswanadham, R.K.; Mingard, K.P.; Mestra Rodríguez, Álvaro Miguel; Llanes Pitarch, Luis Miguel
Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica; Universitat Politècnica de Catalunya. CIEFMA - Centre d'Integritat Estructural i Fiabilitat dels Materials
In an attempt to improve the material selection, design and reliability of rock bit WC-Co cemented carbides (hardmetals), an extensive and detailed study is conducted with the main goal of characterizing the fracture and fatigue crack growth (FCG) behavior of four hardmetal grades. Work includes basic microstructural and mechanical characterization of the materials, assessment of fracture toughness and FCG kinetics. It is found that rock bit cemented carbides exhibit relatively high fracture toughness values (between 17 and 20 MPa root m) in direct association with their specific microstructural characteristics, i.e. medium/coarse carbide grain size and medium cobalt content. The influence of microstructure on the measured crack growth mechanics under monotonic loading may be accounted by considering the effective operation of ductile ligament bridging and crack deflection as the prominent toughening mechanisms. Regarding FCG behavior, it is observed to exhibit a significant Km influence. Furthermore, relative increments in toughness are maintained, in terms of crack growth threshold, under cyclic loading. As a consequence, fatigue sensitivity for rock bit cemented carbides is found to be lower than that extrapolated from data reported for fine-grained grades. Crack growth resistance under cyclic loading for the hardmetals studied may be understood on the basis that prevalent toughening mechanisms (ductile ligament bridging and crack deflection) show distinct susceptibility to fatigue degradation and are thus critical in determining fatigue sensitivity. (C) 2014 Elsevier Ltd. All rights reserved.
Àrees temàtiques de la UPC::Enginyeria dels materials
Àrees temàtiques de la UPC::Enginyeria mecànica::Mecànica
Materials
Fatigue
Fracture mechanics
Crack growth resistance
Rock bit hardmetals
Materials
Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/
info:eu-repo/semantics/publishedVersion
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