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Fatigue behavior and associated binder deformation mechanisms in WC-Co cemented carbides
Vladimir Valle Alvarez, Lauro
Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal•lúrgica
The mechanical integrity of WC-Co hardmetals has been studied by the occurrence of subcritical crack growth and strength degradation under cycling loading. The investigation is conducted on three WC-Co hardmetals grades with different binder content and/or grain size by assessing fatigue crack growth (FCG) behavior and fatigue life tests at room temperature. Experimental fatigue results are compared to fracture toughness and flexural strength data. An analysis of the results within a fatigue mechanics context permits to corroborate FCG threshold as the effective fracture toughness under cyclic loading. Mechanical tests were complemented by a fractographic inspection using field-emission scanning electron microscopy. Critical defects are evidenced to be agglomerates of coarse grains and abnormally coarse grains. Additionally, a roughness study is carried out by atomic force microscopy in order to optimize sample preparation for electron backscatter diffraction (EBSD) imaging. EBSD mapping on stable propagated cracks has been accomplished to characterize the crack-microstructure interactions within the cobalt phase. EBSD results suggest that martensitic transformation of cobalt phase (from fcc to hcp) is not exclusively associated with cyclic loading, as it had been postulated in the literature. On the other hand, it seems to be induced by rough grinding of the exposed surfaces. From the perspective of fatigue micromechanisms, they are clearly localized within the binder phase, although specific nature(slip/twining) of the crystallographic-like path observed may not be defined at this research stage.
Àrees temàtiques de la UPC::Enginyeria dels materials::Assaig de materials::Assaig de fatiga
Àrees temàtiques de la UPC::Enginyeria dels materials::Assaig de materials::Assaig de fractura
Àrees temàtiques de la UPC::Enginyeria dels materials::Materials compostos
Tungsten carbide-colbalt alloys -- Mechanical properties
Materials -- Fatigue
Fracture mechanics
Ceramic materials -- Mechanical properties
Metals -- Mechanical properties
Carbides -- Mechanical properties
Aliatges de carbur de tungstè i cobalt -- Propietats mecàniques
Materials -- Fatiga
Materials -- Fractura
Materials ceràmics -- Propietats mecàniques
Metalls -- Propietats mecàniques
Carburs -- Propietats mecàniques
Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/
info:eu-repo/semantics/masterThesis
Universitat Politècnica de Catalunya
         

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