Content area
Full text
Abstract
The outstanding mechanical and tribological behaviour exhibited by cemented carbides results from the combination of two phases with quite different local properties. However, information on the small-scale mechanical response of these materials is rather scarce. This is true regarding experimental data on the influence of phase nature crystal orientation and interfacial adhesion strength on hardness, deformation and/or damage mechanisms. The knowledge of these issues is crucial to improve the performance of hardmetals and to optimize their microstructure. In this study, a systematic micromechanical study of the intrinsic hardness of the constitutive phases of a W(Ti,Ta,W)C-Co grade is presented by combining nanoindentation technique and statistical analysis. It is found that both hexagonal (WC) and cubic (Ti,Ta,W)C carbide particles are anisotropic in terms of hardness. Furthermore, the relevant influence of these hard phases on the small-scale response of the metallic binder is evidenced by the high hardness measured for the latter, as compared to values reported for similar unconstrained bulk alloys.
Keywords: cemented carbides; Nanoindentation; statistical method; intrinsic hardness; flow stress.
(ProQuest: ... denotes formulae omitted.)
1.Introduction
Cemented carbides (also referred to as hardmetals) are liquid-phase sintered materials that consists of a soft metallic phase from the iron group of metals (commonly cobalt, Co, and its alloys), and at least one hard phase of a refractory carbide, usually tungsten carbide (WC). WC combined with Co is the system most commonly used [1]. In these ceramic-metal composites, the hard phase provides high hardness; and thus, wear resistance, whereas the metallic one supplies ductility and toughness [2]. As a result, cemented carbides are positioned as forefront materials for applications with quite stringent tribomechanical demands, such as tools and components applied in the machining, metalforming, mining and oil/gas industries [3,4].
Hardness and deformation of cemented carbides as composite systems have been extensively addressed in the literature (see e.g. Ref. [5]). However, similar information on the mechanical properties at the micro- and nano-metric length scale is rather scarce. This is particularly true for systems beyond WC-Co alloys. Recently, the authors of this study have validated the implementation of statistical indentation techniques (on the basis of the methodology originally introduced by Ulm and coworkers [6-9]) for determining small-scale properties of the constitutive phases of WC-Co cemented carbides [10]. It was...