Small scale mechanics of cemented carbides: A combined experimental and numerical approach
JIMÉNEZ PIQUE E. 1, SOUSA-MACHADO P. 1, ORTIZ-MEMBRADO L. 1, CANER F. 1, LLANES L. 1
1 Universitat Politècnica de Catalunya, Barcelona, Spain
WC-Co cemented carbides (hardmetals) are one of the most successful examples of effective implementation of multiphase composites for structural applications. Due to the quite different properties of their two constituents: hard ceramic particles (WC) embedded in a metallic binder, hardmetals exhibit an excellent combination of hardness, strength and toughness together with unique wear and abrasive resistance. As a consequence, they are frontrunner candidates for tools used in the manufacturing industry as well as for wear–resistant and structural components in a variety of other industrial sectors.
The microstructure of these materials consist in polyhedral ceramic grains forming a interconnecting skeleton with a metallic binder as the minor phase. Understanding the mechanical behaviour at the scale of the microstructure provides crucial understanding of microstructure-performance relationships, as well as essential inputs for multiscale numerical simulation.
In this contribution we will present the micromechanical characterization of these materials at small scale by using nanoindentaton, as well as small specimens produced by FIB, mainly microcantilevers and micropillars, measuring in this way the performance of individual grains, interphases and small volumes of materials. In addition, FIB is also used to generate a tomography of the microstructure of the material, capturing the three-dimensional nature of this composite, and generating a mesh of this microstructure.
With this mesh and the acquired micromechanical data, a novel computational framework consisting of two different microplane constitutive models developed for WC and metallic phases are proposed. For the metallic matrix, the microplane J2-plasticity, called the model MPJ2, and for the WC particles a modified version of the microplane model M7, called the model M7WC, are employed. After calibrating the aforementioned models, it is shown that the finite element predictions not only confirm the extensive experimental observations but also shed further light into the micro-mechanical behavior of these composites.