Initial degradation of cemented carbides for rock drilling : model studies of the tribological contact against rock

• Hardness and fracture toughness are often used as the prime material parameters to characterise cemented carbides used in rock drilling. However, the deformation and wear of cemented carbide are too complicated to be described by these parameters alone. The cemented carbide and the wearing rock mineral are both composite materials, containing phases with widely varying hardness. Moreover, the deformation behaviour of the individual phases may be strongly anisotropic, as for the WC grains in the cemented carbide. The wear of the cemented carbide typically occurs on the scale of individual grains or smaller. Contrastingly, the hardness stated for both is typically a macroscopic value, averaged over numerous grains, orientations, etc. The present investigation aims to contribute to the understanding of the relations between microstructure, properties and wear mechanisms of cemented carbide buttons in rock drilling. It is focused on the role of scale of deformation in relation to size of the different phases of the cemented carbide. This is achieved by simplifying the contact situation of the rock drill button to a single stylus sliding contact between a granite stylus and a polished cemented carbide surface. The deformation and wear of this well controlled contact is then evaluated on the sub-micrometer scale; using high resolution FEG-SEM with EBSD, FIB cross-sectioning and AFM. The results show that even an extremely local deformation, such as slip within individual WC grains, affects the tribological contact, and that the nominally much softer granite may cause deformation both within individual WC grains, and on the composite scale. The results are discussed with respect to their significance for wear of cemented carbides in rock drilling. (C) 2015 Elsevier Ltd. All rights reserved.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Sliding contact

Granite stylus

Cemented carbide

Transfer

Initial degradation

Rock drilling

Steel Forming and Surface Engineering

Stålformning och ytteknik

Publikations- och innehållstyp

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