Wear of cemented tungsten carbide percussive drill–bit inserts: Laboratory and field study

Dmitry Tkalich, Charlie C. Li, Alexandre Kane, Afaf Saai, Dmitry Tkalich, Vladislav A. Yastrebov, Mikko Hokka, Veli-Tapani Kuokkala, Maria Bengtsson, Anna From

    Research output: Contribution to journalArticleScientificpeer-review

    15 Citations (Scopus)

    Abstract

    Design of the drill–bit and selection of the Cemented Tungsten Carbide (CC) grade for drill–bit inserts are crucial for efficient percussive drilling. This study presents the results of an experimental campaign executed with the aim to identify the distinctive wear mechanisms and behaviour of different CC grades. Three laboratory and one full–scale drilling tests were performed using nine CC grades with different binder contents, binder chemical compositions, mean tungsten carbide (WC) grain sizes, and grain size distributions. Wear traces found on the drill–bit inserts after the full–scale drilling test show noticeable differences depending on their position on the drill–bit. Tensile forces present on the leading edge of the inserts due to the sliding contact with rock are suspected to play a significant role. Laboratory tests performed include: (i) single impact tests using a modified Split Hopkinson Pressure Bar (SHPB) apparatus, (ii) Abrasion Value (AV) rotating disk tests, and (iii) impact abrasion (LCPC) tests. Volume loss and shape change were used as macroscopic measures of wear. Greater volume losses were found for the grades with nickel–based binders compared to those with pure cobalt binder. The use of a narrower WC grain size distribution leads to lesser volume loss in drilling and AV tests. Surface analysis of the damaged microstructure was performed using scanning electron microscope. Distinct meso–scale (few dozens of WC grain sizes) patterns of damaged microstructure zones surrounded by the intact surface were found on the surfaces of specimens after single impact test. The pattern indicates the potential influence of a non–uniform contact due to the rock roughness and internal rock heterogeneities, which is supported by the study of the rock crater roughness. Size of such zones could be seen as a certain length–scale, which determines the insert–rock contact behaviour. A specific “peeling” mechanism of material removal was observed in the full–scale drilling test, where portion of the CC microstructure fused with the rock tribofilm gets removed when that tribofilm peels off.

    Original languageEnglish
    Pages (from-to)106-117
    Number of pages12
    JournalWear
    Volume386-387
    DOIs
    Publication statusPublished - 15 Sep 2017
    Publication typeA1 Journal article-refereed

    Keywords

    • Cemented tungsten carbide
    • Contact area
    • Impact abrasion
    • Rotary–percussive drilling
    • Roughness
    • SEM
    • Sliding abrasion
    • Split Hopkinson pressure bar
    • Surface deterioration mechanisms
    • Volume loss
    • Wear

    Publication forum classification

    • Publication forum level 1

    ASJC Scopus subject areas

    • Condensed Matter Physics
    • Mechanics of Materials
    • Surfaces and Interfaces
    • Surfaces, Coatings and Films
    • Materials Chemistry

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