Identification of abrasion regimes based on mechanisms of wear on the steel stylus used in the Cerchar abrasiveness test

Identification of abrasion regimes based on mechanisms of wear on the steel stylus used in the Cerchar abrasiveness test

The wear of tools in rock excavation is a challenging and costly issue. To predict the added costs arising from wear, field and laboratory investigations can be conducted during the early stages of a project. Accordingly, a measure of particle abrasivity is needed. Abrasivity is defined as the capab...

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Bibliographic Details
Published in:Wear Vol. 410-411; pp. 181 - 189
Main Authors: Piazzetta, Gabriela Reis, Lagoeiro, Leonardo E., Figueira, Isabella Françoso Rebutini, Rabelo, Melina Almeida Gonçalves, Pintaude, Giuseppe
Format: Journal Article
Language:English
Published: Amsterdam Elsevier B.V 15-09-2018
Elsevier Science Ltd
Subjects:
Abrasion
Abrasive wear
Abrasiveness
Abrasives
Deformation mechanisms
Drilling
Geological materials
Laboratory tests
Microstructure
Plastic deformation
Rock drilling
Rocks
Styli
Tool steels
Tool wear
Tribology
Wear
Wear mechanism
Wear mechanisms
Wear testing
Wear mechanism
Abrasive wear
Wear testing
Geological materials
Rock drilling
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Summary:The wear of tools in rock excavation is a challenging and costly issue. To predict the added costs arising from wear, field and laboratory investigations can be conducted during the early stages of a project. Accordingly, a measure of particle abrasivity is needed. Abrasivity is defined as the capability of different kinds of soils and rocks to cause abrasive wear of metallic surfaces. The Cerchar abrasiveness test is a well-recognized lab test for assessing rock abrasivity. The Cerchar Abrasiveness Index (CAI) is determined by measuring the crater diameter [mm] produced by a conical steel stylus moving under a fixed load and sliding distance. Many authors have been trying to correlate CAI with rock properties, but no consensus has been achieved. The main reason for this difficulty arises from the effects of the microstructural complexity of rocks and their tribological response. This investigation proposes a new approach based on the use of a scanning electron microscope to identify the wear mechanisms acting on the Cerchar stylus (AISI A2 tool steel) during testing, and comparing these observations to the corresponding CAI values for nine different rock types (0.1 < CAI < 6). The observed wear mechanisms were classified into two extremes (mild and severe) with a transition region between them. The mild regime is characterized by the polishing action of rocks (CAI ≤ 1.8). The severe regime is characterized by microcutting with extensive plastic deformation (CAI ≥ 3.1). The reliability of the current findings is discussed in the light of a theoretical conversion of CAI values into their respective wear coefficients. Our proposed approach of using wear coefficients is expected to provide better correlation between the results of the Cerchar laboratory test and real drilling rates. •A correlation between the Cherchar Abrasiveness Index (CAI) and the wear coefficient is presented.•The regimes of abrasion are identified – mild, transitional, and severe – for specific values of CAI.•The current findings can be considered as the first step for a future improvement of the ASTM classification of abrasiveness.•A potential application of the proposed values would be to apply in the prediction of disc cutter lives in TBMs projects.
ISSN:0043-1648
1873-2577
DOI:10.1016/j.wear.2018.07.009