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A study on wear characteristics of high strength steels under sliding contact
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In the last decades, significant improvements regarding the design, materials and technology of rock drills have been made. Likewise, in sheet metal forming, forming tools experience very high contact pressures when processing high strength steel sheets. In both applications components operate under extremely tough contact conditions that result in an accelerated component failure. Enhancements on mechanical properties of components material subjected to extreme contact conditions are highly required in order to withstand the application loads and prevent severe wear.

The present thesis was focused on understanding of machinery component damage mechanisms under severe contact conditions. A case study of worn components used in rock drilling and sheet metal cold work was carried out. Thread joints from rock drilling and punches from sheet metal pressing were selected for the investigation. For these components, sliding contact under high contact pressure is a common load condition under the components usage. Then, to understand and quantify the influence of contact parameters, load and surface quality on material performance, laboratory simulations were performed. The results were used for a comparative analysis of the typical damage mechanisms observed in the tests and the case study of the components.

The case study results showed that the threaded surfaces underwent severe plastic deformation due to the high-pressure sliding contact. The microstructure beneath the worn surface was altered and surface cracks and delamination were frequently observed at the worn surface. The dominant damage mechanism found on the investigated punches was adhesive wear. Material transfer adds friction stresses at the punch surface and ultimately, with repeated punch strokes, it leads to initiation and propagation of fatigue cracks.

Wear process in thread joint and punch wear was simulated using the SOFS. The worn specimens tested experimentally showed similar wear mechanisms obtained in the case study. The thread joint wear simulation showed that the total damage at the worn surface was a result of adhesive wear, plastic deformation, and initiation and propagation of fatigue cracks. In addition, the results showed that the type of motion had a significant influence on the worn volume and crack initiation, and more severe wear was observed at reciprocal motion. The punch wear simulation showed that the friction quickly increased as work material from metal sheets transferred to the disc surface. The rate of the material transfer was strongly dependent on the combination of sheet material and tool steel. Further, the present experimental simulations were applicable to characterize and predict wear of components in the application.

Abstract [en]

Components used in rock drilling and sheet metal forming operate under harsh contact conditions that result in an early-life component failure. Wear and fatigue are considered as the most common damage mechanism for these components. Commonly, the service life of a component is designed based on its fatigue life. However, wear might have a significant effect on the components life too. Wear results in a surface damage that in turn may cause a fatigue crack initiation. Therefore, knowledge about wear of materials and components is a key factor in design and prediction of the lifetime of the components. In order to predict wear of a certain component, a thorough understanding of the component with regards to its material properties, application loads and working environment, and damage mechanisms is required. The overall aim of the present work was to define the typical wear mechanisms occurred on machinery components used in rock drilling and sheet metal forming. A comparative analysis of the case studies and results from performed laboratory tests simulated wear mechanisms in the applications highlighted wear mechanisms and factors influencing severity of wear in the applications. Obtained information is crucial for ranking and selection of the best material in the applications.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2020. , p. 36
Series
Karlstad University Studies, ISSN 1403-8099 ; 2020:18
Keywords [en]
High strength steels, thread joint wear, punch wear, sliding wear, surface cracking, reciprocal sliding, fatigue, surface delamination, white etching layer, nano-structured layer, friction
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
URN: urn:nbn:se:kau:diva-77660ISBN: 978-91-7867-112-0 (print)ISBN: 978-91-7867-117-5 (electronic)OAI: oai:DiVA.org:kau-77660DiVA, id: diva2:1426630
Presentation
2020-05-19, 10:00 (English)
Opponent
Supervisors
Note

The presentation will will be via zoom. PhD student will together with the supervisors will be in Karlstad while the opponent is in Luleå. 

Available from: 2020-05-04 Created: 2020-04-27 Last updated: 2020-05-04Bibliographically approved
List of papers
1. Failure analyses and wear mechanisms of rock drill rods: a case study
Open this publication in new window or tab >>Failure analyses and wear mechanisms of rock drill rods: a case study
2019 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 102, p. 69-78Article in journal (Refereed) Published
Abstract [en]

Rock drill rod failure is a big concern for the mining industry. The tough conditions required to break down rock material into small pieces subject rock drill components to high mechanical stresses and corrosion that lead to the failure of the drill rods. This paper describes a detailed examination of rock drill rods failed during field operations. The drill rods were manufactured from a high strength, hardened and tempered steel 22NiCrMo12-5F, carburized for better surface performance. The examination was carried out by means of light optical microscopy and scanning electron microscope. Microhardness profiles were performed for the studied rods. The focus of the present case study was to characterize the failure mechanisms and surface damages of the failed drill rods. The examined drill rods failed due to the initiation and propagation of fatigue microcracks at the outer surface of the thread. Surface cracks propagated to a certain crack length until the fracture toughness of the drill rod was exceeded and the final failure occurred. Multiple short cracks were observed on the fracture surface of the failed rods. The observed cracks propagated perpendicularly to the impacting direction towards the inner surface of the rods. Two different crack initiation mechanisms were observed in the present study, crack initiation from pits and crack initiation from severe plastic surface deformation. Sliding and abrasive wear damage, severe plastic deformation and pitting corrosion were observed on the threaded portion of the rods. Sliding wear was the most common wear damage mechanism observed in the thread joint. Pitting corrosion and severe plastic deformation, made the worn surface susceptible to crack initiation.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
National Category
Materials Engineering
Research subject
Mechanical Engineering; Materials Engineering
Identifiers
urn:nbn:se:kau:diva-72222 (URN)10.1016/j.engfailanal.2019.04.028 (DOI)000467804800007 ()
Available from: 2019-05-31 Created: 2019-05-31 Last updated: 2020-05-26Bibliographically approved
2. Sliding wear and fatigue cracking damage mechanisms in reciprocal and unidirectional sliding of high-strength steels in dry contact
Open this publication in new window or tab >>Sliding wear and fatigue cracking damage mechanisms in reciprocal and unidirectional sliding of high-strength steels in dry contact
2019 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 444, article id 203119Article in journal (Refereed) Published
Abstract [en]

Rock drill components operate under tough contact conditions during rock drilling. Reciprocal and unidirectional motion under high contact stresses are the common contact conditions between interconnected components. It will result in component damage and often the observed surface damage of rock drill tools is due to wear and fatigue cracks. Nevertheless, the effects of the properties and structure of the mating materials on tribological performance, is not fully understood. The present study is dedicated to simulation and investigation of the wear mechanisms observed in reciprocal and unidirectional sliding of high strength steels for rock drill components. A high strength martensitic steel, 22NiCrMo12–F, commonly used in rock drills was tested in self-mating contact. Wear mechanisms were investigated by means of electron microscopy and wear damage was quantified by a 3D optical interferometer. Total damage, as a result of adhesive wear, severe plastic deformation and nucleation and propagation of fatigue cracks, was discussed in relation to test conditions and material properties. It was observed that the coefficient of friction decreased with increasing normal load. Moreover, the results showed that the type of motion had a significant influence on the worn volume and crack nucleation of the specimens in sliding contact. In addition, the reciprocal motion resulted in higher wear than unidirectional motion under the same test conditions.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Fatigue cracks, High strength steel, Reciprocal sliding contact, Rock drill rods, Sliding wear and plastic deformation, Adhesives, Cracks, Fatigue crack propagation, Fatigue damage, Friction, Infill drilling, Nucleation, Plastic deformation, Rock drilling, Rock drills, Rocks, Structural panels, Tribology, Coefficient of frictions, High strength martensitic steels, Optical interferometer, Severe plastic deformations, Sliding contacts, Sliding wear, Tribological performance
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-76487 (URN)10.1016/j.wear.2019.203119 (DOI)000513001800003 ()2-s2.0-85075419083 (Scopus ID)
Available from: 2020-01-23 Created: 2020-01-23 Last updated: 2020-04-27Bibliographically approved
3. Mapping of galling initiation and wear mechanisms at reciprocal sliding of PM tool steels against high performance steel sheets
Open this publication in new window or tab >>Mapping of galling initiation and wear mechanisms at reciprocal sliding of PM tool steels against high performance steel sheets
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-77658 (URN)
Available from: 2020-04-27 Created: 2020-04-27 Last updated: 2020-04-27
4. Wear mechanisms in rock drilling and cold work tooling, a literature review
Open this publication in new window or tab >>Wear mechanisms in rock drilling and cold work tooling, a literature review
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-77659 (URN)
Available from: 2020-04-27 Created: 2020-04-27 Last updated: 2020-04-27

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