The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Staffan Jacobson - One of the best experts on this subject based on the ideXlab platform.
-
on a wear test for Rock Drill inserts
Wear, 2013Co-Authors: Jenny Angseryd, Anna From, Johan E Wallin, Staffan Jacobson, Susanne NorgrenAbstract:Abstract In this work wear of cemented carbide Rock Drill inserts is evaluated by using a rotating Rock cylinder as counter surface. The influence on wear rate and degradation mechanisms from varying dry and wet conditions, cemented carbide grade, abrasive particle type and size as well as load is studied. The used abrasive media are alumina and silica. Test results show high repeatability and the three tested cemented carbide grades can be differentiated, even though their relative difference in sample hardness is modest. The loads used, 100–200 N, are sufficiently high to cause fracture and wear of the granite Rock. The degraded microstructure of inserts tested under wet and dry conditions as well as with added silica particles is similar to field worn inserts. Hence, the same wear mechanisms occur and the test successfully mimics Rock Drill wear. Typical insert wear includes cracking and fragmentation of WC grains, depletion of Co binder phase and adhered material originating from the Rock. Tests under dry conditions always cause less measured wear than tests under wet conditions. Addition of alumina particles, which are harder than the used cemented carbide samples, causes a significant wear rate increase but does not provide wear similar to Rock Drilling.
-
a new view of the deterioration and wear of wc co cemented carbide Rock Drill buttons
Wear, 2008Co-Authors: Ulrik Beste, Staffan JacobsonAbstract:WC/Co cemented carbide is a material developed for highly demanding applications. The unique combination of hardness and toughness makes it especially suitable for wear resistant parts of tools for Rock Drilling. The wear of cemented carbide Rock Drill buttons has been the focus of numerous studies, and a large amount of wear data has been published. However, the broad range of possible wear mechanisms, the large number of Rock types of very different character, and finally the large local property variations even within a single Drill hole, has made it difficult to sort out a good general understanding. One conclusion stands out very clear: the wear data for one Rock Drill in one Rock type is unique to that particular situation and should not be expected to apply to other Rock Drills in other Rock types. Even so, some general wear mechanisms can be observed. Against this backdrop, this paper seeks to present a new, more comprehensive, view on the deterioration and wear mechanisms of cemented carbide Rock Drill buttons. The new view combines some of most important aspects, including two life limiting factors, five classes of mechanisms of deterioration and five classes of material removal mechanisms. The view is based on careful high resolution investigations of worn Rock Drill buttons selected from Drilling of different Rock types. The deterioration includes a fundamental change of material and properties due to intermixing of Rock material and cemented carbide in the surface layer of the button. It further includes corrosive decay and oxidation of WC and formation of large-scale cracks in a reptile skin pattern.
-
wear induced material modifications of cemented carbide Rock Drill buttons
International Journal of Refractory Metals & Hard Materials, 2006Co-Authors: Ulrik Beste, Ernesto Coronel, Staffan JacobsonAbstract:It is well known that thin coatings can provide increased lifetime and reduced energy consumption for tools and components. During use, e.g. in sliding contact, mechanical and chemical reactions often lead to the formation of new surface layers, tribofilms, possessing different properties compared to the original surface, hence affecting the overall performance. In this work, analytical electron microscopy was applied to investigate the structure and composition of tribofilms.Concerning coatings, deposition parameter dependencies, stability and tribology were investigated. The carbon content of hydrogen-free TiCx coatings was shown to significantly influence the morphology. Low carbon content resulted in columnar grains with a strong texture while high carbon content led to the formation of randomly ordered TiCx crystals. The application of positive bias to the substrate as opposed to the normally used negative bias gave a fibrous structure of sputtered TiB2 and low residual stress with maintained hardness. Further, oxidation stability was examined on a (Ta,Al)C:C coating where oxidation led to partial oxidation and formation of AlTaO4 with an 8 nm interface.A focused ion beam instrument was used to extract samples from certain areas of worn specimens. Tribological contact was observed to result in phase changes and intermixing of materials present in the contact. Sliding contact involving a Co-alloy led to a phase change from fcc to hcp. A 30 nm Co-rich tribofilm was observed with basal planes parallel to the surface. Fully formulated oil was found to inflict considerable wear to a metal doped carbon film through chemical reaction with the metal dopant. WC/Co cemented carbide used for Rock Drilling exhibited intermixing of Rock and Co binder phase after field tests. Chemical vapour deposited diamond worn in nitrogen and argon showed formation of wear debris with amorphous structure containing nitrogen and graphitic like structure, respectively.
-
Micro scratch evaluation of Rock types - a means to comprehend Rock Drill wear
Tribology International, 2004Co-Authors: Ulrik Beste, Axel Lundvall, Staffan JacobsonAbstract:Abstract Drilling, transportation and handling of Rock always result in wear of the equipment that comes into contact with the Rock and Rock fragments. Rock is normally considered rather hard, and the contact leads to abrasion, erosion and point fatigue. However, the wear mechanisms of the tools are often complex and vary in character depending on the Rock type. To understand the wear mechanisms of the cemented carbide used in Rock Drill bits, it is central to understand how different Rock types respond to severe scratching from hard tips. A cemented carbide tip with radius 10 μm was used in a scratch tester at progressive loads of 0 to 20 N and at constant loads of 10 N. The tested Rock types were calcite, two types of magnetite, hematite, leptite, mica schist, granite, sandstone and quartz spanning average hardness values from 190 up to 1220 HV. The scratches were investigated in SEM and the friction coefficient between Rock and the tip was measured. In addition, the wear volume of the cemented carbide tip is measured. The Rock types differed significantly with respect to damage mechanism and critical load for transition from a mild to a more severe damage. The friction behaviour correspondingly shifted from rather smooth to very fluctuant. The wear of the tip was found to be correlated to the hardness of the Rocks, but was also influenced by the grain size, the quartz content and isotropy. The implications from the present results on full-scale Rock Drill wear are discussed.
-
micro scale hardness distribution of Rock types related to Rock Drill wear
Wear, 2003Co-Authors: Ulrik Beste, Staffan JacobsonAbstract:Abstract All Rock handling requires tool materials with special qualities. In crushing and screening, speciality steels are used to resist abrasion and other major wear mechanisms. In Drilling and rotary crushing, WC/Co cemented carbides are used. On top of the extremely tough conditions for the material, one of the most difficult problems is the shifting character of the Rock. Even within a single mineral ore, the character often shifts significantly. To optimise a cemented carbide grade for wear life in Rock Drilling, a suitable characterisation of the Rock is required. To perform this characterisation of the Rock, very low load hardness of calcite, magnetite, hematite, leptite, quartz, mica schist, granite and sandstone have been measured using nanoindentation. This fixed depth hardness was measured using 1 μm indentation. To get a high resolution mapping of the local hardness values, 3×160 closely spaced indentations were placed, covering an area of 3.2 mm ×0.075 mm. This study elucidates the importance of scale in hardness measurements of Rock, especially for Rocks of multi-mineral character. The hardness distributions achieved at 1 μm fixed depth indentations also clearly indicated that micro hardness measurements at 500 g load is too blunt a tool for a representative Rock characterisation. For minerals with wide distributions, such as hematite and mica schist, the micro hardness value could be as low as 1/5 of the top hardness values measured at 1 μm fixed depth.
Ulrik Beste - One of the best experts on this subject based on the ideXlab platform.
-
a new view of the deterioration and wear of wc co cemented carbide Rock Drill buttons
Wear, 2008Co-Authors: Ulrik Beste, Staffan JacobsonAbstract:WC/Co cemented carbide is a material developed for highly demanding applications. The unique combination of hardness and toughness makes it especially suitable for wear resistant parts of tools for Rock Drilling. The wear of cemented carbide Rock Drill buttons has been the focus of numerous studies, and a large amount of wear data has been published. However, the broad range of possible wear mechanisms, the large number of Rock types of very different character, and finally the large local property variations even within a single Drill hole, has made it difficult to sort out a good general understanding. One conclusion stands out very clear: the wear data for one Rock Drill in one Rock type is unique to that particular situation and should not be expected to apply to other Rock Drills in other Rock types. Even so, some general wear mechanisms can be observed. Against this backdrop, this paper seeks to present a new, more comprehensive, view on the deterioration and wear mechanisms of cemented carbide Rock Drill buttons. The new view combines some of most important aspects, including two life limiting factors, five classes of mechanisms of deterioration and five classes of material removal mechanisms. The view is based on careful high resolution investigations of worn Rock Drill buttons selected from Drilling of different Rock types. The deterioration includes a fundamental change of material and properties due to intermixing of Rock material and cemented carbide in the surface layer of the button. It further includes corrosive decay and oxidation of WC and formation of large-scale cracks in a reptile skin pattern.
-
wear induced material modifications of cemented carbide Rock Drill buttons
International Journal of Refractory Metals & Hard Materials, 2006Co-Authors: Ulrik Beste, Ernesto Coronel, Staffan JacobsonAbstract:It is well known that thin coatings can provide increased lifetime and reduced energy consumption for tools and components. During use, e.g. in sliding contact, mechanical and chemical reactions often lead to the formation of new surface layers, tribofilms, possessing different properties compared to the original surface, hence affecting the overall performance. In this work, analytical electron microscopy was applied to investigate the structure and composition of tribofilms.Concerning coatings, deposition parameter dependencies, stability and tribology were investigated. The carbon content of hydrogen-free TiCx coatings was shown to significantly influence the morphology. Low carbon content resulted in columnar grains with a strong texture while high carbon content led to the formation of randomly ordered TiCx crystals. The application of positive bias to the substrate as opposed to the normally used negative bias gave a fibrous structure of sputtered TiB2 and low residual stress with maintained hardness. Further, oxidation stability was examined on a (Ta,Al)C:C coating where oxidation led to partial oxidation and formation of AlTaO4 with an 8 nm interface.A focused ion beam instrument was used to extract samples from certain areas of worn specimens. Tribological contact was observed to result in phase changes and intermixing of materials present in the contact. Sliding contact involving a Co-alloy led to a phase change from fcc to hcp. A 30 nm Co-rich tribofilm was observed with basal planes parallel to the surface. Fully formulated oil was found to inflict considerable wear to a metal doped carbon film through chemical reaction with the metal dopant. WC/Co cemented carbide used for Rock Drilling exhibited intermixing of Rock and Co binder phase after field tests. Chemical vapour deposited diamond worn in nitrogen and argon showed formation of wear debris with amorphous structure containing nitrogen and graphitic like structure, respectively.
-
Micro scratch evaluation of Rock types - a means to comprehend Rock Drill wear
Tribology International, 2004Co-Authors: Ulrik Beste, Axel Lundvall, Staffan JacobsonAbstract:Abstract Drilling, transportation and handling of Rock always result in wear of the equipment that comes into contact with the Rock and Rock fragments. Rock is normally considered rather hard, and the contact leads to abrasion, erosion and point fatigue. However, the wear mechanisms of the tools are often complex and vary in character depending on the Rock type. To understand the wear mechanisms of the cemented carbide used in Rock Drill bits, it is central to understand how different Rock types respond to severe scratching from hard tips. A cemented carbide tip with radius 10 μm was used in a scratch tester at progressive loads of 0 to 20 N and at constant loads of 10 N. The tested Rock types were calcite, two types of magnetite, hematite, leptite, mica schist, granite, sandstone and quartz spanning average hardness values from 190 up to 1220 HV. The scratches were investigated in SEM and the friction coefficient between Rock and the tip was measured. In addition, the wear volume of the cemented carbide tip is measured. The Rock types differed significantly with respect to damage mechanism and critical load for transition from a mild to a more severe damage. The friction behaviour correspondingly shifted from rather smooth to very fluctuant. The wear of the tip was found to be correlated to the hardness of the Rocks, but was also influenced by the grain size, the quartz content and isotropy. The implications from the present results on full-scale Rock Drill wear are discussed.
-
micro scale hardness distribution of Rock types related to Rock Drill wear
Wear, 2003Co-Authors: Ulrik Beste, Staffan JacobsonAbstract:Abstract All Rock handling requires tool materials with special qualities. In crushing and screening, speciality steels are used to resist abrasion and other major wear mechanisms. In Drilling and rotary crushing, WC/Co cemented carbides are used. On top of the extremely tough conditions for the material, one of the most difficult problems is the shifting character of the Rock. Even within a single mineral ore, the character often shifts significantly. To optimise a cemented carbide grade for wear life in Rock Drilling, a suitable characterisation of the Rock is required. To perform this characterisation of the Rock, very low load hardness of calcite, magnetite, hematite, leptite, quartz, mica schist, granite and sandstone have been measured using nanoindentation. This fixed depth hardness was measured using 1 μm indentation. To get a high resolution mapping of the local hardness values, 3×160 closely spaced indentations were placed, covering an area of 3.2 mm ×0.075 mm. This study elucidates the importance of scale in hardness measurements of Rock, especially for Rocks of multi-mineral character. The hardness distributions achieved at 1 μm fixed depth indentations also clearly indicated that micro hardness measurements at 500 g load is too blunt a tool for a representative Rock characterisation. For minerals with wide distributions, such as hematite and mica schist, the micro hardness value could be as low as 1/5 of the top hardness values measured at 1 μm fixed depth.
-
surface damage on cemented carbide Rock Drill buttons
Wear, 2001Co-Authors: Ulrik Beste, Torbjorn Hartzell, Hakan Engqvist, Niklas AxenAbstract:Abstract Wear phenomena on cemented carbide Drill buttons tested in percussive Drilling of Kiruna-magnetite under realistic conditions have been studied with scanning electron microscopy, light optical microscopy and energy dispersive X-ray spectroscopy. In addition, a comprehensive literature study has been performed. The aim has been to chart wear phenomena, such as crack formation, occurrence of reptile skin and various wear mechanisms. It is shown that surface cracks form shortly after Drilling has started. Also the valleys and plateaus characterising the reptile skin pattern were found after only short Drilling periods. It appears that the formation of the initial surface cracks and the reptile skin pattern are separate mechanisms, which presumably interact. In addition to the formation of cracks, there is also a continuous wear of the buttons. This is assumed to be caused by wear fracturing and pullout of tungsten carbide (WC) grains and wear of cobalt (Co) by abrasion, possibly assisted by corrosion. A wear mechanism table, based on a comprehensive literature review and on experience from real Drilling conditions, is suggested.
Mikael Olsson - One of the best experts on this subject based on the ideXlab platform.
-
surface failure and wear of cemented carbide Rock Drill buttons the importance of sample preparation and optimized microscopy settings
Wear, 2013Co-Authors: Stefan Olovsjo, Richard Johanson, Flor Falsafi, Ulf Bexell, Mikael OlssonAbstract:The combination of suitable mechanical properties and wear resistance makes cemented carbide one of the most interesting engineering composite materials for tribological applications, such as in Rock Drilling. Despite the fact that cemented carbide buttons have been used in Rock Drilling applications for a long time the detailed understanding of the prevailing wear mechanisms is far from complete and wear and breakage of Rock Drill buttons are still one of the lifetime-limiting factors for Rock Drill bits. Consequently, further research in this area, including detailed characterization of worn Drill button surfaces and sub-surface regions, is needed in order to support the future development of new cemented carbide grades with improved failure and wear resistance. In the present paper, high resolution scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) have been used to characterize the wear and failure mechanisms of worn Drill buttons and samples exposed to well controlled impact and scratch tests performed in the laboratory. The most important mechanisms of surface failure and wear were found to be severe plastic deformation, cracking, crushing of individual WC grains and mechanical/tribochemical degradation of the Co binder phase including Co depletion. Fracture cross-sectioning under tensile stress-state was found to be the best method for achieving large and reliable sub-surface cross-sections within a short time and to a low cost. The importance of optimized microscopy and spectroscopy settings for enhanced surface sensitivity for the examination of small-scale tribological phenomena is illuminated and discussed.
M. Shinji - One of the best experts on this subject based on the ideXlab platform.
-
Prediction of Forward Tunnel Face Score of Rock Mass Classification for Stability by Applying Machine Learning to Drilling Data
Information Technology in Geo-Engineering, 2020Co-Authors: Hisashi Hayashi, Miku Miyanaka, Haruka Gomi, Junichi Tatsumi, Nobuyuki Kawabe, M. ShinjiAbstract:In tunnel construction, it is important to ensure economic efficiency and safety when collecting data on ground condition variations during construction. Therefore, in recent years an increasing number of exploration methods using Rock Drills in front of tunnel faces have been developed. In this paper, a new exploration method called TFS-learning was proposed; this method uses machine data of a Rock Drill. Further, TFS identifies the relationship between the Drilling machine data during the perforation of the blast hole and the assessment score of the tunnel face through machine learning to predict the distribution of assessment scores on the tunnel face. In this study, TFS-learning is focused on Drilling data of the applied A tunnel. Based on the analysis result, a regression equation is derived, from which, the accuracy of the predicted result of the forward face assessment scores is verified. Therefore, the face assessment scores could be roughly predicted in the section with similar Rock types by machine learning; however, it was also found that prediction accuracy decreases when the Rock type changes.
-
prediction of forward tunnel face score of Rock mass classification for stability by applying machine learning to Drilling data
International Conference on Inforatmion technology in Geo-Engineering, 2019Co-Authors: Hisashi Hayashi, Miku Miyanaka, Haruka Gomi, Junichi Tatsumi, Nobuyuki Kawabe, M. ShinjiAbstract:In tunnel construction, it is important to ensure economic efficiency and safety when collecting data on ground condition variations during construction. Therefore, in recent years an increasing number of exploration methods using Rock Drills in front of tunnel faces have been developed. In this paper, a new exploration method called TFS-learning was proposed; this method uses machine data of a Rock Drill. Further, TFS identifies the relationship between the Drilling machine data during the perforation of the blast hole and the assessment score of the tunnel face through machine learning to predict the distribution of assessment scores on the tunnel face. In this study, TFS-learning is focused on Drilling data of the applied A tunnel. Based on the analysis result, a regression equation is derived, from which, the accuracy of the predicted result of the forward face assessment scores is verified.
Niklas Axen - One of the best experts on this subject based on the ideXlab platform.
-
surface damage on cemented carbide Rock Drill buttons
Wear, 2001Co-Authors: Ulrik Beste, Torbjorn Hartzell, Hakan Engqvist, Niklas AxenAbstract:Abstract Wear phenomena on cemented carbide Drill buttons tested in percussive Drilling of Kiruna-magnetite under realistic conditions have been studied with scanning electron microscopy, light optical microscopy and energy dispersive X-ray spectroscopy. In addition, a comprehensive literature study has been performed. The aim has been to chart wear phenomena, such as crack formation, occurrence of reptile skin and various wear mechanisms. It is shown that surface cracks form shortly after Drilling has started. Also the valleys and plateaus characterising the reptile skin pattern were found after only short Drilling periods. It appears that the formation of the initial surface cracks and the reptile skin pattern are separate mechanisms, which presumably interact. In addition to the formation of cracks, there is also a continuous wear of the buttons. This is assumed to be caused by wear fracturing and pullout of tungsten carbide (WC) grains and wear of cobalt (Co) by abrasion, possibly assisted by corrosion. A wear mechanism table, based on a comprehensive literature review and on experience from real Drilling conditions, is suggested.
