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Publikationer (10 of 82) Visa alla publikationer
Mussa, A., Krakhmalev, P. & Bergström, J. (2019). Failure analyses and wear mechanisms of rock drill rods: a case study. Engineering Failure Analysis, 102, 69-78
Öppna denna publikation i ny flik eller fönster >>Failure analyses and wear mechanisms of rock drill rods: a case study
2019 (Engelska)Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 102, s. 69-78Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Nationell ämneskategori
Materialteknik
Identifikatorer
urn:nbn:se:kau:diva-72222 (URN)10.1016/j.engfailanal.2019.04.028 (DOI)000467804800007 ()
Tillgänglig från: 2019-05-31 Skapad: 2019-05-31 Senast uppdaterad: 2019-12-09Bibliografiskt granskad
Vilardell, A. M., Fredriksson, G., Yadroitsev, I. & Krakhmalev, P. (2019). Fracture mechanisms in the as-built and stress-relieved laser powder bed fusion Ti6Al4V ELI alloy. Optics and Laser Technology, 109, 608-615
Öppna denna publikation i ny flik eller fönster >>Fracture mechanisms in the as-built and stress-relieved laser powder bed fusion Ti6Al4V ELI alloy
2019 (Engelska)Ingår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 109, s. 608-615Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The influence of a stress-relief treatment on impact and fatigue properties of Ti6Al4V ELI samples manufactured by laser powder bed fusion was analyzed. The heat treatment resulted in removal of residual stresses, coarsening of needles and formation of precipitations between needles. In both, impact and fatigue tests, crack development was correlated to microstructural features. Fracture analysis was carried out by means of optical and electron microscopy to reveal the influence of microstructure on crack development. Ductile fracture was the dominating fracture mode at impact testing. Pore formation and coalescence were the main crack formation mechanisms. The microstructural changes led to a decrease in impact toughness after heat treatment. Presumably, this was a result of the precipitations between needles. Fatigue results showed multiple crack nucleation at the surface in both, as-built and stress-relieved material. The crack propagation rate was slightly higher and the crack was less deflected in the stress-relieved material due to the stress relief and coarsening of the microstructure.

Ort, förlag, år, upplaga, sidor
Elsevier, 2019
Nyckelord
Fracture analysis, Impact and fatigue properties, Laser powder bed fusion, Stress-relief treatment, Ti6A4V ELI, Aluminum alloys, Coarsening, Cracks, Ductile fracture, Fatigue testing, Fracture testing, Heat treatment, Impact testing, Microstructural evolution, Needles, Residual stresses, Stress relief, Titanium alloys, Crack propagation rate, Laser powders, Microstructural changes, Microstructural features, Optical and electron microscopies, Fatigue of materials
Nationell ämneskategori
Atom- och molekylfysik och optik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kau:diva-69444 (URN)10.1016/j.optlastec.2018.08.042 (DOI)000446949600074 ()2-s2.0-85053287726 (Scopus ID)
Tillgänglig från: 2018-10-02 Skapad: 2018-10-02 Senast uppdaterad: 2019-01-31Bibliografiskt granskad
Åsberg, M., Fredriksson, G., Hatami, S., Fredriksson, W. & Krakhmalev, P. (2019). Influence of post treatment on microstructure, porosity and mechanical properties of additive manufactured H13 tool steel. Materials Science & Engineering: A, 742, 584-589
Öppna denna publikation i ny flik eller fönster >>Influence of post treatment on microstructure, porosity and mechanical properties of additive manufactured H13 tool steel
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2019 (Engelska)Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 742, s. 584-589Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Additive manufacturing (AM) is an attractive manufacturing technology in tooling applications. It provides unique opportunities to manufacture tools with complex shapes, containing inner channels for conformal cooling. In this investigation, H13, a widely used tool steel, was manufactured using a laser powder bed fusion method. Microstructure, tensile mechanical properties, hardness, and porosity of the AM H13 after stress relieve (SR), standard hardening and tempering (SR + HT), and hot isostatic pressing (SR + HIP + HT) were investigated. It was found that the microstructure of directly solidified colonies of prior austenite, which is typical for AM, disappeared after austenitizing at the hardening heat treatment. In specimens SR + HT and SR + HIP + HT, a microstructure similar to the conventional but finer was observed. Electron microscopy showed that SR and SR + HT specimens contained lack of fusion, and spherical gas porosity, which resulted in remarkable scatter in the observed elongation to break values. Application of HIP resulted in the highest strength values, higher than those observed for conventional H13 heat treated in the same way. The conclusion is that HIP promotes reduction of porosity and lack of fusion defects and can be efficiently used to improve the mechanical properties of AM H13 tool steel.

Ort, förlag, år, upplaga, sidor
Elsevier, 2019
Nyckelord
Additive manufacturing, Hot work tool steel H13, Laser powder bed fusion, Mechanical properties, Post treatment, 3D printers, Hardening, Hot isostatic pressing, Hot working, Microstructure, Porosity, Tool steel, Tools, Elongation to break, H-13 tool steels, Hot-work tool steel, Laser powders, Manufacturing technologies, Strength values, Tensile mechanical properties
Nationell ämneskategori
Metallurgi och metalliska material
Forskningsämne
Materialvetenskap
Identifikatorer
urn:nbn:se:kau:diva-70411 (URN)10.1016/j.msea.2018.08.046 (DOI)000457814400060 ()2-s2.0-85056673446 (Scopus ID)
Tillgänglig från: 2018-12-05 Skapad: 2018-12-05 Senast uppdaterad: 2019-02-21Bibliografiskt granskad
Van Meensel, K., Lietaert, K., Vrancken, B., Dadbakhsh, S., Xiaopeng, L., Kruth, J. P., . . . Van Humbeeck, J. (2018). Additively manufactured metals for medical applications (1ed.). In: Jing Zhang, Yeon-Gil Jung (Ed.), Additive Manufacturing: Materials, Processes, Quantifications and Applications (pp. 261-309). Kidlington, U.K.: Butterworth-Heinemann
Öppna denna publikation i ny flik eller fönster >>Additively manufactured metals for medical applications
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2018 (Engelska)Ingår i: Additive Manufacturing: Materials, Processes, Quantifications and Applications / [ed] Jing Zhang, Yeon-Gil Jung, Kidlington, U.K.: Butterworth-Heinemann, 2018, 1, s. 261-309Kapitel i bok, del av antologi (Refereegranskat)
Ort, förlag, år, upplaga, sidor
Kidlington, U.K.: Butterworth-Heinemann, 2018 Upplaga: 1
Nyckelord
additive manufacturing, biomedical applications, bioresorbable implants, electron beam melting, metallic alloys, permanent implants, selective laser melting
Nationell ämneskategori
Metallurgi och metalliska material Bearbetnings-, yt- och fogningsteknik
Forskningsämne
Materialvetenskap
Identifikatorer
urn:nbn:se:kau:diva-75487 (URN)10.1016/B978-0-12-812155-9.00008-6 (DOI)978-0-12-812155-9 (ISBN)
Tillgänglig från: 2019-10-30 Skapad: 2019-10-30 Senast uppdaterad: 2019-11-11Bibliografiskt granskad
Vilardell, A. M., Krakhmalev, P., Fredriksson, G., Cabanettes, F., Sova, A., Valentin, D. & Bertrand, P. (2018). Influence of surface topography on fatigue behavior of Ti6Al4V alloy by laser powder bed fusion. In: Procedia CIRP: . Paper presented at 10th CIRP Conference on Photonic Technologies, LANE 2018, 3 September 2018 through 6 September 2018 (pp. 49-52). Elsevier
Öppna denna publikation i ny flik eller fönster >>Influence of surface topography on fatigue behavior of Ti6Al4V alloy by laser powder bed fusion
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2018 (Engelska)Ingår i: Procedia CIRP, Elsevier, 2018, s. 49-52Konferensbidrag (Refereegranskat)
Abstract [en]

This article deals with the understanding of the influence of surface topography on fatigue behavior of Ti6Al4V alloy specimens produced by laser powder bed fusion (LPBF). The same laser parameters and scan strategy were used for all specimens, giving a sample density higher than 99.5 %. Two different surface topographies were obtained by using the top and side surfaces of the specimens. The surface topography and morphology were investigated by optical surface profilometry and focus variation microscopy. Four-point bending fatigue test was performed on specimens with top and side surfaces as the highest stressed surface respectively. Machined specimens were used as reference. The features of the fracture surface, such as crack initiation and propagation, were analyzed by focus variation and scanning electron microscopy (SEM). Both, fatigue results and fracture surface investigations, were correlated and discussed in relation to surface topography and microstructure, as well as manufacturing parameters. 

Ort, förlag, år, upplaga, sidor
Elsevier, 2018
Nyckelord
Fatigue test, Fracture mechanisms, Laser powder bed fusion, Surface topography, Ti6Al4V alloy, Aluminum alloys, Fatigue of materials, Fatigue testing, Fracture, Scanning electron microscopy, Ternary alloys, Titanium alloys, Topography, Crack initiation and propagation, Fatigue behavior, Four point bending, Fracture surfaces, Laser powders, Manufacturing parameters, Ti-6Al-4V alloy
Nationell ämneskategori
Fysik
Forskningsämne
Materialvetenskap
Identifikatorer
urn:nbn:se:kau:diva-70594 (URN)10.1016/j.procir.2018.08.028 (DOI)2-s2.0-85057393814 (Scopus ID)
Konferens
10th CIRP Conference on Photonic Technologies, LANE 2018, 3 September 2018 through 6 September 2018
Tillgänglig från: 2018-12-20 Skapad: 2018-12-20 Senast uppdaterad: 2019-04-25Bibliografiskt granskad
Krakhmalev, P., Yadroitsev, I., Baker, I. & Yadroitsava, I. (2018). Manufacturing of intermetallic Mn-46%Al by laser powder bed fusion. In: Procedia CIRP: . Paper presented at 10th CIRP Conference on Photonic Technologies, LANE 2018, 3 September 2018 through 6 September 2018 (pp. 64-67). Elsevier, 74
Öppna denna publikation i ny flik eller fönster >>Manufacturing of intermetallic Mn-46%Al by laser powder bed fusion
2018 (Engelska)Ingår i: Procedia CIRP, Elsevier, 2018, Vol. 74, s. 64-67Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Laser powder bed fusion (LPBF) provides an excellent opportunity to use custom powders for complex objects without extensive machining. This opportunity is attractive for brittle and hard intermetallics, but is challenging due to cracking, anisotropy, and the formation of non-equilibrium phases. The present investigation is focused on a development of the process parameters for pre-alloyed Mn-46 at.%Al gas atomized intermetallic powder, which is a promising magnetic material. A hierarchical approach involving optimization of the process parameters for a single track, a single layer, and then a 3D specimen was applied. The manufacturing of single tracks was performed at scanning speeds of 0.06-3.4 m/s and laser powers of 50-350 W. Test parameters guaranteeing stable single track with constant width and height, and sufficient remelting depth were selected for further manufacturing. Surface morphology, chemical composition, crack density and distribution, and the microstructures in the final materials were investigated. It was shown that the consists mostly of the ε-phase with some amounts of equilibrium γ2 and β phases and the ferromagnetic τ-phase. The presence of the ε-phase shows a potential to use heat treatment to form τ-phase magnetic phase in AM Mn-46 at.%Al. Future investigations will clarify the applicability of LPBF to manufacture Mn-46%Al for magnetic applications. 

Ort, förlag, år, upplaga, sidor
Elsevier, 2018
Nyckelord
Hierarchical optimization of process parameters, Intermetallic phase, Laser Powder Bed Fusion, Mn-46 at.%Al alloys, Binary alloys, Intermetallics, Magnetic materials, Magnetism, Manganese alloys, Manufacture, Al-alloy, Chemical compositions, Hierarchical approach, Hierarchical optimization, Laser powders, Magnetic applications, Non-equilibrium phasis, Aluminum alloys
Nationell ämneskategori
Materialteknik
Forskningsämne
Materialvetenskap
Identifikatorer
urn:nbn:se:kau:diva-70595 (URN)10.1016/j.procir.2018.08.031 (DOI)2-s2.0-85057369130 (Scopus ID)
Konferens
10th CIRP Conference on Photonic Technologies, LANE 2018, 3 September 2018 through 6 September 2018
Tillgänglig från: 2018-12-20 Skapad: 2018-12-20 Senast uppdaterad: 2019-06-13Bibliografiskt granskad
Kazantseva, N., Krakhmalev, P., Thuvander, M., Yadroitsev, I., Vinogradova, N. & Ezhov, I. (2018). Martensitic transformations in Ti-6Al-4V (ELI) alloy manufactured by 3D Printing. Materials Characterization, 146, 101-112
Öppna denna publikation i ny flik eller fönster >>Martensitic transformations in Ti-6Al-4V (ELI) alloy manufactured by 3D Printing
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2018 (Engelska)Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 146, s. 101-112Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In the present investigation, Ti-6Al-4V ELI samples were manufactured by the powder-bed fusion (PBF) process using the laser sintering (LS) technology. Microstructure, chemical and phase constitution, and mechanical properties were studied by means of the transmission electron microscopy, atom probe tomography, X-ray diffraction, nanoindentation and mechanical testing. It was found that the structure of LS samples consisted of two different variants of metastable phases, namely the hexagonal alpha' martensitic phase and small amounts of the orthorhombic alpha '' martensitic phase. The martensitic alpha'-phase was formed because of the high cooling rates of the LS method, The {10 (1) over bar2} <(1) over bar 011 > hexagonal martensite tensile twins were observed in the microstructure of the as-build alloy. Small areas with inner twinning martensitic plates, which are typical for the metastable orthor-hombic martensitic phase in titanium alloys, were identified by the transmission electron microscopy. Atom probe tomography (APT) confirmed localization of beta-stabilizing elements at interfaces, presumably at the twin or lamella boundaries. The structure and origin of the martensitic phases in 3D printed Ti-6Al-4V alloys are discussed with respect to in-situ heat treatment during manufacturing.

Ort, förlag, år, upplaga, sidor
Elsevier, 2018
Nyckelord
Material or constituting phase(s) Titanium alloys Laser sintering Metastable phases Mechanical properties
Nationell ämneskategori
Materialteknik
Forskningsämne
Materialteknik
Identifikatorer
urn:nbn:se:kau:diva-70951 (URN)10.1016/j.matchar.2018.09.042 (DOI)000452816700010 ()
Tillgänglig från: 2019-02-07 Skapad: 2019-02-07 Senast uppdaterad: 2019-02-13Bibliografiskt granskad
Krakhmalev, P., Fredriksson, G., Svensson, K., Yadroitsev, I., Yadroitsava, I., Thuvander, M. & Peng, R. (2018). Microstructure, solidification texture, and thermal stability of 316 L stainless steel manufactured by laser powder bed fusion. Metals, 8(8), 1-18, Article ID 643.
Öppna denna publikation i ny flik eller fönster >>Microstructure, solidification texture, and thermal stability of 316 L stainless steel manufactured by laser powder bed fusion
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2018 (Engelska)Ingår i: Metals, ISSN 2075-4701, Vol. 8, nr 8, s. 1-18, artikel-id 643Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, cellular structure, microsegregation, porosity, competitive colony growth, and solidification texture, were experimentally studied by scanning and transmission electron microscopy, diffraction methods, and atom probe tomography. The influence of laser power and laser scanning speed on the microstructure was discussed in the perspective of governing the microstructure by controlling the process parameters. It was shown that the three-dimensional (3D) zig-zag solidification texture observed in the LPBF 316 L was related to the laser scanning strategy. The thermal stability of the microstructure was investigated under isothermal annealing conditions. It was shown that the cells formed at solidification started to disappear at about 800 °C, and that this process leads to a substantial decrease in hardness. Colony boundaries, nevertheless, were quite stable, and no significant grain growth was observed after heat treatment at 1050 °C. The observed experimental results are discussed with respect to the fundamental knowledge of the solidification processes, and compared with the existing literature data.

Ort, förlag, år, upplaga, sidor
MDPI AG, 2018
Nyckelord
316 L stainless steel, Cellular solidification, Electron microscopy, Laser powder bed fusion, Solidification texture, Thermal stability of microstructure
Nationell ämneskategori
Materialteknik
Forskningsämne
Materialteknik
Identifikatorer
urn:nbn:se:kau:diva-69224 (URN)10.3390/met8080643 (DOI)000443616400079 ()2-s2.0-85052594962 (Scopus ID)
Tillgänglig från: 2018-09-14 Skapad: 2018-09-14 Senast uppdaterad: 2020-01-10Bibliografiskt granskad
Yadroitsev, I., Krakhmalev, P., Yadroitsava, I. & Du Plessis, A. (2018). Qualification of Ti6Al4V ELI Alloy Produced by Laser Powder Bed Fusion for Biomedical Applications. Paper presented at Annual International Solid Freeform Fabrication (SFF) Symposium / Additive Manufacturing (AM) Conference, AUG 07-09, 2017, Austin, TX. JOM: The Member Journal of TMS, 70(3), 372-377
Öppna denna publikation i ny flik eller fönster >>Qualification of Ti6Al4V ELI Alloy Produced by Laser Powder Bed Fusion for Biomedical Applications
2018 (Engelska)Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 70, nr 3, s. 372-377Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Rectangular Ti6Al4V extralow interstitials (ELI) samples were manufactured by laser powder bed fusion (LPBF) in vertical and horizontal orientations relative to the build platform and subjected to various heat treatments. Detailed analyses of porosity, microstructure, residual stress, tensile properties, fatigue, and fracture surfaces were performed based on x-ray micro-computed tomography, scanning electron microscopy, and x-ray diffraction methods. The types of fracture and the tensile fracture mechanisms of the LPBF Ti6Al4V ELI alloy were also studied. Detailed analysis of the microstructure and the corresponding mechanical properties were compared against standard specifications for conventional Ti6Al4V alloy for use in surgical implant applications. Conclusions regarding the mechanical properties and heat treatment of LPBF Ti6Al4V ELI for biomedical applications are made.

Ort, förlag, år, upplaga, sidor
Springer, 2018
Nationell ämneskategori
Materialteknik
Forskningsämne
Materialvetenskap
Identifikatorer
urn:nbn:se:kau:diva-66712 (URN)10.1007/s11837-017-2655-5 (DOI)000425324900021 ()
Konferens
Annual International Solid Freeform Fabrication (SFF) Symposium / Additive Manufacturing (AM) Conference, AUG 07-09, 2017, Austin, TX
Tillgänglig från: 2018-03-15 Skapad: 2018-03-15 Senast uppdaterad: 2018-06-25Bibliografiskt granskad
AlMotasem, A. T., Bergström, J., Gåård, A., Krakhmalev, P. & Holleboom, T. J. (2017). Atomistic insights on the wear/friction behavior of nanocrystalline ferrite during nanoscratching as revealed by molecular dynamics. Tribology letters, 65(3), 101
Öppna denna publikation i ny flik eller fönster >>Atomistic insights on the wear/friction behavior of nanocrystalline ferrite during nanoscratching as revealed by molecular dynamics
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2017 (Engelska)Ingår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, nr 3, s. 101-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Using embedded atom method potential, extensive large-scale molecular dynamics (MD) simulations of nanoindentation/nanoscratching of nanocrystalline (nc) iron have been carried out to explore grain size dependence of wear response. MD results show no clear dependence of the frictional and normal forces on the grain size, and the single-crystal (sc) iron has higher frictional and normal force compared to nc-samples. For all samples, the dislocation- mediated mechanism is the primary cause of plastic deformation in both nanoindentation/nanoscratch. However, secondary cooperative mechanisms are varied significantly according to grain size. Pileup formation was observed in the front of and sideways of the tool, and they exhibit strong dependence on grain orientation rather than grain size. Tip size has significant impact on nanoscratch characteristics; both frictional and normal forces monotonically increase as tip radii increase, while the friction coefficient value drops by about 38%. Additionally, the increase in scratch depth leads to an increase in frictional and normal forces as well as friction coefficient. To elucidate the relevance of indentation/scratch results with mechanical properties, uniaxial tensile test was performed for nc-samples, and the result indicates the existence of both the regular and inverse Hall-Petch relations at critical grain size of 110.9 angstrom. The present results suggest that indentation/scratch hardness has no apparent correlation with the mechanical properties of the substrate, whereas the plastic deformation has.

Ort, förlag, år, upplaga, sidor
New York: Springer, 2017
Nyckelord
Atomistic, polycrystalline iron, scratch hardness, wear, dislocations, twinning
Nationell ämneskategori
Materialteknik
Forskningsämne
Materialteknik
Identifikatorer
urn:nbn:se:kau:diva-63698 (URN)10.1007/s11249-017-0876-y (DOI)000405488400027 ()
Tillgänglig från: 2017-09-14 Skapad: 2017-09-14 Senast uppdaterad: 2019-12-02Bibliografiskt granskad
Organisationer
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-9441-2502

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