| 1. |
- Calamba, Katherine, et al.
(author)
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Effect of nitrogen vacancies on the growth, dislocation structure, and decomposition of single crystal epitaxial (Ti1-xAlx)N-y thin films
- 2021
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In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 203
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Journal article (peer-reviewed)abstract
- The effect of varying nitrogen vacancies on the growth, microstructure, spinodal decomposition and hardness values of predominantly single crystal cubic phase c-(Ti1-xAlx)N-y films was investigated. Epitaxial c-(Ti1-xAlx)N-y films with y = 0.67, 0.79, and 0.92 were grown on MgO(001) and MgO(111) substrates by magnetron sputter deposition. High N vacancy c-(Ti1-xAlx)N-0.67 films deposited on MgO(111) contained coherently oriented w-(0001) structures while segregated conical structures were observed on the films grown on MgO(001). High resolution STEM images revealed that the N-deficient growth conditions induced segregation with small compositional fluctuations that increase with the number of N vacancies. Similarly, strain map analysis of the epitaxial c-(Ti1-xAlx)N-y (001) and (111) films show fluctuations in strain concentration that scales with the number of N vacancies and increases during annealing. The spinodal decomposition coarsening rate of the epitaxial c-(Ti1-xAlx)N-y films was observed to increase with decreasing N vacancies. Nanoindentation showed decreasing trends in hardness of the as-deposited films as the N vacancies increase. Isothermal post-anneal at 1100 degrees C in vacuum for 120 min revealed a continuation in the increase in hardness for the film with the largest number of N vacancies (y = 0.67) while the hardness decreased for the films with y = 0.79 and 0.92. These results suggest that nitrogen-deficient depositions of c-(Ti1-xAlx)N-y films help to promote a self-organized phase segregation, while higher N vacancies generally increase the coherency strain which delays the coarsening process and can influence the hardness at high temperatures.
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| 2. |
- Chen, Yu-Hsiang, et al.
(author)
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Enhanced thermal stability and fracture toughness of TiAlN coatings by Cr, Nb and V-alloying
- 2018
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 342, s. 85-93
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Journal article (peer-reviewed)abstract
- The effect of metal alloying on mechanical properties including hardness and fracture toughness were investigated in three alloys, Ti 0.33Al0.50(Me) 0.17N (Me = Cr, Nb and V), and compared to Ti0.50Al0.50N, in the as-deposited state and after annealing. All studied alloys display similar as-deposited hardness while the hardness evolution during annealing is found to be connected to phase transformations, related to the alloy’s thermal stability. The most pronounced hardening was observed in Ti0.50Al0.50N, while all the coatings with additional metal elements sustain their hardness better and they are harder than Ti0.50Al0.50N after annealing at 1100 °C. Fracture toughness properties were extracted from scratch tests. In all tested conditions, as-deposited and annealed at 900 and 1100 °C, Ti0.33Al0.50Nb0.17N show the least surface and sub-surface damage when scratched despite the differences in decomposition behavior and h-AlN formation. Theoretically estimated ductility of phases existing in the coatings correlates well with their crack resistance. In summary, Ti0.33Al0.50Nb0.17N is the toughest alloy in both as-deposited and post-annealed states.
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| 3. |
- Moreno, Maiara, et al.
(author)
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Adhesive wear of TiAlN coatings during low speed turning of stainless steel 316L
- 2023
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In: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 524-525
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Journal article (peer-reviewed)abstract
- The wear behavior of TiAlN coatings during turning of stainless steel 316L at low cutting speeds (60–120 m/min) was investigated using scanning electron microscopy. In this speed range, the coatings fail by fracture due to an adhesive wear mechanism. The fracture of the coating is described in detail, including the strong influence of Al-content and cutting speed on the rate of wear. Low Al-content (x ≤ 0.23) coatings showed worse wear resistance than high Al-content (x ≥ 0.53) samples. Less substrate is exposed when the cutting speed is increased, because of reduced adhesive wear. The TiN and Ti0.77Al0.23N coatings are severely worn for all cutting speeds while Ti0.47Al0.53N and Ti0.38Al0.62N remain essentially unaffected at the highest speed. The difference in wear behavior is interpreted as a difference in the fracture toughness of the coatings.
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| 4. |
- Moreno, Maiara, 1993-, et al.
(author)
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Strain and phase evolution in TiAlN coatings during high-speed metal cutting : An in operando high-energy x-ray diffraction study
- 2024
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In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 263
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Journal article (peer-reviewed)abstract
- We report on phase and strain changes in Ti1-xAlxN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.
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| 5. |
- Schramm, Isabella C., et al.
(author)
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Effects of nitrogen vacancies on phase stability and mechanical properties of arc deposited (Ti0.52Al0.48)Ny (y<1) coatings
- 2017
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 330:Supplement C, s. 77-86
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Journal article (peer-reviewed)abstract
- Nitrogen sub-stoichiometric (Ti0.52Al0.48)Ny (0.92 ≥ y ≥ 0.46) coatings were grown in a mixed Ar/N2 atmosphere by cathodic arc deposition on cemented carbide (WC/Co-based) substrates. The coatings present a columnar structure with decreasing column widths from 250 to 60nm, due to a corresponding reduced N content, accompanied by changes in preferred orientation from 200 to 111 to 220. Among these, coatings prepared with 0.92≥y≥0.75 exhibit spinodal decomposition and consequently age hardening at elevated temperatures. A reduced N content upshifts the hardness maximum by >300 °C. For these samples, the high temperature treatment resulted in interdiffusion of substrate elements, Co and C, mainly along column boundaries. Nevertheless, no detrimental effect in the hardness could be correlated. Conversely, a low N content sample (y=0.46) presents significant lattice diffusion of substrate elements Co, C, W, and Ta in the coating. In this case, the substrate elements are present throughout the coating, forming additional phases such as c-Ti(C,N), c-Co(Al,Ti,W), and c-(Ti,W,Ta)(C,N), with an observed increased hardness from 16 to 25GPa. We suggest that the substitution of nitrogen by carbon and the solution of W and Ta in c-TiN are responsible for the observed hardening. Our investigation shows the potential of sub-stoichiometric (Ti1-xAlx)Ny coatings for high temperature applications such as cutting tools and puts forth corresponding criteria for N content selection.
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| 6. |
- Berlind, Torun, 1965-, et al.
(author)
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Microstructure, mechanical properties, and wetting behaviorof Si-C-N thin films grown by reactive magnetron sputtering
- 2001
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In: Surface and Coatings Technology. - : Elsevier. - 0257-8972. ; 141:2-3, s. 145-155
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Journal article (peer-reviewed)abstract
- Silicon–carbon–nitride (Si–C–N) thin films were deposited by reactive magnetron co-sputtering of C and Si targets in a mixed Ar/N2 discharge. Films were grown to a thickness of more than 0.5 μm on graphite and Si(001) substrates held at a negative floating potential of −35 V, and substrate temperature between 100 and 700°C. The total pressure was constant at 0.4 Pa (3 mtorr), and the nitrogen fraction in the gas mixture was varied between 0 and 100%. As-deposited films were analyzed with respect to composition, state of chemical bonding, microstructure, mechanical properties, and wetting behavior by Rutherford backscattering spectroscopy (RBS), energy dispersive spectroscopy (EDS), X-ray photoelectron spectrometry (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nanoindentation and contact angle measurements, respectively. Depending on the deposition condition, ternary SixCyNz films within the composition range 1≤x≤34 at.%, 34≤y≤81 at.%, and 16.5≤z≤42 at.% were prepared with a textured, amorphous-to-graphite-like microstructure. For Si–C–N films with low Si content, C---C, C---N and Si---C bonds were present. At higher Si content, N preferentially bonds to Si, while less C---N bonds were observed. Films containing more than 12 at.% of Si contained widely dispersed crystallites, 2–20 nm in diameter. Incorporation of a few at.% Si resulted in a dramatic reduction of the film surface energy compared to pure CN films. The measured contact angles using distilled water and glycerol liquids were for some films comparable with those on a polytetrafluoroethylene (PTFE), Teflon® surface. The hardness of Si–C–N films could be varied over the range 9–28 GPa.
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| 7. |
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| 8. |
- Hellgren, Niklas, et al.
(author)
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Fullerene-like B C N thin films a computational andexperimental study
- 2004
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In: Materials Science and Engineering B. - : Elsevier. ; 113:3, s. 242-247
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Journal article (peer-reviewed)abstract
- Ab initio calculations show that the energy cost for incorporating lattice defects such as pentagons and heptagons is significantly reduced for BCN compared to BN, thus promoting bending of basal planes in these compounds. Boron–carbon–nitride (Bsingle bondCsingle bondN) thin films with a fullerene-like (FL) microstructure were then deposited by dual cathode magnetron sputtering from C and B4C targets. Up to 1 μm thick films were grown at a total gas pressure of 3 mTorr (0.4 Pa) in varying Ar/N2 ratios, and substrate temperatures between 225 and 350 °C. Compositional and microstructural studies were performed using RBS, SEM and HREM, respectively. Depending on the deposition condition, ternary BxCyNz films with fullerene-like microstructure could be prepared in agreement with the calculations within the composition range 0 ≤ x ≤ 53, 15 ≤ y ≤ 62, and 24 ≤ z ≤ 50 at.%. Fullerene-like structures also tend to form at lower temperatures in the case of BCN compared to CN. Nanoindentation measurements show that all BxCyNz films exhibited a highly elastic response independent of elemental composition. In addition, the calculations suggest a driving force for C and BN phase separation.
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| 9. |
- Johansson, Mats P., 1965-
(author)
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Growth and microstructure of reactive sputter deposited boron nitride : carbon (BN:C) thin films
- 1995
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Licentiate thesis (other academic/artistic)abstract
- Growth, microstructure and mechanical properties of boron nitride: carbon (BN:C) have been studied in films prepared by reactive r.f. diode sputter deposition as well as by reactive unbalanced d.c. magnetron (UBM) sputter deposition of low resistivity boron carbide (B4C) targets. Due to the fäet that d.c. glow discharges offers a better control of the important growth parameters such as particle flux and energy distribution in both neutral and ionized states at the substrate as compared to r.f. methods, fundamental growth and plasma studies were in some detail performed in the UBM sputtering system.Films were prepared with three characteristic phase compositions; cubic c-BN:C, hexagonal (turbostratic-like) h-BN:C and a mixtures of these on Si (001) substrates. The same phase compositions were obtained in both deposition techniques. While keeping the B/N ratio close to unity, the formation of BN:C phases were mainly correlated to the energy and flux of impinging ions towards the negatively d.c. biased substrate. A c-BN:C phase formation was typically found in mixed c-BN:C and h-BN:C films prepared at high ion-to-neutral flux ratios (UBM: Ji/Jn ~24), within a narrow range in ion energies (UBM: 85 eV < Ei < 135 eV) and at low process temperatures <250 °C. However, almost single phase c-BN:C (~80 % of sp3-bonded B-N) was obtained at deposition conditions of high ion flux (UBM: Ji/Jn ~24) and low ion energy (UBM: Ei = 110 eV) whereas films deposited at much lower ion energy or at a lower ion fluxes contained exclusively h-BN:C. Also, c-BN:C films revealed a BN:C film phase evolution sequence from an initial amorphous BN:C layer followed by a highly oriented h-BN:C layer with the c-axis parallel to the film surface, to a c-BN:C layer exhibiting a (110)preferred orientation. Furthermore, as-deposited films contained 5 - 20 at% of C that was found to decrease with increasing volume fraction of c-BN:C and also with increasing J/Jn. Chemical sputtering of volatile CN species is suggested for the reduction of C in BN:C films. Nevertheless, the C in c-BN:C films is mainly present as C-C and B-C bonds.Unnoticed the presence of C, cubic phase BN:C films are shown to be formed at deposition conditions not included in the present models of c-BN growth. For example, in terms of momentum transfer, values of 200 - 250 (eV emu)% have been reported to be required for the synthesis of c-BN whereas in this study an order of magnitude higher values were found. The results thus point at an extended deposition window for cubic phase formation, with potential for using further reduced ion energies such that intrinsic compressive stress in BN can be minimized.Finally, the mechanical properties of randomly- and highly-oriented h-BN:C as well as of c-BN:C films were studied and compared to the uncoated Si substrate. Although all coated substrates showed an increased stiffness, the maybe most interesting properties were found in the highly oriented h-BN:C films with the c-axis parallel to the film surface. These films showed a predominantly elastic behaviour exhibiting an elastic recovery as high as 82% indicating high hardness values. The improved hardness and elasticity may be explained by the apparent microstructure with buckling of the hexagonal basal planes. This structure is proposed to correspond to a three dimensional strongly covalently bonded network of BN:C, similar to what has been reported for CNx films.
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| 10. |
- Johansson, Mats P., 1965-
(author)
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Reactive Sputtering of Cubic-Phase BN:C and Nanostructured B-N-C Films : Growth, Microstructure, and Mechanical Properties
- 1998
-
Doctoral thesis (other academic/artistic)abstract
- Synthesis, structure, and mechanical property related issues in the carbon-containing boron nitride (BN:C) system have been studied. Magnetron sputtering, comprising a B4C target in mixed Ar-N2 discharges and deposition parameters of low ion energy, high ion-to-neutral flux ratio, and substrate temperatures <350 °C were employed for growth. Transmission electron microscopy and electron energy loss spectroscopy (EELS) served as the mainstructure evaluation tools, while nanoindentation experiments were used for mechanical property evaluation.Studies of the growth process as a function of partial pressure of nitrogenin the gas mixture revealed first a saturation of the nitrogen on the target whereas at slightly higher PN2 values the overall system is nitrided. This effect was ascribed to the relatively low enthalpy of compound formation of BN. Furthermore, by the use of an internal solenoid coil, the plasma density and hence the ion flux impinging on the growing film could be increased by more than one order of magnitude, resulting in a maximum ion-to-condensing atom flux ratio of ~24. At these conditions, i.e., with a saturation of the nitrogenin corporation frequency on the growth surface and a high flux ratio, growth of cubic-phase c-BN:C was demonstrated at ion-energies as low as 110 eV. This opens a new process window for c-BN phase formation at conditions not accounted for in the prevailing mechanistic models of momentum transfer.The system exhibits a phase evolution sequence of textured (hexagonal)h-BN:C prior to the nucleation and growth of crystallographically oriented cBN:C. The h-BN:C material obtained at intermediate flux-ratios and floating potential exhibits interesting mechanical properties of extreme elasticity and a structure consisting of curved and buckled basal planes similar to what previously have been reported in fullerene-like CNx films. Growth of CNx/BN:C multilayers was demonstrated by sequential sputtering from B4C and graphite targets, respectively, in mixed Ar-N2 atmospheres. They exhibit similar structure as the single-layer films, but do offer additional means for mechanical property design including strengthening over the single-layer compounds.Results are presented to demonstrate the possibility of using sputter deposition technique to synthesize CNx and template-synthesized B-N-C tubular nanostructures, which promises important advances to tailor the structure (dimension and shape) and number density of various types of nanostructures.Finally, an immiscibility between BN and C(N) in magnetron sputtered graphitic layered B-N-C materials was established by EELS. Nitrogen-rich films exhibited predominantly B-N and C-N type of bonds whereas films prepared with a much lower nitrogen concentration also revealed B-C bonds. Thus, magnetron discharge conditions at low temperature is a promising approach to produce B-N, C-N and B-C type of bonds for controlling the chemical composition of nanostructures in the B-N-C ternary system.
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| 11. |
- Landälv, Ludvig, 1982-, et al.
(author)
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Structural evolution in reactive RF magnetron sputtered (Cr,Zr)2O3 coatings during annealing
- 2017
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In: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 131, s. 543-552
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Journal article (peer-reviewed)abstract
- Reactive RF-magnetron sputtering is used to grow Cr0.28Zr0.10O0.61 coatings at 500 degrees C. Coatings are annealed at 750 degrees C, 810 degrees C, and 870 degrees C. The microstructure evolution of the pseudobinary oxide compound is characterized through high resolution state of the art HRSTEM and HREDX-maps, revealing the segregation of Cr and Zr on the nm scale. The as-deposited coating comprises cc-(Cr,Zr)(2)O-3 solid solution with a Zr-rich (Zr,Cr)O-x. amorphous phase. After annealing to 750 degrees C tetragonal ZrO2 nucleates and grows from the amorphous phase. The ZrO2 phase is stabilized in its tetragonal structure at these fairly low annealing temperatures, possibly due to the small grain size (below 30 nm). Correlated with the nucleation and growth of the tetragonal-ZrO2 phase is an increase in hardness, with a maximum hardness after annealing to 750 degrees C, followed by a decrease in hardness upon coarsening, bcc metallic Cr phase formation and loss of oxygen, during annealing to 870 degrees C. The observed phase segregation opens up future design routes for pseudobinary oxides with tunable microstructural and mechanical properties. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 12. |
- Rogström, Lina, et al.
(author)
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Decomposition routes and strain evolution in arc deposited TiZrAlN coatings
- 2019
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In: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 779, s. 261-269
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Journal article (peer-reviewed)abstract
- Phase, microstructure, and strain evolution during annealing of arc deposited TiZrAlN coatings are studied using in situ x-ray scattering and ex situ transmission electron microscopy. We find that the decomposition route changes from nucleation and growth of wurtzite AlN to spinodal decomposition when the Zr-content is decreased and the Al-content increases. Decomposition of Ti0.31Zr0.24Al0.45N results in homogeneously distributed wurtzite AlN grains in a cubic, dislocation-dense matrix of TiZrN consisting of domains of different chemical composition. The combination of high dislocation density, variation of chemical composition within the cubic grains, and evenly distributed wurtzite AlN grains results in high compressive strains, -1.1%, which are retained after 3 h at 1100 degrees C. In coatings with higher Zr-content, the strains relax during annealing above 900 degrees C due to grain growth and defect annihilation. (C) 2018 Elsevier B.V. All rights reserved.
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| 13. |
- Rogström, Lina, et al.
(author)
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Wear behavior of ZrAlN coated cutting tools during turning
- 2015
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In: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 282, s. 180-187
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Journal article (peer-reviewed)abstract
- In this study we explore the cutting performance of ZrAlN coatings. WC:Co cutting inserts coated by cathodic arc evaporated Zr1-xAlxN coatings with x between 0 and 0.83 were testeciin a longitudinal turning operation. The progress of wear was studied by optical microscopy and the used inserts were studied by electron microscopy. The cutting performance was correlated to the coating composition and the best performance was found for the coating with highest Al-content consisting of a wurtzite ZrAlN phase which is assigned to its high thermal stability. Material from the work piece was observed to adhere to the inserts during turning and the amount of adhered material and its chemical composition is independent on the Al-content of the coating. (C) 2015 Elsevier B.V. All rights reserved.
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| 14. |
- Yang, Jie, et al.
(author)
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Thermally induced surface integrity changes of ground WC-Co hardmetals
- 2016
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In: 3RD CIRP CONFERENCE ON SURFACE INTEGRITY. - : Elsevier. ; , s. 91-94
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Conference paper (peer-reviewed)abstract
- Ground hardmetals are exposed to high temperatures during both processing (e.g. coating deposition) and use (e.g. as a cutting tool). However, studies on thermally induced changes of surface integrity are limited. Here we address this by means of FIB/FESEM and EBSD investigation, with special focus on the binder phase characterization. Our findings indicate that thermal treatment causes two main surface modifications. First, an unexpected microporosity appears in the binder within the subsurface layer when ground surfaces are heated. Second, the metallic phase underneath the ground surface experiences metallurgical changes, in terms of grain and crystallographic phase structures. The mechanisms responsible for these modifications of the binder are discussed in terms of grinding-induced and thermally-reversed phase transformation as well as recrystallization phenomena. We also note that no additional heat treatment related changes such as microcracking and carbide fragmentation in the subsurface layer, are discerned. (C) 2016 The Authors. Published by Elsevier B.V.
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