Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application

Superhard cutting tool materials were sintered in cBN–(Ti₃SiC₂–TiC) system via high pressure–high temperature method. Sintering was performed under the pressure 8 GPa in the 1400–2400 °C temperature range. The initial mixtures of three compositions were chosen with 90, 80 and 60 vol % cBN. The mixtu...

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Hauptverfasser: Kolabylina, T., Bushlya, V., Petrusha, I., Johansson, D., Ståhl, J.-E., Turkevych, V.
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Zitieren:Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application / T. Kolabylina, V. Bushlya, I. Petrusha, D. Johansson, J.-E. Ståhl, V. Turkevych // Сверхтвердые материалы. — 2017. — № 3. — С. 11-23. — Бібліогр.: 18 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
id nasplib_isofts_kiev_ua-123456789-160115
record_format dspace
spelling Kolabylina, T.
Bushlya, V.
Petrusha, I.
Johansson, D.
Ståhl, J.-E.
Turkevych, V.
2019-10-23T17:52:19Z
2019-10-23T17:52:19Z
2017
Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application / T. Kolabylina, V. Bushlya, I. Petrusha, D. Johansson, J.-E. Ståhl, V. Turkevych // Сверхтвердые материалы. — 2017. — № 3. — С. 11-23. — Бібліогр.: 18 назв. — англ.
0203-3119
https://nasplib.isofts.kiev.ua/handle/123456789/160115
621.9.025.7:621.762.5:661.657.5
Superhard cutting tool materials were sintered in cBN–(Ti₃SiC₂–TiC) system via high pressure–high temperature method. Sintering was performed under the pressure 8 GPa in the 1400–2400 °C temperature range. The initial mixtures of three compositions were chosen with 90, 80 and 60 vol % cBN. The mixtures were prepared by mixing cBN (1–3 μm) and Ti₃SiC₂–TiC (< 2 μm). It was found, that upon sintering, the compositions of the obtained samples differed from the initial mixtures in all cases as a result of chemical reactions. Microstructure observations, phase composition estimation, and mechanical properties of the obtained tool materials were carried out. The results indicate that both the varying cBN content and the applied sintering conditions have a direct effect on the structure, properties, and kinetics of reactions.
Надтверді матеріали системи cBN–(Ti₃SiC₂–TiC) при високому тиску і високій температурі. Спікання проводили при тиску 8 ГПа в температурному діапазоні 1400–2400 °С. Вихідні суміші трьох композицій були обрані з вмістом cBN 90, 80 і 60 % (за об’ємом). Суміші були приготовані шляхом змішування cBN (1–3 мм) и Ti₃SiC₂–TiC (< 2 мм). Було встановлено, що після спікання в результаті хімічних реакцій склад отриманих зразків відрізняється від складу вихідних сумішей. Проводили спостереження мікроструктури, оцінку фазового складу і механічних властивостей отриманих інструментальних матеріалів. Результати вказують на те, що різний зміст cBN і застосовані умови спікання чинять прямий вплив на структуру, властивості і кінетику реакцій.
Сверхтвердые инструментальные материалы системы cBN–(Ti₃SiC₂–TiC) были спечены при высоком давлении и высокой температуре. Спекание проводили при давлении 8 ГПа в температурном диапазоне от 1400 до 2400 °С. Исходные смеси трех композиций были выбраны с содержанием cBN 90, 80 и 60 % (по объему). Смеси были приготовлены смешиванием порошков cBN (1–3 мм) и Ti₃SiC₂–TiC (< 2 мм). Было установлено, что после спекания в результате химических реакций состав полученных образцов во всех случаях отличается от состава исходных смесей. Проводили наблюдения микроструктуры, оценка фазового состава и механических свойств полученных инструментальных материалов. Результаты указывают на то, что разное содержание cBN и применяемые условия спекания оказывают прямое влияние на структуру, свойства и кинетику реакций.
This work was co-funded by the European Union’s Horizon 2020 Research and Innovation Program under Flintstone2020 project (grant agreement No 689279). It is also a part of the strategic research program of the Sustainable Production Initiative SPI, involving cooperation between the Lund University and the Chalmers University of Technology. The author (TK) wishes to acknowledge the support provided by the Swedish Institute scholarship.
en
Інститут надтвердих матеріалів ім. В.М. Бакуля НАН України
Сверхтвердые материалы
Получение, структура, свойства
Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application
spellingShingle Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application
Kolabylina, T.
Bushlya, V.
Petrusha, I.
Johansson, D.
Ståhl, J.-E.
Turkevych, V.
Получение, структура, свойства
title_short Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application
title_full Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application
title_fullStr Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application
title_full_unstemmed Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application
title_sort superhard pcbn tool materials with ti₃sic₂ max-phase binder: structure, properties, application
author Kolabylina, T.
Bushlya, V.
Petrusha, I.
Johansson, D.
Ståhl, J.-E.
Turkevych, V.
author_facet Kolabylina, T.
Bushlya, V.
Petrusha, I.
Johansson, D.
Ståhl, J.-E.
Turkevych, V.
topic Получение, структура, свойства
topic_facet Получение, структура, свойства
publishDate 2017
language English
container_title Сверхтвердые материалы
publisher Інститут надтвердих матеріалів ім. В.М. Бакуля НАН України
format Article
description Superhard cutting tool materials were sintered in cBN–(Ti₃SiC₂–TiC) system via high pressure–high temperature method. Sintering was performed under the pressure 8 GPa in the 1400–2400 °C temperature range. The initial mixtures of three compositions were chosen with 90, 80 and 60 vol % cBN. The mixtures were prepared by mixing cBN (1–3 μm) and Ti₃SiC₂–TiC (< 2 μm). It was found, that upon sintering, the compositions of the obtained samples differed from the initial mixtures in all cases as a result of chemical reactions. Microstructure observations, phase composition estimation, and mechanical properties of the obtained tool materials were carried out. The results indicate that both the varying cBN content and the applied sintering conditions have a direct effect on the structure, properties, and kinetics of reactions. Надтверді матеріали системи cBN–(Ti₃SiC₂–TiC) при високому тиску і високій температурі. Спікання проводили при тиску 8 ГПа в температурному діапазоні 1400–2400 °С. Вихідні суміші трьох композицій були обрані з вмістом cBN 90, 80 і 60 % (за об’ємом). Суміші були приготовані шляхом змішування cBN (1–3 мм) и Ti₃SiC₂–TiC (< 2 мм). Було встановлено, що після спікання в результаті хімічних реакцій склад отриманих зразків відрізняється від складу вихідних сумішей. Проводили спостереження мікроструктури, оцінку фазового складу і механічних властивостей отриманих інструментальних матеріалів. Результати вказують на те, що різний зміст cBN і застосовані умови спікання чинять прямий вплив на структуру, властивості і кінетику реакцій. Сверхтвердые инструментальные материалы системы cBN–(Ti₃SiC₂–TiC) были спечены при высоком давлении и высокой температуре. Спекание проводили при давлении 8 ГПа в температурном диапазоне от 1400 до 2400 °С. Исходные смеси трех композиций были выбраны с содержанием cBN 90, 80 и 60 % (по объему). Смеси были приготовлены смешиванием порошков cBN (1–3 мм) и Ti₃SiC₂–TiC (< 2 мм). Было установлено, что после спекания в результате химических реакций состав полученных образцов во всех случаях отличается от состава исходных смесей. Проводили наблюдения микроструктуры, оценка фазового состава и механических свойств полученных инструментальных материалов. Результаты указывают на то, что разное содержание cBN и применяемые условия спекания оказывают прямое влияние на структуру, свойства и кинетику реакций.
issn 0203-3119
url https://nasplib.isofts.kiev.ua/handle/123456789/160115
citation_txt Superhard pcBN tool materials with Ti₃SiC₂ MAX-phase binder: structure, properties, application / T. Kolabylina, V. Bushlya, I. Petrusha, D. Johansson, J.-E. Ståhl, V. Turkevych // Сверхтвердые материалы. — 2017. — № 3. — С. 11-23. — Бібліогр.: 18 назв. — англ.
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fulltext ISSN 0203-3119. Сверхтвердые материалы, 2017, № 3 11 UDC 621.9.025.7:621.762.5:661.657.5 T. Kolabylina1, 2, *, V. Bushlya2, I. Petrusha1, D. Johansson2, J.-E. Ståhl2, V. Turkevich1, 1Bakul Institute for Superhard Materials, National Academy of Sciences of Ukraine, Kiev, Ukraine 2Division of Production and Materials Engineering, Lund University, Lund, Sweden *tetiana.kolabylina@chemie.tu-freiberg.de Superhard pcBN tool materials with Ti3SiC2 MAX-phase binder: structure, properties, application Superhard cutting tool materials were sintered in cBN–(Ti3SiC2–TiC) system via high pressure–high temperature method. Sintering was performed under the pressure 8 GPa in the 1400–2400 °C temperature range. The initial mixtures of three compositions were chosen with 90, 80 and 60 vol % cBN. The mixtures were prepared by mixing cBN (1–3 μm) and Ti3SiC2–TiC (< 2 μm). It was found, that upon sintering, the compositions of the obtained samples differed from the initial mixtures in all cases as a result of chemical reactions. Microstructure observations, phase composition estimation, and mechanical properties of the obtained tool materials were carried out. The results indicate that both the varying cBN content and the applied sintering conditions have a direct effect on the structure, properties, and kinetics of reactions. Keywords: pcBN, Ti3SiC2 MAX-phase, HPHT. INTRODUCTION The pcBN tool materials have found their applications in machining operations when cutting difficult-to-machine materials and hardened steels [1–3]. ISO 1832:2012 [4] differentiates pcBN materials into grades with low-cBN and high-cBN contents with respective application areas of finish machining and roughing or interrupted cuts. Low-cBN grades often contain TiC, Ti(C,N) or TiN binders [5]. Alternative binding phases, which can handle high temperatures and high level of chemical and abrasive wear, are continuously sought for. First discovered at 60-th layered ternary carbides (so-called MAX-phases1) came back under the spot last decades [6]. Being built of carbide blocks they are still not the same with normal carbides and fall under an intermediate class between metals and ceramics. What makes them behave differently from normal carbides is their structure, which determinates their ability to withstand elevated temperatures, tolerate high stresses, and possess high compactibility of their powder products. Preliminary studies by the authors have shown that compaction 1 Layered, hexagonal carbides and nitrides with general formula: Mn+1AXn, (MAX phases) where n = 1 to 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA, or groups 13 and 14) element and X is either carbon and/or nitrogen possess- ing with whole set of needed properties. © T. KOLABYLINA, V. BUSHLYA, I. PETRUSHA, D. JOHANSSON, J.-E. STÅHL, V. TURKEVYCH, 2017 www.ism.kiev.ua/stm 12 rate for commercially available Ti3SiC2 and Ti2AlC MAX-phases is the highest, slightly below their decomposition temperature. In attempts to introduce these positive MAX-phase properties into tool materi- als many research studies have involved sintering of superhard tool materials based on diamond or cubic boron nitride with commercially available MAX-phases [7–13]. Multiple sintering techniques were used for production of cutting tool materials. Starting from pressureless sintering [8], hot pressing at pressure 20–35 MPa [13], and up to high pressure–high temperature (HPHT) techniques synthesis [9–11]. In these cases Ti3SiC2 MAX-phase was in-situ sintered from starting Ti, Si, SiC, TiC powders together with superhard diamond or cBN filler. Effect of the cBN filler amount on sintering conditions was investigated. For a diamond filler, it was found that the increased diamond content significantly promotes a Ti3SiC2 formation [13]. In many cases a partial reverse transformation of diamond and cBN were observed because superhard phases become unstable under conditions required for the efficient MAX-phase sintering [8, 12, 14]. Alternatively, sintering can involve preliminary obtained MAX-phase used as a binder in order to solve the mentioned reverse transformation difficulties. In such a case both MAX-phase and superhard phase need to be preserved while sintering the cutting tool material. Decomposition of MAX-phase needs to be prevented. High pressure sintering was found to provide a solution due to reduced requirements to sintering temperatures, which decreases by approx. one hundred degrees [14] in comparison to other techniques. Additionally, sintering time is significantly shortened. The application of high pressure may activate decompositions of certain MAX- phases [15]. The use of such MAX-phases as precursors for pcBN tool materials results in multiphase composite material due to chemical reactions. For example in the case of Ti3SiC2, depending on sintering conditions TiB2, TiC, TiN, SiB3, and SiC phases are expected [9, 10, 16]. This phase composition is somewhat similar to cBN–TiC and cBN–TiN commercial materials. At the same time two main differences can be expected. First, the observed decomposition of Ti3SiC2 is ex- pected to result in fine-grained microstructure. Second, this microstructure pos- sesses a multi-phase composition (5–6 phases), where all phases have high hard- ness. The aim of this study is to estimate the influence of the sintering conditions and binder content on the structure and properties of the cBN–Ti3SiC2–TiC composite. The microstructure, phase composition, and phase stoichiometry as well as the microhardness, fracture toughness, density, and tool material performance are established. EXPERIMENTAL PROCEDURE Mixture preparation Sintering of cutting tool materials both in high-cBN and low-cBN systems was intended. The compositions of the initial mixtures are listed in Table 1. cBN powder with grain sizes of 1–3 μm was admixed with Ti3SiC2 and TiC powders. Ti3SiC2 powder was obtained by milling commercial Maxtal 312 ceramic material down to the fineness of 0.2–2 μm. Small amount of graphite and approximately 30 vol % of TiC have been identified in the milled products. ISSN 0203-3119. Сверхтвердые материалы, 2017, № 3 13 Table 1. The compositions of the initial mixtures Mixture Initial components Volume ratio 1 cBN:Ti3SiC2:TiC 90:6:4 2 cBN:Ti3SiC2:TiC 80:12:8 3 cBN:Ti3SiC2:TiC 60:24:16 Premixing was performed by a triple dry co-mixing of cBN and Ti3SiC2–TiC powders through sieves with 20 μm cell size. The final mixing involved wet (iso- propanol) mixing in a tumbler mixer in the presence of ZrO2 grinding bodies for 12 h. Each mixture was quality checked via SEM, XRD and EDX techniques. Sintering of samples The samples were sintered in a toroid type high-pressure apparatus HPA-30 [17] at the pressure of 8 GPa. A sintering temperature was selected as a variable and ranged within 1400–2400 °C with step of 200 °C. Upon stabilization of the pressure the sample was heated up to a predefined temperature within 5 s. The duration of the heating cycle at a constant temperature was 45 s, then the power in the circuit was decreased within 10 s and the pressure released. The obtained samples were ground to RNGN090300T cutting insert shape. Samples characterization Prior to microscopy and indentation studies the samples were polished with diamond suspension (1 and 9 μm) and silica colloidal solution (0.04 μm). FEI NanoLab 600 dual beam microscope was used to analyze the microstructure. A JSM-6700F microscope was used for the energy dispersive X-ray (EDX) analy- sis (SDD X-Maxn EDX system, Oxford Instruments). XRD analysis of materials was done on a STOE Darmstadt diffractometer with CuKα source. The hardness of the tool materials was measured with Vickers and Knoop indenters at a load of 4.9 N on an Ernst Leitz Wetzlar microhardness tester. Fracture toughness was es- timated via the indentation technique [18] at 300 N load. The density was defined via hydrostatic weighing. Cutting performance Cutting performance was estimated through hard turning tests when dry machining cold work tool steel Vanadis 4E (HRC 59). All tests involved constant conditions: cutting speed vc = 150 m/min, feed f = 0.1 mm/rev, depth-of-cut ap = 0.2 mm. RESULTS Mixing The mixtures were found to have different mixing quality. For example, in mix- ture with 90 vol % cBN the majority of the Ti3SiC2–TiC binder (10 vol %) was agglomerated. Sizes of the agglomerates were in the range of 5–15 μm, while the original binder grain size was below 2 μm. The agglomeration of Ti3SiC2–TiC was not observed in the mixtures with 80 and 60 vol % of cBN. For all mixtures an additional reduction of grain sizes due to grinding and flaking of MAX-phase was present. www.ism.kiev.ua/stm 14 All three prepared mixtures appeared to be contaminated by the presence of small (∼ 0.2 μm) ZrO2 inclusions as detected via EDX. The source of such ZrO2 contamination is due to milling of zirconia grinding bodies themselves. The amount, size and dispersion of zirconia inclusions was approximately the same for all prepared mixtures. The amount of ZrO2 was not sufficient to be detected with XRD (Fig. 1). While sintering no reactions between ZrO2 inclusions and surrounding binder neither with cBN materials were observed. Therefore, the presence of ZrO2 was not considered further on in the study. 10 20 30 40 50 60 70 80 90 2θ, deg 0 0.2 0.4 0.6 0.8 1.0 –cBN –Ti 3 SiC 2 –TiC –Graphite    In te ns it y, a rb . u ni ts              Fig. 1. XRD pattern of the composition of a powder mixture with 60 vol % cBN. Phase composition of sintered samples Phase compositions of the sintered samples were determined by the XRD. It was found that the phase compositions of all obtained samples were different from the compositions of the initial mixtures. The main initial binder component Ti3SiC2 is not observed in the XRD patterns (Fig. 2), despite the presence of TiC in the initial mixture, which inhibits the Ti3SiC2 decomposition [13]. Also several new phases were detected (see Fig. 2). 30 40 50 60 70 80 0 0.5 1.0 1.5 2.0 2.5 –TiC –SiC –Ti(C,N) –cBN ♦–TiB2 ♣–TiSi2 2θ, deg   ♦ ♦  ♦ ♦♦  In te ns it y, a rb . u ni ts 1 ♦    ♣  2 3 4 5 6 Fig. 2. XRD pattern for 60 vol % cBN samples sintered under different HPHT conditions: 1400 (1), 1600 (2), 1800 (3), 2000 (4), 2200 (5), 2400 (6) °C. ISSN 0203-3119. Сверхтвердые материалы, 2017, № 3 15 Some of these new phases are determined explicitly, like TiSi2, SiC, and TiB2. The presence of Ti(C,N) is also confirmed by the XRD, yet the exact stoichiometry described as TiCxNy changes with the temperature. More data on the stoichiometry can be obtained through EDX; however, the accuracy for carbon and nitrogen light elements is relatively low for this method. It is worth noting that the decomposition of TiSi2 still observed at 1400 °C (see Fig. 2) does not result in the formation of Si-containing phases up to 2000 °C. This Si containing phase is SiC. Its low intensity SiC maximum has been detected with XRD only for 60 vol % cBN sample. The EDX data in Fig. 3 confirm the XRD observations by indicating the decomposition of Ti3SiC2 at 1400 °C to form TiSi2, TiC, and TiCxNy. The majority of TiSi2 grains were found in the central region of Ti3SiC2 decomposition and reaction products. 1 2 3 4 5 6 Fig. 3. EDX line-scan data for 80 vol % cBN sample sintered under p = 8 GPa and T = 1400 °C: OKα1 (1), NKα1_2 (2), SiKα1 (3), TiKα1 (4), BKα1_2 (5), CKα1_2 (6). As is seen from Fig. 4, the situation changes at the higher sintering temperature of 2400 °C. The EDX line-scan data indicate the formation of SiC also in the cen- tral region of the Ti3SiC2 decomposition area. It also shows that a nitrogen content in the Ti(C,N) phase found on the sides of SiC has increased the N concentration compared to the case of 1400 °C. Quantitative point analysis data presented in Fig. 5 indicate that spectrum 31 corresponds to SiC, even though silicon carbide was not observed with the XRD. Data for spectrum 32 confirm the presence of TiB2 also found with the X-ray dif- fraction. Additionally, the EDX data indicate the presence of oxygen, which in the aver- age corresponds to approx. 2 at % for this sample sintered at 2400 °C. Similar analysis for other samples sintered at different temperatures shows that higher oxygen amount of up to 4 at % was present for T = 1400 to 1800 °C. For the entire temperature range above 1800 °C the oxygen content decreases almost twice. Possible reactions between the initial components of the mixture under given sintering conditions have already been reported [6, 13]: TiC + Ti3SiC2 → TiC + TixCy + TiSi2; (1) cBN + TiC + TixCy + TiSi2 → cBN + TiC + TixCy + SiC + TizCv(N) + TiB2 + Siamorf . (2) www.ism.kiev.ua/stm 16 1 2 3 4 5 Fig. 4. EDX line-scan for 90 vol % cBN sample sintered under p = 8 GPa and T = 2400 °C: NKα1_2 (1), SiKα1 (2), TiKα1 (3), BKα1_2 (4), CKα1_2 (5). 29 30 31 32 33 34 0 10 20 30 40 50 Spectrum number at % B C N O Si Ti Fig. 5. EDX point analysis for the region shown in Fig. 4. In our case, the list of the initial components is slightly wider than the one for reaction (2) due to the presence of minor amounts of graphite in the original mix- tures. ISSN 0203-3119. Сверхтвердые материалы, 2017, № 3 17 Only very weak reflections of the SiC phase were found in the XRD (see Fig. 2). The TiB2 and SiC presence was confirmed via the EDX and XRD (Fig. 5). The presence of amorphous silicon, however, was not confirmed in this study. The EDX mapping presented in Fig. 6 shows that even at high sintering temperature TiSi2 phase remains stable but not seen using the XRD, as it most likely has amorphous nature. Figure 6 also confirms a high oxygen content in the material microstructure. The XRD does not show the presence of oxide phases and this indicates a dissolution of surface oxygen into the binder phases [6]. a b c d e f Fig. 6. EDX mapping of the sample with 80 vol % of cBN in the initial mixture (p = 8 GPa and T = 2200 °C): BKα1_2 (a), CKα1_2 (b), TiKα1 (c), OKα1 (d), NKα1_1 (e), SiKα1 (f). Microstructure The formation of a matrix for sintered samples is determined by the compositions of the initial mixtures. 90 vol % of cBN samples received a predominantly cBN matrix with separate inclusions of products of Ti3SiC2 decomposition and reaction. In the case of 60 vol % cBN sample the matrix is fully realized through the Ti3SiC2 decomposition and reaction products described in the previous section. An intermediate situation was observed for 80 vol % cBN www.ism.kiev.ua/stm 18 samples. However, the main influence on the obtained microstructure was observed from the sintering temperature. The general tendency for the influence of sintering temperature follows the next pattern. In the temperature range of 1400–1600 °C the decomposition of Ti3SiC2 leads to the formation of products, which react with cBN; that is visible as rounding of cBN grains. At 1800 °C the initial sintering between cBN grains was observed, while at 2000 °C the formation of nano- and micro-pores appears on the grain boundaries. At 2200–2400 °C the pores grow in size and have a tendency to move to triple junctions (Fig. 7). Neither total recrystallization, nor grain growth or grain coarsening was detected for cBN phase even at 2400 °C. Fig. 7. SEM image of the microstructure for the sample with 80 vol % cBN sintered at T = 2400 °C. The sintering temperature has more prominent effect on the Ti3SiC2 binder component than on the cBN phase. Morphology of this binder component changes in the following way: the MAX-phase decomposition in the region of T = 1400– 1600 °C results in the formation of submicron grains (Fig. 8) of phases described in the earlier sections. At T = 1600–1800 °C the recrystallization and grain growth processes begin. Fig. 8. SEM image of the microstructure for the 60 vol % cBN sample sintered at T = 1400 °C. ISSN 0203-3119. Сверхтвердые материалы, 2017, № 3 19 At temperatures above 1800 °C the microstructural transformation of the decomposition and reaction products of Ti3SiC2 MAX-phase looks to be complete where a clear separation of TiC, TiB2, SiC, Ti(C,N) phases is observed (Fig. 9). This is accompanied by the formation and growth of pores on triple junctions. It should be mentioned that some of the spheroidal grains, as shown in Fig. 8, were present in the binder even at 2400 °C. Decomposition and reaction products of Ti3SiC2 demonstrate the start of the recrystallization at temperatures by approx. 200–300 °C earlier. Fig. 9. SEM image of the microstructure for the 60 vol % cBN sample sintered at T = 2000 °C. Being sintered above 1800 °C, only samples with lowest cBN content show density decreasing (Fig. 10). This can be related to the formation of multiple pores in the microstructure, and also to volume changes due to the formation of new phases as a result of a complete decomposition the (see Fig. 9). 1400 1600 1800 2000 2200 2400 3.50 3.55 3.60 3.65 3.70 3.75 3 2 1 Sintering temperature, °C D en si ty , g /c m 3 Fig. 10. Average density variations for different sintering temperatures and cBN content: 60 (1), 80 (2), 90 (3) vol % cBN. The microhardness and fracture-toughness changes closely follow (Figs. 11 and 12) the behavior of the sample density. www.ism.kiev.ua/stm 20 1400 1600 1800 2000 2200 2400 15 20 25 30 35 3 2 1 Sintering temperature, °C H V , GPa Fig. 11. Microhardness variations for different sintering temperatures and cBN contents: 60 (1), 80 (2), 90 (3) vol % cBN. 1400 1600 1800 2000 2200 2400 3 4 5 6 7 8 9 10 3 2 1 K Ic , M P a⋅ m 1/ 2 Sintering temperature, °C Fig. 12. Fracture toughness variations for different sintering temperatures and cBN contents: 60 (1), 80 (2), 90 (3) vol % cBN. It shows that for high-cBN samples the hardness does not change significantly with the sintering temperature but for low-cBN samples it is decreasing. This is most likely to be related to the formation of porosity in the sample microstructure. The indentation fracture toughness for the low-cBN sample is the lowest among the obtained cutting tool materials. Cutting performance A series of samples with the highest mechanical properties were selected for the estimation of their application performance in machining. The results of the cutting tests, alongside with respective mechanical properties, are listed in Table 2. The results show that the materials with the lowest cBN content (60 vol % cBN) and with the highest cBN content (90 vol % cBN) exhibit the best perform- ance in terms of wear resistance to the formation of a crater on the rake face (KT) and flank wear (VB). More descriptive information on the correlation between mechanical properties and machining performance for samples with 60, 80, and 90 vol % cBN sintered at 2000 °C is shown in Figs. 13 and 14. ISSN 0203-3119. Сверхтвердые материалы, 2017, № 3 21 Table 2. Results of the cutting test for samples having the best mechanical properties cBN content, vol % T, °C HV, GPa KIc, MPa·m1/2 KT, μm VB, μm 80 1600 30.3 6.4 55 157 90 2000 33.8 5.7 58 190 80 2000 30.0 6.0 83 269 60 2000 21.0 4.9 70 183 90 2400 35.5 6.0 44 167 90 2200 33.8 6.7 – – 90 80 60 5.0 5.5 6.0 20 25 30 35 H V , G P a cBN content, vol % K Ic , M P a⋅ m 1/ 2 1 2 Fig. 13. Microhardness (1) and fracture toughness (2) for samples sintered at 2000 °C. 90 80 60 60 70 80 cBN content, vol % K T , μm 180 200 220 240 260 V B , μm 1 2 90 Fig. 14. Crater depth KT (1) and flank wear VB (2) for samples sintered at 2000 °C. These diagrams show that the fracture toughness, which more closely reflects microstructural transformations and the present defects, is more indicative of tool performance in hard turning. CONCLUSIONS This study addresses the HPHT sintering of superhard composite materials in the system of cubic boron nitride with Ti3SiC2 MAX-phase binder. Three systems www.ism.kiev.ua/stm 22 of varying cBN content sintered in the temperature range of 1400–2400 °C are studied. The mechanisms of the decomposition of Ti3SiC2 at the temperature of sintering govern the formation of binder matrices for the studied composites. The decomposition products were found to enter into the reactions with the superhard cBN phase. The following products that create the binder matrix were found via XRD and EDX analyses: TiC, Ti(C,N), SiC, TiB2. Additionally, in the lower temperature range of 1400–1600 °C the products of incomplete decomposition, such as TiSi2 and Si were also observed. The formation of pores in triple junctions was observed for all samples, yet the most intensive formation was found for low cBN (60 vol %) content samples. This was associated with volumetric change ob- served when intermediate decomposition products were transformed into Ti(C,N), SiC, and TiB2–based matrix. The best combination of mechanical properties for cBN–Ti3SiC2–TiС fine- grained tool materials was obtained for the sintering temperature range of T = 1800–2200 °C. This work was co-funded by the European Union’s Horizon 2020 Research and Innovation Program under Flintstone2020 project (grant agreement No 689279). It is also a part of the strategic research program of the Sustainable Production Initiative SPI, involving cooperation between the Lund University and the Chalmers University of Technology. The author (TK) wishes to acknowledge the support provided by the Swedish Institute scholarship. Надтверді матеріали системи cBN–(Ti3SiC2–TiC) при високому тиску і високій температурі. Спікання проводили при тиску 8 ГПа в температурному діапазоні 1400–2400 °С. Вихідні суміші трьох композицій були обрані з вмістом cBN 90, 80 і 60 % (за об’ємом). Суміші були приготовані шляхом змішування cBN (1–3 мм) и Ti3SiC2–TiC (< 2 мм). Було встановлено, що після спікання в результаті хімічних реакцій склад отри- маних зразків відрізняється від складу вихідних сумішей. Проводили спостереження мік- роструктури, оцінку фазового складу і механічних властивостей отриманих інструмен- тальних матеріалів. Результати вказують на те, що різний зміст cBN і застосовані умови спікання чинять прямий вплив на структуру, властивості і кінетику реакцій. Ключові слова: pcBN, Ti3SiC2 MAX-фаза, HPHT. Сверхтвердые инструментальные материалы системы cBN–(Ti3SiC2– TiC) были спечены при высоком давлении и высокой температуре. Спекание проводили при давлении 8 ГПа в температурном диапазоне от 1400 до 2400 °С. Исходные смеси трех композиций были выбраны с содержанием cBN 90, 80 и 60 % (по объему). Смеси были приготовлены смешиванием порошков cBN (1–3 мм) и Ti3SiC2–TiC (< 2 мм). Было установлено, что после спекания в результате химических реакций состав полученных образцов во всех случаях отличается от состава исходных смесей. Проводили наблюдения микроструктуры, оценка фазового состава и механических свойств полученных инстру- ментальных материалов. Результаты указывают на то, что разное содержание cBN и применяемые условия спекания оказывают прямое влияние на структуру, свойства и кинетику реакций. Ключевые слова: pcBN, Ti3SiC2 MAX-фаза, HPHT. 1. Haplin T., Byrne G., Barry J., Ahearne E. The performance of polycrystalline cubic boron nitride tools in continuous, semi-interrupted, and interrupted hard machining // J. Eng. Manuf. – 2009. – 223. – P. 947–953. 2. Bushlya V. M., Gutnichenko O. A., Zhou J. M. et al. Tool wear and tool life of PCBN, binder- less cBN and wBN–cBN tools in continuous finish hard turning of cold work tool steel // J. Superhard Mater. – 2014. – 36, N 1. – P. 49–60. ISSN 0203-3119. Сверхтвердые материалы, 2017, № 3 23 3. Bushlya V. Gutnichenko O., Zhou J. et al. Effects of cutting speed when turning age hardened Inconel 718 with PCBN tools of binderless and low-CBN grades // Mach. Sci. Technol. – 2013. – 17, N 4. – P. 497–523. 4. ISO 1832:2012. Indexable inserts for cutting tools – Designation. 5. Barsoum M. W., Brodkin D., El-Raghy T. Layered machinable ceramics for high temperature applications // Scripta Materialia. – 1997. – 36, N 5. – P. 535–541. 6. Angseryd J., Elfwing M., Olsson E., Andrén H.-O. Detailed microstructure of a cBN based cutting tool material // Int. J. Refract. Met. Hard Mater. – 2009. – 27, N 2. – P. 249–255. 7. Zhu Y., Jia J., Zhou A. et al. Sintering of Ti3SiC2 ceramics by hot press from commercial powders // Proc. 5th Int. Congress on Ceramics (ICC5), Beijing, China, 17–21 August, 2014, publ. in Key Eng. Mater. – 2014. – 655. – P. 68–71. 8. Li Z., Zhou A., Li L. et al. Synthesis and characterization of novel Ti3SiC2–cBN composites // Diamond Relat. Mater. – 2014. – 43. – P. 29–33. 9. Benko E., Klimczyk P., Mackiewicz S. et al. cBN–Ti3SiC2 composites // Diamond Relat. Mater. – 2004. – 13, N 3. – P. 521–525. 10. Xue Y., Qin J., Zhang X. et al. In situ high pressure synthesis of cBN-based composites // Funct. Mater. Lett. – 2014. – 7, N 4, art. 1450040. 11. Mu Y., Guo J., Liang B., Wang Q. Rapid fabrication of the Ti3SiC2 bonded diamond compos- ite by spark plasma sintering // Int. J. Refract. Met. Hard Mater. – 2011. – 13. – P. 397–400. 12. Mu Y.-C., Han J.-X., Liu J.-L. et al. Microstructure of Ti3SiC2/diamond composite materials prepared by hot-pressing // Fenmo Yejin Cailiao Kexue yu Gongcheng/Mater. Sci. Eng. Pow- der Metal. – 2015. – 1. – P. 139–143. 13. Rampai T., Lang C. I., Sigalas I. Investigation of MAX phase/c-BN composites // Ceram. Int. – 2013. – 39, N 5. – P. 4739–4748. 14. Zhou A., Li Z., Li L. et al. Preparation and microstructure of Ti3SiC2 bonded cubic boron nitride superhard composites // Kuei Suan Jen Hsueh Pao/J. Chinese Ceram. Soc. – 2014. – 42, N 2. – P. 220–224. 15. Qin J., He D. Phase stability of Ti3SiC2 at high pressure and high temperature // Ceram. 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De gemaakte PDF-documenten kunnen worden geopend met Acrobat en Adobe Reader 5.0 en hoger.) /NOR <FEFF004200720075006b00200064006900730073006500200069006e006e007300740069006c006c0069006e00670065006e0065002000740069006c002000e50020006f0070007000720065007400740065002000410064006f006200650020005000440046002d0064006f006b0075006d0065006e00740065007200200066006f00720020007500740073006b00720069006600740020006100760020006800f800790020006b00760061006c00690074006500740020007000e500200062006f007200640073006b0072006900760065007200200065006c006c00650072002000700072006f006f006600650072002e0020005000440046002d0064006f006b0075006d0065006e00740065006e00650020006b0061006e002000e50070006e00650073002000690020004100630072006f00620061007400200065006c006c00650072002000410064006f00620065002000520065006100640065007200200035002e003000200065006c006c00650072002000730065006e006500720065002e> /PTB <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> /SUO <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> /SVE <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> /ENU (Use these settings to create Adobe PDF documents for quality printing on desktop printers and proofers. Created PDF documents can be opened with Acrobat and Adobe Reader 5.0 and later.) /RUS () >> /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ << /AsReaderSpreads false /CropImagesToFrames true /ErrorControl /WarnAndContinue /FlattenerIgnoreSpreadOverrides false /IncludeGuidesGrids false /IncludeNonPrinting false /IncludeSlug false /Namespace [ (Adobe) (InDesign) (4.0) ] /OmitPlacedBitmaps false /OmitPlacedEPS false /OmitPlacedPDF false /SimulateOverprint /Legacy >> << /AddBleedMarks false /AddColorBars false /AddCropMarks false /AddPageInfo false /AddRegMarks false /ConvertColors /NoConversion /DestinationProfileName () /DestinationProfileSelector /NA /Downsample16BitImages true /FlattenerPreset << /PresetSelector /MediumResolution >> /FormElements false /GenerateStructure true /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles true /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /NA /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /LeaveUntagged /UseDocumentBleed false >> ] >> setdistillerparams << /HWResolution [2400 2400] /PageSize [612.000 792.000] >> setpagedevice