Extending the SHS combustion concentration limits in Ti + C + Fe powder mixtures by preliminary mechanical activation

Extending the SHS combustion concentration limits in Ti + C + Fe powder mixtures by preliminary mechanical activation

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Materials Today: Proceedings xxx (xxxx) xxx

Contents lists available at ScienceDirect

Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr

Extending the SHS combustion concentration limits in Ti + C + Fe powder mixtures by preliminary mechanical activation A.V. Baranovskiy a,b,⇑, G.A. Pribytkov a, M.G. Krinitcyn a,b, V.V. Homyakov b, G.O. Dankovcev b a b

Institute of Strength Physics and Materials Science, Akademicheskii pr., 2/4, Tomsk 634055, Russia National Research Tomsk Polytechnic University, Lenin pr.,30, Tomsk 634050, Russia

a r t i c l e

i n f o

Article history: Received 4 November 2019 Received in revised form 15 December 2019 Accepted 20 December 2019 Available online xxxx Keywords: Mechanical activation Metal matrix composites (MMC) Titanium carbide Self-propagating high temperature synthesis Combustion limits

a b s t r a c t Preliminary mechanical activation of titanium, carbon black, high speed steel (HSS) and high chromium cast iron (HCCI) powder mixtures were held. These powders were used for self-propagating high temperature synthesis in wave combustion mode. It was shown, that the preliminary MA makes possible to initiate SHS in reaction mixtures with a HSS binder content up to 60 vol%. However, the MA effect is sufficiently lower, than expected, especially with HCCI. The unefficiency of MA on SHS is assumed to be connected with different binder’s mechanical properties and behaviors in milling processes. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the III All-Russian Conference (with International Participation) Hot Topics of Solid State Chemistry: From New Ideas to New Materials.

1. Introduction Iron binder metal matrix composites (MMC) are of great interest as functional and coating materials. Main advantages of Fe-based coatings are their relatively lower costs as well as their good environmental behavior compared to other protective coatings [1,2]. TiC hardening phase additives is also of interest because of its greatest hardness parameters among other transition metal carbides. The most time-productive and efficient method to produce MMCs is refer to self-propagating high temperature synthesis (SHS). High enthalpy of TiC formation [3] makes possible to use large amounts of inert binders in reaction mixtures. In these conditions, an equiaxed fine carbide grains are formed in MMC structure. These fine grains sufficiently increase the hardness and wear resistance of coatings, surfaced by different methods with composite powders [4–6]. The way to extend lron binder concentration limit and subsequently decrease TiC particles size in synthesized powders can be provided by preliminary mechanical activation (MA) [3,7–9]. 2. Materials and methods Powder mixtures of titanium (TPP-8 Russian trademark, <160 lm), carbon black (P-803, 0.3 lm), high-speed steel (HSS, ⇑ Corresponding author.

<56 lm), high chromium cast iron (HCCI, PG-C27 Russian trademark, <56 lm) were used. The HSS powder was obtained by melt spraying method and had a specific spherical particles shape (Fig. 1a). Steel contained 1% carbon, alloying elements (Cr – 4%; W – 6.5%; Mo – 5%; V – 2%) and impurities (Si – 0.5%; Mn – 0.55%; Ni 0.4%). The HCCI powder (Fig. 1b) consisted of a eqiaxed particles mixture. Cast iron contained 3.8% carbon, alloying elements (Cr 25.16%; Ni 3.09%; Mo 0.25%; W 0.35%) and impurities (Si 1.33%; Mn 1.32%; S 0.024%; P 0.023%). The titanium powder (Fig. 1c) contained at least 99.4% of the main component and impurity: Fe – 0.33%; Cl 0, 12%; O2 – <0.1%. The carbon black powder (Fig. 1d) had submicron particle sizes and amorphous structure. The content of titanium and carbon in the reaction mixtures corresponded to the equiatomic composition of titanium carbide as 4:1 wt%. Powder mixtures were prepared by dry mixing for 4 h. The mechanical activation of powder mixtures was carried out in a planetary mill ‘‘Activator 2S” with a 20/1 ball/powder mass ratio or 300 g of balls to 15 g of powder mixture. The ball diameter was 6 mm. The planetary disk rotation speed was varied to receive different intensities of mechanical activation: high (960 rpm 88g) and medium (720 rpm 49g) load. To prevent oxidation during MA, the activator vials were filled with argon at 1–1.5 bar excess pressure.

E-mail address: [email protected] (A.V. Baranovskiy). https://doi.org/10.1016/j.matpr.2019.12.176 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the III All-Russian Conference (with International Participation) Hot Topics of Solid State Chemistry: From New Ideas to New Materials.

Please cite this article as: A. V. Baranovskiy, G. A. Pribytkov, M. G. Krinitcyn et al., Extending the SHS combustion concentration limits in Ti + C + Fe powder mixtures by preliminary mechanical activation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.176

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A.V. Baranovskiy et al. / Materials Today: Proceedings xxx (xxxx) xxx

Fig. 1. Starting powders morphology: a) HSS, b) HCCT, c) Titanium powder, d) Carbon black.

The mechanically activated powder was placed in a cylindershape paper container Ø 2.5 cm. The average height of the samples was 2.5 cm, and the porosity was about 60%. Synthesis were carried out in air-tight reactor in argon gas medium under 0.5 bar excess pressure. The ignition was initiated by molybdenum coil heated by electric current. WRe20-WRe5 thermocouple was placed in a hole pierced at about half the sample height. The combustion temperature was calculated as the average of 4–5 experiments. Structural studies of powders were carried out at NANOTECH Common Use Center of ISPMS SB RAS by XRD (DRON-7 diffractometer, ASTM X-ray diffraction database, PDWIN program) and scanning electron microscopy (LEO EVO 50, Zeiss, Germany). An EDX mapping was performed on powder mixtures and MA powders. The powders screen analysis was held on automatic device with accordance to ISO4497-83.

3. Results and discussion Before MA of powder mixtures steel and cast iron powders were treated in planetary ball mill to compare their crushing abilities. 125–80 lm starting fractions were milled with different modes and time. The results are shown in Fig. 2. Milling regimes for steel and cast iron powders were different. Balls and vials coating effect by HSS powder appear in high energy milling mode (88 g). So only medium milling mode (49 g) was used for HSS. There was no balls and vials coating effect with the HCCI powder. 70 wt% of HCCI powder were <25 lm after 3 min of intense MA. HSS powder with that conditions have only 10 wt% with that dispersity and reach size of80 lm after 5 min MA (49 g). Such a tendencies are strongly connected with powders mechanical characteristics. So, it is well known, that HCCI structure contains a lot of (Cr, Fe)7C3 acicular shape carbides, what results in high brittleness. HSS powder has comparatively lower concentration of Me6C carbides and a-Fe matrix with relatively high viscosity,

therefore 5 min medium milling mode was not enough to crush the powder. MA of titanium, HSS and HCCI powder mixtures with carbon black was carried out further. As a result, the mechanocomposite granules were formed (Fig. 3). HSS spherical particles with coarse titanium powder form granules with a size of 24 ± 10 mm after 15 min 49 g MA. The HCCI mixture granules has size of 10 ± 5 mm after 10 min 88 g MA. So, it can be concluded, that MA sufficiently fine the powder mixture with formation of composite granules with even distribution of different components. According to XRD results no dependence of phase composition evolution on MA duration was observed. According to the EDX mapping results, after 4 h dry mixing a relatively fine carbon, steel and cast iron particles covered the Ti particles surface. After MA an uniform distribution of Ti, Fe and C on the particles surface occured. Mechanically activated powder mixtures were used for SHS. Powder mixture with 60 vol% HSS did not ignite without MA, and also after MA at the medium energy mode (15 min., 49 g). At high energy mode MA (10 min, 88 g), a wave combustion front stopped in the middle part of the sample. Temperatures recorded in this case differed greatly from sample to sample. Synthesis reaction of 50 vol% HSS mixture without MA was unstable. However, after medium mode MA the combustion stability was achieved and the temperature was measured with sufficient accuracy. This positive effect is referred to intensive mixing of the reaction components in MA process and simultaneous comminution of the metal powder. The both investigated mixture compositions with cast iron powder (table 1) do not combust without mechanical activation. After 15 min high-energy mode MA (88 g) of each mixtures, the synthesis initiation was observed only on TiC + 60 vol% HCCI. However, the combustion front stopped near the thermocouple position and the registered temperature was too low. The reason of such inefficiency of MA could be connected with the formation of titanium carbide layers on the surface of titanium particles with 15 min processing (TiC mechanical synthesis). These layers segre-

Fig. 2. Fraction content after planetary ball mill treatment: a) < 25 lm, b) 25–56 lm, 1) HSS (49 g), 2) HCCI (49 g), 3) HCCI (88 g).

Please cite this article as: A. V. Baranovskiy, G. A. Pribytkov, M. G. Krinitcyn et al., Extending the SHS combustion concentration limits in Ti + C + Fe powder mixtures by preliminary mechanical activation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.176

A.V. Baranovskiy et al. / Materials Today: Proceedings xxx (xxxx) xxx

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Fig. 3. Structures of powder mixtures after MA: a) Ti + C + 60 vol% HSS after MA (49 g, 15 min); b) Ti + C + 50 vol% HCCI after MA (88 g, 10 min).

Table 1 Combustion behavior in Ti + C + HSS and Ti + C + HCCI reaction mixtures. Target phase composition

MA mode

Combustion temperature

TiC + 50 vol% HSS

No activation MA 49 g, 15 min MA 49 g, 15 min MA 88 g, 10 min No activation MA 88 g, 10 min MA 88 g, 15 min No activation MA 49 g, 10 min MA 88 g, 15 min

1090 ± 293 °C, unstable 1361 ± 20 °C No ignition Unstable No ignition 1215 ± 5 °C No ignition No ignition No ignition Unstable

TiC + 60 vol% HSS TiC + 50 vol% HCCI

TiC + 60 vol% HCCI

gate titanium and carbon reagents and prevent the chemical reaction propagation in the wave combustion mode in addition to inert binder heat absorption. Stable combustion was obtained only in the mixture with 50 vol% HCCI after high energy mode (10 min, 88 g) MA, when the mechanical synthesis has not yet started.

4. Conclusion The preliminary MA makes possible to initiate SHS in wave combustion mode in reaction mixtures with a high metal binder content. However, it is necessary to take into account the binder powders behavior during MA process. The excessive processing of reaction mixtures (as shown at Ti + C + HCCI mixtures) with a brittle binder leads to chemical reaction inhibition. Probably, the large number of small cast iron particles in mechanocomposite, as well as the formation of TiC barrier layers after MA have negative effect on SHS. On the other hand, high-energy mode MA of titanium, carbon and HSS powders with the formation of relatively coarse mechanocomposite granules shows a noticeable positive effect due to reactive surface area increase. Thus, the MA of titanium, carbon, HSS and HCCI reaction powder mixtures allows to increase the thermally inert binder content in SHS composites up to 60 vol%, however, this effect for high content of inert additives

is much weaker than expected and strongly depends on the binder mechanical properties. CRediT authorship contribution statement A.V. Baranovskiy: Writing - original draft, Funding acquisition. G.A. Pribytkov: Supervision. M.G. Krinitcyn: . V.V. Homyakov: Investigation, Data curation. G.O. Dankovcev: Investigation, Visualization. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements The work was carried out within the framework of the Program of Fundamental Scientific Research of the State Academies of Sciences (line of research III.23) with the financial support of the Russian Foundation for Basic research (Grant № 18-32-00330). References [1] K. Bobzin, L. Zhao, M. Öte, T. Königstein, Surf. Coatings Technol. 362 (2019) 12– 20. [2] J. Jiang, S. Li, W. Yu, Y. Zhou, Mat. Chem. and Phys. 224 (2019) 169–174. [3] S.M. Ghiasabadi, S. Raygan, J. Mater. Eng. Perform. 21 (11) (2012) 2295–2302. [4] Z. Wang, T. Lin, X. He, H. Shao, B. Tang, X. Qu, Int. J. Refract. Met. Hard Mater. 58 (2016) 14–21. [5] V.I. Kalita, D.I. Komlev, G.A. Pribytkov, A.V. Baranovsky, A.A. Radyuk, V.V. Korzhova, A.B. Mikhaylova, Inorg. Mater. Appl. Res. 10–3 (2019) 549–555. [6] G.A. Pribytkov, V.I. Kalita, D.I. Komlev, V.V. Korzhova, A.A. Radyuk, A.V. Baranovsky, A.B. Mikhailova, Inorg. Mater. Appl. Res. 9–3 (2018) 442–450. [7] F. Bernard, S. Paris, E. Gaffet, Adv. in Sci. Tech. 45 (2006) 979–988. [8] E.A. Levashov, V.V. Kurbatkina, A.S. Rogachev, N.A. Kochetov, Int. J. of SHS 16–1 (2007) 46–50. [9] N.Z. Lyakhov, T.L. Talako, T.F. Grigorieva, Effect of Mechanical Activation on the Processes of Phase and Structure Formation During Self-Propagating HighTemperature Synthesis, Parallel, Novosibirsk, 2008.

Please cite this article as: A. V. Baranovskiy, G. A. Pribytkov, M. G. Krinitcyn et al., Extending the SHS combustion concentration limits in Ti + C + Fe powder mixtures by preliminary mechanical activation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.176