Hard alloy production by SHS compaction in an open die

The paper investigates the possibility of carrying out  SHS  for the Ti (81.5 wt.%)  + B (18.5 wt.%)  composition in the air followed by pressing combustion products in an open steel die with walls limiting their radial flow under tough heat dissipation conditions without the use of an intermediate loose medium of the heat insulator. Modes of reaction powder mixture preparation for synthesis were optimized. Such process characteristics as bulk density, compaction, elastic aftereffect were determined for initial powders and reaction mixtures, and the strength of compactions was estimated. It is shown that there is a relationship between the strength of charge compacts, combustion rate and  changes in their volume after combustion in the air under intensive gas liberation during combustion. The optimal charge compact density was found equal to 0.75  corresponding to the maximum combustion rate without charge emissions with a minimum change in volume. As a result of the optimization, the possibility of effective and  safe conduct synthesis process without the use of an intermediate loose medium of the heat insulator is shown. Hard-alloy plates with a diameter of 60 mm and  a thickness of 11 mm were obtained in the open steel die under SHS compaction conditions. The structure of the resulting hard alloy is unique with a porosity of less than  0.5  %. It consists of titanium diboride (~60  wt.%)  and  titanium-based binder phase (~ 40 wt.%).  Such a structure obtained as a result of accelerated cooling can  be defined as nonequilibrium, since the main phase for the studied composition should be titanium monoboride (TiB) in accordance with the Ti–B state diagram. The microhardness of the fabricated hard alloy is HV = 18000 MPa.

1. Merzhanov A.G. Self-propagating high-temperature synthesis: twenty years of searches and finds. Chernogolovka: ISMAN R AS, 1989 (In Russ.).

2. Pityulin A.N. Power compaction in SHS processes. In: Self-propagating high-temperature synthesis: theory and practice. Chernogolovka: Territoriya, 2001. P. 333—353 (In Russ.).

3. Epishin K.L., Pityulin A.N., Merzhanov A.G. Compaction of materials formed during SHS. Poroshkovaya metallurgiya. 1992. No. 6. P. 14—19 (In Russ.).

4. Stolin A.M., Bazhin P.M., Konstantinov A.S., Alymov M.I. Production of large compact plates of ceram ic powder mater ials by free SHS-compression. Doklady Akademii nauk. 2018. Vol. 480. No. 6. P. 681— 683 (In Russ.).

5. Bazhin P.M., Stolin A.M., Konstantinov A.S., Kostitsyna E.V., Ignatov A.S. Ceramic Ti—B composites synthesized by combustion followed by high-temperature deformation. Materials. 2016. Vol. 9. Iss. 12. No. 1027. DOI: 10.3390/ma9121027.

6. Konstantinov A.S., Bazhin P.M., Stolin A.M., Kostitsyna E.V., Ignatov A.S. Ti—B—based composite materials: Properties, basic fabrication methods, and fields of application (review). Composites. Part A: Appl. Sci. Manufact. 2018. Vol. 108. P. 79—88.

7. Fedotov A.F. Regularities of compaction and forming during SHS-pressing with a loose shell. Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya. 2008. No. 1. P. 16—23 (In Russ.).

8. Kiparisov S.S., Libenson G.A. Powder metallurgy. Moscow: Metallurgiya, 1991 (In Russ.).

9. Balshin M.Yu. Scientific basis of fiber powder metallurgy. Moscow: Metallurgiya, 1972 (In Russ.).

10. Rogachev A.S., Mukasyan A.S. Combustion for materials synthesis: Introduction to structural macrokinetics. Moscow: Fizmatlit, 2012 (In Russ.).

11. Kochetov N.A. Rogachev A.S., Emelyanov A.N., Illarionova E.V., Shkiro V.M. Microstructure of heterogeneous mixtures for gas-free combustion. Fizika goreniya i vzryva. 2004. Vol. 40. No. 5. P. 74—80 (In Russ.).

12. Kirdyashkin A.I., Maksimov Yu.M., Merzhanov A.G. On the inf luence of capillary spreading on the combustion process of gas-free systems. Fizika goreniya i vzryva. 1981. No. 6. P. 10—15 (In Russ.).

13. Vadchenko S.G., Mukhina N.I., Shchukin A.S. Investigation of the kinetics of the interaction of boron with molten titanium (In Russ.). http://www.ism.ac.ru/events/isman2016/pdf/Vadchenko_2.pdf.

14. Akopyan A.G., Dolukhanyan S.K., Borovinskaya I.P. Interaction of titanium, boron and carbon in the combustion mode. Fizika goreniya i vzryva. 1978. No. 3. P. 70—75 (In Russ.).

15. Tavadze G.F., Shteinberg A.S. Production of advanced materials by methods of self-propagating high-temperature synthesis. Springer, 2013. Vol. XIX. DOI10.1007/978-3-642-35205-8

16. Tavadze G., Khantadze J. The impact of fractional difference of components on theproperties of hard alloys produced by the SHS method. Bull. Georg. Natl. Acad. Sci. 2010. Vol. 4. P. 70—73.

17. Zhang Xinghong, Xu Qianga, Han Jiecai, V.L. Kvanin. Self-propagating high temperature combustion synthesis of TiB/Ti composites. Mater. Sci. Eng. A. 2003. Vol. 348. Iss. 1—2. P. 41—46.

18. Shcherbakov V.A., Gryadunov A.N., Sachkova N.V., Samokhin A.V. SHS-compaction of ceramic composites based on titanium and chrome borides. Pis’ma o materialakh. 2015. Vol. 5. No. 1. P. 20—23 (In Russ.).

19. Scherbakov V.A., Gryadunov A.N., Alymov M.I. Synthesis and characteristics of B4C—TiB2 composite. Adv. Mater. Technol. 2016. Iss. 4. Р. 16—21. https://doi.org/10.17277/amt.2016.04.pp.016-021.

20. Hamza Cheloui, Zhaohui Zhang, Xiangbo Shen. Microstructure and mechanical properties of TiB—TiB2 Ceramic matrix composites fabricated by spark plasma sintering. Mater. Sci. Eng. A. 2011. Vol. 528. No. 10—11. P. 3849—3853. DOI: 10.1016/j.msea.2011.01.096.

21. Hu J., Dong X., Tosto S. Microstructure of face centered cubic (fcc) TiB powder synthesized by boronizing of Ti powder. J. Am. Ceram. Soc. 2012. Vol. 95. Iss. 7. P. 1—4. DOI: 10.1111/j.1551-2916.2012.05229.x.

22. Hu Y.B., Zhao B., Ning F.D., Wang H., Cong W.L. In-situ ultrafine three-dimensional quasi-continuous network microstructural TiB reinforced titanium matrix composites fabrication using laser engineered net shaping. Mater. Lett. 2017. Vol. 195. P. 116—119. DOI: 10.1166/sam.2018.2853.

23. GOST R ISO 6507-1 2007. Metals and alloys. Measurement of Vickers hardness (In Russ.).