All-Russian Institute of Aviation Materials, Moscow, Russia:

E. I. Iakovlev, Leading Engineer, e-mail: y-e-i@yandex.ru

The first part of this paper shows the analysis of the conditions of qualitative structure formation in the turbine blades casting by directional solidification techniques. The main method to obtain the single crystal and directionally solidified turbine blades in Western Europe and the US is the Bridgman – Stockbarger technique, when liquation defects, significantly reducing the blades performance, arise due to the low temperature pressure and low-speed solidification of large castings. In attempts to increase the solidification rate by raising the pulling speed, increase ratio of the transverse and longitudinal vector components of the temperature gradient on the front liquidus occurs, leading to a shift in liquidus front cooling zone and causing harmful spurious crystals in the blades with directional and single crystal structures. One way of cooling rate increase during directional solidification is to raise the heat transfer coefficient on the shapes' outer surface. Liquid metal cooling technique in the melt aluminum was realized in 1975 on VIAM’s pilot unit. Currently Russia accumulated sufficiently large industrial experience using the aluminum casting baths for 200 mm blades with directional and single crystal structures, where liquation defects are excluded due to low cooling rate during solidification. The VIAM specialists developed the technological processes for the production of single crystal blades of aircraft turbines with macrostructure yield ratio over 80%. However, there is a number of technological issues in the casting of large rotor blades of advanced groundbased gas turbines. Due to the increased residence time in the casting mold with a cooler and a large hydrostatic pressure, the coolant shell mold cracking occurs and causes parts faulty. The analysis of recently conducted research of new methods for the preparation of large single-crystal blades and designed structures will be shown in the second part of this paper.

1. Shein E. A. Trends in alloying and microalloying of nickel-based single crystal superalloys (review). Trudy VIAM. 2016. No. 3. DOI: 10.18577/2307-6046-2016-0-3-2-2.
2. Wahl J., Harris K. New single crystal superalloys, CMSX^®-7 and CMSX^®-8. Supperalloys 2012. Proceedings of the 12^th International Simposium of Superalloys. Hoboken : Wiley, 2012. pp. 179–188.

3. Reed R., Moverare J., Sato A., Karlsson F., Hasselqvist M. A new single crystal superalloy for power generation applications. Supperalloys 2012.
Proceedings of the 12 th International Simposium of Superalloys. Hoboken : Wiley, 2012. pp. 197–204.
4. McLean M. Directionally solidified materials for high temperature service. London : The Metals Society, 1983. 337 p.
5. Kablov E. N. Production of turbine blades of gas-turbine engines by directional solidification. Gazoturbinnye tekhnologii. 2000. No. 3. pp. 10–13.
6. Kablov E. N., Gerasimov V. V., Shalimov A. S. et al. Vacuum casting equipment for high-velocity directional solidification. Liteynoe proizvodstvo. 1995. No. 10. pp. 30–32.
7. Tolorayya V. N., Orekhov N. G., Kablov E. N. Advanced Method for Single Crystal Casting of Turbine Blades for Gas Turbine Engines and Plants. Metallovedenie i termicheskaya obrabotka metallov. 2002. No. 7. pp. 11–15.
8. Versnyder F. L., Shank M. E. The development of columnar grain and single crystal high temperature materials though directional solidification. Mater. Sci. and Eng. 1970. Vol. 6, No. 4. 213–247 pp.
9. Miller J., Pollock T. Development and application of an optimization protocol for directional solidification: integrating fundamental theory, experimentation and modeling tools. Supperalloys 2012. Proceedings of the 12^th International Simposium of Superalloys. Hoboken : Wiley, 2012. pp. 653–662.
10. Kutateladze S. S., Borishanskiy V. M. Heat transmission reference book. Moscow : GEI, 1959. 418 p.
11. Fok V. A. Intensity of illumination from arbitary shape surfaces. Trudy Gosudarstvennogo opticheskogo instituta. 1924. Vol. III, No. 28. pp. 1–12.
12. Mikheev M. A., Mikheeva I. M. Short course of heat transfer. Moscow, Leningrad : Gosenergoizdat, 1960. 208 p.
13. Kats E. L. Technological basis of solidification control during the gas turbine blades casting: Dissertation … of Doctor of Engineering Sciences. Moscow : TsNIITMASh, 1986. 555 p.
14. Bouse G. K., Schaeffer J. C., Henry M. F. Optimizing SC rene N4 alloy for DS AFT-stage bucket applications for industrial gas turbine. Supperalloys 2008. Proceedings of the 11^th International Symposium of Superalloys. 2008. pp. 99–108.
15. Kats E. L., Skorobogatykh V. N., Lubenets V. P., Yakovlev E. I. Processes of directional solidification for large-dimensional blades of gas turbines. Tekhnologiya metallov. 2015. No. 3. pp. 22–28.
16. Tschinkel J., Giamei A., Kearn B. Apparatus for casting of directionally solidified articles. Patent 3763926 US. Filed: 15.09.1974. Published: 09.10.1973.
17. Borishanskiy V. M., Kutateladze S. S., Novikov I. I., Fedynskiy O. S. Liquid-metallic heat-transfer agents : third еdition. Moscow : Atomizdat, 1976. 328 p.
18. Elliott A. J., Karney G. B., Gigliotti M. F. X., Polloc T. M. Issues in processing by the liquid-Sn assisted DS technique. Superalloys 2004. Proceedings of the 10^th International Symposium of Superalloys. 2004. pp. 421–430.
19. Elliott A. J., Pollock T. M., Tin S., King W. T., Huang S.-C., Gigliotti M. F. X. Directional solidification of large superalloy castings with radiation and luquid-metal cooling: a comparative assessment. Metallurgical and Materials Transactions: A. 2004. Vol. 35, No. 10. pp. 3221–3231.
20. Echin A. B., Bondarenko Yu. A. Modern equipment for turbine blades production designed with a glance of high-gradient directional solidification process. Trudy VIAM. 2014. No. 12. DOI: 10.18577/2307-6046-2014-0-12-3-3
21. Kats E. L. Manufacturing of alloys and technological processes of casting of stationary gas turbine blades. Collection of proceedings “Increasing of quality and efficiency of casting on cast models”. Materials of the seminar of the “Znanie” society. Moscow, 1989. pp. 20–22.
22. Stroganov G. B., Logunov A. V., Kats E. L., Gerasimov V. V. et al. Highvelocity directional solidification of heat-resistant alloys. Liteynoe proizvodstvo. 1983. No. 12. pp. 20–22.
23. Kats E. L., Gerasimov V. V. High-velocity directional solidification of heat-resistant alloys. Novye tekhnologicheskie protsessy i nadezhnost GTD / TsIAM. 1979. No. 2 (18). pp. 73–78.
24. Petrov D. A., Toloraуya V. N., Rogov A. V., Toropov V. M., Nikishin V. A., Yakovleva A. V. Method of casts production from heat-resistant alloys with monocrystalline structure. Patent USSR, No. 839153. Applied: 16.01.1980. Published: 27.07.2000.
25. Kablov E. N., Gerasimov V. V., Visik E. M., Demonis I. M. Role of the directed solidification in the resource-saving production technologies of details of GTD. Trudy VIAM. 2013. No. 3.
26. Kablov E. N., Tolorayya V. N. VIAM — Founder of Domestic Technology for Casting Single-Crystal Turbine Blades of GTE and GTS. Aviatsionnye materialy i tekhnologii. 2012. No. S. pp. 105–117.
27. Gerasimov V. V., Visik E. M., Kolyadov E. V. Development of technology of large-size castings blades with single-crystal structure. Liteynoe proizvodstvo. 2014. No. 3. pp. 29–32.