National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia:

A. N. Suchkov, Assistant Professor, e-mail: ansuchkov221283@mail.ru
A. A. Ivannikov, Assistant
R. V. Sokolov, Student
A. P. Klimova, Student
A. S. Nosenko, Student

Presence of silver in composition of such solders as PSr 72 (ПСр 72) and BCuP-5 severely limits their application field after brazing of structural elements, operated under neutron irradiation. Rapidly quenched alloys of Cu – Ni – Sn – P system (STEMET 1105, STEMET 1101, MVA-2005) with different phosphorus content are the solders, alternative to silver-containing alloys. In the recent years, the solders STEMET 1101 (Cu – 3,6 Sn – 9,1 Ni — (8,0–8,5) P) and STEMET 1105 (Cu – 9,2 Sn – 5,4 Ni – 6,3 P) have been successfully used as a replacement of the solder STEMET 1108 (Cu – (2,0–4,0) Ni – (11,0–13,0) Sn – (4,0–8,0) In % (wt.)) in the manufacturing of the first wall of the fusion reactor ITER. This was caused by the fact that brazing of Cu – Cr – Zr bronze and beryllium can be carried out at the temperatures below 700 ^oC, which will not cause degradation of mechanical properties of the bronze during a thermal cycle. Therefore, it is also appropriate to use the same solders for brazing of elements of the ITER divertor, which is currently carried out using STEMET 1108 with compound of tungsten-surfaced copper with heat-removing bronze BrKhTsr (БрХЦр) at the temperature of up to 970 ^oC, which requires subsequent heat treatment of copper alloy to restore strength characteristics. This paper gives the comparative results of copper brazing, using rapidly-quenched filler metal STEMET 1101 and STEMET 1105 (Cu – Ni – Sn – P system) in the temperature range of 650–700 ^oC and delay time from 3 to 30 minutes. The temperatures and ranges of melting of brazing alloys in crystalline and rapidlyquenched stage were determined using differential thermal analysis. Structures of brazing alloys in original crystalline form were studied together with structures of brazed joins, using scanning electron microscopy. Changes of structural-phase state of rapidly-quenched brazing alloys STEMET 1101 were determined after a number of heat treatments, using X-ray analysis. Microhardness in brazed copper seams was measured, using STEMET 1101 and STEMET 1105 solders. Impact strength of the brazed joins was defined.

1. Kalin B. A., Plyushchev A. N., Fedotov V. T., Sevryukov O. N., Goltsev V. Yu. Vliyanie strukturnogo sostoyaniya pripoya na fiziko-mekhanicheskie svoystva payanykh soedineniy (Influence of structural state of solder on physical-mechanical properties of brazed joint). Svarochnoe proizvodstvo = Welding industry. 2001. No. 8. pp. 38–41.
2. Rabinkin A., Pounds S. Effects of load on brazing with Metglass MBF-2005 filler metal. Welding journal. 1998. May. pp. 33–45.
3. Kalin В. A., Suchkov A. N. et al. Brazing of the ITER first wall by a copper based rapidly quenched ribbon-type filler metal. Fusion Science and Technology. 2014. Vol. 65. pp. 212–221.
4. Litunovsky N. et al. Fusion Engineering and Design. 2013. Vol. 88. pp. 1739–1743.
5. Litunovsky N. et al. Fusion Engineering and Design. 2011. Vol. 86. pp. 1749– 1752.
6. Ruiz-Vargas J. et al. Journal of Materials Processing Technology. 2013. Vol. 213. pp. 2074–2080.