National Technical University of Ukraine Kyiv Polytechnic Institute

National Technical University of Ukraine – Kyiv Polytechnic Institute, 37, Peremogi ave. , Kyiv, 03056, Ukraine, Ph. : +38 044 4890164, E-mail: kvas 69@rambler. ru *Institute of High Current Electronics SB RAS, 2/3. , Akademichesky ave. , Tomsk, 634055, Russia **The E. O. Paton electric Welding Institute of the NAS of Ukraine, 11, Bozhenkastr. , Kyiv, 03680, Ukraine ***Admiral Makarov National University of Shipbuilding, 9, Geroev Stalingrada ave. , Mykolaiv, 54025, Ukraine, Ph. : +38 0512 431174, F. : +38 0512 421081, E-mail: welding@nuos. edu. ua The Application of High-Current Low-Energy Electron Beam for Diffusion Welding and Brazing of Materials. Abstract – The structure and strength of the surface coating layers of iron, stainless steel and heat-resistant alloy treated by high-current low-energy electron beam have been considered. The microstructure and properties of diffusion bonded and brazed joints have been studied. V. V. Kvasnytskyy, N. N. Koval*, Yu. F. Ivanov*, L. I. Markashova**, V. D. Kuznetsov, V. F. Kvasnytskyy***

Diffusion welding (DW) is the effective method of bond of materials and belongs to method of welding with pressure. In pressure welding a very important issue is surface condition. Presence on the surface of adsorbed gases and oxide films requires that surfaces be activated in order to form bonds between atoms of materials being joint. To activate surfaces there were proposed: cyclic loading, use of ultra dispersed powders, intermediate gaskets (may be fusible and infusible) and many other methods that do not always prove to be effective. Often solders are used as fusible gaskets, which requires placing of solders and complicates assembly of articles. There also problems in manufacture of modern solders. Therefore, search of new diffusion welding and brazing technologies is vital. Purpose of this work is to study impact of surfaces, modified with high-current lowenergy electron beams, on formation of joints in diffusion welding of iron with stainless steel and heat-resistant alloys and brazing of heat-resistant nickel alloys.

Fig. 1 Microstructure of welded joint during traditional DW of alloy. ЧС 88 У-ВИ, × 800

a b Fig. 2. Microstructure of modified layer of steel grade 10895 (a, × 250) and its fine structure (b, × 28000).

a b Fig. 3. Fine structure of modified layer of steel grade 12 Х 18 Н 10 Т (a, × 20000) and nickel - base alloy ЧС 88 У-ВИ (b, × 30000).

Microhardness, MPa Condition of metal Parent metal (condition of delivery) Modified Steel of 10 895 Steel of 12 Х 18 Н 10 Т Alloy ЧС 88 У-ВИ

Dз~1, 5 мкм Dз~15 мкм Fig. 4. Microstructure of modified layer of steel grade 10895 × 250 7

Fig. 5. Microstructure of welded joint of steel grades 12 Х 18 Н 10 Т and 10895 with modified surfaces: × 400

b, х20 000 а Fig. 6. Microstructure of DW joint of alloy ЧС 88 У -ВИ with modified surfaces: (a× 400), fine structure (b, c) c, х37 000 9

a, х 20 000 b, х 37 000 Fig. 7. Fine structure of DW joint with modified layer of steel grade 10895 and 12 Х 18 Н 10 Т. 10

Fig. 8. Change of TKLD by heating at a speed of 28 °С/с (1, 2), 2 °С/с (4, 5), 1 °С/с (3) alloy of ЧС 88 У‑ВИ, driving complete heat treatment (1, 3, 4) and driving hardening in water (2, 5) 11

a b c d Fig. 9. Epures of plastic deformation εx (а), εy (b), εху (c) and ε ecv (d) at the temperature of 1050°С (1), 1075°С (2), 1100°С (3), 1125°С (4) and 1150°С (5) 12

1 2 3 а 4 5 1 1 2 3 b 4 5 3 5 c Fig. 10. Fields of plastic deformation εy (а), εxy (b) and εecv (c) at heating of DW bond of alloy ЧС 88 in different structural conditions: at a temperature 1050 °С (1), 1075 °С (2), 1100 °С (3), 1125 °С (4) и 1150 °С (5) (above – heat-treated, down is the hardened metal) 13

b а Fig. 11. Surface of sample (a) and spectrum on the elements of the alloyed (b) and covered (c) surfaces layer on the alloy of ЧС 88 У-ВИ c 14

a Concentration of Zr, % mass b Distance , micrometer d c Fig. 12. Morphology of cross-sectional (a, b, c) and distribution of Zr (d) in a alloy of ЧС 88 У-ВИ after alloying of Zr (10 imp. at density of energies 25 J/sm 2 and depths of the 15 alloyed bench of 4 micrometer

b Concentration of Zr, % mass a Distance , micrometer d c Fig. 13. Morphology of cross-sectional (a, b, c) and distribution of Zr (d) in a alloy of ЧС 88 У-ВИ after alloying of Zr (10 imp. at density of energies 25 J/sm 2 and depths of the 16 alloyed bench of 8 micrometer

а b d c Fig. 14. Surface of heatproof alloys of ЧС 88 У-ВИ (a), Inconel 718 (b), brazing (c, d) 17

а c b d Fig. 15. Microstructure of bond of alloy of ЧС 88 У-ВИ by alloying of Zr δ=1, 0 micrometer: (a, b) - alloyed two of bond surface, (c, d) - alloyed one of bond surface 18

Conclusions: 1. Comparison of diffusion welding of steel grades 10 895 and 12 Х 18 Н 10 Т with different preparation of surfaces showed, that formation of bonded joint is most effectively conduced by modification of both surfaces to be joint. If only one surface is to be modified, it should be surface of α-iron, whose energy of crystalline structure defects is much greater than that of γ-Fe. 2. Positive effect of surface modification of dispersion-strengthened nickel alloy is caused by both modification effect (highly dispersive structure, dislocations density, etc. ) and build up of high level of strains in contact of modified (hardened) layer and alloy with excessive phase producing plastic deformations in their contact zone, which is confirmed by deformation strips in the butt joint area. At this, more preferable is bonded joint of modified and non-modified surfaces. 3. It was established for the first time that impact of HCLEEB permits to braze surface of heat-resistant alloys with elements reducing melting temperature of surface layer, specifically with Zr, Hf, Nb, with bringing of introduced element concentration close to concentration in solders by changing thickness of its previously applied layer, energy density in electron beam, duration and number of pulses. 4. Brazed layer functions not only as solder but conduces to development of plastic deformations and formation of common grains in the joint. 5. Modification of surface layer of materials to be fused by change of its structure, level of structural strains, 3 -d category strains, brazing with elements reducing welding temperature, is an effective means to raise quality and simplify technology of diffusion welding.