New sintered materials & processes of joining of nickel super alloys and metal-ceramics using nanostructured interlayers

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1 New sintered materials & processes of joining of nickel super alloys and metal-ceramics using nanostructured interlayers I. Smirnov, V. Kvasnitskiy, Ye. Chvertko*

2 Application of high-current low-energy electron beam for diffusion welding and brazing of materials Objectives In pressure welding the surface condition is a very important issue. Presence of adsorbed gases and oxide films on the surfaces requires their activation in order to form bonds between atoms of materials being fused. To activate surfaces there are commonly used: cyclic loading, ultra dispersed powders, intermediate gaskets (fusible and infusible) and other methods that do not always prove to be effective. Solders are often used as fusible gaskets, which requires placing of solders and complicates assembly of articles. There are also problems in manufacture of modern solders. Therefore, search of new diffusion welding and brazing technologies is vital. Purpose is to study impact of surfaces, modified with high-current lowenergy electron beams, on formation of joints in diffusion welding and brazing of heat-resistant nickel alloys

3 Application of high-current low-energy electron beam for surface activation in diffusion welding a b Microstructure of welded joint during traditional DW of nickel - base alloy ЧС88У-ВИ (a, 800), and fine structure of modified layer of ЧС88У-ВИ (b, 30000). Properties of nickel-base alloy ЧС88У-ВИ Parent metal (condition of delivery) Modified layer Microhardness, MPa

4 Application of high-current low-energy electron beam for surface activation in diffusion welding Change of temperature linear expansion coefficient by heating at a speed of cooling 28 С/с (1, 2), 2 С/с (4,5), 1 С/с (3) alloy of ЧС88У-ВИ, driving complete heat treatment (1,3,4) and driving hardening in water (2,5)

5 Application of high-current low-energy electron beam for surface activation in diffusion welding а y, % 0-0, 05-0, 10-0, 15-0, 20-0, 25-0, c экв, % 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0 Fields of plastic deformation ε y (а), ε xy (b) and ε ecv (c) at heating of DW bond of alloy ЧС88 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) b, % 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0

6 Application of high-current low-energy electron beam for surface activation in diffusion welding b, х а Microstructure of DW joint of alloy ЧС88У-ВИ with modified surfaces: (a 400), fine structure (b, c) c, х37 000

7 Application of high-current low-energy electron beam for surface activation in diffusion welding Positive effect of surface modification of dispersion-strengthened nickel alloy is caused by both modification effect (highly dispersive structure, dislocations density, etc.) and buildup 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. The developed technology results in possibility to change the welding parameters in comparison to their recommended values: Required pressure reduction up to 2 times (20 MPa vs MPa) Welding time reduction up to 10 times (3 6 minutes vs 30 minutes) Required heating temperature reduction lower then the lowest recommended value (1175 С vs 1200 С)

8 Application of high-current low-energy electron beam for surface treatment in diffusion brazing а b d c Surface of heatproof alloys of ЧС88У-ВИ (a), Inconel 718 (b), brazing (c, d)

9 Application of high-current low-energy electron beam for surface treatment in diffusion brazing b а Surface of sample (a) and spectrum on the elements of the alloyed (b) and covered (c) surfaces layer on the alloy of ЧС88У-ВИ c

10 Concentration of Zr, % mass Application of high-current low-energy electron beam for surface treatment in diffusion brazing Никелевый сплав (ЧС-88) (образец 8/25) Напыляли поверхность - Zr Обработка электронным пучком косой шлиф a b а Ч600 б Ч1550 h 3,5 4мкм 1 7 c d в Ч3100 г Morphology of cross-sectional (a, b, c) and distribution of Zr (d) in a alloy of ЧС88У-ВИ after alloying 1 of Zr 2 (103 imp. 4 at density 5 6 of energies 7 25 J/sm 2 and depths of the alloyed bench of 4 micrometers Ni 51,57 54,6 55,76 56,95 57,96 57,19 57,58 Co 9,36 9,74 9,61 10,27 11,21 11,08 10,87 Cr 13,96 14,66 15,42 15,57 15,16 15,79 15,75 Ti 3,57 4,6 5,5 5,67 5,37 5,23 4,82 National Technical Mo 2,84 3,0 University 3,19 3,08 of 2,17 Ukraine 2,25 1,72 Kyiv Polytechnic Institute, Welding Department W 8,14 5,34 6,18 5,63 5,06 5,43 6,23 Al 1,83 1,58 2,14 2,36 3,04 3,01 3,0 Distance, micrometer

11 Application of high-current low-energy electron beam for surface treatment in diffusion brazing а b c Microstructure of bond of alloy of ЧС88У-ВИ by alloying of Zr δ=1,0 micrometer: (a, b) - alloyed two of bond surface, (c, d) - alloyed one of bond surface d

12 Application of high-current low-energy electron beam for surface treatment in diffusion brazing Microstructure of metal in the fusion area of two polished surfaces of alloy ЧС88У-Ви being in the same structural state; 200

13 Application of high-current low-energy electron beam for surface treatment in diffusion brazing The impact of HCLE 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. The alloyed layer functions not only as solder but conduces to development of plastic deformations and formation of common grains in the joint. 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.

14 Development of new sintered materials with superdispersed elements Objectives Development of new powders rises the interest to gas-thermal coating application. A great attention is payed to composite metal-ceramic coatings, dispersion strengthened coatings and coatings with nanosized particles. Resent research have shown a great effect of ultradispersed and nano-sized components of the coating on their physical and mechanical properties. Purpose is to develop physical and technological fundamentals of forming of plasma coatings with the use of composite ultra-dispersed powders and powders with nano-structured coatings obtained by vacuum-arc technology.

15 Development of new sintered materials with superdispersed elements Morphology of cladded powder Al 2 O 3 Powder Al 2 O 3 cladded with Ti and Al (thickness of Ti coating nm, Al micrometers) Powder WC (W 2 C) cladded with Cu Plasmatron for coating with cladded powders

16 Development of new sintered materials with superdispersed elements 1 Surface coated with Al 2 O 3 (х 1000) Al 2 O 3 coating microstructure: 1 coating, 2 base material; 3 underlayer NiAl 3 2 (х 250) 1 (х 1000) 2 (х 250) Surface coated with Al 2 O 3 cladded with Ti and Сu Al 2 O 3 cladded with Ti and Сu coating microstructure: 1 coating, 2 base material

17 AlNi AlNi al AlNi al после отжига ПГ-10Н ПГ-10Н al ПГ-10Н al после отжига Development of new sintered materials with superdispersed elements s,мпа 800 m/s, г/мм 2 0, , , , , , t, год Tensile strength of heat-resistant alloys with coatings Wear kinetics of plasma coatings 1 Al 2 O 3, 2 Al2O3/Ті/Al

18 Development of new sintered materials with superdispersed elements Plasma coatings with Al 2 O 3 cladded with Ti and Cu in comparison with those of Al 2 O 3 have reduced porosity (1-3 % vs 10 %). Cladding with Ti and Al also reduces the coating porosity (4-6 %). Cladded powders allow to obtain coating with low amount of surface microcracks due to healing of defects effect. The cladding of ceramics with Ti and Al or Cu allows to obtain coatings with good bonding with base metal without application of interlayers (NiAl).

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