TLP diffusion welding technology of the hottest IC

2022-07-31
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The development of TLP diffusion welding technology for IC10 alloy

aviation science and technology has promoted the continuous improvement of aero-engine performance, which is specifically reflected in the development of aero-engine towards high temperature and lightweight. At present, the superalloys used to manufacture the hot end components of aero-engine can not meet the requirements of high thrust ratio engine for temperature resistance. Therefore, research on new high-temperature materials such as Ni3Al based intergeneric compound materials has been carried out. Due to the long-range ordered structure of the atoms of Ni3Al intermetallics and the coexistence of metal bonds and covalent bonds between atoms [1], Ni3Al intermetallics have the characteristics of high melting point, low density, good oxidation resistance and high temperature resistance strength. This paper introduces the improvement of the calibration device of the nest tensile testing machine, which has a good application prospect in the aero-engine

trace boron can significantly improve the room temperature plasticity of Ni3Al γ Phase can improve the strength and toughness of Ni3Al at the same time, and high melting point elements such as Mo, Co, W, TA can γ Phase sum γ′ Phase plays the role of solid solution strengthening [], and the properties of Ni3Al based Duplex Alloy developed now have been significantly improved, meeting the application requirements of aircraft engines. For example, nx-188, waz-20, ic163, ic164 and ic72 in the United States; Russia's bkha-4 has been used in the armed helicopter []; The IC6 alloy developed in China is used for the secondary turbine guide vane of an engine, and the IC10 alloy will be used for the combined turbine guide vane of high thrust ratio engine. In this paper, the transient liquid phase (TLP) diffusion welding technology [6] is studied for Ni3Al based alloy IC10, the special interlayer is developed, the change law of joint structure and its relationship with joint strength are analyzed, and the engineering application of TLP diffusion welding technology in IC10 alloy guide vane is realized

selection of test materials and methods

1 test materials

Ni3Al based alloy IC10 is selected as the test material and cast by directional solidification method. The nominal chemical composition of IC10 alloy is shown in Table 1. As cast IC10 alloy is mainly composed of γ Phase and γ′ Phase composition, between dendrites γ′ Most of the phases are 0.1~0.3 μ The cubic shape and size of M are greater than 10 μ M large irregular, dendrite dry γ′ Phase size is 1~3 μ Irregular shape of M and 0.1~0.3 μ Cubic shape of M, γ Phase is distributed in γ′ Around, about 0.01~0.2 thick μ m. After homogenization treatment at 1260 ± 10 ℃/2h under oil cooling or air cooling conditions, interdendritic γ′ Phase is 0.3~0.5 μ Cubic shape of M, dendrite dry γ′ Phase 1~3 μ Cubic shape of M, γ Phase is distributed in γ′ Around the phase, i.e γ′+γ Biphasic structure. Homogenized IC10 alloy γ′ The phase content is about 70%~80%, γ The phase is about 20%~30%, and a small amount of boride and carbide. The high temperature durability is shown in Table 2

2 selection of test method

ni3al belongs to Li2 structure and has obvious room temperature brittleness. Even if B element is used to improve the room temperature plasticity of the alloy, the γ The room temperature plasticity of Ni3Al alloy is still far behind that of common metal materials. Research on fusion welding of Ni3Al alloy such as EBW, LBW and TIG at home and abroad shows that [] solidification cracks and strain aging cracks are easy to appear in the melting zone and heat affected zone of the joint. Although the process method can reduce the cracks, it can not eliminate the cracks. This indicates that the fusion welding performance of Ni3Al alloy, which will include new satellite functions in LEGO factories around the world, is very poor, and the Ni3Al matrix non melting connection method should be adopted

tlp diffusion welding [6] is a new connection method formed by combining the advantages of brazing and solid-phase diffusion welding. Its principle is to place the intermediate layer alloy matching the base material on the connection surface, and form a liquid phase to fill the connection gap at the connection temperature. Due to the diffusion of atoms, the liquid has an appropriate amount of dissolution relative to the base metal, and then the liquid phase solidifies to obtain a structure similar to the base metal, and then carry out diffusion treatment to make the joint composition The structure is similar to that of the base metal, and a high-performance joint is obtained. The single crystal split blade of F119 engine and the porous laminated structure of MA956 alloy are manufactured by TLP diffusion welding technology abroad. This technology has been widely used in the connection of nickel base, iron base, cobalt base and oxide dispersion strengthened superalloys. Using TLP diffusion welding technology, Ni3Al based alloy IC10 was developed to match with IC10. The connection test was carried out to analyze the joint microstructure and mechanical properties, and to optimize the connection process and intermediate layer alloy

sample preparation and TLP welding process test

1 sample preparation

ni3al based alloy IC10 has high hardness and is difficult to be machined by ordinary tools. The raw materials are in the form of plate and bar. The raw materials are processed into pre welding samples by wire cutting and grinding methods; The energy storage spot welding method is used to fix the sample to be welded with a high-temperature alloy sheet, use a 0.04mm thick metal sheet to support both sides of the welding surface to control the weld gap, and add powder interlayer solder around the welding surface; After TLP diffusion welding, high temperature tensile properties shall be tested according to gb/t4338 2006 standard, and high temperature endurance properties shall be tested according to gb/t2039 1997 standard

2 TLP diffusion welding process test

the prepared sample shall be cleaned with ultrasonic before welding, and the surface to be welded shall be wiped with acetone after drying. The prepared paste like intermediate layer shall be placed on the welding surface and installed in hbf80 vacuum furnace. TLP connection process tests at 1240 ℃ for different holding times shall be carried out respectively. The interlayer alloy used is the kni3a nickel based interlayer developed for TLP diffusion welding of Ni3Al based alloy in this test (Fig. 1)

tlp diffusion welding test and analysis

for IC10 alloy samples welded by TLP Bonding Process with different holding time, the joint structure, composition and linear scanning element diffusion degree were analyzed by jenaphot-2000 optical microscope, jsw-840 scanning electron microscope and tn-5500 energy spectrometer

1 effect of holding time on the microstructure of IC10 alloy TLP joint

the microstructure of IC10 alloy joint with kni3a intermediate layer, 1240 ℃± 10 ℃ and different holding time (Fig. 2). After 4H of heat preservation, the welded joint has been isothermal solidified, and the joint structure is composed of γ Phase matrix, bulk simultaneity γ′ Phase, massive boride and a small amount of carbide; After 10h of insulation, large block γ′ Phase, massive boride and a small amount of carbides become fine particles and are uniformly distributed in γ In the phase matrix, the joint structure is similar to the welded matrix, and there is no visible interface between the welding surface and the matrix. This shows that the process of TLP diffusion welding of IC10 alloy for 10h can achieve the purpose of obtaining a joint similar to the matrix, and its joint structure has good continuity with the matrix structure, which is beneficial to improve the high-temperature mechanical properties of the joint

2 strength of IC10 alloy TLP diffusion welded joint

IC10 alloy is welded by using kni3a intermediate layer and 1240 ℃± 10 ℃ heat preservation for 10h furnace cooling process. The structure of the welded joint is shown in Figure 3. The strength samples were processed according to the standard and tested for high-temperature tensile and high-temperature endurance properties. The test results are shown in Table 3 and table 4. The endurance time of 982 ℃ and 128mpa stress of IC10 longitudinal welding samples exceeded 120h, that is, the high-temperature endurance strength was close to more than 77% of the matrix strength (165mpa); The endurance time of 980 ℃ and 100MPa stress of transverse welding sample exceeds 120h, that is, the high-temperature endurance strength reaches more than 83% of the matrix strength (120MPa)

3 effect of solid solution treatment after TLP diffusion welding on joint strength

ic10 models made of iron and glass are subject to 1260 ℃ solid solution treatment after TLP diffusion welding, and the microstructure and properties of matrix materials are recovered through heat treatment, so as to reduce the impact of welding process on the microstructure and properties of matrix materials. The high temperature tensile and high temperature endurance properties of the strength samples were tested after processing according to the standard. The test results are shown in Table 5 and table 6. It can be seen that the tensile strength of longitudinal welded specimens at 1000 ℃ reaches more than 89% of the matrix, and the tensile strength of transverse welded specimens reaches more than 91% of the matrix. The endurance time of longitudinal welded specimen at 980 ℃ and 144mpa stress reaches more than 97.5h, that is, the endurance strength of longitudinal welded specimen at 980 ℃ and 100h is close to 87% of the matrix strength; The lasting time of 980 ℃ and 120MPa stress of the transverse welding sample reaches more than 120h, that is, the lasting strength of 980 ℃ and 100h of the transverse welding sample is equal to the strength of the matrix

4 fracture analysis of tensile specimen

fracture morphology of tensile specimen is shown in Figure 4. The fracture surface of the high-temperature tensile fracture specimen is relatively flat and has little fluctuation; It has columnar dimple characteristics in the micro view, which is the same as the fracture morphology of directionally solidified superalloy, and also corresponds to the directionally solidified structure of IC10 alloy. It is a typical dimple morphology in the micro view

conclusion

(1) TLP diffusion welding can realize effective connection of IC10 alloy and obtain welded joints with similar microstructure and matrix

(2) Ni3Al based alloy ic10tlp intermediate layer alloy kni3a for diffusion welding was developed. The rupture strength of welded joint at 980 ℃ reached 128mpa

(3) solid solution treatment after TLP diffusion welding can improve the strength of base material and welded joints. The strength of longitudinal welded joints can be increased to 144mpa and the strength of transverse welded joints can be increased to 120MPa. (end)

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