Patent Application
20220281027
The invention relates to the welding, and a device by means of electron beams, of nickel-based alloys.
The idea concerns the welded joining of components of nickel-based superalloys with a high y′ content, in particular moving turbine blades, or generally long, thin-walled components. On account of the size, it is becoming increasingly difficult for hollow blades to be produced by casting. On account of the thin wall thicknesses at the tip of the blade and the size of the blade cores, casting defects may occur during production and lead to the turbine blade being rejected.
The welding of Ni-based or Co-based superalloys with a high tendency to hot crack has not previously been possible without the occurrence of at least minor hot cracks. Various phenomena, solidification cracks, remelting cracks, cracks caused by a decrease in toughness or so-called phased melting are the reason for extremely complex technologies for connecting such materials.
Previously, numerous methods have been used to obtain an extreme reduction in the introduction of heat, for example low-volume laser-powder welding, which leads to very high cooling-down gradients, but has the consequence of a low building-up rate. On the other hand, such materials are associated with low-value, tougher and/or less oxidation-resistant substances, in order to reduce stresses during the cooling-down phase. It has so far only been possible with great effort to achieve a bond close to the base material, i.e. identical in its properties.
One possible alternative is to use casting to produce two blade components that are joined to one another.
A welding process has not previously been used for joining moving turbine blades of nickel-based superalloys with a high y′ content.
An object of the invention is therefore to solve this problem.
The object is achieved by a method and a device as claimed.
The dependent claims list further advantageous measures which can be combined with one another as desired to achieve further advantages.
The idea is to use casting to produce two blade components that are joined to one another by means of electron-beam welding.
Investigations have shown that weldable nickel-based superalloys can be joined without cracks at slow feed rates, in particular of 40 mm-80 mm/min, and with sheet thicknesses of up to 12 mm. Such a process may be used for joining blade parts on hollow blades.
Beam welding of a large hollow blade of a nickel-based superalloy, i.e. from row 3 and/or 4 of a gas turbine, with electron radiation in a process chamber is proposed. Electron radiation means electron beams or a focused beam of electrons.
The advantageous procedure is broken down into the following stages: -producing two turbine blade parts or a turbine blade and a blade tip by casting;—the two components are processed or produced in particular with a shoulder all around at the joining zone; -clamping the two sub-components in a vacuum chamber, in order that a displacement of the two components during the welding process is avoided (alternatively: pre-fixing by means of high-temperature brazing); —joining the two components in the vacuum chamber by means of electron-beam welding; —electron-beam welding is carried out with a relatively low feed rate of 12 mm/min-120 mm/min, thereby avoiding crack initiation; —dissimilar joining zones are likewise realized, in particular of DS materials on SX materials, and so blade tip production/blade tip repair on turbine blades with improved oxidation resistance is possible.
Advantages: joining a hot-gas component made up of simple castable sub-components; lowering the reject rates in the production of large turbine blades by casting; and saving costs and material.
The method described here is based on an increased introduction of heat, which however is not achieved by means of a preheating technique, such as induction, but is obtained from the liquid component of the welding.
In combination with the extremely slow feed rate of advantageously 30 mm/min to 60 mm/min, this leads to cooling-down conditions that prevent/extremely minimize hot crack formation. Purely computationally, this results in very high energy per unit length, which is specified in the prior art as a reference for welding systems. However, because of the uneven geometrical distribution, this value is more of a nuisance here.
The figures and the description only represent exemplary embodiments of the invention.
The electron-beam gun 7 or the laser may also be arranged outside the vacuum chamber 3, the beams then being coupled into the vacuum chamber 3.
The component 4 to be produced is advantageously pressed together at both opposite ends 22′, 22″ with a force 19′, 19″, and so the joining zone 16 is pressed together.
Preferably, a peripheral weld seam or join is produced, achieved by the component being turned about an axis 13 by means of a turning device.
The joining zone has a shoulder, which has a length of 8 mm to 12 mm.
The following parameters are advantageously used: welding with energy per unit length of higher than 600 J/mm; or a feed rate of 0.2 . . . 0.5 . . . 1.0 . . . 2.0 mm/s; an accelerating voltage of 80 . . . 120 . . . 160 kV; a beam current of 8 . . . 14 . . . 20 mA; a focal position as surface focus ±3 mm; a vacuum of 103-105 mbar; use of running-in and out devices required.
Beam welding of a hollow component, in particular a hollow blade of a nickel-based superalloy, with electron beams in a process chamber with optional internal bath support is proposed, as shown in the present schematic representation.
The electron radiation 10 impinges on the opposite surface 33.
The shoulder 30 is present on the inner side 36 facing away from the electron radiation 10.
Thus, slipping transversely to the longitudinal direction or direction of the force 19′, 19″ is avoided.
The principle can also be applied to laser irradiation in a vacuum.
The components (4′, 4″) may comprise the same alloy or different alloys.
Different means that at least one alloying element (not an impurity) is present to a greater or lesser extent or that at least a proportion of the same alloying element differs by at least 20%
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 210 430.4 | Jul 2019 | DE | national |
This application is the US National Stage of International Application No. PCT/EP2020/068178 filed 29 Jun. 2020, and claims the benefit thereof. The International Application claims the benefit of German Application No. DE 10 2019 210 430.4 filed 15 Jul. 2019. All of the applications are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/068178 | 6/29/2020 | WO |
