Cobalt base alloy, powder, process and components

Abstract

The invention relates to a cobalt superalloy comprising (in % by weight): carbon (C): 0.04% - 0.05%; chromium (Cr): 21.0% - 23.0%; tungsten (W): 7.2% - 8.2%; titanium (Ti): 0.05% - 0.14%; aluminum (Al): 1.7% - 2.7%; tantalum (Ta): 2.9% - 3.6%; yttrium (Y): 0.01% - 0.03%; nickel (Ni): 11.5% bis 13.5%; hafnium (Hf): 0.45% - 0.65%; cobalt (Co): 49.0% - 53.0%; zirconium (Zr): up to 0.02%; boron (B): up to 0.0014%; silicon (Si): up to 0.018%.

Description

[0001]Description Cobalt-based alloy, powder, process and components The invention relates to a cobalt-based alloy, a powder, process and components. For turbine blades of next-generation gas turbines, a more oxidation-resistant material is required at the tips of the turbine blades due to the high temperature load (> 1373 K). Even as a new part, the tip of a turbine blade can also have a different material than the material (substrate) of the blade. Cobalt-based superalloys to improve oxidation resistance are currently used as filler material for blade tip repairs (EP 3,077,572 A1). The aim is to improve the mechanical properties and oxidation resistance while simultaneously achieving good weldability. The object of the invention is therefore to solve the above-mentioned problem.The object is achieved by a cobalt-based alloy according to claim 1, a powder according to claim 3, components according to claims 4, 5 and methods according to claims 6, 7. The subclaims list further advantageous measures which can be combined with one another as desired in order to achieve further advantages. The description only represents exemplary embodiments of the invention. The idea consists in a cobalt-based alloy which is particularly weldable and has, in particular, consists of (in wt. %): Carbon (C): 0.4% to 0.5% Chromium (Cr): 21.0% to 23.0% Tungsten (W): 7.2% to 8.2% Titanium (Ti): 0.05% to 0.14% Aluminum (Al): 1.7% to 2.7% Tantalum (Ta): 2.9% to 3.6% Yttrium (Y): 0.01% to 0.03% Nickel (Ni): 11.5% to 13.5% Hafnium (Hf): 0.45% to 0.65% Cobalt (Co): 49.0% to 53.0%, optionally Zirconium (Zr): up to 0.02% Boron (B): up to 0.0014% silicon (Si): up to 0.018%. Another advantageous alloy comprises, in particular, (in wt.%): Carbon (C): 0.45% Chromium (Cr): 22.0% Tungsten (W): 8.0% Titanium (Ti): 0.1% Aluminum (Al): 2.2% Tantalum (Ta): 3.25% Yttrium (Y): 0.02% Cobalt (Co): 50.93% Nickel (Ni): 12.5% ​​Hafnium (Hf): 0.55%. Carbon (C) is added, which, in addition to its function as a deoxidizing element, has further functions of combining with titanium (Ti) and tantalum (Ta) to form stable MC-type primary carbides, suppressing the coarsening of austenitic grains during hot deformation and improving hot sliding properties. The desired effect of carbon (C) is achieved. Silicon (Si) can be optionally added as a deoxidizer and also acts to improve the adhesion of a developing oxide layer. However, its excessive addition causes a reduction in both hot formability and ductility at room temperatures.Chromium (Cr) forms an oxide layer with highly tight adhesion to the surface during heating to high temperatures and improves oxidation resistance. In addition, chromium (Cr) can also improve hot workability. Tungsten (W) is an additional element that essentially strengthens the austenitic solid solution up to high temperatures. Aluminum (Al) is an additional element that is essential for the formation of a stable γ′ phase after tempering. A portion of the titanium (Ti) combines with carbon (C) to form a stable MC-type primary carbide and has a strength-enhancing function in non-γ′-hardened alloys. The remainder of the titanium (Ti) exists in the γ′ phase in the solid solution state, which strengthens the γ′ phase and serves to improve high-temperature strength.Furthermore, aluminum (Al), tantalum (Ta), and titanium (Ti) also play an important role in improving oxidation resistance, especially when combined with other elements to form stable oxide layer systems. Similar to titanium (Ti), a portion of both tantalum (Ta) and carbon (C) combine to form stable MC-type primary carbides, and they have strength-enhancing functions, especially for non-γ′-hardened alloys. Zirconium (Zr) and boron (B) are effective in optionally improving high-temperature strength and ductility through their grain boundary active function, and at least one of them can be added to the alloy of the invention in an appropriate amount. Their effect is maintained with a small addition amount. The addition of hafnium (Hf) stabilizes the grain boundaries, thus improving the mechanical properties at high temperatures.The alloy or powder can be used in the production of new solid components, in repairs or in the modular production of new parts in which at least one section has a different chemical composition. Coatings are also carried out using the alloy or powder. A complete component, in particular a turbine component, can be produced using the alloy or powder. Likewise, the alloy or powder can be used to produce a modular new part, in particular a turbine component, or also in particular a component to be repaired. In this case, the alloy according to the invention or the powder according to the invention is applied, in particular by means of build-up welding, to a substrate, in particular a metallic substrate, which is different from the alloy or powder, which is in particular a nickel-based alloy.Different alloy generally means that at least one alloying element is present in greater or lesser quantities and / or that the proportion of at least one alloying component differs by at least 10%, in particular by at least 20%. Processes (new parts, repairs) such as deposition welding, in particular laser deposition welding, especially laser powder deposition welding with or without abrasive particles, as well as additive processes (3D printing), in particular powder bed processes (i.e., also possible with a binder), or spray processes (APS, HVOF, etc.) can be used.

Claims

Patent claims 1. Cobalt superalloy, comprising, in particular consisting of (in wt%): Carbon (C): 0.4% to 0.5% Chromium (Cr): 21.0% to 23.0% Tungsten (W): 7.2% to 8.2% Titanium (Ti): 0.05% to 0.14% Aluminum (Al): 1.7% to 2.7% Tantalum (Ta): 2.9% to 3.6% Yttrium (Y): 0.01% to 0.03% Nickel (Ni): 11.5% to 13.5% Hafnium (Hf): 0.45% to 0.65% Cobalt (Co): 49.0% to 53.0%, optionally Zirconium (Zr): up to 0.02% Boron (B): up to 0.0014% Silicon (Si): up to 0.018%.

2. Alloy according to claim 1, comprising, in particular consisting of (in wt. %): Carbon (C): 0.45% Chromium (Cr): 22.0% Tungsten (W): 8.0% Titanium (Ti): 0.1% Aluminum (Al): 2.2% Tantalum (Ta): 3.25% Yttrium (Y): 0.02% Cobalt (Co): 50.9% Nickel (Ni): 12.5% ​​Hafnium (Hf): 0.

55.

3. A powder comprising an alloy, in particular consisting of an alloy, according to one of claims 1 or 2, optionally with a binder and / or with abrasive particles.

4. A component, in particular a turbine component, comprising an alloy according to one or both of claims 1 or 2, in particular consisting of an alloy according to one or both of claims 1 or 2 or produced using a powder according to claim 3.

5. A component, in particular a turbine component, very particularly a repaired component, comprising a metallic substrate, in particular a nickel-based substrate, which is different from an alloy according to claim 1 or 2 and a part of the component on the substrate, in particular a blade tip of a turbine blade, which comprises an alloy according to one or both of claims 1 or 2. 6.Method for producing a component, in particular a turbine component, in which by deposition welding, in particular by laser deposition welding,. or by additive processes, in particular by means of a powder bed process, an alloy according to one or both of claims 1 or 2 or a powder according to claim 3 is used.

7. A method for producing a component, in particular for repairing a component, in which an alloy according to one or both of claims 1 or 2 or a powder according to claim 3 is applied to a substrate, in particular to a nickel-based substrate, of the component by build-up welding, in particular by laser build-up welding, or by additive processes, in particular by means of a powder bed process.