| WO/2023/175266 | NICKEL-BASED SUPERALLOY |
| JPS62170883 | CONTROL-ROD DRIVE MECHANISM |
| JP5100023 | Biomaterials, artificial joints using them, and methods for manufacturing them |
JAIN APURV (IN)
LAUX BRITTA (DE)
STAMM WERNER (DE)
TAN WINNIE (US)
| WO2013037391A1 | 2013-03-21 | |||
| WO2013056934A1 | 2013-04-25 | |||
| WO2012069305A1 | 2012-05-31 |
| US20090162692A1 | 2009-06-25 |
| Patent claims 1. Alloy, at least comprising (in wt%) : Cobalt (Co) 16.0% +/- 10%, Chromium (Cr) 15.0% +/- 10%, Aluminum (Al) 8.0% +/- 10%, Tantalum (Ta) 2.0% +/- 10%, Yttrium (Y) 0.5% +/- 10%, base nickel (Ni) , especially consisting of Nickel (Ni) , Cobalt (Co) , Chromium (Cr) , Aluminum (Al) , Tantalum (Ta) and Yttrium (Y) . 2. Powder, at least comprising an alloy according to claim 1, especially consisting of this alloy. 3. Layer system (1), at least comprising: a metallic substrate (4), especially of a nickel- or a cobalt-based super alloy, at least one metallic layer (7', Ί ' ' ) made of an alloy according to claim 1 or produced by using a powder according to claim 2 and especially an outer most ceramic layer (10) . 4. Ceramic Layer system according to claim 3, wherein the ceramic layer (10) is a two layered system, which comprises: a partially stabilized zirconia layer and an outer most fully stabilized zirconia layer, or zirconia based ceramic layer with an outer most pyrochlore layer . 5. Layer system according to one or both of the claims 3 or 4, wherein the metallic bond coat is a two layered metallic bond coat (7', Ί'') with an underlying metallic bond coat (7') according to claim 1 and an outer metallic bond coat H") , which {1 ' ' ) especially selected from the compositions (in wt%) : Ni- (24-26) Co- (11-14) Cr- (10-12) Al- (0.1-0.5) Y, Ni- (24-26) Co- (23-25) Cr- (10-11) Al- (0.2-0. ) Y, Ni- (24-26) Co- (14-17) Cr- (10-11) Al- (0.2-0. ) Y, Ni- (24-26) Co- (14-17) Cr- (10-11) l- (0.4-0.8) -(0.3-0.7) a, Ni- (24-26) Co- (16-18) Cr- (10-11) Al- (1.0 -2.0) Re- (0.1-0.5) , Co- (29-31)Ni- (27-29) Cr- (7-8)Al-(0.5-0.7)Y (0.3-0.7) Si. Layer system according to any of the claims 3 to wherein only a single ceramic layer (10) is present, especially made of zirconia. |
The invention relates to a NiCoCrAly-Alloy, a powder and a layer system using this alloy.
Due to the high temperatures involved in the operation of modern gas turbines the titanium (Ti) from Ni- or Co-base material diffuses to a bond coat of NiCoCrAlY and forms spinels. These spinels subsequently lead to reduced creep resistance of the bond coat, thereby increasing the chances of failure.
In case of the older machines the operating temperatures were not so high and the problem of failure of the coating due to titanium spinels was not so prevalent. But with the rela ¬ tively newer machines, in the pursuit of achieving higher efficiency the operating temperatures are increasing and this problem could become more prevalent. It is therefore the aim of the invention to overcome the problems described above.
The problem is solved by an alloy according to claim 1, a powder according to claim 2 and a layer system according to claim 3.
In the subclaims further advantageous features are listed, which can be arbitrarily combined with each other to yield further advantages.
Instead of using a single bond coat layer, it is preferably proposed to use a bi-layered bond coat system where the top layer is made of the usual metallic coating material while the bottom layer is made of a newly developed coating mate ¬ rial which is richer in nickel (Ni) and has a reduced amount of cobalt (Co) as cobalt (Co) encourages the formation of spinels by destabilizing gamma prime state. A new developed first layer NiCoCrAlY alloy coating comprises a gamma and gamma prime system whereas the gamma prime state has lower than 25 at% (Al,Ta) but a very high gamma/gamma prime transition temperature.
Titan (Ti) will be caught because the free energy of for ¬ mation of Ni3Ti is more negative than that of N13AI and it will be formed preferably. Hence the titanium (Ti) cannot diffuse to the upper bond coat layer to form spinels.
The composition of the alloy or the new first layer coating is (in wt%) :
16.0% +/- 10% Co
15.0% +/- 10% Cr
8.0% +/- 10% Al
2.0% +/- 10% Ta
0.5% +/- 10% Y
base Nickel (Ni) .
+/- 10% has to be read as relative, e.g. 2% +/- 10% means
One inventive step is the addition of another metallic layer in the bond coat leading to a bi-layer bond coat system. The invention is expected to result in increased efficiency of the turbine because the blades will be able to withstand higher temperatures with a lesser probability of coating failure by Titan (Ti) .
The figure shows a layer system 1.
The layer system 1 comprises at least a substrate 4, at least one metallic bond coat 7', 1'' and an outer most ceramic layer 10. The metallic substrate 4 is preferably a nickel or a cobalt based super alloy which is used for turbine components, espe ¬ cially turbine blades, very especially for gas turbines. Direct on this metallic substrate 4 a metallic bond coat 7' is present, which acts as an oxidation and corrosion resistance for the metallic substrate and the bond coat for the preferably used outer most ceramic layer 10. This metallic bond coat 7' is preferably a NiCoCrAlY-alloy and could be also be a single layer made of the inventive alloy .
In a further embodiment of the invention there is a two lay- ered metallic NiCoCrAlY layer 7', 1'' with the underlying metallic layer 1' according to the inventive alloy and on top a further but different NiCoCrAlY-alloy 7''.
For the top layer 1' ' other coatings like (in wt%) :
Ni- (24-26) Co- (11-14) Cr- (10-12) Al- (0.1-0.5) Y,
Ni- (24-26) Co- (23-25) Cr- (10-11) Al- (0.2-0.4)Y,
Ni- (24-26) Co- (14-17) Cr- (10-11) Al- (0.2-0.4)Y,
Ni- (24-26) Co- (14-17) Cr- (10-11) Al- (0.4-0.8) -(0.3-0.7) Ta, Ni- (24-26) Co- (16-18) Cr- (10-11) Al- (1.0 -2.0) Re- (0.1-0.5) Y, Co- (29-31)Ni- (27-29) Cr- (7-8)Al-(0.5-0.7)Y (0.3-0.7) Si, are preferably used.
Not shown but during coating with a ceramic layer or at least during operation a thermal crown oxide layer (TGO) is grown on top of the outermost metallic bond coat 1' or 7'', which is responsible for oxidation resistance.
The ceramic layer 10 can be a zirconia based layer as a sin ¬ gle layer or as a double layer with an underlying partially stabilized zirconia and outer most fully stabilized zirconia layer or an outermost DVC layer or a two layered ceramic system with a pyrochlore layer as an outer most ceramic layer .