ADHESION OF COATINGS USING ADHESIVE BONDING COMPOSITIONS
A multi-layer article (1) disclosed herein contains a metallic substrate (2), a protective layer (6), and an adhesive bonding layer (14) including an oxygen-containing compound that bonds the adhesive bonding layer to the metallic substrate, the protective layer, or both. A method for forming the multi-layer article includes the steps of heating a protective bonding composition (20) to form a molten material (24) in contact with a metal-containing surface (2), allowing the molten material to cool and solidify into the adhesion bonding layer (14) affixed to the metal-containing surface, depositing a ceramic material (26) onto the adhesive bonding layer, and heating the ceramic material to form the protective layer (6) affixed to the adhesive bonding layer.
This invention relates generally to the field of materials technology, and more particularly to the fabrication and repair of multi-layer metallic articles containing adhesive coatings.
BACKGROUND OF THE INVENTIONHot section components of modern gas turbine engines are often made of high-temperature alloys including superalloys based on nickel, iron and cobalt. Cast superalloys (e.g., 247, 738, CMSX4, Rene 5, etc.) and high performance wrought alloys (e.g., X, 625, 617, etc.) are often used in such high-temperature applications (e.g., turbine blades, vanes, combustion transition liners). These superalloys have been developed to withstand increasingly higher operating temperatures as well as the presence of corrosive and oxidative conditions. To withstand these extreme environments, protective coating systems are often applied to the surface of superalloy components to form multi-layer articles. These coating systems include an environmental coating, which can also serve as a metallic bond coat layer, and usually a ceramic thermal barrier coating (TBC) overlying the environmental or bond coat layer.
Such environmental coatings (or bond coats) are typically metallic overlay coatings of the formula “MCrAlX” (where M is a Group VIIIB element such as Co, Ni, or a mixture thereof, and X is a rare earth element such as Y, Hf, W, Zr, La, or a mixture thereof) or diffusion aluminide coatings such as NiAl or a modified NiAl that includes an element such as Pt, Rh or Pd. In thermal barrier coating (TBC) systems containing both a metallic bond coat and a ceramic TBC layer, the TBC layer is often formed from metal oxides such as yttria-stabilized zirconias (YSZs). One of the purposes of the bond coat layer in a TBC system is to improve adhesion between the outer TBC layer and the underlying substrate being protected.
In such multi-layered coating systems, adhesion of the outer protective layer to the underlying metallic substrate is an important consideration that can greatly affect the efficiency and longevity of a hot section component. Protective coatings are subject to degradation as a function of service. Elevated temperatures, high stresses (both sustained and cyclic), reactions with process gas, and foreign object impact can cause a variety of chemical and physical property changes leading to loss of coating (via e.g. cracking and spalling) resulting in exposure of the underlying substrate and further component damage.
A need exists to somehow improve adhesion between these outer protective layers 4, 6 and the underlying substrate 2 to improve component longevity and efficiency.
The invention is explained in the following description in view of the drawings that show:
The inventors were aware that certain welding and cladding flux formulations produce slag deposits that are difficult to remove. This adhesion is generally considered to be problematic in the welding industry—especially with multi-pass welds where it becomes both labor intensive to remove the deposits and where incomplete removal can result in the formation of inclusions and inferior weld deposits. For this reason welding compositions (e.g., flux compositions) are generally formulated to enhance detachability of the resulting slag deposits, see, e.g., Oladipupo, A. O., “Slag Detachability from Submerged Arc Welds,” Doctoral Thesis (Massachusetts Institute of Technology) February 1987 and US 2006/0266799.
Although contrary to the accepted wisdom in the relevant art, the inventors recognized a possible utility of welding compositions capable of forming such deposits having low detachability, as a way to improve adhesion between protective coating systems and underlying metallic substrates. It was also envisioned that certain deposits could also be formulated to provide protective features that either supplement the outer protective layer (e.g., TBC/bond coat) or replace it altogether. Based upon this recognition, the inventors have developed protective bonding compositions and methods for using such compositions in the fabrication and repair of multi-layer articles having improved adhesion between protective outer layer(s) and underlying metallic substrates.
The metallic substrate 2 of
The protective layer 6 of
The adhesive bonding layer 14 of
To attain the desired low detachability of the adhesive bonding layer 14, the protective bonding composition is formulated to contain certain mixtures of compounds (described below in greater detail) which react in the heated environment of the molten material to form at least one oxygen-containing compound that promotes the bonding of the adhesive bonding layer 14 to the metallic substrate 2, the protective layer 6, or both.
In some embodiments the oxygen-containing compound is selected from a spinel compound, a perovskite compound, a cuspidine compound, and mixtures thereof. In some embodiments the oxygen-containing compound is selected from MgAlCrO4, FeCrO4, CaTiO3, Ca4(Si2O7)(F,OH)2, and mixtures thereof.
The term “spinel compound” is used herein in a general sense to describe an inorganic compound or mineral of the general formula MgAlMO4 wherein the element “M” refers to a metallic element such as Al or a transition metal such as Cr. The term “spinel compound” is also used herein in the same manner as this term is commonly understood in the relevant art. The term “perovskite compound” is used herein in a general sense to describe an inorganic compound or mineral of the general formula CaTiO3. The term “perovskite compound” is also used herein in the same manner as this term is commonly understood in the relevant art. The term “cuspidine compound” is used herein in a general sense to describe an inorganic compound or mineral of the general formula Ca4(Si2O7)(F,OH)2. The term “cuspidine compound” is also used herein in the same manner as this term is commonly understood in the relevant art.
In some embodiments the oxygen-containing compound is believed to enhance adhesion between the adhesive bonding layer 14 and the metallic substrate 2, the protective layer 6, or both, by forming rigid crystalline structures serving as hooks or anchors to which the respective materials can inter-bond.
As also illustrated in
In some embodiments, for example, the metallic substrate 2 of
Step 2 of
In Step 3 of
Protective bonding compositions 20 may contain inorganic compounds such as metal oxides, metal halides, metal oxometallates, metal carbonates, a mixtures thereof—as well as elemental metals, lanthanides and metalloids. Protective bonding compositions 20 may also include organic compounds such as high-molecular weight hydrocarbons (e.g., beeswax, paraffin), carbohydrates (e.g., cellulose), natural and synthetic oils (e.g., palm oil), organic reducing agents (e.g., charcoal, coke), carboxylic acids and dicarboxylic acids (e.g., abietic acid, isopimaric acid, neoabietic acid, dehydroabietic acid, rosins), carboxylic acid salts (e.g., rosin salts), carboxylic acid derivatives (e.g., dehydro-abietylamine), amines (e.g., triethanolamine), alcohols (e.g., high polyglycols, glycerols), natural and synthetic resins (e.g., polyol esters of fatty acids), and other organic compounds, as well a mixture thereof.
The term “metal oxides” is used herein in a general sense to describe compounds having the general formula MaOb in which the variable “M” represents a metal atom, and the variables “a” and “b” represent integers greater than zero. Non-limiting examples of metal oxides include compounds such as Li2O, BeO, B2O3, B6O, MgO, Al2O3, SiO2, CaO, Sc2O3, TiO, TiO2, Ti2O3, VO, V2O3, V2O4, V2O5, Cr2O3, CrO3, MnO, MnO2, Mn2O3, Mn3O4, FeO, Fe2O3, Fe3O4, CoO, Co3O4, NiO, Ni2O3, Cu2O, CuO, ZnO, Ga2O3, GeO2, As2O3, Rb2O, SrO, Y2O3, ZrO2, NiO, NiO2, Ni2O5, MoO3, MoO2, RuO2, Rh2O3, RhO2, PdO, Ag2O, CdO, In2O3, SnO, SnO2, Sb2O3, TeO2, TeO3, Cs2O, BaO, HfO2, Ta2O5, WO2, WO3, ReO3, Re2O7, PtO2, Au2O3, La2O3, CeO2, Ce2O3, and mixtures thereof, to name a few. The term “metal oxides” is also used herein in the same manner as this term is commonly understood in the relevant art.
The term “metal halides” is used herein in a general sense to describe compounds containing a metal atom and at least one halogen atom. Non-limiting examples of metal halides include compounds such as LiF, LiCl, LiBr, LiI, Li2NiBr4, Li2CuCl4, LiAsF6, LiPF6, LiAlCl4, LiGaCl4, Li2PdCl4, NaF, NaCl, NaBr, Na3AlF6, NaSbF6, NaAsF6, NaAuBr4, NaAlCl4, Na2PdCl4, Na2PtCl4, MgF2, MgCl2, MgBr2, AlF3, KCl, KF, KBr, K2RuCl5, K2IrCl6, K2PtCl6, K2PtCl6, K2ReCl6, K3RhCl6, KSbF6, KAsF6, K2NiF6, K2TiF6, K2ZrF6, K2PtI6, KAuBr4, K2PdBr4, K2PdCl4, CaF2, CaF, CaBr2, CaCl2, CaI2, ScBr3, ScCl3, ScF3, ScI3, TiF3, VCl2, VCl3, CrCl3, CrBr3, CrCl2, CrF2, MnCl2, MnBr2, MnF2, MnF3, MnI2, FeBr2, FeBr3, FeCl2, FeCl3, FeI2, CoBr2, CoCl2, CoF3, CoF2, CoI2, NiBr2, NiCl2, NiF2, NiI2, CuBr, CuBr2, CuCl, CuCl2, CuF2, CuI, ZnF2, ZnBr2, ZnCl2, ZnI2, GaBr3, Ga2Cl4, GaCl3, GaF3, GaI3, GaBr2, GeBr2, GeI2, GeI4, RbBr, RbCl, RbF, RbI, SrBr2, SrCl2, SrF2, SrI2, YCl3, YF3, YI3, YBr3, ZrBr4, ZrCl4, ZrI2, YBr, ZrBr4, ZrCl4, ZrF4, ZrI4, NbCl5, NbF5, MoCl3, MoCl5, RuI3, RhCl3, PdBr2, PdCl2, PdI2, AgCl, AgF, AgF2, AgSbF6, AgI, CdBr2, CdCl2, CdI2, InBr, InBr3, InCl, InCl2, InCl3, InF3, InI, InI3, SnBr2, SnCl2, SnI2, SnI4, SnCl3, SbF3, SbI3, CsBr, CsCl, CsF, CsI, BaCl2, BaF2, BaI2, BaCoF4, BaNiF4, HfCl4, HfF4, TaCl5, TaF5, WCl4, WCl6, ReCl3, ReCl5, IrCl3, PtBr2, PtCl2, AuBr3, AuCl, AuCl3, AuI, KAuCl4, LaBr3, LaCl3, LaF3, LaI3, CeBr3, CeCl3, CeF3, CeF4, CeI3, and mixtures thereof, to name a few. The term “metal halides” is also used herein in the same manner as this term is commonly understood in the relevant art.
The term “metal oxometallates” is used herein in a general sense to describe compounds having the general formula MaXbOc in which the variable “M” represents a metal atom, the variable “X” represents a metal or non-metal atom, and the variables “a,” “b,” and “c” represent integers greater than zero. Non-limiting examples of metal oxometallates include compounds such as LiIO3, LiBO2, Li2SiO3, LiClO4, Na2B4O7, NaBO3, Na2SiO3, NaVO3, Na2MoO4, Na2SeO4, Na2SeO3, Na2TeO3, K2SiO3, K2CrO4, K2Cr2O7, CaSiO3, BaMnO4, and mixtures thereof, to name a few. The term “metal oxometallates” is also used herein in the same manner as this term is commonly understood in the relevant art.
The term “metal carbonates” is used herein in a general sense to describe compounds containing a metal atom and at least one carbonate group. Non-limiting example of metal carbonates include compounds such as Li2CO3, Na2CO3, NaHCO3, MgCO3, K2CO3, CaCO3, Cr2(CO3)3, MnCO3, CoCO3, NiCO3, CuCO3, Rb2CO3, SrCO3, Y2(CO3)3, Ag2CO3, CdCO3, In2(CO3)3, Sb2(CO3)3, C2CO3, BaCO3, La2(CO3)3, Ce2(CO3)3, NaAl(CO3) (OH)2, and mixtures thereof, to name a few. The term “metal carbonates” is also used herein in the same manner as this term is commonly understood in the relevant art.
In some embodiments TBC 6 adhesion to a MCrAlY bond-coat underlayer 4 (such as, for example, in
MgO+Al2O3→MgAlCrO4
These spinels represent solid reaction products that embed and attach to the underlying metallic substrate and can therefore serve as chemical anchors 16 that can greatly increase attachability (bond integrity) in multi-layer articles of the present disclosure.
Protective bonding compositions 20 in some embodiments contain MgO and Al2O3 in respective proportions such that a molten mixture containing the composition 20 and Cr forms MgAlCrO4. In some embodiments a molar ratio of the MgO to the Al2O3 in the protective bonding composition 20 ranges from about 1.5:1 to about 1:1.5, or from about 1.3:1 to about 1:1.3, or from about 1.1:1 to about 1:1.1 respectively. In other embodiments the molar ratio of the MgO to the Al2O3 is about 1:1.
Some MgO/Al2O3-containing compositions 20 comprise at least one of: (1) greater than about 25 percent by weight of MgO; and (2) greater than out 25 percent by weight of Al2O3, based on a total weight of the protective bonding composition 20. In other embodiments compositions 20 comprise at least one of: (1) greater than about 35 percent by weight of MgO; and (2) greater than about 35 percent by weight of Al2O3, based on a total weight of the protective bonding composition 20. In some embodiments the MgO/Al2O3-containing compositions 20 may further comprise Cr, such as for example greater than about 10 percent by weight of Cr or greater than about 15 percent by weight of Cr. In other embodiments the MgO/Al2O3-containing compositions 20 may further comprise at least one selected from the group consisting of Cr, CrO2, Cr2O3 and CrO3.
Some MgO/Al2O3-containing compositions 20 further contain TiO2, SiO2 and ZrO2, such that a sum of the weights of the Al2O3, TiO2, SiO2 and the ZrO2 is less than about 6.5 percent by weight or more than about 12 percent by weight, based on a total weight of the protective bonding composition 20. Still in other embodiments the MgO/Al2O3-containing compositions 20 further contain at least one of: (1) CaO and TiO2 in respective proportions such that a molten mixture containing the composition 20 also forms CaTiO3; and (2) CaF2 and SiO2 in respective proportions such that a molten mixture containing the composition 20 also forms Ca4(Si2O7)(F,OH)2.
Flux compositions containing calcium oxide and rutile are also known in the relevant art to be problematic (in terms of slag detachability from a weld) and to form calcium titanate perovskites by reactions such as:
CaO+TiO2→CaTiO3
These perovskites may also act as chemical anchors 16 that reduce detachability. The inventors have recognized that protective bonding compositions 20 that contain mixtures of compounds selected from MgO, Al2O3, CaO and TiO2 can increase TBC 6 adherence to chromium-containing MCrAlY bond coats 4.
Some protective bonding compositions 20 contain CaO and TiO2 in respective proportions such that a molten mixture containing the composition 20 forms CaTiO3. In some embodiments a molar ratio of the CaO to the TiO2 ranges from about 1.5:1 to about 1:1.5, or from about 1.3:1 to about 1:1.3, or from about 1.1:1 to about 1:1.1 respectively. In other embodiments the molar ratio of the CaO to the TiO2 is about 1:1.
Some CaO/TiO2-containing compositions 20 comprise at least one of: (1) greater than about 5 percent by weight of the CaO; and (2) greater than about 5 percent by weight of the TiO2, based on a total weight of the protective bonding composition 20. In other embodiments compositions 20 comprise at least one of: (1) greater than about 10 percent by weight of the CaO; and (2) greater than about 10 percent by weight of the TiO2, based on a total weight of the protective bonding composition 20.
Some CaO/TiO2-containing compositions 20 further contain SiO2, Al2O3 and ZrO2, such that a sum of the weights of the Al2O3, TiO2, SiO2 and the ZrO2 is less than about 6.5 percent by weight or more than about 12 percent by weight, based on a total weight of the protective bonding composition 20. Still in other embodiments the CaO/TiO2-containing compositions 20 further contain at least one of: (1) CaF2 and SiO2 in respective proportions such that a molten mixture containing the composition 20 also forms Ca4(Si2O7)(F,OH)2; and (2) MgO and Al2O3 in respective proportions such that a molten mixture containing the composition 20 and Cr forms MgAlCrO4.
Flux compositions containing calcium fluoride and silica are also known in the relevant art to be problematic and to form cuspidine [Ca4(Si2O7)(F,OH)2] which also hinders slag removal. Cuspis is Greek and means “spear” which is related to the shape of crystalline cuspidine (see
Some protective bonding compositions 20 of the present disclosure contain CaF2 and SiO2 in respective proportions such that a molten mixture containing the composition 20 forms Ca4(Si2O7)(F,OH)2. In some embodiments a molar ratio of the CaF2 to the SiO2 ranges from about 1.5:1 to about 2.5:1, or from about 1.7:1 to about 2.3:1, or from about 1.9:1 to about 2.1:1, respectively. In other embodiments the molar ratio of the CaF2 to the SiO2 is about 2:1 respectively.
Some CaF2/SiO2-containing compositions 20 comprise at least one of: (1) greater than about 25 percent by weight of CaF2; and (2) greater than about 25 percent by weight of SiO2. In other embodiments CaF2/SiO2-containing compositions 20 comprise at least one of: (1) greater than about 35 percent by weight of CaF2; and (2) greater than about 35 percent by weight of SiO2.
Some CaF2/SiO2-containing compositions 20 further contain Al2O3, TiO2 and ZrO2, such that a sum of the weights of the Al2O3, TiO2, SiO2 and the ZrO2 is less than about 6.5 percent by weight or more than about 12 percent by weight, based on a total weight of the protective bonding composition 20. Still in other embodiments the CaF2/SiO2-containing compositions 20 further contain at least one of: (1) CaO and TiO2 in respective proportions such that the molten mixture also forms CaTiO3; and (2) MgO and Al2O3 in respective proportions such that a molten mixture containing the composition 20 and Cr forms MgAlCrO4.
While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein.
Claims
1. A multi-layer article, comprising:
- a metallic substrate;
- a protective layer; and
- an adhesive bonding layer comprising an oxygen-containing compound that bonds the adhesive bonding layer to the metallic substrate, the protective layer, or both.
2. The article of claim 1, further comprising a plurality of anchors bonded to the adhesive bonding layer and to at least one of the metallic substrate and the protective layer,
- wherein:
- the anchors comprise the oxygen-containing compound; and
- a structure of the anchors is effective to adhere the metallic substrate, the protective layer, or both, to the adhesive bonding layer by forming inter-layer linkages such that one portion of the anchors is attached to the adhesive bonding layer and another portion of the anchors is attached to the metallic substrate or to the protective layer.
3. The article of claim 1, comprising:
- a superalloy substrate;
- a MCrAlY bond coat layer bonded to a surface of the superalloy substrate;
- the adhesive bonding layer bonded to a surface of the MCrAlY bond coat layer; and
- a ceramic thermal barrier layer bonded to a surface of the adhesive bonding layer.
4. The article of claim 1, comprising:
- a superalloy substrate;
- the adhesive bonding layer bonded to a surface of the superalloy substrate; and
- a ceramic thermal barrier layer bonded to a surface of the adhesive bonding layer.
5. The article of claim 1, wherein the oxygen-containing compound is at least one selected from the group consisting of a spinel compound, a perovskite compound, and a cuspidine compound.
6. The article of claim 1, wherein the oxygen-containing compound is at least one selected from the group consisting of MgAlCrO4, FeCrO4, CaTiO3, and Ca4(Si2O7)(F,OH)2.
7. The article of claim 1, wherein the adhesive bonding layer is formed from a protective bonding composition comprising at least one of:
- a mixture of MgO and Al2O3 in respective proportions such that an adhesive bonding layer comprising Cr further comprises MgAlCrO4;
- a mixture of CaO and TiO2 in respective proportions such that the adhesive bonding layer comprises CaTiO3; and
- a mixture of CaF2 and SiO2 in respective proportions such that the adhesive bonding layer comprises Ca4(Si2O7)(F,OH)2.
8. The article of claim 7, satisfying at least one of the following conditions: based on a total weight of the protective bonding composition.
- (i) the protective bonding composition comprises at least one of greater than about 25 percent by weight of the MgO, and greater than about 25 percent by weight of the Al2O3;
- (ii) the protective bonding composition comprises at least one of greater than about 5 percent by weight of the CaO, and greater than about 5 percent by weight of the TiO2; and
- (iii) the protective bonding composition comprises at least one of greater than about 25 percent by weight of the CaF2, and greater than about 20 percent by weight of the SiO2,
9. A multi-layer article, comprising:
- a metallic layer;
- a protective layer; and
- a plurality of anchors bonded to both the metallic layer and the protective layer,
- wherein:
- the anchors comprise an oxygen-containing inorganic compound; and
- a structure of the anchors is effective to adhere the metallic layer to the protective layer by forming inter-layer linkages such that one portion of the anchors is attached to the metallic layer and another portion of the anchors is attached to the protective layer.
10. The article of claim 9, further comprising an adhesive bonding layer disposed between the metallic layer and the protective layer and in direct contact with the anchors, wherein the anchors form the inter-layer linkages such that a first portion of the anchors is attached to the metallic layer, a second portion of the anchors is attached to the adhesive bonding layer, and a third portion of the anchors is attached to the protective layer.
11. The article of claim 9, wherein the oxygen-containing inorganic compound is at least one selected from the group consisting of a spinel compound, a perovskite compound, and a cuspidine compound.
12. The article of claim 9, wherein the oxygen-containing inorganic compound is at least one selected from the group consisting of MgAlCrO4, FeCrO4, CaTiO3, and Ca4(Si2O7)(F,OH)2.
13. A method for forming a multi-layer article of claim 1, the method comprising:
- heating a protective bonding composition to form a molten material in contact with a metal-containing surface;
- allowing the molten material to cool and solidify into the adhesive bonding layer affixed to the metal-containing surface;
- depositing a ceramic material onto the adhesive bonding layer; and
- heating the ceramic material to form the protective layer affixed to the adhesive bonding layer, to form the multi-layer article.
14. The method of claim 13, wherein the protective bonding composition comprises at least two selected from the group consisting of MgO, Al2O3, CaO, TiO2, CaF2 and SiO2.
15. The method of claim 13, wherein the protective bonding composition comprises MgO and Al2O3 in respective proportions such that the molten material in the presence of Cr contains MgAlCrO4.
16. The method of claim 15, wherein a molar ratio of the MgO to the Al2O3 ranges from about 1.5:1 to about 1:1.5 respectively.
17. The method of claim 15, wherein the protective bonding composition comprises at least one of: based on a total weight of the protective bonding composition.
- greater than about 25 percent by weight of the MgO; and
- greater than about 25 percent by weight of the Al2O3,
18. The method of claim 13, wherein the protective bonding composition comprises CaO and TiO2 in respective proportions such that the molten material contains CaTiO3.
19. The method of claim 18, wherein a molar ratio of the CaO to the TiO2 ranges from about 1.5:1 to about 1:1.5 respectively.
20. The method of claim 18, wherein the protective bonding composition comprises at least one of: based on a total weight of the protective bonding composition.
- greater than about 5 percent by weight of the CaO; and
- greater than about 5 percent by weight of the TiO2,
21. The method of claim 13, wherein the protective bonding composition comprises CaF2 and SiO2 in respective proportions such that the molten material contains Ca4(Si2O7)(F,OH)2.
22. The method of claim 21, wherein a molar ratio of the CaF2 to the SiO2 ranges from about 1.5:1 to about 2.5:1 respectively.
23. The method of claim 21, wherein the protective bonding composition comprises at least one of: based on a total weight of the protective bonding composition.
- greater than about 25 percent by weight of the CaF2; and
- greater than about 20 percent by weight of the SiO2,
24. The method of claim 13, wherein the metal-containing surface is a metallic substrate or is a bond coat layer affixed to a surface of the metallic substrate.
25. The method of claim 13, further comprising removing a portion of the adhesive bonding layer before the depositing of the ceramic material, such that:
- anchors contained in the adhesive bonding layer are not removed and remain attached to the metal-containing surface; and
- exposed portions of the anchors become attached to the protective layer during the heating of the ceramic material.
Type: Application
Filed: Jan 14, 2015
Publication Date: Jul 14, 2016
Inventors: Gerald J. Bruck (Oviedo, FL), Ahmed Kamel (Orlando, FL)
Application Number: 14/596,283