Selective oxide-forming alloys, coatings formed therefrom, and mechanical parts containing them.

Abstract

A selective oxide-forming alloy, a coating formed therefrom, and a mechanical part including the coating are provided. The selective oxide-forming alloy comprises 20 to 26 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 30 to 39 atomic percent aluminum (Al), 2 to 10 atomic percent hafnium (Hf), and the remainder niobium (Nb).

Description

Technical Field

[0001] The present disclosure generally relates to alloys, coatings formed from alloys, and machine parts including coatings. More particularly, the present disclosure relates to coatings formed from selective oxide-forming alloys (also referred to as "selective oxide-forming coatings" and used interchangeably throughout the present disclosure) suitable for Nb-based materials. The selective oxide-forming coatings have properties that enable the Nb-based materials to be applied to high-temperature parts such as turbine parts.

Background Art

[0002] Gas turbines (and their components), such as, but not limited to, aircraft turbines, land turbines, and marine turbines, are typically formed from superalloys that are typically nickel (Ni)-based. Gas turbine components formed from Ni-based superalloys generally exhibit desirable mechanical, chemical, and physical properties under the high temperatures, high stresses, and high pressure conditions typically encountered during gas turbine operation. For example, turbine components such as the airfoils of modern jet engines can reach temperatures of up to about 1050 °C, which can correspond to temperatures of up to about 85% of the melting temperature (T m ) of many Ni-based superalloys.

[0003] Since Ni-based superalloys have provided the desired level of performance in such applications, the development of such Ni-based superalloys has been widely studied. As a result, this field is mature, and few significant improvements have been realized in this area in recent years. Meanwhile, efforts have been made to develop alternative turbine component materials. These alternative materials include Nb-based high melting point metal intermetallic composites (hereinafter, "RMICs"). Most RMICs have a melting temperature of about 1700 °C. If RMICs can be used at about 80% of their melting temperature, they may be used in applications where the temperature exceeds the current use limit of Ni-based superalloys.

[0004] Examples of such RMICs include various Nb silicide in-situ composites. Nb silicide in-situ composites possess a useful range of mechanical properties, including low-temperature toughness as well as reasonable high-temperature strength and creep resistance. However, an obstacle to the development of Nb silicide in-situ composites and Nb alloys for high-temperature applications, including turbines and turbine components, is that their environmental resistance, such as oxidation behavior, is not sufficiently adequate to meet the stringent requirements imposed on applications in high-temperature section engine components, particularly airfoils, rotors, nozzles, shrouds, and exhaust components. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] U.S. Patent Application Publication No. 2011 / 0146848 [Overview of the Initiative]

[0006] All aspects, examples, and features described below can be combined in any technically possible way.

[0007] One aspect of the present disclosure provides an alloy comprising 20 to 26 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 30 to 39 atomic percent aluminum (Al), 2 to 10 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0008] Another aspect of the present disclosure, including the preceding aspects, comprises an alloy comprising 20 to 24 atomic percent silicon (Si), 23 to 27 atomic percent titanium (Ti), 30 to 37 atomic percent aluminum (Al), 4 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0009] Another aspect of the present disclosure includes any of the preceding aspects, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 32 to 39 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0010] Another aspect of the present disclosure includes any of the preceding aspects, wherein the alloy comprises 22 to 24 atomic percent silicon (Si), 23 to 25 atomic percent titanium (Ti), 35 to 37 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0011] Another aspect of the present disclosure includes any of the preceding aspects, wherein the alloy comprises about 23 atomic percent silicon (Si), about 24 atomic percent titanium (Ti), about 36 atomic percent aluminum (Al), about 5 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0012] Another aspect of the present disclosure includes any of the preceding aspects, wherein when the alloy is exposed to an oxidizing environment of 1200°C or higher, the alloy selectively forms a substantially continuous layer of aluminum oxide across the surface of the alloy.

[0013] Another aspect of the present disclosure includes any of the prior aspects, wherein the alloy has a microstructure comprising (Nb,Ti)Al3 phase and (Nb,Ti,Hf)5Si4 phase.

[0014] Another aspect of the present disclosure includes any of the preceding aspects, wherein the (Nb,Ti)Al3 phase comprises 6 to 26 atomic percent of niobium (Nb), 1 to 5 atomic percent of silicon (Si), 10 to 16 atomic percent of titanium (Ti), 71 to 77 atomic percent of aluminum (Al), and about 1 atomic percent of hafnium (Hf).

[0015] Another aspect of the present disclosure includes any of the prior aspects, wherein the (Nb,Ti,Hf)5Si4 phase comprises 13 to 19 atomic percent of niobium (Nb), 42 to 48 atomic percent of silicon (Si), 19 to 25 atomic percent of titanium (Ti), 1 to 3 atomic percent of aluminum (Al), and 12 to 18 atomic percent of hafnium (Hf).

[0016] One aspect of the present disclosure provides a coating composition comprising an alloy containing 20 to 26 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 30 to 39 atomic percent aluminum (Al), 2 to 10 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0017] Another aspect of the present disclosure includes any of the prior aspects, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 23 to 27 atomic percent titanium (Ti), 30 to 37 atomic percent aluminum (Al), 4 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0018] Another aspect of the present disclosure includes any of the preceding aspects, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 32 to 39 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0019] Another aspect of the present disclosure includes any of the preceding aspects, wherein the coating comprises a substantially continuous layer of aluminum oxide across the surface of the alloy when exposed to temperatures of 1200°C or higher.

[0020] Another aspect of the present disclosure includes any of the prior aspects, wherein the alloy has a microstructure comprising (Nb,Ti)Al3 phase and (Nb,Ti,Hf)5Si4 phase.

[0021] One aspect of the present disclosure provides a mechanical part comprising a substrate having a coating thereon, wherein the coating comprises an alloy containing 20 to 26 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 30 to 39 atomic percent aluminum (Al), 2 to 10 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0022] Another aspect of the present disclosure includes any of the prior aspects, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 23 to 27 atomic percent titanium (Ti), 30 to 37 atomic percent aluminum (Al), 4 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0023] Another aspect of the present disclosure includes any of the preceding aspects, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 32 to 39 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0024] Another aspect of this disclosure includes any of the prior aspects, wherein the substrate includes a niobium-based alloy.

[0025] Another aspect of this disclosure includes any of the prior aspects, wherein the mechanical component is a turbine component.

[0026] Another aspect of the present disclosure includes any of the prior aspects, wherein the turbine component is a component of a gas turbine selected from the group consisting of onshore turbines, offshore turbines, aircraft turbines, and power generation turbines.

[0027] Two or more embodiments described in this disclosure, including those described in this summary section, may be combined to form embodiments not specifically described herein.

[0028] Details of one or more embodiments are described in the accompanying drawings and the following description. Other features, purposes, and advantages will become apparent from the description and drawings, as well as the claims.

[0029] This application includes at least one drawing drawn in color. A copy of this publication of the patent application accompanied by the color drawing will be provided by the Patent Office upon request and payment of the necessary fees.

[0030] These and other features of the Disclosure will be more readily apparent from the following detailed description of various embodiments of the Disclosure, in conjunction with the accompanying drawings illustrating various embodiments of the Disclosure. [Brief explanation of the drawing]

[0031] [Figure 1A] This is a contour map showing the effect of the atomic percentage (at%) of element Al on the aluminum (Al) activity of approximately 7800 alloys evaluated at 800°C, according to embodiments of the present disclosure. [Figure 1B] This is a contour map showing the effect of the atomic percentage (at%) of element Nb on the aluminum (Al) activity of approximately 7800 alloys evaluated at 800°C, according to embodiments of the present disclosure. [Figure 1C] This is a contour map showing the effect of the atomic percentage (at%) of element Si on the aluminum (Al) activity of approximately 7800 alloys evaluated at 800°C, according to embodiments of the present disclosure. [Figure 1D] This is a contour map showing the effect of the atomic percentage (at%) of element Ti on the aluminum (Al) activity of approximately 7800 alloys evaluated at 800°C, according to embodiments of the present disclosure. [Figure 1E] This is a contour map showing the effect of the atomic percentage (at%) of element Hf on the aluminum (Al) activity of approximately 7800 alloys evaluated at 800°C, according to embodiments of the present disclosure. [Figure 2A] This is a contour map showing the effect of the atomic percentage (at%) of element Al on the aluminum (Al) activity of more than 7800 alloys evaluated at 1400°C, according to embodiments of the present disclosure. [Figure 2B] This is a contour map showing the effect of the atomic percentage (at%) of element Nb on the aluminum (Al) activity of more than 7800 alloys evaluated at 1400°C, according to embodiments of the present disclosure. [Figure 2C] This is a contour map showing the effect of the atomic percentage (at%) of element Si on the aluminum (Al) activity of more than 7800 alloys evaluated at 1400°C, according to embodiments of the present disclosure. [Figure 2D] This is a contour map showing the effect of the atomic percentage (at%) of element Ti on the aluminum (Al) activity of more than 7800 alloys evaluated at 1400°C, according to embodiments of the present disclosure. [Figure 2E]This is a contour map showing the effect of the atomic percentage (at%) of element Hf on the aluminum (Al) activity of more than 7800 alloys evaluated at 1400°C, according to embodiments of the present disclosure. [Figure 3] This plot shows the effect of atomic percentages of elements on the melting behavior of more than 7800 alloys at 1400°C, according to embodiments of the present disclosure. [Figure 4A] This figure shows the effect of the change in the atomic percentage of element Al on the phase equilibrium at 1400°C for a non-limiting example of a selected alloy Nb12Si23Ti24Al36Hf5 according to embodiments of the present disclosure, where the x-axis represents the atomic percentage of Al and the y-axis represents the equilibrium phase fraction. [Figure 4B] This figure shows the effect of the change in the atomic percentage of element Nb on the phase equilibrium at 1400°C for a non-limiting example of a selected alloy Nb12Si23Ti24Al36Hf5 according to embodiments of the present disclosure, where the x-axis represents the atomic percentage of Nb and the y-axis represents the equilibrium phase fraction. [Figure 4C] This figure shows the effect of the change in the atomic percentage of element Si on the phase equilibrium at 1400°C for a non-limiting example of a selected alloy Nb12Si23Ti24Al36Hf5 according to embodiments of the present disclosure, where the x-axis represents the atomic percentage of Si and the y-axis represents the equilibrium phase fraction. [Figure 4D] This figure shows the effect of the change in the atomic percentage of element Ti on the phase equilibrium at 1400°C for a non-limiting example of a selected alloy Nb12Si23Ti24Al36Hf5 of the present disclosure according to embodiments of the present disclosure, where the x-axis represents the atomic percentage of Ti and the y-axis represents the equilibrium phase fraction. [Figure 4E] This figure shows the effect of the change in the atomic percentage of element Hf on the phase equilibrium at 1400°C for a non-limiting example of a selected alloy Nb12Si23Ti24Al36Hf5 according to embodiments of the present disclosure, where the x-axis represents the atomic percentage of Hf and the y-axis represents the equilibrium phase fraction. [Figure 5]This is a scanning electron microscope (SEM) image showing the microstructure of a cross-section of a bulk ingot of a non-limiting example of an alloy, separated from the oxidized surface, after the bulk ingot has been exposed to an oxidizing environment at 1200°C for 100 hours, according to embodiments of the present disclosure. [Figure 6] This is a scanning electron microscope (SEM) image showing the microstructure of a cross-section of a bulk ingot of a non-limiting alloy after exposure to an oxidizing environment at 1400°C for 100 hours, according to an embodiment of the present disclosure. [Figure 7A] This is a scanning electron microscope image of the microstructure of a cross-section of a bulk ingot of a non-limiting example of an alloy after exposure of the alloy to an oxidizing environment at 1200°C for 1 hour, according to embodiments of the present disclosure. [Figure 7B] This is a scanning electron microscope image of the microstructure of a cross-section of a bulk ingot of a non-limiting example of an alloy after exposure of the alloy to an oxidizing environment at 1200°C for 100 hours, according to embodiments of the present disclosure. [Figure 8A] This is a scanning electron microscope image of the microstructure of a cross-section of a bulk ingot of a non-limiting example of an alloy after exposure of the alloy to an oxidizing environment at 1400°C for 1 hour, according to embodiments of the present disclosure. [Figure 8B] This is a scanning electron microscope image of the microstructure of a cross-section of a bulk ingot of a non-limiting example of an alloy after exposure of the alloy to an oxidizing environment at 1400°C for 100 hours, according to embodiments of the present disclosure. [Figure 9] This is a schematic cross-sectional view of a machine part having a coating of the alloy of the present disclosure formed thereon, according to an embodiment of the present disclosure. [Figure 10] This is a flowchart illustrating a method for coating a machine part coated with the alloy of the present disclosure, according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0032] Please note that the drawings in this disclosure are not necessarily to scale. The drawings are intended to illustrate only typical embodiments of this disclosure and should not be considered to limit the scope of this disclosure. In the drawings, similar reference numerals represent similar elements between drawings.

[0033] As a first issue, in order to clearly explain the subject matter of this disclosure, it is necessary to select certain terminology when referring to and describing relevant machine parts within this disclosure. Wherever possible, common industry terms are used and adopted in a manner that does not contradict their accepted meaning. Unless otherwise stated, such terms should be given a broad interpretation to be consistent with the context of this application and the scope of the appended claims. Those skilled in the art will understand that in many cases certain components may be referred to using several different or overlapping terms. What may be described herein as a single part may include multiple components and be referred to in another context as consisting of multiple components. Or, what may be described herein as including multiple components may be referred elsewhere as a single part.

[0034] The terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another, and are not intended to indicate the location or importance of any individual component.

[0035] The terminology used herein is for the sole purpose of describing specific embodiments and is not intended to limit the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural form unless the context otherwise explicitly indicates. The terms “comprises” and / or “comprising,” as used herein, indicate the presence of the described features, integers, steps, actions, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, actions, elements, components, and / or groups thereof. “Optional” or “optionally” means that the events or circumstances described below may or may not occur, or that the components or elements described below may or may not exist, and that the descriptions include instances in which the events occur or the components exist, and instances in which the events do not occur or the components do not exist.

[0036] When an element or layer is referred to as “on top of,” “engaged with,” “connected to,” or “joined with” another element or layer, it may be directly engaged with, connected to, or joined to the other element or layer, or there may be an intervening element or layer. Conversely, when an element is referred to as “directly on top of,” “directly engaged with,” “directly connected to,” or “directly joined with” another element or layer, there may be no intervening element or layer. Other words used to describe relationships between elements should be interpreted similarly (e.g., “between” versus “directly between,” “adjacent to” versus “directly adjacent to.”). As used herein, the term “and / or” includes any combination of one or more of the related enumerated items.

[0037] As described above, an obstacle to the development of Nb-based materials for high-temperature applications, including gas turbines and gas turbine components, is that their environmental resistance, such as oxidation behavior, is not always fully satisfactory to meet the stringent requirements imposed on engine component applications, particularly in high-temperature sections.

[0038] The coating composition is desirable for coatings that can improve the high-temperature performance of Nb substrates. This disclosure provides selective oxide-forming coatings suitable for use as protective oxide-forming coatings on Nb substrates, particularly Nb substrates exposed to high-temperature and oxidizing environments, including the harsh environments of gas turbine engines. The alloys of this disclosure are stable up to 1400°C, whereas conventional alloys are expected to partially melt by 1400°C. As described in later sections, the alloys of this disclosure mainly consist of two phases (trialuminide and 5-4 silicide), in contrast to the three phases of conventional alloys, which include trialuminide, 5-3 silicide, and 5-4 silicide. Furthermore, the alloys of this disclosure have excellent oxidation resistance when exposed to oxidizing environments above 1200°C, for example, 1200-1400°C. In some embodiments, the alloys of this disclosure selectively form a substantially continuous layer of aluminum oxide across the surface of the alloy when the alloy is exposed to an oxidizing environment of 1200-1400°C.

[0039] Examples of Nb-based materials include, but are not limited to, Nb-based alloys and Nb-based RMICs, the latter of which include niobium-silicide (Nb-Si) composites.

[0040] Non-limiting examples of alloys suitable for forming coatings on Nb substrates are described. These alloys may be referred to throughout this disclosure as “selective oxide-forming alloys” or “alumina-forming alloys.” Coatings formed from the alloys of this disclosure may be referred to throughout this disclosure as “selective oxide-forming coatings.” The elemental composition of the alloys is enumerated in atomic percentages (at%) as embodied in this disclosure.

[0041] In embodiments, the alloy of the present disclosure comprises 20 to 26 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 30 to 39 atomic percent aluminum (Al), 2 to 10 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0042] In this embodiment, the alloy comprises 20 to 24 atomic percent silicon (Si), 23 to 27 atomic percent titanium (Ti), 30 to 37 atomic percent aluminum (Al), 4 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0043] In this embodiment, the alloy comprises 20 to 24 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 32 to 39 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0044] In this embodiment, the alloy comprises 22 to 24 atomic percent silicon (Si), 23 to 25 atomic percent titanium (Ti), 35 to 37 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0045] In this embodiment, the alloy comprises about 23 atomic percent silicon (Si), about 24 atomic percent titanium (Ti), about 36 atomic percent aluminum (Al), about 5 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0046] In embodiments, the atomic percentage of silicon (Si) in the alloys of the present disclosure is about 20 to about 26, for example, about 20, about 21, about 22, about 23, about 24, about 25, about 26, or a value in the range of any two of the above values. In non-limiting embodiments, the atomic percentage of silicon (Si) in the alloy may be in the range of 20 to 26 atomic percent, or 21 to 25 atomic percent, or 22 to 24 atomic percent, or 20 to 24 atomic percent.

[0047] In embodiments, the atomic percentage of titanium (Ti) in the alloys of the present disclosure is about 21 to about 27, for example, about 21, about 22, about 23, about 24, about 25, about 26, about 27, or a value in the range of any two of the above values. In non-limiting embodiments, the atomic percentage of titanium (Ti) in the alloy may be in the range of 21 to 27 atomic percent, or 22 to 26 atomic percent, or 23 to 25 atomic percent, or 23 to 27 atomic percent.

[0048] In embodiments, the atomic percentage of aluminum (Al) in the alloys of the present disclosure is about 30 to about 39, for example, about 30, about 31, about 32, about 33, about 34, about 35, about 36, about 37, about 38, about 39, or a value in the range of any two of the above values. In non-limiting embodiments, the atomic percentage of aluminum (Al) in the alloy may be in the range of 30 to 39 atomic percent, or 30 to 37 atomic percent, or 30 to 36 atomic percent, or 31 to 38 atomic percent, 32 to 39 atomic percent, or 33 to 39 atomic percent, or 35 to 37 atomic percent, or 36 to 39 atomic percent.

[0049] In embodiments, the atomic percentage of hafnium (Hf) in the alloys of the present disclosure is about 2 to about 10, for example, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, or a value in the range of any two of the above values. In non-limiting embodiments, the atomic percentage of hafnium (Hf) in the alloy may be in the range of 2 to 10 atomic percent, or 2 to 9 atomic percent, or 2 to 8 atomic percent, or 2 to 7 atomic percent, or 4 to 7 atomic percent, or 4 to 6 atomic percent, or 5 to 7 atomic percent, or 5 to 6 atomic percent.

[0050] In embodiments, the alloy of the present disclosure comprises about 23 atomic percent silicon (Si), about 24 atomic percent titanium (Ti), about 36 atomic percent aluminum (Al), about 5 atomic percent hafnium (Hf), and the remainder niobium (Nb).

[0051] Design of alloy / coating compositions In designing the alloy / coating compositions of this disclosure, various factors were considered. The alloy may be referred to as the “coating composition” or “composition,” and these terms are used interchangeably throughout this disclosure. These factors include, but are not limited to, Al activity, melting behavior, and phase components of the alloy / coating composition.

[0052] Approximately 7800 coating compositions were evaluated by analyzing the computationally predicted thermodynamic properties of each composition. For example, Figures 1A to 1E include contour plots showing the effect of atomic percentages (at%) of individual elements in the alloy on aluminum (Al) activity, evaluated at 800°C. The x-axis represents the atomic percentage of each element in the composition, and the y-axis represents the Al activity, which is the effective concentration of Al in each composition. The Al activity of the evaluated compositions is generally classified into three clusters, with the upper cluster (green) representing relatively high Al activity, and the middle (blue-green) and lower (blue) clusters representing lower Al activity. Higher Al activity indicates a greater likelihood of aluminum oxide layer formation when the composition is coated onto a substrate and exposed to an oxidizing environment, which is desirable for applications including but not limited to coatings.

[0053] Referring to Figure 1A, the blue, blue-green, and green curves (A, B, and C) at the top of Figure 1A represent the corresponding distributions of Al at% of the alloy within the respective blue, blue-green, and green clusters in the contour plot. As shown in Figure 1A, as Al at% increases (reading x-axis values ​​from left to right), Al activity also increases (indicated by the shift to the right of the center point of the blue-blue-green-green curve in the contour plot, and the shift upward of the blue-blue-green-green cluster). Higher Al at% contributes to higher Al activity at 800°C.

[0054] Referring to Figure 1B, as the mean Nb at% decreases (reading x-axis values ​​from right to left), Al activity increases (indicated by the upward shift of the blue-blue-green-green clusters in the contour plot). Lower Nb at% contributes to higher Al activity at 800°C.

[0055] Applying a similar analysis, Figure 1C suggests that when Si is in the range of 20–26 at%, higher Si at% contributes to higher Al activity at 800°C. Figures 1D and 1E show that varying atomic percentages of Ti or Hf do not appear to significantly contribute to higher Al activity.

[0056] Figures 2A–2E include the analysis of the same 7800 alloy / coating compositions used in Figures 1A–1E, the only difference being that the temperature in Figures 2A–2E is 1400°C. Similarly, the Al activity of the evaluated alloys is generally classified into three clusters, with the upper cluster (green) representing relatively high Al activity, and the middle (blue-green) and lower (blue) clusters representing lower Al activity. The effect of the atomic percentage of each element on Al activity, as shown in Figures 2A–2E, is similar to the effect observed in the corresponding Figures 1A–1E and is omitted here for brevity.

[0057] The calculated and predicted thermodynamic phase composition of the same group of 7800 alloy / coating compositions was evaluated at 1400°C. Each plot in Figure 3 represents an alloy containing elements with atomic percentages that fall within their respective specified ranges. For example, in (a1), the atomic percentage range for Nb (represented by the x-axis value) is 10–20 at%, and the atomic percentage range for Si (represented by the y-axis value) is 20–30 at%. Similarly, (a2) represents an alloy containing 10–20 at% Nb and 20–27.5 at% Ti, and (b1) represents an alloy containing 20–30 at% Si and 20–27.5 at% Ti. The explanations for the other plots can be derived similarly and are omitted here for brevity.

[0058] In these pairwise plots, alloys that remain completely solid at 1400°C and alloys that form some liquid are represented by green and orange ball-shaped clusters in the plot, respectively. The top green and orange curves in the first column represent the distribution of Nb at% for all alloys in each green and orange cluster in plots (a1) to (a4). Similarly, the top curves in the second, third, and fourth columns represent the distribution of Si at%, Ti at%, and Al at% for all alloys in each green and orange cluster. The curve in the fifth column represents the distribution of Hf at% for all alloys in each green and orange cluster (based on the green and orange clusters shown from left to right, e.g., a4, b3, c2, d1).

[0059] By comparing plots (a1) to (a4), it is shown that alloys without a liquid form (green cluster) have a higher Nb at% than alloys with some liquid form (orange cluster), as indicated by the rightward shift of the green curve along the x-axis. Alloys with a high Nb at% are less likely to melt.

[0060] Similarly, comparing plots (b1) to (b3), it is shown that alloys that do not form a liquid (green cluster) have a lower Si at% than alloys that form some liquid (orange cluster), as indicated by the leftward shift of the green curve. Alloys with a low Si at% are less likely to melt. Comparing plots (c1) and (c2), it is shown that alloys that do not form a liquid (green cluster) have a slightly higher Ti at% than alloys that form some liquid (orange cluster), as indicated by the slight rightward shift of the green curve. The effect of Ti at% on the melting behavior of alloys is moderate. Similarly, the effects of Al at% (shown in plot (d1) and the corresponding curve) and Hf at% on the melting behavior of alloys are moderate.

[0061] Figure 3 also provides some important insights into alloy design. As shown by plot (b2), there are narrow regions of thermal stability for Al and Si. In plot (b2), the alloy contains Al in atomic percent in the range of 30–40 at% and Si in the range of 20–30 at%. When Al at% is at the upper end of the range, Si at% must be at the lower end of the range for the alloy to remain in the green cluster. Conversely, when Si at% is at the upper end of the range, Al at% must be at the lower end of the range for the alloy to remain in the green cluster. When both Al and Si are at the upper end of their ranges, the alloy tends to melt (orange cluster). Therefore, alloys can be designed to contain high Al or high Si for good melting behavior, but alloys with both high Al at% and high Si at% may be undesirable for good thermal stability.

[0062] Furthermore, as previously mentioned with respect to Figures 1A-1E and 2A-2E, lower Nb at% contributes to higher Al activity at 800°C and 1400°C. As shown in Figure 3, higher Nb at% is desirable for good thermal stability of the alloy (as previously mentioned), but lower Nb at% can also be tolerated when accompanied by lower Si (plot a1), higher Ti (plot a2), and higher Hf (plot a3).

[0063] The observations revealed in the evaluation of over 7800 alloy / coating compositions are remarkable and significant. Through rational design supported by these observations, the inventors of this disclosure were able to develop the desirable elemental composition space for the alloys of this disclosure. These data discussed above and throughout this disclosure, without limit, once again demonstrate that designing alloys with appropriate profiles, including oxidation resistance, thermal stability, and microstructure, requires careful and balanced consideration of various factors and the complex interactions between them.

[0064] Figures 4A to 4E show the selected alloy Nb of this disclosure. 12 Si23 Ti 24 Al 36 For non-limiting examples of Hf5, the effect of the change in atomic percentage of elements on the phase equilibrium at 1400 °C is shown. In FIGS. 4A-4E, the x-axis represents the values of the atomic percentages of Al (FIG. 4A), Nb (FIG. 4B), Si (FIG. 4C), Ti (FIG. 4D), and Hf (FIG. 4E), respectively, and the y-axis represents the mole fractions of the various phases of the corresponding alloy at equilibrium. Each of FIGS. 4A-4E also shows the general formula of the alloy represented in each figure. For example, in FIG. 4A, the alloy is Al x (Nb 12 Si 23 Ti 24 Hf5) (100 / (64+x)) having the general formula of. The central dashed line represents the selected alloy Nb 12 Si 23 Ti 24 Al 36 Hf5, where the atomic percentages of the elements Nb, Si, Ti, Al, and Hf are 12, 23, 24, 36, and 5, respectively. Moving from the central line to the left, the atomic percentage of Al decreases from 36 at% to 26 at%, and moving from the central line to the right, the atomic percentage of Al increases from 36 at% to 46 at%. While the atomic percentage of Al changes, the ratio between the atomic percentages of the other elements is kept constant, that is, in the alloy of FIG. 4A, Nb:Si:Ti:Hf is 12:23:24:5. For example, when Al is 41 at%, the alloy of FIG. 4A is Al 41 (Nb 12 Si 14 Ti 24 Hf5) 0.95 , that is, Al 41 Nb 11.4 Si 13.3 Ti 22.8 Hf 4.8 having the formula of. Similarly, in FIGS. 4B, 4C, 4D, and 4E, the alloys are Nb x (Si 23 Ti 24 Al 36 Hf5) (100 / (88+x)) , Si x (Nb 12 Ti 24 Al 36Hf5) (100 / (77+x)) Ti x (Nb 12 Si 23 Al 36 Hf5) (100 / (76+x)) , and Hf x (Nb 12 Si 23 Ti 24 Al 36 ) (100 / (95+x)) Each of these has a general formula, and a detailed explanation of these is the same as that given in Figure 4A, so for brevity, it will be omitted here.

[0065] In the figure, the y-axis represents the mole fraction of various phases at equilibrium. The alloy phases include the MAl3 trialuminide phase (Nb,Ti)Al3 (also called "trialuminide"), the M5Si4 silicide phase (Nb,Ti,Hf)5Si4 (also called "5-4 silicide"), the M5Si3 silicide phase (Nb,Ti,Hf)5Si3 (also called "5-3 silicide") having a hexagonal structure ("5-3 silicide (h)"), the M5Si3 silicide phase (Nb,Ti,Hf)5Si3 having a tetragonal structure ("5-3 silicide (t)"), and the liquid phase resulting from the melting of the alloy ("liquid") shown in each color in Figures 4A to 4E, with the same color representing the same type of phase. The ranges of elemental composition in Figures 4A to 4E were selected such that one end of the range is defined by the onset of melting when the concentration of one of the elements increases and / or decreases while the proportion of the remaining elements in the alloy remains constant, and the other end of the selected range is defined by maintaining high concentrations of trialuminide and 5-4 silicide (i.e., minimizing 5-3 silicide).

[0066] Nb 12 Si 23 Ti 24 Al 36 The phases of Hf5 are shown in the center of each of Figures 4A to 4E. Nb 12 Si 23 Ti 24 Al 36Hf5 alloys primarily exist in two phases: trialuminide and 5-4 silicide phases, with no 5-3 silicide (h), 5-3 silicide (t), or liquid phases observed. For the alloys evaluated in Figure 4A, the atomic percentage of Al is in the range of 26–46 at%. As Al at% increases from 36 at% to 46 at%, more melting occurs in the alloy, as indicated by the increase in the amount of liquid phase. As Al at% decreases from 36 at% to 26 at%, no melting is observed, but the 5-3 silicide (h) and 5-3 silicide (t) phases begin to form. The inventors have discovered that there is a narrow, unique window for the alloy to exist in a two-phase space primarily consisting of the trialuminide and 5-4 silicide phases. For example, as shown in Figure 4A, Al is in the range of 30-39 at%, 30-37 at%, 31-41 at%, 32-39 at%, 35-37 at%, or approximately 36 at%. x (Nb 12 Si 23 Ti 24 Hf5) (100 / (64+x)) The alloy is primarily composed of the trialuminide phase and the 5-4 silicide phase, with the 5-3 silicide phase or liquid phase present in small proportions. The above range (and the ranges described with reference to Figures 4B-4E) are provided as non-limiting examples and should be understood as not being limited to the listed ranges.

[0067] The alloy in Figure 4B has the general formula Nb x (Si 23 Ti 24 Al 36 Hf5) (100 / (88+x)) It has the following characteristics. Similarly, Figure 4B also shows that the alloy is mainly present in the trialuminide phase and the 5-4 silicide phase, with a narrow, distinctive window in which it is present in small proportions in the 5-3 silicide phase or liquid phase. For example, as shown in Figure 4B, Nb is in the range of 7-18 at%. x (Si 23 Ti 24 Al 36 Hf5) (100 / (88+x))Regarding this alloy, the alloy mainly consists of the trialuminide phase and the 5-4 silicide phase, with the 5-3 silicide phase or liquid phase present in small proportions.

[0068] As shown in Figure 4C, Si is in the range of 20-26 at%, 20-24 at%, 22-24 at%, or approximately 23 at%. x (Nb 12 Ti 24 Al 36 Hf5) (100 / (77+x)) The alloy is mainly composed of the trialuminide phase and the 5-4 silicide phase, with the 5-3 silicide phase or liquid phase present in small proportions.

[0069] As shown in Figure 4D, Ti is in the range of 21-27 at%, 23-27 at%, 23-25 ​​at%, or approximately 24 at%. x (Nb 12 Si 23 Al 36 Hf5) (100 / (76+x)) Regarding the alloy, the alloy mainly exists as trialuminide and 5-4 silicide phases, with 5-3 silicide phase or liquid phase present in small proportions.

[0070] As shown in Figure 4E, Hf is in the range of 2-10 at%, 2-7 at%, or 4-7 at%, or 5-7 at%, or approximately 5 at%. x (Nb 12 Si 23 Ti 24 Al 36 ) (100 / (95+x)) The alloy is mainly composed of trialuminide and 5-4 silicide phases, with 5-3 silicide or liquid phases present in small proportions.

[0071] Figures 4A to 4E further demonstrate that designing an alloy with an appropriate profile requires careful and balanced consideration of various factors.

[0072] Referring to Figures 5 and 6, these are scanning electron microscope (SEM) images showing the surface microstructure of bulk ingots of non-limiting alloys of this disclosure. For SEM studies, bulk ingots of alloys were cut into pieces, polished, sectioned, and polished for subsequent exposure to oxidation prior to microstructure measurements. During the oxidation experiment, alloy samples were heated in laboratory air in a box furnace with a lamp at 20°C / min. Measurements were performed after exposing the bulk ingots to an oxidizing environment for 100 hours at 1200°C (Figure 5) and 1400°C (Figure 6), respectively. In both Figures 5 and 6, the two main phases observed are the 5-4 silicide phase (representative bright area labeled "A") and the trialuminide phase (representative medium gray area labeled "B").

[0073] Table 1 shows the elemental composition (in atomic percent (at%)) of the 5-4 silicide phase and trialuminide phase in Figure 5. The elemental composition was measured by energy-dispersive spectroscopy (EDS) according to embodiments of this disclosure. [Table 1]

[0074] Table 2 shows the elemental composition (in atomic percent (at%)) of the 5-4 silicide phase and trialuminide phase in Figure 6. The elemental composition was measured by energy-dispersive spectroscopy (EDS) according to embodiments of this disclosure. [Table 2]

[0075] The examples in the table above are non-limiting. In certain embodiments, the (Nb,Ti)Al3 phase contains 6 to 26 atomic percent niobium (Nb), 1 to 5 atomic percent silicon (Si), 10 to 16 atomic percent titanium (Ti), 71 to 77 atomic percent aluminum (Al), and about 1 atomic percent hafnium (Hf). In embodiments, the (Nb,Ti,Hf)5Si4 phase contains 13 to 19 atomic percent niobium (Nb), 42 to 48 atomic percent silicon (Si), 19 to 25 atomic percent titanium (Ti), 1 to 3 atomic percent aluminum (Al), and 12 to 18 atomic percent hafnium (Hf).

[0076] Figures 7A, 7B, 8A, and 8B are scanning electron microscope images of the microstructure of cross-sections of bulk ingots of non-limiting examples of the alloys of this disclosure after exposure of the alloys to an oxidizing environment for 1 hour at 1200°C (Figure 7A), 100 hours at 1200°C (Figure 7B), 1 hour at 1400°C (Figure 8A), and 100 hours at 1400°C (Figure 8B), respectively. The phases identified in Figures 7A, 7B, 8A, and 8B include trialuminide (1), 5-4 silicide (2), aluminum oxide Al2O3 (3, also called "Al-rich oxide"), epoxy (4), 5-3 silicide (5), and discrete particles of mixed oxides of Nb, Si, Ti, and / or Hf (6, also called "Al-dilute oxide"). It is assumed that the mixed oxide of Nb, Si, Ti, and / or Hf (6) was formed early in the oxidation process and subsequently covered by aluminum oxide Al2O3 (3). It is further assumed that the growth of the mixed oxide of Nb, Si, Ti, and / or Hf stops once a continuous layer of aluminum oxide Al2O3 (3) is formed, as shown in Figures 7B and 8B.

[0077] Figures 7A, 7B, 8A, and 8B demonstrate the selective oxide-forming ability of the alloys of this disclosure at high temperatures, including 1200°C and 1400°C, but are not limited to these. As shown in Figures 7A and 8A, aluminum oxide Al2O3(3) rapidly forms as a continuous layer in just 1 hour at 1200°C (Figure 7A) and 1400°C (Figure 8A). The continuous layer aluminum oxide Al2O3(3) remains stable even after 100 hours at 1200°C (Figure 7B) and 1400°C (Figure 8B).

[0078] Surprisingly, as shown in Figures 7A, 7B, 8A, and 8B, a substantially continuous aluminum oxide layer (3) was formed over the region containing the (Nb,Ti,Hf)5Si4 phase (2) and the (Nb,Ti)Al3 phase (1). A continuous aluminum oxide layer (3) could also be formed on the region mainly containing the (Nb,Ti,Hf)5Si4 phase. This result is surprising because the region mainly containing the (Nb,Ti,Hf)5Si4 phase likely does not have a substantial atomic percentage of aluminum (Al) as a source for forming the aluminum oxide layer on the (Nb,Ti,Hf)5Si4 phase (2). The oxide layer initially formed on the (Nb,Ti,Hf)5Si4 phase (2) is assumed to contain oxides of Nb, Si, Ti, or Hf present as discrete particles in the (Nb,Ti,Hf)5Si4 phase. As more aluminum oxide is formed, preferably in the trialuminide phase (1), the aluminum oxide layer (3) continues to grow on top of the initially formed oxide layer (6), forming a substantially continuous layer over regions containing the (Nb,Ti)Al3 phase (1) and the (Nb,Ti,Hf)5Si4 phase (2).

[0079] In some embodiments, the aluminum oxide layer has a thickness greater than about 5 μm. In some embodiments, the aluminum oxide layer has a thickness of about 5 μm to about 7 μm.

[0080] The selective oxide-forming alloys of the present disclosure can be used to form protective coatings for applications requiring high temperatures (e.g., above about 1400°C). For example, in non-limiting embodiments, the protective coatings of the present disclosure can be used on substrates exposed to high temperatures. In embodiments, the substrate may be a substrate exposed to the harsh environment of a gas turbine engine. In embodiments, the substrate is an Nb-based substrate. In embodiments, the substrate is an Nb-based substrate used in a turbine or turbine component. In some embodiments, the turbine component is one or more of blades, rotors, or nozzles. In certain embodiments, the gas turbine is selected from the group consisting of onshore turbines, offshore turbines, aerospace turbines, and power generation turbines.

[0081] Figure 9 is a schematic cross-sectional view of a machine part 300 having a coating made of the alloy of the present disclosure. The machine part 300 may include a substrate 302 having a coating 304 thereon. The coating 304 may be formed from the alloy of the present disclosure. In some embodiments, the coating 304 includes an alloy comprising 20 to 26 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 30 to 39 atomic percent aluminum (Al), 2 to 10 atomic percent hafnium (Hf), and the remainder niobium (Nb). In embodiments, the machine part 300 may optionally include an additional layer (indicated by dashed lines) of thermal barrier coating (TBC) 306 placed on top of the coating 304. In embodiments, the TBC layer 306 may have a thickness greater than the thickness of the coating 304. The thermal barrier coating (TBC) 306 may include any currently known or later developed TBC material suitable for providing further protection to the coating. The mechanical component 300 may be exposed to high temperatures, such as those encountered by high-temperature gas path components within a turbine. High-temperature gas path components include, but are not limited to, combustion liners, transition pieces, turbine nozzles, and turbine blades ("also known as turbine buckets").

[0082] Figure 10 is a flowchart of a method for coating a machine part 300 (Figure 9) coated with a coating 304 (and optionally TBC 306). The method includes the steps of: providing a coating composition 400 comprising a selective oxide-forming alloy of the present disclosure in step S402; applying the coating composition 400 to a substrate 302 of the machine part 300 in step S404; and forming a coating 304 on the substrate 302 in step S406. The method may include an optional step S408 to form a TBC 306 on the machine part 300 by placing a TBC on the coating 304. The selective oxide-forming alloy may include 20 to 26 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 30 to 39 atomic percent aluminum (Al), 2 to 10 atomic percent hafnium (Hf), and the remainder niobium (Nb). Applying the coating composition 400 to the substrate 302 may include, but are not limited to, applying or depositing the coating composition 400 onto one or more surfaces of the substrate 302 using currently known or later developed deposition techniques, including, but not limited to, thermal spraying (e.g., plasma, flame, or high-speed oxygen fuel (HVOF)), high-speed air fuel (HVAF) thermal spraying, sputtering, electron beam physical vapor deposition (EBPVD), or chemical vapor deposition, or a combination thereof.

[0083] A coating 304 is formed by applying the coating composition 400 onto the substrate 302 (for example, using a hot spray). The coating 304 of the machine part 300 may include a microstructure containing (Nb,Ti)Al3 phase and (Nb,Ti,Hf)5Si4 phase, as previously described with respect to Figures 4A-4E, 5, 6, 7A, 7B, 8A, and 8B.

[0084] Forming the coating 304 on the substrate 302 may further include heat treatment (e.g., heating) of the coating 304 to generate an aluminum oxide layer. The aluminum oxide layer (3, Figures 7A, 8A, 7B, 8B) may be formed over regions containing the (Nb,Ti)Al3 phase and the (Nb,Ti,Hf)5Si4 phase. In some embodiments, the aluminum oxide layer may have a thickness greater than about 1 μm. In some embodiments, the aluminum oxide layer may have a thickness including, but is not limited to, 1 μm to 30 μm, or 1 μm to 20 μm, or 1 μm to 15 μm, or 1 μm to 10 μm, or 5 μm to 30 μm, or 5 μm to 20 μm, or 5 μm to 15 μm, or 5 μm to 10 μm, or 15 μm to 30 μm.

[0085] The drawings above illustrate some of the processes related to certain embodiments of the present disclosure. In this regard, each drawing or block in the flowchart of the drawings represents a process related to an embodiment of the described method. It should also be noted that in some alternative embodiments, the actions shown in the drawings or blocks may occur out of order shown in the drawings, or may actually be performed substantially simultaneously or in reverse order, depending on the related actions. Furthermore, those skilled in the art will recognize that additional blocks illustrating the processes may be added.

[0086] Throughout this specification and the claims, the approximation language used herein may be applied to modify any quantitative expression that may vary to a reasonable degree without altering the fundamental function of the expression. Thus, values ​​modified by one or more terms such as “about,” “approximately,” and “substantially,” are not limited to the exact values ​​specified. In at least some cases, the approximation language may correspond to the precision of the instrument used to measure the value. Herein, and throughout this specification and the claims, limitations on ranges may be combined and / or replaced, and unless otherwise indicated by the context or language, such ranges are identified and include all subranges encompassed therein. “About,” “approximately,” and “substantially,” applied to specific values ​​within a range, may indicate + / - 10% of the stated value, unless applied to the values ​​at both ends and otherwise depend on the precision of the instrument used to measure the value.

[0087] All corresponding structures, materials, actions, and equivalents of all elements of means-plus-function or step-plus-function in the following claims include any structures, materials, or actions to perform a function in combination with any other claimed elements specifically claimed. The descriptions in this disclosure are presented for illustrative and explanatory purposes and are not intended to be exhaustive or to limit the disclosure to the forms disclosed herein. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of this disclosure. The embodiments have been selected and described in order to best illustrate the principles and practical applications of this disclosure and to enable those skilled in the art to understand this disclosure in terms of various embodiments with various modifications suitable for specific uses envisioned by others skilled in the art. [Explanation of Symbols]

[0088] 300 machine parts 302 Base material 304 Coating 306 Heat-shielding coating 400 Coating Compositions

Claims

1. 20 to 26 atomic percent silicon (Si), Titanium (Ti) in a concentration of 21 to 27 atomic percent, 30 to 39 atomic percent aluminum (Al), Hafnium (Hf) in concentrations of 2 to 10 atomic percent, The remaining niobium (Nb) and An alloy containing [a specific component].

2. The alloy according to claim 1, comprising 20 to 24 atomic percent silicon (Si), 23 to 27 atomic percent titanium (Ti), 30 to 37 atomic percent aluminum (Al), 4 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

3. The alloy according to claim 1, comprising 20 to 24 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 32 to 39 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

4. The alloy according to claim 1, comprising 22 to 24 atomic percent silicon (Si), 23 to 25 atomic percent titanium (Ti), 35 to 37 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

5. The alloy according to claim 1, comprising approximately 23 atomic percent silicon (Si), approximately 24 atomic percent titanium (Ti), approximately 36 atomic percent aluminum (Al), approximately 5 atomic percent hafnium (Hf), and the remainder niobium (Nb).

6. The alloy according to claim 1, wherein when the alloy is exposed to an oxidizing environment of 1200°C or higher, it forms a substantially continuous layer of aluminum oxide across the surface of the alloy.

7. (Nb, Ti) Al ３ Phase and (Nb, Ti, Hf) ５ Si ４ The alloy according to claim 1, having a microstructure that includes a phase.

8. The above (Nb,Ti)Al ３ The relationship is, Niobium (Nb) in concentrations of 6 to 12 atomic percent, Silicon (Si) in amounts of 1 to 5 atomic percent, Titanium (Ti) in a concentration of 10 to 16 atomic percent, 71 to 77 atomic percent aluminum (Al), Approximately 1 atomic percent of hafnium (Hf) and The alloy according to claim 7, including the alloy described in claim 7.

9. The above (Nb, Ti, Hf) ５ Si ４ The relationship is, Niobium (Nb) in 13 to 19 atomic percent concentrations, 42 to 48 atomic percent silicon (Si), Titanium (Ti) in a concentration of 19 to 25 atomic percent, Aluminum (Al) in amounts of 1 to 3 atomic percent, 12 to 18 atomic percent hafnium (Hf) and The alloy according to claim 7, including the alloy described in claim 7.

10. 20 to 26 atomic percent silicon (Si), Titanium (Ti) in a concentration of 21 to 27 atomic percent, 30 to 39 atomic percent aluminum (Al), Hafnium (Hf) in concentrations of 2 to 10 atomic percent, The remaining niobium (Nb) and alloys containing A coating composition (400) containing the following.

11. The coating composition (400) according to claim 10, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 23 to 27 atomic percent titanium (Ti), 30 to 37 atomic percent aluminum (Al), 4 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

12. The coating composition (400) according to claim 10, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 32 to 39 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

13. The coating composition (400) according to claim 10, wherein the coating comprises a substantially continuous layer of aluminum oxide across the surface of the alloy when exposed to a temperature of 1200°C or higher.

14. The alloy is (Nb, Ti)Al ３ phase and (Nb, Ti, Hf) ５ Si ４ The coating composition (400) according to claim 10, having a microstructure containing a phase

15. A substrate (302) having a coating (304) thereon, wherein the coating (304) 20 to 26 atomic percent silicon (Si), Titanium (Ti) in a concentration of 21 to 27 atomic percent, 30 to 39 atomic percent aluminum (Al), Hafnium (Hf) in concentrations of 2 to 10 atomic percent, The remaining niobium (Nb) and A base material (302) containing an alloy including Machine parts (300), including those mentioned above.

16. The machine part (300) according to claim 15, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 23 to 27 atomic percent titanium (Ti), 30 to 37 atomic percent aluminum (Al), 4 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

17. The machine part (300) according to claim 15, wherein the alloy comprises 20 to 24 atomic percent silicon (Si), 21 to 27 atomic percent titanium (Ti), 32 to 39 atomic percent aluminum (Al), 5 to 7 atomic percent hafnium (Hf), and the remainder niobium (Nb).

18. The mechanical part (300) according to claim 15, wherein the base material (302) contains a niobium-based alloy.

19. A turbine component, the mechanical component (300) according to claim 15.

20. The mechanical part (300) according to claim 19, which is a turbine component selected from the group consisting of land-based turbines, offshore turbines, aircraft turbines, and power generation turbines.

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