Patent Publication Number: US-2023151738-A1

Title: Hybrid bonded configuration for blade outer air seal (boas)

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 63/212,325 filed Jun. 18, 2021, and U.S. Provisional Application No. 63/232,972 filed Aug. 13, 2021, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to blade outer are seal (BOAS) and, more particularly, to a hybrid bonded configuration for BOAS. 
     BOAS are actively cooled by BOAS cooling flow to meet thermal requirements in certain operating environments. This BOAS cooling flow is often parasitic to engine performance and is thus controlled to minimize allocation. Therefore, active cooling can subject the BOAS to thermal gradients due to the one-sided heat loads. Thermal gradients affect BOAS distortion and result in variance in tip clearance to the turbine blade and reduced part life. 
     Accordingly, an improved method of designing and configuring a BOAS is needed. 
     Also, BOAS are often exposed to high temperature products of combustion on a “hot” surface and cooler compressor cooling air on a “cold” surface. Exposure to air at different temperatures can lead to different phenomena. In the case of the hot side, products of combustion can cause oxidation to the surface of the BOAS. On the cold side, temperatures exist in a range where corrosion can occur. When designing a BOAS, an alloy is chosen to best balance the hot and cold side modes, but many not be optimal for either. Coatings may also be applied to resist each mode but such coating present issues relating to processing and durability. 
     In addition, BOAS often require highly effective cooling in advanced engines with higher temperatures. Current manufacturing limits on ceramic cores restrict the channel height of cooling circuits, however. 
     Accordingly, an improved method of designing and configuring a BOAS is needed so that cooling capabilities can be improved. 
     BRIEF DESCRIPTION 
     According to an aspect of the disclosure, a method of assembling a part is provided and includes forming a first section of the part, defining, in the first section, passages with dimensions as small as 0.005 inches (0.127 mm), forming a second section of the part, metallurgically bonding the first and second sections whereby the passages are delimited by the first and second sections and executing the metallurgically bonding without modifying a condition of the passages. 
     In accordance with additional or alternative embodiments, the part includes a blade outer air seal (BOAS) of a gas turbine engine and the passages are fluidly coupled to a cooling circuit. 
     In accordance with additional or alternative embodiments, the first and second sections include similar or dissimilar materials. 
     In accordance with additional or alternative embodiments, the method further includes coating the passages. 
     In accordance with additional or alternative embodiments, the forming of the first section includes at least one of casting and machining and the forming of the second section includes at least one of casting and machining. 
     In accordance with additional or alternative embodiments, the defining includes recessing the passages into the first section from an edge of the first section and the metallurgically bonding includes bonding the edge of the first section to a corresponding edge of the second section. 
     In accordance with additional or alternative embodiments, the metallurgically bonding includes at least one of field assisted sintering technology (FAST) and/or spark plasma sintering (SPS). 
     According to an aspect of the disclosure, a method of assembling a blade outer air seal (BOAS) of a gas turbine engine with a cooling circuit is provided and includes forming a first section of the BOAS, defining, in the first section, passages fluidly coupled to the cooling circuit with dimensions as small as 0.005 inches (0.127 mm), forming a second section of the BOAS, metallurgically bonding the first and second sections whereby the passages are delimited by the first and second sections and executing the metallurgically bonding without modifying a condition of the passages. 
     In accordance with additional or alternative embodiments, the first and second sections include similar or dissimilar materials. 
     In accordance with additional or alternative embodiments, the method further includes coating the passages. 
     In accordance with additional or alternative embodiments, the first section includes a corrosion resistant alloy and the second section includes an oxidation resistant alloy. 
     In accordance with additional or alternative embodiments, the second section further includes at least one of a thermal barrier coating or an abradable coating. 
     In accordance with additional or alternative embodiments, the forming of the first section includes at least one of casting and machining and the forming of the second section includes at least one of casting and machining. 
     In accordance with additional or alternative embodiments, the defining includes recessing the passages into the first section from an edge of the first section and the metallurgically bonding includes bonding the edge of the first section to a corresponding edge of the second section. 
     In accordance with additional or alternative embodiments, the metallurgically bonding includes at least one of field assisted sintering technology (FAST) and/or spark plasma sintering (SPS). 
     According to another aspect of the disclosure, a method of assembling a part is provided and includes building up a multi-layered first section of the part, defining, in the multi-layered first section, passages with dimensions as small as 0.005 inches (0.127 mm), building up a multi-layered second section of the part, metallurgically bonding each layer of the multi-layered first and second sections to neighboring layers whereby the passages are delimited by respective layers of the multi-layered first and second sections and executing the metallurgically bonding without modifying a condition of the passages. 
     In accordance with additional or alternative embodiments, the part includes a blade outer air seal (BOAS) of a gas turbine engine and the passages are fluidly coupled to a cooling circuit. 
     In accordance with additional or alternative embodiments, the multi-layered first and second sections include similar or dissimilar materials. 
     In accordance with additional or alternative embodiments, the method further includes coating the passages. 
     In accordance with additional or alternative embodiments, the building up of the multi-layered first and second sections include at least one of field assisted sintering technology (FAST) and spark plasma sintering (SPS). 
     Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed technical concept. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts: 
         FIG.  1    is a partial cross-sectional view of a gas turbine engine in accordance with embodiments; 
         FIG.  2    is a flow diagram illustrating a method of assembling a part in accordance with embodiments; 
         FIG.  3    is a diagram illustrating the method of assembling the part of  FIG.  2    in accordance with embodiments; 
         FIG.  4    is a side view of a blade outer air seal (BOAS) of a gas turbine engine in accordance with embodiments; 
         FIG.  5    is a flow diagram illustrating a method of assembling a blade outer air seal (BOAS) in accordance with embodiments; 
         FIG.  6    is a flow diagram illustrating a method of assembling a part in accordance with alternative embodiments; and 
         FIG.  7    is a diagram illustrating the method of assembling the part of  FIG.  2    with an intervening part section in accordance with further embodiments. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include other systems or features. The fan section  22  drives air along a bypass flow path B in a bypass duct, while the compressor section  24  drives air along a core flow path C for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with two-spool turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
     The exemplary engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided, and the location of bearing systems  38  may be varied as appropriate to the application. 
     The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  and a low pressure turbine  46 . The inner shaft  40  is connected to the fan  42  through a speed change mechanism, which in exemplary gas turbine engine  20  is illustrated as a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  and high pressure turbine  54 . A combustor  56  is arranged in exemplary gas turbine  20  between the high pressure compressor  52  and the high pressure turbine  54 . An engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The engine static structure  36  further supports bearing systems  38  in the turbine section  28 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
     The core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. It will be appreciated that each of the positions of the fan section  22 , compressor section  24 , combustor section  26 , turbine section  28 , and fan drive gear system  48  may be varied. For example, gear system  48  may be located aft of combustor section  26  or even aft of turbine section  28 , and fan section  22  may be positioned forward or aft of the location of gear system  48 . 
     The engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the engine  20  bypass ratio is greater than about six (6), with an example embodiment being greater than about ten (10), the geared architecture  48  is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine  46  has a pressure ratio that is greater than about five. In one disclosed embodiment, the engine  20  bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor  44 , and the low pressure turbine  46  has a pressure ratio that is greater than about five 5:1. Low pressure turbine  46  pressure ratio is pressure measured prior to inlet of low pressure turbine  46  as related to the pressure at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. The geared architecture  48  may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans. 
     A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section  22  of the engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet (10,688 meters). The flight condition of 0.8 Mach and 35,000 ft (10,688 meters), with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.45. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram ° R)/(518.7° R)] 0.5 . The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second (350.5 m/sec). 
     Field assisted sintering technology (FAST) is a consolidation process at temperatures lower than the melting point of the materials being worked on. Similar to hot pressing, FAST forms bonds between materials but at temperatures that are about ˜200° C. lower than their melting point(s). FAST utilizes a high amperage pulsed direct current (DC) electrical current to heat the materials to be bonded through Joule heating while under uniaxial compression. The consolidation is a combination of solid-state transport mechanisms including primarily diffusion and creep. The result is a metallurgical bond between the materials to be joined. Consolidation or joining can be accomplished in a variety of conductive and non-conductive materials and forms. Spark plasma sintering (SPS), though different from FAST, is also a consolidation process. Recently, FAST/SPS has been gaining acceptance for consolidation of powder materials into dense compacts with significantly greater efficiency than hot pressing. Due to the lower processing temperatures over other consolidation methods, FAST/SPS mitigates significant grain growth common in other diffusional bonding methods. 
     FAST is advantageous over other sources of bonding such as diffusional bonding, dual alloy casting, brazing, transient liquid phase bonding or welding under high temperature protective atmosphere. Some of the advantages of FAST over these other methods are detailed below. 
     Diffusional bonding does not use (is devoid of) the application of a DC current for heating that enhances bond line diffusion. It however uses a much higher temperature (than temperatures used in FAST) and a longer bonding cycle than FAST but is also conducted below the melting point of the alloy. Due to the higher temperatures and longer cycles, diffusional bonding can result in aging of the alloys (e.g., coursing of gamma prime phase in nickel-based alloys) or detrimental feature formations (e.g., recrystallization in single crystal alloys) that are generally considered detrimental. 
     Dual alloy casting includes casting a first piece then remelting an interface and casting a second piece onto the molten portion of the first piece. This process is typically conducted above a melting point of the subject alloy as it is a method that includes casting (pouring of a molten metal). 
     In FAST, it is easier to locate the bond line (between the first portion and the second portion) with high precision as it relies on machining of two pieces to a specific shape with little or no displacement of that contact surface thereafter. Dual casting relies on a partial fill of the first casting, remelting of the interface and a mixing of the interface thereby making the bond line location more variable. Metallurgy of the bond line is going to be a composite of the alloys selected as they will undergo mixing in the melt or in a partially molten state. This may result in the formation of deleterious phases as a result of dissimilar alloy combinations. These deleterious phases will come out (i.e., precipitate) much more quickly and over larger zone sizes in dual alloy casting. 
     Brazing requires low melt alloy (in the case of nickel superalloy bonding commonly a boron or silicon enriched alloy) to be placed between two alloys to be bonded. The low melt alloy is melted and then solidified forming the joint between the two alloys. A capability of the joint is dependent on the low melt alloy which will have obviously lower temperature capability but also generally lower mechanical and environmental properties as it is selected for its melt point. It therefore includes mechanical and environmental properties. The strength of brazed joints is generally low (typically no greater than a few kilopounds per square inch (KSI)). Brazing has a much lower performance capability than FAST or dual alloy casting. 
     Transient Liquid Phase (TLP) bonding is similar to brazing but uses more complex alloys (in lieu of the low melt alloy using in brazing) and uses more complete mixing during the diffusion cycle. This results in generally higher mechanical and environmental capabilities over brazing but significantly less than the individual alloys used to form the bond. TLP has a much lower expected capability than FAST or dual alloy casting. 
     Welding high temperature protective atmosphere (example includes superalloy welding at elevated temperature or SWET) involves welding and therefore requires melting of the alloy and consequent re-solidification. The bond line between the two alloys will be a welded feature with an equiaxed grain structure and associated weld defects (e.g., quench cracking is one common challenge). The bond line will have its own unique capability and be different than the alloys bonded. This technique (SWET) is not capable of maintaining a single crystal continuous structure and therefore is a detriment in physical and environmental properties. 
     In summary, FAST is advantageous over these other methods because it can retain the single crystal characteristics across the bond line and because it can facilitate retention of the structure that existed before the bonding process to retain material performance of the alloys involved and to maximize the performance across the bond line. It also results in a continuum of structure (e.g., crystalline structure) from the first portion to the second portion after the bonding process. 
     As will be described below, a multi-layer build-up of a substrate by FAST processing can allow for cooling channels to be constructed. Cooling passages can be near-surface cooling passages for a duration, cross-layers by voids in layers or orifices and turned into and through different radial layers so as to deliver warmed air to outer diameter (OD) structures or to the benefit of a having an exit location with reduced pressure. 
     In addition, as will be described below, the BOAS is formed from two individual castings that include the hot side (gaspath) and cold side (attachment). Cooling channels may be formed between the two parts. After machining preparation of a bond joint, the two parts are bonded using FAST processing to enclose the channels in highly effective cooling circuits. This FAST processing can occur between similar or dissimilar materials. For example, the hot side part can be constructed of an alloy optimized for oxidation and the cold side part can be constructed from an alloy optimized for corrosion resistance. 
     With continued reference to  FIG.  1    and with additional reference to  FIGS.  2  and  3   , a method  200  of assembling a part  300  is provided where the part  300  can be used, for example, in the engine  20 . As shown in  FIGS.  2  and  3   , the method  200  includes forming a first section  301  of the part  300  ( 201 ) by at least one of casting and machining, defining, in the first section  301 , passages  302  with dimensions (e.g., diameters) as small as 0.005 inches or 0.127 mm ( 202 ), forming a second section  303  of the part  300  ( 203 ) by at least one of casting and machining and metallurgically bonding the first section  301  and the second section  303  whereby the passages  302  are delimited by the first section  301  and the second section  303  ( 204 ). The metallurgically bonding of operation  204  can be preceded by an operation of preparing the first section  301  and the second section  303  for the metallurgically bonding by, for example, surface machining and/or cleaning that provides for good contact-making bonding surfaces. In addition, the method  200  includes executing the metallurgically bonding of operation  204  without modifying a condition of the passages  302  ( 205 ) whereby there is no significant change in the shapes or sizes of the passages  302 . The defining of operation  202  (see  FIG.  2   ) can include recessing the passages  302  into the first section  301  from an edge  3010  of the first section  301 . The metallurgically bonding of operation  205  can include bonding the edge  3010  of the first section  301  to a corresponding edge  3030  of the second section  303  so that each passage  302  is bordered on each side by the first section  301  or the second section  303 . In any case, the metallurgically bonding of operation  205  can include at least one of FAST and SPS. 
     The method  200  of  FIG.  2    can further include an optional operation of coating the passages  302  ( 206 ) prior to the metallurgical bonding of operation  204 . 
     The executing of the metallurgically bonding of operation  204  without modifying the condition of the passages  302  of operation  205  serves to preserve a shape and size of the passages  302 . That is, in the case of the passages  302  having dimensions of about 0.005 inches or 0.127 mm prior to the metallurgically bonding of operation  204 , the passages  302  will continue to have dimensions of about 0.005 inches or 0.127 mm following the metallurgically bonding of operation  204 . 
     While the description provided above refers to passages  302  being defined in the first section  301 , it is to be understood that other embodiments exist. For example, additional passages may be defined in the second section  303 . These additional passages can mirror the passages  302  or can be arranged differently from the passages  302 . In the mirrored case, the diffusion line can be centered between the passages  302  and the additional passages. In the case where the passages  302  and the additional passages are arranged differently, the passages  302  and the additional passages can be arranged to provide for cross-flow or multi-directional flow. 
     In any case, the passages  302  and the additional passages can have various shapes and sizes. For example, while the passages  302  are illustrated in  FIG.  3    as being rectangular passages  302  with widths of about 0.005 inches or 0.127 mm, it is to be understood that the passages could have circular, nearly circular or otherwise rounded cross-sectional shapes. Moreover, the passages  302  can be straight in a longitudinal axis, curved or bent. In these or other cases, each individual passage  302  can be shaped and sized similarly to the other passages  302  or uniquely shaped or sized to provide for correspondingly unique flow patterns. 
     Using FAST or SPS processing allows the dimensions of the passages  302  to be reduced to a far smaller scale than what would be possible using conventional processing techniques. For example, conventional processing that does not include FAST or SPS would permit a part to be assembled or formed with passages having dimensions of about 0.050 inches. By contrast, the use of the FAST or SPS processing permits a reduction in the dimensions of the passages by about an order of magnitude or more. 
     With continued reference to  FIGS.  1  and  2    and with additional reference to  FIG.  4   , the part  300  can include or can be provided as a blade outer air seal (BOAS)  401  of a gas turbine engine  400 . In these or other cases, the BOAS  401  forms an outer air passage  402  with a distal tip  403  of a turbine blade  404  and the passages  302  are fluidly coupled to a cooling circuit  405  of the gas turbine engine  400 . 
     In accordance with embodiments, the first section  301  and the second section  303  can be formed of similar or dissimilar materials (i.e., similar single crystal alloy materials or dissimilar single crystal alloy materials, material pairs can include, e.g., a same alloy such as PWA 1429 and dissimilar alloys such as PWA 1429 to CM247). Additionally, the ability to bond both single crystal (SX) and equiaxed (EQ) materials and the ability to retain fine features along bond lines have been demonstrated). In the latter case, particularly where the part  300  includes or is provided as the BOAS  401  of the gas turbine engine  400  of  FIG.  4   , the first section  301  (i.e., the cold side of the part  400 , which is normally exposed to relatively cool temperatures and an environment in which a primary damage mode is corrosion) can include a corrosion resistant alloy and the second section  303  (i.e., the hot side of the part  300 , which is normally exposed to relatively high temperatures and an environment in which a primary damage mode is oxidation and thermal damage) can include an oxidation resistant alloy. In addition, the second section  303  can also include at least one of a thermal barrier coating  410 , which is provided to protect the part  400  from high temperature and high pressure fluids in the outer air passage  402 , and an abradable coating  420 , which is provided to establish an appropriate size of the outer air passage  402  by allowing for abrasion of the abradable coating  402  by the distal tip  403  of the turbine blade  404  during operations of the gas turbine engine  400 . 
     Passages  302  can optionally be coated prior to the metallurgically bonding of operation  204  to protect from environmental attack. In conventional cases, internal cooling circuits may be coated using non-line-of-sight processes, such as vapor phase aluminiding. These processes tend to have limitations, such as those arising from chemistry. For example, there are not viable production routes to make a platinum modified aluminide, which is generally known to be better than simple aluminides in environmental resistance due to the platinum plating step. However, by having two separate pieces that allow for line-of-sight access, as is the here in the instant application, improved capability coating systems can be utilized. Additionally, the edge  3010  of the first section  301  and the edge  3030  of the second section can be prepared (ground or otherwise machined) post-coating such that contact points between the first and second sections  301  and  303  are not affected by the intra-passage coating. 
     With reference to  FIG.  5   , a method  500  of assembling a BOAS of a gas turbine engine with a cooling circuit is provided and can be generally similar to the method  200  described above. As shown in  FIG.  5   , the method includes forming a first section of the BOAS ( 501 ), defining, in the first section, passages fluidly coupled to the cooling circuit with dimensions as small as 0.005 inches or 0.127 mm ( 502 ), forming a second section of the BOAS ( 503 ), metallurgically bonding the first and second sections whereby the passages are delimited by the first and second sections ( 504 ) and executing the metallurgically bonding without modifying a condition of the passages ( 505 ). 
     With reference to  FIG.  6   , a method  600  of assembling a part, such as a BOAS of a gas turbine engine, is provided and can be generally similar to the method  200  described above. As shown in  FIG.  6   , the method  600  includes building up a multi-layered first section of the part ( 601 ), defining, in the multi-layered first section, passages coupled to a cooling circuit of the gas turbine engine with dimensions as small as 0.005 inches or 0.127 mm ( 602 ), building up a multi-layered second section of the part ( 603 ), metallurgically bonding each layer of the multi-layered first and second sections to neighboring layers whereby the passages are delimited by respective layers of the multi-layered first and second sections ( 604 ) and executing the metallurgically bonding without modifying a condition of the passage ( 605 ). 
     The methods  500  and  600  of  FIGS.  5  and  6   , respectively, can further include an optional operation of coating the passages ( 506  and  606 ) prior to the metallurgical bonding of operations  504  and  604 . 
     In accordance with embodiments, the multi-layered first and second sections can include similar or dissimilar materials and the building up of the multi-layered first and second sections can include at least one of FAST and SPS. 
     With reference to  FIG.  7   , the part  300  as described above with reference to  FIG.  3   , can include one or more interposer sections  701  between the first section  301  and the second section  303 . In these or other cases, the part  300  is formed as a stack of sections with multiple passages (e.g., passages  302  and additional passages  702  in the one or more interposer sections  701 ) in one or more of the first section  301 , the second section  303  and the one or more interposer sections. These multiple passages can provide for various internal and external cooling, using cross-flow or multi-directional flow patterns. 
     In an embodiment, a first alloy for use in the methods described herein may be a “high strength” metal alloy. Examples of the first alloy include Alloy D, René N5, CMSX-4, CMSX-10, TMS-138 or TMS-162. The metal alloys are nickel-based metals that in addition to nickel comprise one or more of chromium, cobalt, molybdenum, aluminum, titanium, tantalum, niobium, ruthenium, rhenium, boron and carbon. The metal alloys contain one or more of the following metals in addition to nickel—2 to 10 wt % of chromium, 2 to 11 wt % of cobalt, 0.5 to 5 wt % molybdenum, 4 to 7.5 wt % of tungsten, 3-7 wt % of aluminum, 0 to 5 wt % of titanium, 3 to 10 wt % of tantalum and 2-8 wt % of rhenium. The metal alloys may also contain ruthenium, carbon and boron. 
     The composition of these alloys is defined to maximize mechanical properties in a single crystal form while maintaining an adequate level of environmental resistance. Table 1 and Table 2 shows preferred ranges (of the ingredients) for the compositions (in weight percent) that may be used for the first alloy. Table 2 contains broader ranges for some of the alloys (than those indicated in Table 1) that may be used in the first portion. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 COMPOSITION (WT. %) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 ALLOY 
                 Cr 
                 Co 
                 Mo 
                 W 
                 Al 
                 Ti 
                 Ta 
                 Nb 
                 Re 
                 Ru 
                 Hf 
                 C 
                 B 
                 Zr 
                 Ni 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 IN-713LC 
                 12 
                 — 
                 4.5 
                 — 
                 5.9 
                 0.6 
                 — 
                 2 
                 — 
                 — 
                 — 
                 0.05 
                 0.01 
                 0.1 
                 BAL 
               
               
                 IN-730LC 
                 16 
                 8.5 
                 1.75 
                 2.6 
                 3.4 
                 3.4 
                 1.75 
                   0.9 
                 — 
                 — 
                 — 
                 0.11 
                 0.01 
                 0.04 
                 BAL 
               
               
                 RENE 80 
                 14 
                 9 
                 4 
                 4 
                 3 
                 4.7 
                 — 
                 — 
                 — 
                 — 
                 0.8 
                 0.16 
                 0.015 
                 0.01 
                 BAL 
               
               
                 MAR-M247 
                 8 
                 10 
                 0.6 
                 10 
                 5.5 
                 1 
                 3 
                 — 
                 — 
                 — 
                 1.5 
                 0.15 
                 0.015 
                 0.03 
                 BAL 
               
               
                 MAR-M200HF 
                 8 
                 9 
                 — 
                 12 
                 5 
                 1.9 
                 — 
                 1 
                 — 
                 — 
                 2 
                 0.13 
                 0.015 
                 0.03 
                 BAL 
               
               
                 CM247LC 
                 8.1 
                 9.2 
                 0.5 
                 9.5 
                 5.6 
                 0.7 
                 3.2 
                 — 
                 — 
                 — 
                 1.4 
                 0.07 
                 0.015 
                 0.007 
                 BAL 
               
               
                 CM186LC 
                 6 
                 9.3 
                 0.5 
                 8.4 
                 5.7 
                 0.7 
                 3.4 
                 — 
                 3.0 
                 — 
                 1.4 
                 0.07 
                 0.015 
                 0.005 
                 BAL 
               
               
                 ALLOY A 
                 6.5 
                 10 
                 1.7 
                 6.5 
                 6 
                 — 
                 4 
                 — 
                 3.0 
                 — 
                 1.5 
                 0.1 
                 0.015 
                 0.1 
                 BAL 
               
               
                 CMSX-2 
                 8 
                 5 
                 0.6 
                 8 
                 5.6 
                 1 
                 6 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 ALLOY B 
                 10 
                 5 
                 — 
                 4 
                 5 
                 1.5 
                 12 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 RENE N4 
                 9 
                 8 
                 2 
                 6 
                 3.7 
                 4.2 
                 4 
                   0.5 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 AM1 
                 7 
                 8 
                 2 
                 5 
                 5 
                 1.8 
                 8 
                 1 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 RR2000 
                 10 
                 15 
                 3 
                 — 
                 5.5 
                 4 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 CMSX-4 
                 6.5 
                 9.6 
                 0.6 
                 6.4 
                 5.6 
                 1 
                 6.5 
                 — 
                 3 
                 — 
                 0.1 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 ALLOY C 
                 5 
                 10 
                 2 
                 6 
                 5.6 
                 — 
                 9 
                 — 
                 3 
                 — 
                 0.1 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 RENE N5 
                 7 
                 8 
                 2 
                 5 
                 6.2 
                 — 
                 7 
                 — 
                 3 
                 — 
                 0.2 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 CMSX-10 
                 2 
                 3 
                 0.4 
                 5 
                 5.7 
                 0.2 
                 8 
                 — 
                 6 
                 — 
                 0.03 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 TMS-138 
                 2.9 
                 5.9 
                 2.9 
                 5.9 
                 5.9 
                 — 
                 5.6 
                 — 
                 4.9 
                 2 
                 0.1 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 TMS-162 
                 2.9 
                 5.8 
                 3.9 
                 5.8 
                 5.8 
                 — 
                 5.6 
                 — 
                 4.9 
                 6 
                 0.09 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 CMSX-7 
                 6 
                 10 
                 0.6 
                 9 
                 5.7 
                 0.8 
                 9 
                 — 
                 — 
                 — 
                 0.2 
                 — 
                 — 
                 — 
                 BAL 
               
               
                 CMSX-8 
                 5.4 
                 10 
                 0.6 
                 5 
                 5.7 
                 0.7 
                 8 
                 — 
                 1.5 
                 — 
                 0.1 
                 — 
                 — 
                 — 
                 BAL 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Cr 
                 Co 
                 Mo 
                 W 
                 Al 
                 Ti 
                 Ta 
                 Nb 
                 Re 
                 Ni 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Alloy D 
                 5-7 
                  9-11 
                 1.5-2.5 
                 5.5-7.5 
                 5-7 
                 — 
                  3-10 
                 — 
                 2-4 
                 Balance 
               
               
                 René N5 
                  6-10 
                 7-9 
                 1.5-2.5 
                 4-7 
                 3-7 
                 0-5 
                 3-8 
                 0-1 
                 0-4 
                 Balance 
               
               
                 CMSX-4 
                 4-8 
                  7-10 
                 0.5-1.5 
                 5.5-7.5 
                 5-6 
                 0-2 
                 5-8 
                 — 
                 2-4 
                 balance 
               
               
                 CMSX-10 
                 1-3 
                 2-4 
                 0.1-1     
                 4-6 
                 5-7 
                 0.1-0.4 
                  6-10 
                   
                 4-8 
                 balance 
               
               
                 TMS-138 
                 2-4 
                 3.5-6.5 
                 2-4 
                 5-7 
                 5-7 
                 — 
                 5-7 
                   
                 4-6 
                 balance 
               
               
                 TMS-162 
                 2-4 
                 3.5-6.5 
                 3-5 
                 5-7 
                 5-7 
                 — 
                 5-7 
                   
                 5-7 
                 balance 
               
               
                   
               
            
           
         
       
     
     The high strength alloys can withstand stresses of greater than 800 MPa at temperatures greater than 600° C. and stresses of greater than 200 MPa at temperatures of greater than 800° C. 
     Second alloys for use in the methods described herein are selected for their ability to handle harsh environmental conditions and can include René 195 and René N2. These compositions were developed with an eye to improved environmental resistance. This can be seen in the Al and Cr levels as compared with Re, W, Mo shown in the Table 3. The cobalt to chromium ratios are lower for the second alloys, while the aluminum to cobalt ratio is much higher for the second alloys when compared with the first alloys. 
     The second alloys can be a nickel-based alloy that in addition to nickel includes one or more of chromium, cobalt, molybdenum, aluminum, titanium, tantalum, niobium, ruthenium, rhenium, boron and carbon. The metal alloys contain one or more of the following metals in addition to nickel—7 to 14 wt % of chromium, 3 to 9 wt % of cobalt, 0.1 to 0.2 wt % molybdenum, 3 to 5 wt % of tungsten, 6-9 wt % of aluminum, 0 to 5 wt % of titanium, 4 to 6 wt % of tantalum, 0.1 to 0.2 wt % f hafnium and 1-2 wt % of rhenium. The metal alloys may also contain ruthenium, carbon and boron. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Cr 
                 Co 
                 Al 
                 Ta 
                 Mo 
                 W 
                 Re 
                 Hf 
                 Ni 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 René 195 
                 7-9 
                 3-4 
                 7-9 
                 5-6 
                 0.1-0.2 
                 3-5 
                 1-2 
                 0.1-0.2 
                 balance 
               
               
                 René N2 
                 12-14 
                 7-9 
                 6-8 
                 4-6 
                   
                 3-4 
                 1-2 
                 0.1-0.2 
                 balance 
               
               
                   
               
            
           
         
       
     
     The high strength alloys used in the second alloys can withstand stresses of at least 50% of the first alloys. In an embodiment, the high strength alloys used in the second alloys are environmentally resistant and withstand temperatures of greater than 1200° C. (under oxidation conditions) while undergoing less than 0.05 grams of weight loss per unit weight. 
     Technical effects and benefits of the present disclosure are the provision of forming multi-layer passages that can carry heated air radially outboard for reduced thermal gradients thus improving part life and/or to alternate dump locations for maximized cooling effectiveness. Additional technical effects and benefits of the present disclosure are the provision of methods of assembling a hybrid BOAS by bonding a hot side alloy optimized for oxidation and a cold side alloy optimized for corrosion resistance so that maximum durability of the component is achieved. Applying optimal coatings to each of the pieces prior to assembly can also simplify manufacturing and reduce the risk of cross contamination between the different coating zones. Oxidation and thermal barrier coatings applied to the hot side component may also require specific wear characteristics due to rub interactions with turbine blade tips. An additional abradable coating may be applied to minimize tip clearances when rub interaction occurs with the turbine blades. Depending on the thermal environment, the hot surface may not require coating and in that case, the hot side alloy may be selected to achieve optimal wear interactions with the turbine blade. By utilizing hybrid alloy bonding, the flexibility still exists to select a cold side alloy which maximizes overall part durability. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the technical concepts in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated. 
     While the preferred embodiments to the disclosure have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure first described.