Patent Publication Number: US-2021189891-A1

Title: Barrier to prevent super alloy depletion into nickel-cbn blade tip coating

Description:
BACKGROUND 
     The present disclosure is directed to a barrier layer for integrally bladed rotor tip Nickel-Cubic Boron Nitride (Ni—CBN) plating. 
     In certain gas turbine engines, the nickel integrally bladed rotor is suffering lost life time of the tip Ni—CBN coating. Elements of the base super alloy diffuse from the base super alloy into the Ni—CBN layer after engine run or heat treatment. Elements such as Cr and Al diffuse from the base super alloy into the Ni—CBN coating layer. 
     As a result of the diffusion of the elements from the base super alloy and the propensity of these elements to oxidize during engine operation, oxides form along surfaces and grain boundaries within the coating. These oxides reduce the strength of the coating causing loss of CBN particles and recession of the coating. 
     What is needed is a technique to diminish the diffusion and subsequent nickel alloy depletion. 
     SUMMARY 
     In accordance with the present disclosure, there is provided a diffusion barrier coating on a nickel-based alloy substrate comprising the diffusion barrier coupled to the substrate between the substrate and a composite material opposite the substrate, wherein the diffusion barrier comprises a nickel cobalt and chromium-aluminum-yttria powder material. 
     In another and alternative embodiment, the nickel cobalt and chromium-aluminum-yttria powder material comprises a layered coating structure. 
     In another and alternative embodiment, the diffusion barrier consists of plated layers. 
     In another and alternative embodiment, the layered coating includes multiple layers. 
     In another and alternative embodiment, the composite material comprises a nickel-cubic boron nitride material. 
     In another and alternative embodiment, the diffusion barrier comprises a bond coat between the substrate and the composite material. 
     In another and alternative embodiment, the diffusion barrier comprises a nickel strike layer between the substrate and the diffusion barrier. 
     In accordance with the present disclosure, there is provided a gas turbine engine component comprising a compressor integrally bladed rotor having a blade with an airfoil section and a tip having a substrate; a diffusion barrier coupled to the substrate between the substrate and a composite material opposite the substrate, wherein the diffusion barrier comprises a nickel cobalt and chromium-aluminum-yttria powder material. 
     In another and alternative embodiment, the nickel cobalt and chromium-aluminum-yttria powder material comprises a bond layer. 
     In another and alternative embodiment, the diffusion barrier includes multiple layers. 
     In another and alternative embodiment, the diffusion barrier comprises a nickel strike layer between the substrate and the diffusion barrier. 
     In another and alternative embodiment, the substrate comprises a nickel-based alloy. 
     In another and alternative embodiment, the integrally bladed rotor is located in a high pressure compressor section of the gas turbine engine. 
     In accordance with the present disclosure, there is provided a process for diffusion inhibition in a nickel-based alloy substrate of a gas turbine engine component comprising applying a diffusion barrier coupled to the substrate, wherein the diffusion barrier comprises a nickel cobalt and chromium-aluminum-yttria powder material; coating the diffusion barrier with a matrix composite; and subjecting the gas turbine engine component with nickel-based alloy substrate to at least one of a heat treatment and an engine operation. 
     In another and alternative embodiment, the process further comprises coating the nickel cobalt and chromium-aluminum-yttria powder material coating comprises a bond coat. 
     In another and alternative embodiment, the diffusion barrier includes multiple layers. 
     In another and alternative embodiment, the diffusion barrier comprises a nickel CBN tack layer. 
     In another and alternative embodiment, the process further comprises plating the diffusion barrier in layers. 
     In another and alternative embodiment, the matrix composite material comprises a nickel-cubic boron nitride material. 
     In another and alternative embodiment, the process further comprises preventing Cr, Al, and Ti depletion from the nickel-based alloy substrate by reducing diffusion between the nickel-based alloy substrate and the matrix composite with the diffusion barrier. 
     Other details of the diffusion barrier are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified cross-sectional view of a gas turbine engine. 
         FIG. 2  is a cross sectional schematic of an exemplary coating system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a simplified cross-sectional view of a gas turbine engine  10  in accordance with embodiments of the present disclosure. Turbine engine  10  includes fan  12  positioned in bypass duct  14 . Turbine engine  10  also includes compressor section  16 , combustor (or combustors)  18 , and turbine section  20  arranged in a flow series with upstream inlet  22  and downstream exhaust  24 . During the operation of turbine engine  10 , incoming airflow F 1  enters inlet  22  and divides into core flow F C  and bypass flow F B , downstream of fan  12 . Core flow F C  continues along the core flowpath through compressor section  16 , combustor  18 , and turbine section  20 , and bypass flow F B  proceeds along the bypass flowpath through bypass duct  14 . 
     Compressor  16  includes stages of compressor vanes  26  and blades  28  arranged in low pressure compressor (LPC) section  30  and high pressure compressor (HPC) section  32 . Turbine section  20  includes stages of turbine vanes  34  and turbine blades  36  arranged in high pressure turbine (HPT) section  38  and low pressure turbine (LPT) section  40 . HPT section  38  is coupled to HPC section  32  via HPT shaft  42 , forming the high pressure spool. LPT section  40  is coupled to LPC section  30  and fan  12  via LPT shaft  44 , forming the low pressure spool. HPT shaft  42  and LPT shaft  44  are typically coaxially mounted, with the high and low pressure spools independently rotating about turbine axis (centerline) CL. 
     Combustion gas exits combustor  18  and enters HPT section  38  of turbine  20 , encountering turbine vanes  34  and turbines blades  36 . Turbine vanes  34  turn and accelerate the flow of combustion gas, and turbine blades  36  generate lift for conversion to rotational energy via HPT shaft  42 , driving HPC section  32  of compressor  16 . Partially expanded combustion gas flows from HPT section  38  to LPT section  40 , driving LPC section  30  and fan  12  via LPT shaft  44 . Exhaust flow exits LPT section  40  and turbine engine  10  via exhaust nozzle  24 . In this manner, the thermodynamic efficiency of turbine engine  10  is tied to the overall pressure ratio (OPR), as defined between the delivery pressure at inlet  22  and the compressed air pressure entering combustor  18  from compressor section  16 . As discussed above, a higher OPR offers increased efficiency and improved performance. It will be appreciated that various other types of turbine engines can be used in accordance with the embodiments of the present disclosure. 
     Referring now to  FIG. 2 , there is illustrated a turbine engine component  50 , such as a compressor integrally bladed rotor or blade or vane. The component  50  can be an integrally bladed rotor in the high pressure compressor section  32  of the gas turbine engine  10  The turbine engine component  50  has an airfoil portion  52  with a tip  54 . 
     The turbine engine component  50  may be formed from a titanium-based alloy or a nickel-based alloy. On the substrate tip  54  of the airfoil portion  52 , a composite material  56  is applied for rub and abradability against an abradable coating (not shown). In an exemplary embodiment the composite material  56  can be a nickel-cubic boron nitride (Ni—CBN) material. 
     A diffusion barrier  58  can be coupled to the tip substrate  54  between the tip substrate  54  and the composite material  56 . In an exemplary embodiment, the diffusion barrier  58  comprises an electrolytic nickel cobalt with a chromium aluminum yttria powder (Ni—Co with Cr—Al—Y) coating. In an exemplary embodiment, the diffusion barrier  58  including Ni—Co with Cr—Al—Y  58  can act as a bond coat. 
     There are grits  62  of CBN in the composite matrix material  56 . The diffusion barrier  58  can help to secure the grits  62  to the tip substrate  54 . 
     In an exemplary embodiment, the coating  56  can replace the traditional columnar structure of prior coating systems. In an exemplary embodiment, the coating  56  can replace the traditional unalloyed Ni of prior coating systems. The addition of alloying elements (esp. Al, Cr) to the diffusion barrier  58  reduces the chemical potential for diffusion of these elements from the blade tip  52 . In addition, the addition of alloying elements to the diffusion barrier  58  results in oxidation of those elements in place, rather than diffusion and oxidation of elements from the blade tip  52  resulting in a network of mechanically weak oxides. 
     The inclusion of the Ni—Co with Cr—Al—Y eliminates the Cr diffusion from the nickel alloy substrate  54 . In an exemplary embodiment, aluminum depletion occurs from the Cr—Al—Y thus forming AlOx layer under the grits  62 . 
     In an exemplary embodiment, the diffusion barrier  58  can include a Ni—CBN tack layer  64  on top of the Ni—Co/Cr—Al—Y powder layer  66 . A top coat  68  of Ni powder can be applied over the tack layer  64 . A nickel strike layer  70  can be applied to the tip substrate  54 . 
     A technical advantage of the diffusion barrier is that it prevents Cr, Al, and Ti depletion from the base alloy of the substrate. 
     Another technical advantage of the diffusion barrier includes formation of a very thin, uniform and homogenous oxidation layer (0.1 mil), that indicates a high corrosion/oxidation resistant property. 
     Another technical advantage of the diffusion barrier includes very low grain boundary oxidation. 
     Another technical advantage of the disclosed diffusion barrier includes prevention of the Ni super alloy depletion after engine operation. 
     Another technical advantage of the disclosed diffusion barrier includes elimination of potential mechanical strength reduction due to the depletion of the alloy chemistry. 
     Another technical advantage of the disclosed diffusion barrier includes extending the lifetime of the IBR used in the HPC section. 
     There has been provided a diffusion barrier. While the diffusion barrier has been described in the context of specific embodiments thereof, other unforeseen alternatives, modifications, and variations may become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.