Turbine engine rotor piston seal ring contact hard coatings

Abstract

A gas turbine engine (800) rotor (150) has: a shaft (98) having an outer diameter groove (100) having a forward surface (104), an aft surface (102), and an inner diameter base surface (106); a seal ring in the groove and having a forward surface (34), an aft surface (36), and an outer diameter (OD) surface (30); and a disk (152) having an inner diameter (ID) surface (156) with a portion (110) facing or contacting the seal ring OD surface. Along at least one of the disk ID surface portion, a portion of said groove forward surface, and a portion of said groove aft surface a layering is formed from WC-Co and MCrAlY (214, 224).

Description

TURBINE ENGINE ROTOR PISTON SEAL RING CONTACT HARD COATINGSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Benefit is claimed of US Patent Application No. 63755857, filed February 7, 2025, entitled “Turbine Engine Rotor Piston Seal Ring Contact Hard Coatings”, US Patent Application No. 63696281, filed September 18, 2024, and entitled “Turbine Engine Rotor Piston Seal Ring Contact Hard Coatings”, and US Patent Application No. 63696276, filed September 18, 2024, and entitled “Turbine Engine Rotor Piston Seal Ring Contact Hard Coatings”, the disclosures of which are incorporated by reference herein in their entireties as if set forth at length.BACKGROUND

[0002] The disclosure relates to gas turbine engines. More particularly, the disclosure relates to piston seal rings (PSR) and their interfaces.

[0003] Gas turbine engines (used in propulsion and power applications and broadly inclusive of turbojets, turboprops, turbofans, turboshafts, industrial gas turbines, and the like) use PSR in several situations.

[0004] A PSR seals between an inner member and an outer member. The inner member and outer member may be static structure such as case components. Or, the inner member and the outer member may be rotating structure such as components of a spool or rotor. The inner member and the outer member may be subject to small excursions relative to each other. For example, torque loads may cause small rotational movements; thrust loads or differential thermal expansion may cause small axial movements. Vibration may also cause small rotational, radial, or axial movements. Such small or transient rotational movements, however, are distinguished from continuous relative rotational movement such as in face seal or shaft seal between two relatively rotating components (e.g., two different spools or a spool and a static structure).

[0005] The PSR is accommodated in an outer diameter groove in the inner member. Under dynamic and / or pressure loading, the PSR seals against a sidewall of the groove and an inner diameter surface of the outer member. In one example of such a situation involving a rotor, the inner member is a shaft and the outer member is a rotor stack of the associated spool. In a more particular example, the outer member is a seal runner or bore foot protruding axially from a protuberant bore of a disk of the rotor stack. Tension in the shaft holds the rotor stack in precompression. Small rotational, axial, and / or radial displacements of the shaft and seal runner may be caused by factors including transients and changes in operationalconditions such as torque and thrust loads (which will vary between one steady state condition and another steady state condition). In such an example, the PSR is accommodated in an outer diameter (OD) groove in the shaft.

[0006] PSRs are often small in cross section so as to be relatively compliant compared to the contacting structure (e.g., members forming the groove and runner). The ring is split for assembly purposes and / or to allow radial expansion under centrifugal loading. The ring circumferential ends may form an overlapping joint (e.g., a shiplap joint). The small cross section and split provide the ring with little hoop strength and twist resistance. For example, with a nickel alloy shaft and nickel alloy runner, ring material may be nickel or cobalt alloy and may have generally similar material hardness (at least of a substrate if coated). Example coatings are one or more sprayed or brushed solid lubricant layers directly atop the substrate outer diameter surface and extending onto the substrate axial end surfaces.

[0007] One group of examples of PSR substrates involves cobalt-based chromium-tungsten alloys. One particular alloy is Stellite® 6 Co-Cr alloy of Kennametal Inc., Latrobe PA. There are several related Stellite® family alloys. An example alloy is AMS5894 / Cobalt Alloy 6B / UNS R30016 in wrought form. Wrought micro structure is characterized by evenly distributed isolated (rather than interconnected) carbides.Interconnected carbides of cast micro structure contributes to brittleness. The PSR substrate may have a coating as discussed above.

[0008] In an example manufacture process, the substrate may be formed from forged rod stock. Ring precursors are cut / machined from the rod (e.g., on a cutting lathe or the like) to an annulus with the PSR nominal cross-sectional shape. The resulting precursor may be grit blasted, particularly on the outer diameter (OD) surface to clean and roughen in preparation for coating application. Then, the annulus may be cut (e.g., by CNC mill, wire EDM, water jet or other tool) to form a shiplap or similar joint (to allow PSR expansion / contraction).Then, the coating, if any, may be applied as discussed above.SUMMARY

[0009] One aspect of the disclosure involves a gas turbine engine rotor comprising: a shaft having an outer diameter groove having a forward surface, an aft surface, and an inner diameter base surface; a seal ring in the groove and having a forward surface, an aft surface, and an outer diameter (OD) surface; and a disk having an inner diameter (ID) surface with a portion facing or contacting the seal ring OD surface. Along at least one of said disk ID surface portion, a portion of said groove forward surface, and a portion of said groove aft surface a layering comprises a layer formed from MCrAlY and WC-Co.

[0010] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, along said at least one of said disk ID surface portion, said portion of said groove forward surface, and said portion of said groove aft surface said layering comprises an NiCrAl bondcoat atop metallic substrate with the layer atop the NiCrAl bondcoat.

[0011] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the NiCrAl bondcoat is directly atop the metallic substrate; and the layer is directly atop the NiCrAl bondcoat.

[0012] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the NiCrAl bondcoat has a by weight percent composition of 15.5 to 22 Cr, 3.5- 8.0 Al, balance Ni and up to 6% other total.

[0013] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the NiCrAl bondcoat has a thickness of 0.001 inch to 0.020 inch (0.025 millimeter to 0.51 millimeter).

[0014] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the layering consists essentially of said layer directly atop substrate, optionally with a lubricant.

[0015] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the layer has a thickness of 0.005 inch to 0.020 inch (0.13 millimeter to 0.51 millimeter).

[0016] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the layer has a by-weight composition of at least 70% MCrAlY and at least 4.0% WC-Co.

[0017] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the layer has a by-weight composition of at least 90% combined MCrAlY and WC-Co.

[0018] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the MCrAlY has a by weight percent composition of Ni bal., 18.0 to 28.0 Co, 14.0 to 22.0 Cr, 8.0 to 14.0 Al, 0.1 to 1.0 Y, W, Ta, Mo, up to 5.0 combined if any, and Zr if any up to 1.0.

[0019] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the WC-Co has a by weight composition of at least 70%WC and at least 10%Co.

[0020] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, said at least one includes both of said portion of said groove forward surface and said portion of said groove aft surface.

[0021] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the seal ring has formed from WC-Co and MCrAlY at least along the OD surface and directly atop a substrate of the seal ring, optionally wherein the substrate of the seal ring is a cobalt based chromium- tungsten alloy.

[0022] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include a gas turbine engine including the gas turbine engine rotor wherein the disk is a compressor disk.

[0023] A further aspect of the disclosure involves a method for manufacturing the gas turbine engine rotor, the method comprising applying a feedstock blend of: WC-Co from powder feedstock having a by-weight percent composition of at least 70% WC and at least 10% Co; and MCrAlY from powder feedstock having a by-weight percent composition of Ni bal, 18.0 to 28.0 Co, 14.0 to 22.0 Cr, 8.0 to 14.0 Al, 0.1 to 1.0 Y, W, Ta, Mo, up to 5.0 combined if any, and Zr if any up to 1.0.

[0024] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the applying is via thermal spray.

[0025] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include a method for manufacturing the gas turbine engine rotor, the method comprising: machining said at least one of said disk ID surface portion, said portion of said groove forward surface, and said portion of said groove aft surface; applying the MCrAlY and WC Co; and machining the applied MCrAlY and WC Co.

[0026] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include: applying an NiCrAl bondcoat to the machined surface via thermal spray; and machining the applied NiCrAl bondcoat, wherein the applying the MCrAlY and WC-Co is to the machined bondcoat.

[0027] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include installing the seal ring to the groove and assembling the disk to the shaft.

[0028] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the method is a remanufacturing from prior condition wherein: in the prior condition: said at least one of said disk ID surface portion, said portion of said grooveforward surface, and said portion of said groove aft surface lacked a layering comprising an MCrAlY or WC-Co.

[0029] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the seal ring has a second coating formed from WC-Co and MCrAlY for interfacing with the layering comprising said layer; and in the prior condition: a prior seal ring in said groove lacked an MCrAlY- or WC-Co-containing coating.

[0030] A further aspect of the disclosure involves a gas turbine engine rotor comprising: a shaft having an outer diameter groove having a forward surface, an aft surface, and an inner diameter base surface; a seal ring in the groove and having a forward surface, an aft surface, and an outer diameter (OD) surface; and a disk having an inner diameter (ID) surface with a portion facing or contacting the seal ring OD surface. The seal ring has a coating formed from WC-Co and MCrAlY.

[0031] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the seal ring coating is at least along the OD surface.

[0032] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the seal ring coating is directly atop a substrate of the seal ring.

[0033] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the substrate of the seal ring is a cobalt based chromium-tungsten alloy.

[0034] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, along at least one of said disk ID surface portion, a portion of said groove forward surface, and a portion of said groove aft surface a layering comprises the coating.

[0035] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, along said at least one of said disk ID surface portion, said portion of said groove forward surface, and said portion of said groove aft surface said layering comprises an NiCrAl bondcoat atop metallic substrate with the coating atop the NiCrAl bondcoat.

[0036] A further aspect of the disclosure involves a method for manufacturing the gas turbine engine rotor, the method comprising thermal spraying the coating from: WC-Co from powder feedstock having a by-weight percent composition of at least 70% WC and at least 10% Co; and MCrAlY from powder feedstock having a by-weight percent composition of Ni bal, 18.0 to 28.0 Co, 14.0 to 22.0 Cr, 8.0 to 14.0 Al, 0.1 to 1.0 Y, W, Ta, Mo, up to 5.0 combined if any, and Zr if any up to 1.0.

[0037] A further aspect of the disclosure involves a seal ring comprising: a metallic substrate; and a coating formed from WC-Co and MCrAlY.

[0038] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the seal is a split ring seal.

[0039] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the substrate is a single piece with a shiplap joint.

[0040] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the substrate comprises a circumferential array of pieces with respective shiplap joints between adjacent pieces.

[0041] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the coating is an outer diameter (OD) coating and / or the substrate is a cobalt-based chromium- tungsten alloy.

[0042] A further aspect of the disclosure involves a method for coating an article selected from the group consisting of a seal ring, a seal ring groove, and a seal ring counterface, the method comprising: co-spraying WC-Co and MCrAlY to a surface of a metallic substrate of the article.

[0043] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the seal ring is a split ring seal.

[0044] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the substrate is a single piece with a shiplap joint.

[0045] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the substrate comprises a circumferential array of pieces with respective shiplap joints between adjacent pieces.

[0046] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the substrate is a cobalt based chromium tungsten alloy.

[0047] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the spraying is directly to the cobalt based chromium tungsten alloy without an intervening bondcoat.

[0048] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, said MCrAlY has a by weight percent composition of: Ni bal; up to 28.0 Co; 14.0 to 31.0 Cr; 6.0 to 14.0 Al; 0.1 to 1.0 Y; W, Ta, Mo, up to 8.0 combined if any; and Zr if any up to 1.0.

[0049] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, said MCrAlY has by weight percent: to 1.0 Hf; to 1.0 Si; and 2.0 total other.

[0050] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, a ratio of the WC-Co to the MCrAlY is between 1:25 and 1:4, inclusive.

[0051] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the WC-Co has a by weight composition of at least 70% WC and at least 10% Co.

[0052] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the co-spraying comprises by weight: 4.0% to 20.0% WC-Co; and at least 70% MCrAlY.

[0053] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the co-spraying is of a powder blend of the WC-Co and the MCrAlY.

[0054] A further aspect of the disclosure involves a method for manufacturing a gas turbine engine rotor including coating according to above methods a seal ring, the method further comprising: installing the seal ring to a groove in a shaft, the groove having a forward surface and an aft surface; and assembling a disk to the shaft, the disk having a disk bore with an inner diameter surface at least facing the outer diameter surface of the seal ring.

[0055] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include: co-spraying WC-Co and MCrAlY to at least one of a portion of said disk inner diameter surface, a portion of said groove forward surface, and a portion of said groove aft surface.

[0056] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the co-spraying WC-Co and MCrAlY to the seal ring substrate is at a lower WC-Co to MCrAlY ratio than is the co-spraying WC-Co and MCrAlY to said at least one of a portion of said disk inner diameter surface, a portion of said groove forward surface, and a portion of said groove aft surface.

[0057] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include: machining said at least one of said disk inner diameter surface portion, said portion of said groove forward surface, and said portion of said groove aft surface prior to the co-spraying WC-Co and MCrAlY thereto; and machining the co-sprayed WC Co and MCrAlY on said at least one of said disk inner diameter surface portion, said portion of said groove forward surface, and said portion of said groove aft surface.

[0058] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the co-spraying WC-Co and MCrAlY is to said disk inner diameter surface portion.

[0059] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include: applying an NiCrAl bondcoat to the machined surface viathermal spray; and machining the applied NiCrAl bondcoat, wherein the applying the layer is to the machined bondcoat.

[0060] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the co-spraying WC-Co and MCrAlY to at least one of a portion of said disk inner diameter surface, a portion of said groove forward surface, and a portion of said groove aft surface the spraying is directly to substrate alloy without an intervening bondcoat.

[0061] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0062] FIG. 1 is a view of a piston seal ring (PSR).

[0063] FIG. 1 A is a view of joint of the PSR.

[0064] FIG. 2 is a view of a gas turbine engine containing the PSR.

[0065] FIG. 2A is an enlarged view of a rotor region of the gas turbine engine showing sealing engagement by the PSR sealing a rotor disk and shaft.

[0066] FIG. 2B is an enlarged view of the sealing engagement with damage shown in broken lines.

[0067] FIG. 2C is a schematic sectional view of the repaired seal engagement.

[0068] FIG. 2D is a schematic sectional view of an alternative seal engagement.

[0069] Eike reference numbers and designations in the various drawings indicate like elements.DETAILED DESCRIPTION

[0070] PSRs and their mating surfaces are subject to wear and other damage.

[0071] FIG. 2B shows a rotor having a piston seal ring (PSR) sealing between a shaft and an inner diameter bore of a disk. FIG. 2B shows the PSR as having a metallic substrate 200, the shaft as having a metallic substrate 210, and the disk bore as having a metallic substrate 220. As noted above, example rotor disk and shaft substrate materials are nickel-based superalloys. Example PSR substrate materials are nickel-based superalloys and cobaltchromium alloys.

[0072] Example cobalt-chromium PSR substrate alloys have Co as a largest by weight constituent element and at least 18.0 weight percent Cr and no more than 20.0 weight percent any element other than Co, Cr, and Ni. More narrowly, the example PSR substrate comprises by weight percent: <2.0 C; <2.5 Mn; <2.5 Si; <0.1 P; <0.1 S; 18.0-35.0Cr; <30.0 Ni; <8.0 max Mo; <16.0 W; <4.0 Fe; and balance Co and no more than 7.0 each other element, if any, individually and 15.0 all other elements total. More narrowly, the example PSR substrate comprises by weight percent: 0.60-1.90 C; 0.50-2.00 Mn; 0.20-2.00 Si; 0.04 max P; 0.03 max S; 28.00-32.00 Cr; 3.00 max Ni; 1.50 max Mo; 3.50-5.50 W; 3.0 max Fe; and balance Co and no more than 1.0 each other element, if any, individually and 5.0 all other elements total. In alternative embodiments the limits on “other” may be 1.0 total and 0.5 each other or may be at commercial or inevitable impurity levels. Other candidate substrates are disclosed in PCT / US24 / 20351, filed March 18, 2024, by RTX Corporation, with inventors Hamidreza Mohseni et al., and entitled “Laser Treatment of Piston Seal Rings”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length.

[0073] In one repair / remanufacture situation, the original in-service engine had uncoated disk bore substrate inner diameter (ID) surface and disk shaft groove surfaces engaging the original PSR. Wear or damage may require repair / remanufacture of the worn / damaged surface and replacement of the PSR. As is discussed below, this may involve material removal followed by a two-layer repair / restoration wherein an inner layer / underlayer 212, 222 (FIG. 2C) provides both bond and bulk thickness and an outer layer 214, 224 may provide a relative hard interface surface 215, 225.

[0074] Particularly if the bulk thickness is not needed (e.g., damage depth is low enough), there may be a one-layer repair / restoration with only said outer layer, there may also be combination situations where one surface has a one-layer repair / restoration and another has a two-layer repair / restoration. For example, there may be a two-layer repair / restoration of the bore ID surface and a one-layer repair of the groove sidewall(s) or vice versa.

[0075] The example inner layer / under layer is an NiCrAl. Example outer layers are a blend of MCrAlY and WC-Co or a blend thereof. In MCrAlY, M stands for Ni, Co, Fe or combination of two or three of the three. However typical commercially MCrAlY used as bondcoats have little, if any, Fe (such as NiCrAlY, NiCoCrAlY and CoNiCrAlY with not more than 5 weight percent Fe, if any). Common intentional additions include small amounts of Si, Hf, and Zr. The outer layer material provides a hard wear-resistant surface. The inner layer material fills bulk potentially providing bonding and a ductility that the outer layer material would not be able to provide at the combined thickness. The ductility issue is more a factor with the WC-Co outer layer than with the MCrAlY. Eack of ductility may magnify the thickness consideration for the WC-Co. However, the crack-isolating effect of the NiCrAl-to- MCrAlY boundary may provide benefits (despite the ductility of MCrAlY) to provide crack isolation benefits relative to a full depth MCrAlY. The particular use of an NiCrAl as an inner layer and also provides good wear resistance so that once there is wear through the outer layer, there is not a runaway failure. A blend of MCrAlY and WC-Co may provide an advantageous combination of wear resistance and crack isolation. In various embodiments, the blend may have sufficient ductility to avoid a separate bondcoat. Nevertheless such a bondcoat may be useful particularly to build up thickness in restoration situations for grooves and outer diameter (OD) counterfaces.

[0076] The outer layer feedstock (e.g., thermal spray powder) composition, size / morphology, and spray parameters may be selected to limit oxidation of one or more components during deposition (e.g., in flight of the spray) so that the resulting as-applied coating has a low oxide content. In the blend, the MCrAlY will have a greater tendency toward oxidation during spray application than the WC-Co. Some MCrAlY oxidation products add hardness that is redundant with the hardness offered by the WC-Co content.

[0077] In general, the use of fine (particle size) powder of a given component increases the specific surface area of that component and increases its relative tendency toward oxidation. Accordingly, a relatively coarse MCrAlY feedstock may be used such as a mesh of 98% max. +325 and 30% max. -325. The WC-Co powder may be SAE / AMS7879G spec.

[0078] In service, oxidation of the coating may be largely at the wear surface. Particularly with pairings of different coating composition or coating against uncoated substrate, there may be a net material transfer in either direction.

[0079] In service simulation of like on like 88WC-12Co APS coatings on IN718 substrates, WO3 and CoWO4 glaze layer oxides were observed at 710°F (377°C) and 930°F(499°C). These are surface oxides with the bulk material underneath remaining substantially unoxidized.

[0080] Example inner layer or bondcoat thickness TB is 25 micrometers to 0.51 millimeter, more particularly, 75 micrometers to 300 micrometers.

[0081] Example outer layer or topcoat thickness TT is 13 micrometers to 0.51 millimeter, more particularly, 13 micrometers to 250 micrometers or 50 micrometers to 250 micrometers or 75 micrometers to 200 micrometers or 100 micrometers to 150 micrometers. As noted above, the upper end of the thickness range of WC-Co may be more sensitive to ductility issues than that of MCrAlY. Accordingly, an additional more narrow set of ranges for the WC-Co outer layer is 13 micrometers to 250 micrometers, more particularly, 50 micrometers to 250 micrometers or 75 micrometers to 200 micrometers or 100 micrometers to 150 micrometers. For the topcoat blend, when the bondcoat is present, the thickness TT may be the same as for the MCrAlY or WC-Co. For the single-layer system (no bondcoat), the thickness TT may be equivalent to the combined thicknesses in the two-layer system. For example, this may involve a nominal blend layer thickness of about 200 micrometers, more broadly 200 micrometers to 250 micrometers or 100 micrometers to 300 micrometers. For each of the ranges herein, any of the lower ends may be paired with any of the upper ends for further ranges.

[0082] FIG. 2B shows, in broken line, a damage boundary 800A on the forward groove wall, 800B on the aft groove wall, and 802 on the bore foot ID surface. FIG. 2B also shows corresponding machining depths 804A, 804B, and 804C to remove damaged material prior to restoration.

[0083] In this example, the uncoated nature of those original PSR-engaging surfaces ignores things such as assembly lubricants and any lubricious coating that may be transferred from the PSR upon assembly. Additionally, the reference to these inner and outer layers does not preclude a hypothetical further outermost layer such as a lubricious layer.

[0084] A first group of examples involves NiCrAl bondcoat / underlayer 212, 222 and an MCrAlY outer layer 214, 224. An example application technique for both layers are thermal spray (e.g., air plasma spray (APS)).

[0085] A second group of examples involves a similar NiCrAl bondcoat / underlayer to the first group but the outer layer 212, 222 being a tungsten carbide-cobalt cermet (WC-Co). Example cermet application techniques include APS, HVOF, HVAF, cold spray, high energy plasma spray, and detonation gun spray.

[0086] A third group of examples involves a similar NiCrAl bondcoat / underlayer to the first group but the outer layer 212, 222 being applied from a combination of an MCrAlY and a tungsten carbide-cobalt cermet (WC-Co). Example blend application techniques include APS, HVOF, HVAF, cold spray, high energy plasma spray, and detonation gun spray.

[0087] It is expected that in such a repair or restoration situation, the PSR will be replaced with a new replacement PSR. The replacement PSR may be similar to the original or may be different. In one example of a difference, the replaced PSR originally had a metallic substrate with an outer diameter (OD) coating of CuAl (e.g., applied by air plasma spray (APS)). It may also have included a dry film lubricant (DFE) on axial end faces and atop the OD CuAl. This dry film lubricant is typically relevant for assembly purposes and will erode, melt, or decompose away relatively shortly.

[0088] In one example of a differential replacement, the replacement PSR lacks the CuAl OD coating. Instead, the replacement seal has a WC-Co or MCrAlY or blend coating 202 on the substrate (e.g., cobalt-based chromium-tungsten alloy) OD surface and, optionally, on the substrate axial end faces. This may ultimately provide like-on-like WC-Co or MCrAlY engagement between the PSR and bore foot and the PSR and groove. However, eliminating the WC-Co in the PSR coating or substantially reducing it relative to the content on the groove and bore allows preferential wear of the PSR coating. Similarly, an uncoated PSR may preferentially wear. This preferential wear may allow PSR replacement without needing to do coating or substrate restoration of the counterfaces, or it may limit the extent of such counterface restoration needed at a given service. As with the baseline example, there may be a transient dry film lubricant. An example coating 202 thickness TH may be in the ranges given above for TT.

[0089] In an example repair situation, wear or damage may be circumferentially uniform or may be localized. In either event, for uniformity of end product, the surface to be repaired may be machined down in a full annulus. Example machining is by a depth DM of 0.005 inch to 0.040 inch (0.127 millimeter to 1.0 millimeter). FIG. 2B shows somewhat schematically, wear or damage sites in broken lines and a subsequent machined surface also in broken lines. For purposes of illustration, the rotor is shown in an assembled condition. However, the machining would only be performed after disassembling the disk and shaft and removing the old PSR. Depth / thickness is exaggerated for illustration. The example illustrated situation is an all of the above situation wherein wear / damage and repair / restoration is performed on all three of the relevant surfaces: the ID surface of the bore; and the forward and aft wallsurfaces of the groove. Nevertheless, in some situations, fewer of the surfaces may be the subject of such a repair / restoration.

[0090] In an example situation, the bondcoat / underlayer is applied (e.g., thermal sprayed) to a thickness in excess of the ultimate desired thickness and then there is a machining to level and smooth the bondcoat. Example as-applied thickness is 75 micrometers to 650 micrometers. Example bondcoat machining is a grinding such as by diamond grind (e.g., with a diamond-coated wheel) to yield a roughness of between 100 micro inches and 200 micro inches Ra (2.5 micrometers to 5.1 micrometers Ra). Alternatively, the bondcoat or underlayer may be left as sprayed with its roughness contributing to adhesion of the outer layer / topcoat.

[0091] The outer layer may similarly be applied (e.g., thermal sprayed) to excess thickness and then ground / machined (e.g., also by diamond grind) to a desired profile and roughness. Example as-applied thickness is 75 micrometers to 250 micrometers. The particular profile may yield a target nominal wall-to-wall shaft groove width or bore inner diameter dimension. Example outer layer roughness is up to 63 micro inches Ra (1.6 micrometers Ra). The example grinding / machining leaves the layers smoothly flush to the adjacent bore ID surface. This avoids creating a physical discontinuity which would complicate assembly (e.g., causing the PSR to catch during relative translation of components in assembly).

[0092] Regarding composition, example NiCrAl is 96%(Ni-Cr)-4% Al with about 16- 18% by weight Cr. More broadly, an example is, by weight percent, 15.5 to 22 Cr, 3.5-8.0 Al (more narrowly 4.5 to 7.5), and up to 6% other total. Notable “other” elements include Mn at up to 3.5% (more narrowly up to 3.0% or up to 2.0%), Fe at up to 3.5% (more narrowly up to 3.0%), Si at up to 2.5% (more narrowly up to 2.0% or up to 1.5%) and C at up to 0.50% (more narrowly up to 0.30%). Example further other elements, individually, may be at up to 1.0 % total (more narrowly) 0.5%. Within said other, example Y is up to 0.10% or up to 0.050% or up to 0.010%. Example: commercial NiCrAl compositions include Haynes / CABOT 214 (Haynes International, Inc., Kokomo, Indiana); Metco 443NA and 8443 (Oerlikon Metco (US) Inc., Westbury, New York); and Praxair Ni-122 and Ni-528 (Linde plc / Praxair, Danbury, Connecticut).

[0093] This may be distinguished from an MCrAlY in any of several ways. First, is that there is insufficient Co to be a NiCoCrAlY (discussed below - let alone something with more cobalt) and insufficient Fe to be a NiFeCrAlY (let alone something with more iron). Also, as a general matter, Ni weight content in NiCrAl will be higher than in a NiCoCrAlY. Also, as ageneral matter the Al content will be lower than for a high- Al MCrAlY. Also, as a general matter, Y will be lower than for an MCrAlY (e.g., up to 0.10% v. 0.10% to 1.0%).

[0094] An example MCrAlY is a NiCoCrAlY or a NiCrAlY. A NiCoCrAlY will have nickel as its largest by-weight elemental constituent with cobalt. Typically, at least about 5% by-weight cobalt may be a minimum to identify the alloy as a NiCoCrAlY relative to a NiCrAlY. In commercial MCrAlYs, the cobalt composition tends to be generally binary: either zero or in the range of about 19 to 26 weight percent. Typically, a NiCoCrAlY will have cobalt as a second largest by-weight constituent. Often, the cobalt content is close to the chromium content.

[0095] Table I below provides several MCrAlY examples found in literature. Several intermediate / medium cobalt compositions are found in addition to th traditional higher cobalt contents. The Med. 1 example is based on a bondcoat disclosed in Chao Zhu et al., “The Effect of Initial Oxidation on Long-Term Oxidation of NiCoCrAlY Alloy”, Engineering, 2010, June 5, 2010, pages 602-607, Scientific Research, Wuhan, China. The Med. 2 and Med. 3 examples are taken from Michael N. Task, “The Effects of Composition and Micro structure on the Reaction Behavior of MCrAlY Alloys under a Variety of Aggressive Environmental Conditions”, Master of Science thesis, November 19, 2009, University of Pittsburgh, Pittsburgh, Pennsylvania.

[0096] An example high-Co Ni is Ni-20Co-15Cr-12.5Al-0.2Y. More broadly, an example is a cobalt-containing MCrAlY with a Co content of at least 18 weight percent (more narrowly, 18 to 28 or 19 to 26) and / or as a second highest weight content after Ni. The cobalt provides high temperature oxide formation for lubricity. The example is also relatively medium to high in Al content 8 to 15 weight percent Al. An example such range is Ni bal, 18.0 to 28.0 Co, 14.0 to 22.0 Cr, 8.0 to 14.0 Al, 0.1 to 1.0 Y. Other examples include Ni bal, 19.0 to 26.0 Co, 14.0 to 21.0 Cr, 11.0 to 14.0 Al, 0.1 to 0.8 Y.

[0097] Where MCrAlY is mixed with WC-Co, the Co in the WC-Co allows use of a relatively lower content of cobalt in the MCrAlY than in a blend of MCrAlY and WC. The cobalt in the WC-Co can make up for reduced cobalt in the MCrAlY allowing Co reduction relative to traditional NiCoCrAlY compositions. This suggests the use of a relatively low cobalt content which may occupy an orphan zone between about 5.0 weight percent and about 15.0 weight percent Co generally not found in commercial MCrAlY.

[0098] In further variations on any of these ranges or the ranges in Table I below, narrower Y content may be 0.4 to 0.8, an Hf content may be up to 1.0 or 0.1 to 0.05, a Si content may be up to 1.0 or 0.1 to 0.07. A total of further “other” may be up to 2.0 or 1.0.Within said “other”, further narrowing may involve up to 0.030 or 0.020 C, up to 0.020 or 0.010 P, up to 0.020 or 0.010 S, up to 0.01 or 0.0025 Pb, up to 0.001 or 0.0001 Bi, up to 0.050 or 0.010 N. Among other intentional elements that may exceed said other are up to moderate quantities of a combination of W, Ta, Mo, for example up to 8.0 combined (e.g., optionally with up to 6.0 or 4.0 individually) or up to 4.0 and / or up to moderate quantities of Zr, for example up to 1.0.Table IExample MCrAlY and Rangest 0.4Hf, 0.25 Si ft 0.1 to 1.0 Hf, 0.1 to 0.7 Si, 0 to 1.0 other (total) ttt 0.5Hf, l.OSi, 6.0Ta, 2.0Re tttt 0.1 to 0.5 Hf, 0.1 to 0.7 Si, 0 to 0.5 other (total) ttttt 4 Ta

[0099] Cobalt and chromium may both provide hot corrosion resistance. Thus, there may be a tendency for Cr to increase as Co is reduced.

[0100] In terms of the blend, one group of hard coating examples involves by-weight ratios of the WC-Co to MCrAlY of between 1:25 and 1:3, inclusive. The WC-Co content may be reduced below that for various purposes such as to a 1:4 or a 1:8 upper limit.

[0101] In general, it may be desirable to preferentially wear the PSR relative to the counterface and / or the groove. Accordingly, several options involve an uncoated PSR (or, more broadly, a PSR lacking a hard coating) while the counterface and / or groove have the hard coating. Yet further alternatives involve hard coating on the PSR as well but softer than the counterface and / or groove hard coating. For example, within the WC-Co / MCrAlY blend domain, the counterface and / or groove hard coating may have a higher tungsten carbide content than the hard coating on the PSR (which may thus have a low WC-Co content if any). Also, depending on application, the hard coating may be omitted from the groove or limited such as to the low pressure side (forward in a typical compressor application).

[0102] Table II below provides some examples of PSR coating (OD and / or axial end faces) and counterface (bore ID) / groove (sidewall) coating pairings:Table IIWC-Co to MCrAlY Ratio Pairings

[0103] The Ex. 6 and 7 pairings provide key examples of the intended preferential wear of the PSR. The more balanced examples (similar coatings on PSR and conterface) may offer durability benefits via reduced cracking / spallation.

[0104] Although the spray or other deposition feedstock may be a blend of discrete WC- Co powder on the one hand and MCrAlY powder on the other hand, the application process may at least partially obscure the distinction. The blend of WC-Co and MCrAlY will result in a different microstructure of the finished coating than conventional thermal spray WC-Co.Thermal spray of a conventional WC-Co feedstock powder results in distinct tungsten carbide particles in a cobalt matrix, readily observable in a prepared metallographic cross-section mount under magnification (e.g., on a metallograph). Thermal spray of the WC-Co powderplus MCrAlY blend may result in distinct tungsten carbide particles, partially or completely surrounded by a thin layer of Co, in an MCrAlY matrix.

[0105] Depending on the powder manufacturing method (typically fused and crushed, agglomerated and sintered, sintered and crushed, or clad), the primary carbide particle size in the feedstock powder, and the spray parameters used, islands of cobalt may also be observed in the MCrAlY matrix without captured WC particles. MCrAlY matrix may also occasionally be observed in direct contact with carbide particles in the finished coating. A limited amount of diffusion of elements in the MCrAlY into the pure Co sites / phases may occur during spraying and cooling, resulting in sites of Co alloy with some extent of alloying with Ni, Cr, Al, Y, and any other elements in the MCrAlY, but less highly alloyed than the original MCrAlY.

[0106] The volume fraction of carbide particles observed in the finished coating microstructure may differ from the volume fraction of carbide particles in the powder blend. This occurs because dissolution of a portion of the WC phase into the metal matrix is common with high-temperature thermal spray WC-Co processes. The extent of dissolution can be managed by altering the temperature reached by the feedstock powder during thermal spray; lower temperatures will result in lower carbide dissolution, which will also influence the wear performance and mechanical properties of the coating.

[0107] Another notable difference in composition between feedstock powder and finished coating may be the oxygen content. It is common for metallic phases to experience oxidation during high-temperature thermal spray operations. These oxides may appear as “oxide stringers” along splat boundaries in the microstructure, and they will contribute to measurable oxygen content when the coating is analyzed for composition by methods such as energy dispersive x-ray spectroscopy.

[0108] An optional diffusion heat treatment (e.g., a protective atmosphere such as vacuum) after spraying may be desirable to provide partial diffusion of elements in the MCrAlY into the sites of pure cobalt. Example temperature may be up to about 600°C, above which phase changes may be undesirable.

[0109] While this heat treatment will alter the distribution of elements in the metallic matrix, it is not intended to alter the morphology of the coating. Similarly, depending on the time spent at elevated temperature in service it can be expected that elements of the MCrAlY will diffuse into the thin pure cobalt layer. Whether induced during manufacturing or naturally occurring during service, this diffusion is desirable as it will improve the uniformity of chemistry and mechanical and thermal properties of the metal phase of the coating.However, increased oxidation of the coating due to elevated temperature exposure in air is not desirable.

[0110] The surface roughness of a WC-Co coating is strongly influenced by the morphology of the feedstock powder. Coarser carbide particles are associated with higher surface roughness in the as-sprayed condition. Certain powder manufacturers produce feedstock powders with sub-micron carbide particle sizes for certain applications, which can yield smooth coatings that may not require post-spray surface grinding. However, it may be desirable for the WC-Co-MCrAlY coating to use coarser carbide particles for optimal wear resistance, which may result in an as-sprayed surface roughness of 125 micro-inch Ra (3.2 micrometer Ra) or greater. For these roughness levels a post-spray diamond grinding operation is may be advantageous.

[0111] Example WC-Co is nominal 88% WC by weight and 12% Co by weight (e.g., AMS 7879). An example weight percent specification for such is W bal., Co 10.0-13.0, C 03.5-6.0, Fe. 2.0 max., others 1.0 max. total. Another is W 81 min., Co 11.5-13., C 3.6-5.0, Fe. 1.5 max., others 1.0 max. total.

[0112] An alternative WC-Co is a nominal 83%WC-17%Co combination. An example weight specification for such is W bal., Co 14.5-19.5, C 4.7-5.6, Fe. 1.5 max., others 1.0 max. Another alternative WC-Co is a nominal 80%WC-20%Co combination. An example weight specification for such is W bal., Co 18.0-23.0, C 4.7-6.0, Fe. 1.5 max., others 1.0 max. total. Another alternative WC-Co is a nominal 75%WC-25%Co combination.

[0113] In general, a by weight WC-Co composition may be W bal., Co 10.0-26.0, C 3.0- 6.5, Fe 2.0 max., others 2.0. max. total. Narrower options in any combination may be a minimum W of 65.0, a max. other total of 1.5 or 1.0 and a max other individual of 0.50 or 0.75.

[0114] As mentioned above, further variations may add lubricious coatings atop the MCrAlY or WC-Co or blend. Example of such coatings are dry film lubricants. An example dry film lubricant is graphite-based or M0S2 based or combination of the two.

[0115] Another possible scenario involves original manufacture (original equipment manufacture (OEM)) scenarios wherein the thickness-filling function of the bondcoat / underlayer is unnecessary. In such a situation, the bondcoat / underlayer may be omitted and the MCrAlY or WC-Co or blend applied directly to the substrate. In such situations, layer thickness may be that given for TT above. In such a situation relative to a baseline, the thicknesses of the MCrAlY or WC-Co or blend may be low enough so that no other change needs to be made to the disk or shaft and a baseline piston seal ring may beused. However, as noted above, there may be issues of a discontinuity such as if a local circumferential band of the MCrAlY or WC-Co or blend was applied to the smooth bore ID surface 110. Thus, relative to a baseline engine configuration, there may be a local grinding / machining to create a recess in the bore substrate ID surface which is then filled with the MCrAlY or WC-Co or blend. The MCrAlY or WC-Co or blend may then be ground / machined flush with adjacent bore ID surface 110. FIG. 2D shows such a situation. The illustrated recess is formed as an annular channel having respective fore and aft walls and an outer diameter (OD) base. An alternative is to machine from one end (e.g., the aft end of the bore) so that the recesses is open to such end and only has one end wall (e.g., the forward end wall in that example). Or, the machining may go all the way forward to the annular ID channel of FIG. 2 so that there is neither a fore nor an aft end wall to the material removal zone.

[0116] For an OEM coating of the groove, however, the issues of surface discontinuity are less relevant. Thus, it may be possible to, without any initial grinding or other alteration, apply the MCrAlY or WC-Co or blend to a baseline groove configuration and then grind for smoothness. This may leave the groove slightly shorter in longitudinal extent (or shallower if also applied to the base). But such loss of dimension may be tolerable. Nevertheless, there may alternatively be a recessing similar to that for the OEM bore ID situation or the repair situations discussed above. FIG. 2D shows such a situation. As noted above, relative to the repair situation, the features shown in the example OEM situation may be implemented independently. Thus, the OEM coating 224 or 214 may be applied independently of the other and independently of the PSR coating 202 with the other subject surfaces potentially being the same as baseline / prior art discussed above or otherwise.

[0117] The MCrAlY or WC-Co or blend coated PSR may also be used in such a situation of OEM MCrAlY or WC-Co coating on bore and / or groove. In general, where the PSR has an MCrAlY or WC-Co or blend coating, the bore and / or groove counterface to such coating is preferably also so coated, particularly with a like on like coating (e.g., MCrAlY on both PSR and bore and / or groove or WC-Co on both PSR and bore and / or groove or blend on both PSR and bore and / or groove). This is particularly true for the WC-Co which is harder than MCrAlY and more likely to wear a conventional counterface (or even an MCrAlY counterface) lacking a similarly hard coating. Thus, with MCrAlY or WC-Co on both PSR and bore and / or groove on OD and sides of the PSR, MCrAlY or WC-Co on both PSR and bore and / or groove is also likely on the counterfaces (bore ID and at least the low pressuresidewall of the groove). With only an OD MCrAlY or WC-Co on both PSR and bore and / or groove PSR coating, it is more likely that only the bore ID would have the coating.

[0118] Additionally, such an OEM situation may, itself, be subject to repair as discussed above. In that situation, the machining may at least locally remove the original MCrAlY or WC-Co layer partially or fully. Full removal plus some substrate removal may be appropriate for the two-layer repair.

[0119] Additionally, the repairs described above may be re-repairs wherein the damage site(s) are to already-repaired material and the machining steps may fully or partially remove the prior inner layer / under layer / bondcoat while fully removing any remaining outer layer.

[0120] FIG. 1 shows a piston seal ring (PSR) formed as a split ring seal 20 having a first circumferential end 24, a second circumferential end 26, an inner diameter (ID) surface 28, an outer diameter (OD) surface 30, a first axial end face 32, and a second axial end face 34. The PSR has a nominal central longitudinal axis (centerline) 500 shared with the members it seals when in a nominally centered condition. FIG. 1A shows the ID surface 28 as having a straight (circular cylindrical) central portion 35 and more frustoconical transitions 36 and 38 to the axial end faces 32 and 34, respectively. In the example, there are more radiused transitions at the extremes of the transitions 36 and 38 than centrally within those transitions. Viewed in section, junctions between the axial end faces and ID and OD surfaces are shown as radiused comers. However, other junctions are possible.

[0121] An alternative PSR (not shown) is a multi- segment PSR. An example of such a PSR is seen in US Patent No. 11028713B2, of Webb, June 8, 2021, and entitled “Rotating Carbon Piston Ring Seal”. Such a seal may include a metallic substrate and may have an example number of segments of four to six. Adjacent segments may have shiplap lap joints as discussed above. In some embodiments, the segments may be loosely held for assembly and alignment purposes such as via a garter spring in an outer diameter (OD) groove. The spring constant of the garter spring may be light enough to be overcome by centrifugal loading, allowing sealing contact between the PSR outer diameter (OD) surface and the bore inner diameter (ID) surface.

[0122] In the example, first circumferential end 24 and second circumferential end 26 form a joint or junction 40 (FIG. 1A). The example joint 40 is a shiplap joint with a projecting portion 42 of the first circumferential end received in a rebate 48 of the second circumferential end and a projecting portion 44 of the second circumferential end received in a rebate 46 in the first circumferential end. The example projecting portions have matingfaces / surfaces 50, 52 which, in the example, closely face or contact along a transverse radial centerplane 502 (FIG. 2A) of the PSR.

[0123] The PSR comprises a single piece alloy substrate or first zone 200 (FIG. 2B) with one or more coating layers 202 or second zones along portions of its exterior surface (and thus forming associated portions of the exterior surface of the PSR).

[0124] FIG. 2A shows the PSR 20 seated in an outer diameter groove 100 in an inner member (e.g., shaft or shaft section) 98 and sealing against an ID surface 110 of an outer member 112 (e.g., a seal runner). The groove 100 has a first sidewall or end wall 102, a second sidewall or end wall 104, and a base 106 joining the two. The groove has a transverse centerplane 503 which may be coincident with the PSR centerplane 502 when the PSR is centered in the groove. In the example gas turbine engine, the first sidewall is an aft sidewall and the second sidewall is a forward sidewall. Example junctions between the sidewalls and the base are shown as quarter-rounds, chamfers, or bevels in FIG. 2A. However, right angle junctions or other transitions are possible. The groove 100 extends radially inward from an outer diameter (OD) surface section or portion 101 of the inner member.

[0125] FIG. 2A shows the PSR in a gas turbine engine rotor 150 including the shaft section 98. Such a situation is discussed as background above. The example rotor is the high pressure compressor (HPC) portion of a high pressure spool of a two-spool engine. The rotor includes a stack of blade disks 152. Each blade disk includes a protuberant inner diameter (ID) bore 154 having an ID surface 156. A radial web 158 extends outward from the bore to a rim structure 160. A circumferential array of blades 162 (shown with airfoil tips cut away) may be mounted to the rim (e.g., via fir tree or dovetail mounting). Or, blade airfoils may be unitarily formed with the rim and the rest of the disk (e.g., an integrally bladed rotor (IBR)).

[0126] The example PSR seals between the rotor shaft section 98 and one of the disk bores 154 as they rotate as a unit. The PSR accommodates small excursions between the two members it seals due to dynamic or static loading, thermal effects, and the like. The example seal runner 112 is unitarily formed with the particular disk bore and protrudes axially from the disk bore near the ID surface thereof to a free distal end / rim of the seal runner. This is one non-limiting example of one baseline.

[0127] The example PSR has a relaxed condition wherein the circumferential ends 24 and 26 are not completely nested / bottomed against each other (there is a slight circumferential gap 124 (FIG. 1A). When assembled over the shaft and seated in the groove, there may be a small ID gap 120 FIG. 2A). However, the PSR OD surface 30 may be close to flush and even potentially sub-flush to the adjacent shaft OD surface 101. Thus, when the seal runner isassembled over the shaft and PSR, there is an at least local OD radial gap between the PSR OD surface 30 and the seal runner ID surface 110. However, when the shaft rotates, centrifugal action will radially expand the PSR, closing the OD gap and expanding the ID gap 120 (or creating the ID gap) and expanding the circumferential gap 124. This centrifugal action biases the PSR OD surface 30 into sealing engagement with the ID surface 110 of the seal runner.

[0128] FIG. 2A shows the sealing between a first region or volume 600 and a second region or volume 602. In an example dynamic operating condition, the first region is a high pressure region and the second region is a low pressure region.

[0129] Alternatively to sealing a disk bore to a shaft, such a seal may be applied to static structures such as cases.

[0130] Alternatively, applications beyond gas turbine engines include pumps, turbochargers, and other turbomachines.

[0131] FIG. 2 shows an example gas turbine engine 800 as a two-spool turbofan engine. Although shown as a high bypass turbofan, a low bypass turbofan may have similar features. The engine 800 has an engine case 822 surrounding a centerline or central longitudinal axis 500. An example engine has a fan section 824 including a fan 826 within a fan case 828. The example engine includes an inlet 830 at an upstream end of the fan case receiving an inlet flow along an inlet flowpath 520. The fan 826 has one or more stages 832 of fan blades (typically one in a high bypass turbofan and more in a low bypass turbofan). Downstream of the fan blades, the flowpath 520 splits into an inboard portion 522 being a core flowpath and passing through a core of the engine and an outboard portion 524 being a bypass flowpath exiting an outlet 834 of the fan case.

[0132] The core flowpath 522 proceeds downstream to an engine outlet 836 through one or more compressor sections, a combustor, and one or more turbine sections. The example engine has two axial compressor sections and two axial turbine sections, although other configurations are equally applicable. From upstream to downstream there is a low pressure compressor section (LPC) 840, a high pressure compressor section (HPC) 842, a combustor section 844, a high pressure turbine section (HPT) 846, and a low pressure turbine section (LPT) 848. Each of the LPC, HPC, HPT, and LPT comprises one or more stages of blades which may be interspersed with one or more stages of stator vanes. In many low bypass turbofan configurations, the core and bypass flows rejoin to exit a nozzle (e.g., a variable nozzle).

[0133] In the example engine, the blade stages of the LPC and LPT are part of a low pressure spool mounted for rotation about the axis 500. The example low pressure spool includes a shaft (low pressure shaft) 850 which couples the blade stages of the LPT to those of the LPC and allows the LPT to drive rotation of the LPC. In the example engine, the shaft 850 also drives the fan. In the example implementation, the fan is driven via a transmission (not shown, e.g., a fan gear drive system such as an epicyclic transmission) to allow the fan to rotate at a lower speed than the low pressure shaft.

[0134] The example engine further includes a high pressure shaft 852 (of which the shaft section 98 forms a section) mounted for rotation about the axis 500 and coupling the blade stages of the HPT to those of the HPC to allow the HPT to drive rotation of the HPC. In the combustor 844, fuel is introduced to compressed air from the HPC and combusted to produce a high pressure gas which, in turn, is expanded in the turbine sections to extract energy and drive rotation of the respective turbine sections and their associated compressor sections (to provide the compressed air to the combustor) and fan.

[0135] The coating and layer thickness, composition, and properties may be measured at a single location or across an area. Such area may be a total or continuous area (e.g., truly continuous or continuous ignoring cooling hole outlets). With an area, that may be at all locations or an average (mean, median, or mode). A representative area is at least 1.0 square centimeters. Or, a representative area may be a fraction or percentage of a relevant area. For example, the relevant area may be the ID surface of the borefoot along the axial span of the adjacent shaft groove. Or it may be the entire fore or aft sidewall of the groove or base of the groove. Or it may be the entire OD surface of the PSR or axial end surface. Or it may be a fraction of any such area. A representative such fraction or percentage is at least 10% or at least 50% or at least 90%. Measurements may be over a depth of up to an entire layer at such a location or in such an area. To consider boundary conditions, example measurement depths may be a fraction such as at least 25% or at least 50% (e.g., a select 50% which may be an example central 50% ignoring 25% at each of interior and exterior directions). The listed compositions may be subject to commercial or inevitable impurity levels.

[0136] The use of “first”, “second”, and the like in the following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description.

[0137] One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing baseline configuration, details of such baseline may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.

Claims

CLAIMSWhat is claimed is:

1. A gas turbine engine (800) rotor (150) comprising: a shaft (98) having an outer diameter groove (100) having a forward surface (104), an aft surface (102), and an inner diameter base surface (106); a seal ring in the groove and having a forward surface (34), an aft surface (36), and an outer diameter (OD) surface (30); and a disk (152) having an inner diameter (ID) surface (156) with a portion (110) facing or contacting the seal ring OD surface, wherein: along at least one of said disk ID surface portion, a portion of said groove forward surface, and a portion of said groove aft surface a layering comprises: a layer formed from WC-Co and MCrAlY (214, 224).

2. The gas turbine engine rotor of claim 1 wherein along said at least one of said disk ID surface portion, said portion of said groove forward surface, and said portion of said groove aft surface said layering comprises: an NiCrAl bondcoat (212, 222) atop metallic substrate (210, 220) with the layer atop the NiCrAl bondcoat.

3. The gas turbine engine rotor of claim 2 wherein: the NiCrAl bondcoat is directly atop the metallic substrate; and the layer is directly atop the NiCrAl bondcoat.

4. The gas turbine engine rotor of claim 2 wherein: the NiCrAl bondcoat has a by weight percent composition of 15.5 to 22 Cr, 3.5-8.0 Al, balance Ni and up to 6% other total.

5. The gas turbine engine rotor of claim 2 wherein: the NiCrAl bondcoat has a thickness of 0.001 inch to 0.020 inch (0.025 millimeter to 0.51 millimeter).

6. The gas turbine engine rotor of claim 1 wherein:the layering consists essentially of said layer directly atop substrate, optionally with a lubricant.

7. The gas turbine engine rotor of claim 1 wherein: the layer has a thickness of 0.005 inch to 0.020 inch (0.13 millimeter to 0.51 millimeter).

8. The gas turbine engine rotor of claim 1 wherein: the layer has a by-weight composition of at least 70% MCrAlY and at least 4.0% WC-Co.

9. The gas turbine engine rotor of claim 1 wherein: the layer has a by-weight composition of at least 90% combined MCrAlY and WC-Co.

10. The gas turbine engine rotor of claim 1 wherein: the WC-Co has a by weight composition of at least 70% WC and at least 10% Co.

11. The gas turbine engine rotor of claim 1 wherein said at least one includes both of: said portion of said groove forward surface and said portion of said groove aft surface.

12. The gas turbine engine rotor of claim 1 wherein: the seal ring has a coating formed from WC-Co and MCrAlY (202) at least along the OD surface and directly atop a substrate of the seal ring, optionally wherein the substrate of the seal ring is a cobalt-based chromium-tungsten alloy.

13. A gas turbine engine (800) including the gas turbine engine rotor of claim 1 wherein the disk is a compressor disk.

14. A method for manufacturing the gas turbine engine rotor of claim 1, the method comprising applying a feedstock blend of:WC-Co from powder feedstock having a by-weight percent composition of at least 70% WC and at least 10% Co; andMCrAlY from powder feedstock having a by-weight percent composition of Ni bal, 18.0 to 28.0 Co, 14.0 to 22.0 Cr, 8.0 to 14.0 Al, 0.1 to 1.0 Y, W, Ta, Mo, up to 5.0 combined if any, and Zr if any up to 1.0.

15. The method of claim 14 wherein: the applying is via thermal spray.

16. A method for manufacturing the gas turbine engine rotor of claim 1, the method comprising: machining said at least one of said disk ID surface portion, said portion of said groove forward surface, and said portion of said groove aft surface; co-applying the WC-Co and MCrAlY ; and machining the co-applied WC-Co and MCrAlY.

17. The method of claim 16 wherein the co-applying comprises thermal spray of:WC-Co from powder feedstock having a by-weight percent composition of at least 70% WC and at least 10% Co; andMCrAlY from powder feedstock having a by-weight percent composition of Ni bal, 18.0 to 28.0 Co, 14.0 to 22.0 Cr, 8.0 to 14.0 Al, 0.1 to 1.0 Y, W, Ta, Mo, up to 5.0 combined if any, and Zr if any up to 1.0.

18. The method of claim 16 further comprising: applying an NiCrAl bondcoat to the machined surface via thermal spray; and machining the applied NiCrAl bondcoat, wherein the applying the layer is to the machined bondcoat.

19. The method of claim 16 further comprising: installing the seal ring to the groove; and assembling the disk to the shaft.

20. The method of claim 16 being a remanufacturing from prior condition wherein: in the prior condition: said at least one of said disk ID surface portion, said portion of said groove forward surface, and said portion of said groove aft surface lacked a layering comprising WC-Co.

21. The method of claim 20 wherein:the seal ring has a second coating formed from WC-Co and MCrAlY for interfacing with the layering comprising said layer; and in the prior condition: a prior seal ring in said groove lacked a WC-Co-containing coating (202).

22. A gas turbine engine rotor comprising: a shaft having an outer diameter groove having a forward surface, an aft surface, and an inner diameter base surface; a seal ring in the groove and having a forward surface, an aft surface, and an outer diameter (OD) surface; and a disk having an inner diameter (ID) surface with a portion facing or contacting the seal ring OD surface, wherein: the seal ring has coating (202) formed from WC-Co and MCrAlY.

23. The gas turbine engine rotor of claim 22 wherein: the seal ring coating is at least along the OD surface.

24. The gas turbine engine rotor of claim 22 wherein: the seal ring coating is directly atop a substrate of the seal ring.

25. The gas turbine engine rotor of claim 24 wherein: the substrate of the seal ring is a cobalt-based chromium-tungsten alloy.

26. The gas turbine engine rotor of claim 22 wherein: along at least one of said disk ID surface portion, a portion of said groove forward surface, and a portion of said groove aft surface a layering comprises: the coating.

27. The gas turbine engine rotor of claim 22 wherein along said at least one of said disk ID surface portion, said portion of said groove forward surface, and said portion of said groove aft surface said layering comprises: an NiCrAl bondcoat atop metallic substrate with the coating atop the NiCrAl bondcoat.

28. A method for manufacturing the gas turbine engine rotor of claim 22, the method comprising thermal spraying the coating from:WC-Co from powder feedstock having a by-weight percent composition of at least 70% WC and at least 10% Co; andMCrAlY from powder feedstock having a by-weight percent composition of Ni bal, 18.0 to 28.0 Co, 14.0 to 22.0 Cr, 8.0 to 14.0 Al, 0.1 to 1.0 Y, W, Ta, Mo, up to 5.0 combined if any, and Zr if any up to 1.0.

29. A seal ring (20) comprising: a metallic substrate (200); and coating formed from WC-Co and MCrAlY (202).

30. The seal ring of claim 29 wherein: the seal is a split ring seal.

31. The seal ring of claim 29 wherein: the substrate is a single piece with a shiplap joint.

32. The seal ring of claim 29 wherein: the substrate comprises a circumferential array of pieces with respective shiplap joints between adjacent pieces.

33. The seal ring of claim 29 wherein: the coating is an outer diameter (OD) coating and / or the substrate is a cobalt-based chromium-tungsten alloy.

34. A method for coating an article (20; selected from the group consisting of a seal ring, a seal ring groove, and a seal ring counterface, the method comprising: co-spraying WC-Co and MCrAlY to an outer diameter (OD) surface of a metallic substrate (200, 210, 220); of the article.

35. The method of claim 34 wherein: the seal ring is a split ring seal.

36. The method of claim 34 wherein: the substrate is a single piece with a shiplap joint.

37. The method of claim 34 wherein: the substrate comprises a circumferential array of pieces with respective shiplap joints between adjacent pieces.

38. The method of claim 34 wherein: the substrate is a cobalt-based chromium-tungsten alloy.

39. The method of claim 34 wherein: the spraying is directly to the cobalt-based chromium-tungsten alloy without an intervening bondcoat.

40. The seal ring of claim 34 wherein: said MCrAlY has a by weight percent composition of: Ni bal; up to 28.0 Co; 14.0 to 31.0 Cr; 6.0 to 14.0 Al; 0.1 to 1.0 Y; W, Ta, Mo, up to 8.0 combined if any; and Zr if any up to 1.0.

41. The seal ring of claim 40 wherein said MCrAlY has by weight percent: to 1.0 Hf; to 1.0 Si; and2.0 total other.

42. The method of claim 34 wherein: a ratio of the WC-Co to the MCrAlY is between 1:25 and 1:4, inclusive.

43. The method of claim 34 wherein: the WC-Co has a by weight composition of at least 70% WC and at least 10% Co.

44. The method of claim 34 wherein the co-spraying comprises by weight:4.0% to 20.0% WC-Co; and at least 70% MCrAlY.

45. The method of claim 34 wherein: the co-spraying is of a powder blend of the WC-Co and the MCrAlY.

46. A method for manufacturing a gas turbine engine rotor including coating according to claim 34 a seal ring, the method further comprising: installing the seal ring to a groove in a shaft, the groove having a forward surface and an aft surface; and assembling a disk to the shaft, the disk having a disk bore with an inner diameter surface at least facing the outer diameter surface of the seal ring.

47. The method of claim 46 further comprising: co-spraying WC-Co and MCrAlY to at least one of a portion of said disk inner diameter surface, a portion of said groove forward surface, and a portion of said groove aft surface.

48. The method of claim 47 wherein: the co-spraying WC-Co and MCrAlY to the seal ring substrate is at a lower WC-Co to MCrAlY ratio than is the co-spraying WC-Co and MCrAlY to said at least one of a portion of said disk inner diameter surface, a portion of said groove forward surface, and a portion of said groove aft surface.

49. The method of claim 47 further comprising: machining said at least one of said disk inner diameter surface portion, said portion of said groove forward surface, and said portion of said groove aft surface prior to the co-spraying WC-Co and MCrAlY thereto; and machining the co-sprayed WC-Co and MCrAlY on said at least one of said disk inner diameter surface portion, said portion of said groove forward surface, and said portion of said groove aft surface.

50. The method of claim 49 wherein: the co-spraying WC-Co and MCrAlY is to said disk inner diameter surface portion.

51. The method of claim 49 further comprising: applying an NiCrAl bondcoat to the machined surface via thermal spray; andmachining the applied NiCrAl bondcoat, wherein the applying the layer is to the machined bondcoat.

52. The method of claim 47 further comprising: the co-spraying WC-Co and MCrAlY to at least one of a portion of said disk inner diameter surface, a portion of said groove forward surface, and a portion of said groove aft surface the spraying is directly to substrate alloy without an intervening bondcoat.

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