EP4728126A2 - Nickel plating - Google Patents

Abstract

A plating method includes: providing a nickel-containing plating solution; immersing a metallic substrate in the plating solution; and applying a voltage between the substrate and an anode to apply a plating. The providing comprises blending chromium powder with a precursor of the plating solution so that the plating solution is a Cr-containing plating solution. The as-applied plating forms a layer containing chromium particles from the powder.

Description

NICKEL PLATING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Benefit is claimed of US Patent Application No. 63/659,278, filed June 12, 2024, and entitled “Nickel Plating”, U.S. Patent Application No. 63/538,826, filed September 16, 2023, and entitled “Nickel Plating”, and US Patent Application No. 63/472,805, filed June 13, 2023, and entitled “Nickel Plating”, 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 nickel plating for dimensional restoration and other coatings.

[0003] Gas turbine engines (used in propulsion and power applications and broadly inclusive of turbojets, turboprops, turbofans, turboshafts, industrial gas turbines, and the like) have metallic components (e.g., nickel-based superalloy) which may be subject to surface wear or damage. In many circumstances, thermal spray techniques are used for dimensional restoration of such components.

[0004] Some locations in some components do not permit line of sight access for thermal spray guns to restore the worn or damaged surfaces.

[0005] Separately, nickel plating is used to apply abrasive coatings to blade tips.

SUMMARY

[0006] One aspect of the disclosure involves a method comprising: providing a plating solution; immersing a metallic substrate in the plating solution; and applying a voltage between the substrate and an anode to apply a plating. The providing comprises blending chromium powder with a precursor of said plating solution so that the plating solution is a Cr- containing plating solution; and the as-applied nickel sulfamate plating forms a layer containing chromium particles from said powder.

[0007] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively: the blending further comprises blending alumina powder so that the plating solution is an alumina-containing plating solution; and the as-applied plating forms said layer containing alumina particles.

[0008] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively: the plating solution has 1.0 to 100.0 g/L combined chromium particulate and alumina particulate; the plating solution has at least 15.0 g/L each chromium particulate and alumina particulate; and the chromium particulate and alumina particulate each have sizes of 1.0 micrometers to 12.0 micrometers.

[0009] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively: the plating solution has at least 15.0 g/L chromium particulate in a size range of 1.0 micrometers to 12.0 micrometers.

[0010] A further embodiment of any of the foregoing embodiments additionally and/or alternatively includes forming the precursor by adding to water: nickel sulfate; cobalt sulfate; boric acid; and nickel chloride.

[0011] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plating solution comprises: 1.0 to 100.0 g/L Cr and, if any, alumina, combined; 48 to 93 g/L Ni; 1.2 to 3.6 g/ L Co; 10 to 80 g/L boric acid; 4.0 to 20.0 g/L Cl; and a pH of 4.3 to 5.7.

[0012] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises forming the precursor by adding to water: ^N NiOeS ; boric acid; and nickel chloride.

[0013] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plating solution comprises: 1.0 to 100.0 g/L Cr; and 60 to 135 g/L Ni; 20 to 80 g/L boric acid; 4.0 to 20.0 g/L Cl; and a pH of 3.5 to 5.5.

[0014] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plating solution has one or more of: 15.0 g/L to 50.0 g/L Cr; 70 to 110 g/L Ni; 20 to 60 g/L boric acid; 6.0 to 12.0 g/L Cl; and a pH of 3.5 to 5.0.

[0015] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the substrate comprises Ni as a largest by weight component.

[0016] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises a cBN tack, wherein the applied plating forms a matrix for particles of the cBN.

[0017] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the applying of the plating is in: a first stage before the cBN tack; and a second stage after the cBN tack, the two stages in the same said plating solution or separate said plating solutions.

[0018] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the metallic substrate forms a gas turbine engine blade airfoil; and the plating is applied to a tip of the airfoil. [0019] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises a nickel strike, wherein the plating is atop the nickel strike.

[0020] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the metallic substrate forms a gas turbine engine case segment and the plating is applied to a vane-mounting hook section.

[0021] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises mounting a vane to the vane-mounting hook section to contact the plating.

[0022] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively: the vane-mounting hook section has: an axially-extending portion having distal axial end surface and an outer diameter surface; and a flange extending radially outward from a junction with the axially-extending portion to a body of the case segment and having an axially-facing surface. A channel for receiving a mounting projection of the vane is formed by: the axially-extending portion outer diameter surface; the flange axially-facing surface; and a portion of an inner diameter surface of the body.

[0023] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises heat treating: at a temperature of 600°C to 760 °C for a time of 2.0 to 10.0 hours.

[0024] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the heat treating diffuses a majority of the chromium powder with the nickel.

[0025] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the heat treating diffuses not more than a majority of the chromium powder with the nickel.

[0026] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method of further comprises machining of the plating after the heat treating. [0027] A further aspect of the disclosure involves a plating method comprising: a nickel strike; and after the nickel strike, plating, wherein the plating comprises plating in a plating solution having a chromium particulate concentration of at least 1.0 g/L.

[0028] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, one or more of: the plating is a nickel or nickel-cobalt plating; the chromium particulate is at least 95% pure Cr by weight; the nickel strike is a Wood’s nickel strike; the nickel strike is directly or indirectly to a nickel-based alloy substrate; and the plating solution has a chromium particulate concentration of 1.0 g/L to 100.0 g/L in a size range of 1.0 micrometers to 12.0 micrometers.

[0029] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, one or more of: the chromium particulate has a size distribution of 1.0 micrometers to 12.0 micrometers; the nickel-based alloy substrate comprises, by weight, at least 20.0% combined Co, Cr, Al, and Ti; and the plating solution has a chromium particulate concentration of 15.0 g/L to 50.0 g/L.

[0030] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, one or more of: the chromium particulate has a size distribution of 1.0 micrometers to 4.0 micrometers; the nickel-based alloy substrate comprises, by weight, at least 10.0% to 40.0% combined Co, Al, and Ti; the nickel-based alloy substrate comprises, by weight, at least 20.0% combined Co, Cr, Al, and Ti; and the plating solution has a chromium particulate concentration of 1.0 g/L to 15.0 g/L.

[0031] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, one or more of: the nickel-based alloy substrate comprises, by weight, at least 10.0% combined Co, Al, and Ti.

[0032] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises, after the plating, a cBN tack.

[0033] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises a further plating in a plating solution having a chromium particulate concentration of at least 1.0 g/L.

[0034] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the method further comprises a heat treatment.

[0035] A further aspect of the disclosure involves a coated article comprising: a metallic substrate; a plating layer on a surface of the metallic substrate comprising chromium particulate.

[0036] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plating layer is a matrix for an abrasive.

[0037] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plating layer further comprises alumina particulate.

[0038] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the chromium particulate is at least 1.0% of the layer by volume.

[0039] In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the coated article may be made by any of the foregoing methods. [0040] 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

[0041] FIG. 1 is a micrograph of an as-deposited chromium-containing nickel sulfamate plating.

[0042] FIG. 1A is an enlarged view of the plating FIG. 1.

[0043] FIG. 2 is a micrograph of a coated substrate similar to FIG. 1 but after heat treatment at 1300°F (~704°C) for four hours in air.

[0044] FIG. 2A is an enlarged view of the coating of FIG. 2.

[0045] FIG. 2B is a further enlarged view of the coating of FIG. 2.

[0046] FIG. 3 is a micrograph of a coated substrate similar to FIG. 1 but after heat treatment at 1300°F (~704°C) for 192 hours in air.

[0047] FIG. 3 A is an enlarged view of the coating of FIG. 3.

[0048] FIG. 3B is a further enlarged view of the coating of FIG. 3.

[0049] FIG. 4 is an SEM/EDX map of such a coated substrate.

[0050] FIGs. 4A-4E correspond to the FIG. 4 map but respectively targeting chromium, nickel, oxygen, cobalt, and titanium.

[0051] FIG. 5 is an SEM/EDX map of such a coated substrate but after heat treatment at 1300°F (~704°C) for four hours in air.

[0052] FIGs. 5A-5E correspond to the FIG. 5 map but respectively targeting chromium, nickel, oxygen, cobalt, and titanium.

[0053] FIG. 6 is an SEM/EDX map of such a coated substrate but after heat treatment at 1300°F (~704°C) for 192 hours in air.

[0054] FIGs. 6A-6E correspond to the FIG. 6 map but respectively targeting chromium, nickel, oxygen, cobalt, and titanium.

[0055] FIG. 6F is a further enlarged SEM/EDX map of the FIG 6 substrate at a boundary region.

[0056] FIGs. 6G-6E correspond to the FIG. 6F map but respectively targeting chromium, nickel, cobalt, titanium, aluminum, and molybdenum.

[0057] FIG. 7 is a schematic view of a plating apparatus.

[0058] FIG. 8 is an SEM/EDX map of a baseline cBN abrasive coating with a nickel sulfamate plating matrix after engine run. [0059] FIGs. 8A and 8B correspond to the FIG. 8 map but respectively targeting chromium and titanium.

[0060] FIG. 9 is an SEM/EDX map of a cBN abrasive coating with a chromium-containing nickel sulfamate plating matrix after engine run. [0061] FIG. 9A is an enlarged view of the map of FIG. 9.

[0062] FIGs. 9B and 9C correspond to the FIG. 9 map but respectively targeting oxygen and titanium.

[0063] FIG. 10 is a sectional view of a forward/upstream portion of a turbine section case segment showing mounting of vanes.

[0064] FIG. 10A is an enlarged view of a mounting feature on the case segment engaging a corresponding mounting feature of a vane shroud.

[0065] FIG. 11 is an isolated view of the case segment.

[0066] FIG. 11 A is an isolated view of the mounting feature.

[0067] FIG. 12 is a cutaway view of the case segment.

[0068] FIG. 13 is an SEM/EDX map of a cBN abrasive coating with a chromium- and alumina -containing nickel-cobalt sulfate plating matrix after 1300°F (~704°C) for 192 hours in vacuum.

[0069] FIG. 13A is an enlarged view of the map of FIG. 13.

[0070] FIGs. 13B-13G correspond to the FIG. 13A map but respectively targeting chromium, nickel, oxygen, aluminum, cobalt, and titanium.

[0071] FIG. 14A is an SEM/EDX map of a cBN abrasive coating with a chromium- containing nickel-cobalt sulfate plating matrix after 1300°F (~704°C) for 192 hours in air. [0072] FIGs. 14B-14F correspond to the FIG. 14A map but respectively targeting chromium, nickel, aluminum, oxygen, and cobalt.

[0073] FIG. 15A is an SEM/EDX map of a cBN abrasive coating with a chromium- and alumina -containing nickel-cobalt sulfate plating matrix after 1300°F (~704°C) for 192 hours in air.

[0074] FIGs. 15B-15F correspond to the FIG. 15A map but respectively targeting chromium, nickel, aluminum, oxygen, and cobalt.

[0075] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0076] As discussed further below, it is shown herein how the addition of a fine chromium particulate to a nickel plating solution (notably nickel sulfamate) can produce a beneficial coating layer upon diffusion of the Cr (e.g., via heat treat or in-service heating). Such coating layer may be used to restore lost substrate alloy in a restoration/remanufacturing situation but also may have other uses in original manufacture or restoration/remanufacturing situations (e.g., replacing a baseline coating layer used in a baseline manufacture or restoration/remanufacture situation) .

[0077] Upon heat treatment (a step in the manufacture or restoration/remanufacture process or possibly in-service operational heating), the chromium may diffuse into the nickel and create an alloy with beneficial properties relative to alternative nickel platings. These beneficial properties may include typical mechanical properties but also may include enhanced resistance to interdiffusion with the substrate material and thus reduced chances for compromise of substrate integrity.

[0078] FIG. 1 shows an article 20 comprising a substrate 22 with an as-applied layer 24 of nickel sulfamate plating with chromium particles. The substrate has an outer surface 26 and the layer has an outer surface 28 A layer thickness is shown as Tp. The example substrate is a nickel-based superalloy (ME-16 discussed below). The substrate contains various alloying elements. The nickel sulfamate plating was performed after a Wood’s nickel strike. [0079] FIG. 2 shows the article after heat treatment at 1300°F (~704°C) for four hours in air. FIG. 2A is an enlarged view of the coating of FIG. 2. FIG. 2B is a further enlarged view of the coating of FIG. 2. These show uniform coating both before (FIG. 1/1 A) and after (FIG. 2/2A/2B) heat treatment, with no development of cracks or other defects (e.g., porosity) during heat treatment.

[0080] FIG. 3 shows the article after heat treatment at 1300°F (~704°C) for 192 hours in air. FIG. 3 A is an enlarged view of the coating of FIG. 3. FIG. 3B is a further enlarged view of the coating of FIG. 3. These show that no defects (e.g., porosity) or cracks develop after extended heat treatment, and that only minimal surface oxidation develops.

[0081] FIGs. 4A-4E show distribution chromium, nickel, oxygen, cobalt, and titanium in the coating. All but oxygen are present in the substrate. Substantial chromium is seen due to the well distributed chromium particles. Very little other elements are present. This indicates little if any diffusion of substrate elements and little if any oxidation.

[0082] FIGs. 5A-5E respectively correspond to FIGs. 4A-4E but after a heat treatment at 1300°F (~704°C) for four hours in air. Except for larger particles, the chromium has substantially inter-diffused with the nickel. There has been no significant diffusion of other elements from the substrate. A negligible oxygen surface layer is visible with essentially no penetration into the plating. This indicates good oxidation resistance.

[0083] FIGs. 6A-6E respectively correspond to FIGs. 4A-4E and 5A-5E but after a heat treatment at 1300°F (~704°C) for 192 hours in air. Except for larger particles, the chromium has substantially inter-diffused with the nickel. There has been no significant diffusion of other elements from the substrate with only a very small amount of Ti diffusing a short distance into the plating. The oxygen surface layer is minor.

[0084] FIGs. 6G-6L are further enlarged views of the substrate-coating interface respectively identifying chromium, nickel, cobalt, titanium, aluminum, and molybdenum. The low atomic weight Al, like Ti, exhibits a clearly visible small amount of diffusion a short distance into the plating. The heavier Co shows even less but a slight gradient is seen. Mo exhibits even less, if any.

[0085] FIG. 7 schematically shows a plating apparatus 400 which may be otherwise representative of a baseline apparatus except for the inclusion of the chromium powder in the solution. The apparatus comprises a vessel 402 having an interior 404 for containing the plating solution 406. The component 408 to be plated forms a cathode electrically connected to an anode 410 via a voltage source 412 (e.g., a DC power supply) and wiring 414. The example anode is pure nickel or essentially pure nickel. A mixer 420 (e.g., motor driven) (not shown) may be operated to maintain circulation within the vessel. Additionally, a standard laboratory hot plate was used to heat the tank and the materials inside to a temperature of about 50°C. Such heating is optional and may be performed with other resistance heating or similar devices to heat the tank and the materials inside to an example temperature of 40°C to 60°C.

[0086] As discussed yet further below, the nickel-chromium material may be used for other purposes such as a matrix for an abrasive. FIG. 8 shows an engine -run baseline coated article 50 (e.g., blade tip) with an ME16 substrate 52 and a baseline cBN abrasive coating 54 with a nickel sulfamate plating matrix 56 partially encapsulating cBN particles 58. A substrate surface 53 is approximately shown. 60 and 61 show two bands of diffusion of substrate elements. Example blades are of an integrally-bladed rotor (IBR) or separate blades having blade mounting features (e.g., dovetails or firtree roots for mounting in complementary disk slots). Example blade location is in a high pressure compressor (HPC) section. An example IBR or an example separate blade may be formed of a Ni-based superalloy. Example IBR alloys are ME16 and IN 100; example separate blade alloys are IN 718 and Waspaloy.

[0087] FIGs. 8A and 8B correspond to the FIG. 8 map but respectively targeting chromium and titanium and show substantial chromium 62 and titanium 64 diffusion from the substrate. FIG. 8 A also shows chromium oxides 63.

[0088] FIG. 9 shows an engine-run coated article 70 (e.g., blade of an integrally-bladed rotor (IBR) with the abrasive coating on blade tips) with an IN 718 substrate 52 and cBN abrasive coating 74 with a Ni-Cr nickel sulfamate plating matrix 76 partially encapsulating cBN particles 58. FIG. 9B shows an essential lack of oxidation. FIG. 9C shows an essential lack of titanium diffusion from the substrate.

[0089] FIGs. 10 and 11 show a gas turbine engine 200 having a case 202 that is longitudinally and circumferentially segmented. For ease of reference, a 360° array of circumferential segments forms a section of the case with multiple sections connected (longitudinal) end-to-end. Example circumferential segmentation is two 180° halves. Each example segment 204 (FIG. 11) has axially-extending bolting flanges (not shown) along its circumferential ends to connect to the one or more adjacent segments of the section and circumferentially-extending bolting flanges 206, 208 at longitudinal ends for mounting to the adjacent longitudinal section(s). Each segment 204 has an inner diameter (ID) surface 210 and an outer diameter (OD) surface 212. The inner diameter surface along a given section has one or more circumferential arrays of mounting features 220 for mounting associated stator vane arrays (stages). An example stage location is in a turbine section (e.g., a high pressure turbine (HPT) section of a two-spool engine also having a low pressure turbine (EPT) downstream/aft thereof).

[0090] The example case 202 is similar to that in US Patent 9869202B2, to Eutjen et al., January 16, 2018, and entitled “Blade outer air seal for a gas turbine engine”. FIG. 10 shows vane stages 260 and 262 alternating with blade stages 261 and 263. The vanes have airfoils 264 between an ID platform 265 and an OD shroud 266. The blades have airfoils 268 extending from ID platforms 269 to tips 270. Attachments 271 (e.g., firtrees or dovetails) mount the blades to slots in a disk.

[0091] The example mounting features comprise structures forming axially open-ended slots 222 having one open axial end 224 and an opposite closed axial end or base 226. The slots have an inner diameter surface 228 and an outer diameter surface 230. The outer diameter surface is formed by the inner diameter surface of a main body portion 232 of the case. [0092] The slot inner diameter surface 228 is formed by an outer diameter surface of a distal wall structure 240 connected to the main body portion by a radially inwardly extending proximal wall structure 242. The proximal wall structure has a pair of axial end faces with one forming the base surface 226 of the slot 222. The distal portion 240 also has an inner diameter surface 246 and a distal axial end surface 248. The example slot OD surface 230, base surface 226, and ID surface 228, along with the distal portion distal axial end surface 248 form bearing surfaces for contacting complementary surfaces of an engagement feature 280 (FIG. 10A) of the vane. The example feature 280 is a forwardly extending hook or tab of an OD portion of a forward section of the shroud 266. The bearing surfaces of the case segment are subject to wear and are restored with the Ni-Cr plating process discussed.

[0093] The example vanes are formed as singlets or clusters secured circumferential end to circumferential end (e.g., via an inner diameter ring fastened to inner diameter platform portions of the vane elements). At outer diameter ends, the vane elements have shrouds one (in the case of a singlet) or more (in a case of a doublet or greater cluster) airfoils span between the platform and shroud. The example vane mounting features 280 are axial projections having an outer diameter surface 286, an inner diameter surface 284, a distal end surface 282 joining the outer diameter surface to the inner diameter surface, and an inner diameter shoulder surface 288. These respectively contact or face the slot OD surface 230, slot ID surface 228, slot base surface 226, and axial portion distal axial end surface 248. In this example, there is no direct contact between surfaces 248 and 288, but rather a spring seal 290 intervenes. For the other surfaces, there may be clearance but at least intermittent direct contact an wearing movement. In operation, the contacting surfaces become worn and must be restored. The slot-like nature of the case mounting feature prevents normal line of sight access for a spray gun or other technique. Accordingly, the Ni-Cr plating process may be used to relatively evenly add material.

[0094] Example case section segments (halves) and vanes may be formed of nickel-based superalloy. In example situations, the contact surface of each case half may, on entry into service, have been essentially uncoated (e.g., lacking any environmental barrier coating, thermal barrier coating, or the like but potentially having a transient assembly lubricant). The contacting surfaces of the vanes may likewise be uncoated.

[0095] In an example restoration process, the engine may be partially disassembled in a disassembly process appropriate to the particular engine configuration. The disassembly disengages the case segments from each other and from the mounted components including the vanes. The disassembly may similarly disassemble the vanes from each other (e.g., from inner diameter rings and the like). The vanes may be restored/remanufactured (e.g., with resurfacing of their mounting features) in a conventional fashion. The case segments may be prepared by cleaning (e.g., in an alkaline dip process optionally followed by a rinse and/or neutralization).

[0096] The case segments may then be masked to prevent plating of areas where plating is not desired (e.g., all areas away from a zone 250 comprising the slot 222 OD surface 230, base surface 226, and ID surface 228, and the distal portion distal axial end surface 248 may be so masked). Example masking may include an initial masking of essentially the entire component followed by local mask removal in the bearing surface/contact areas. Example mask application comprises a dipping. Example dipping is in a lacquer masking material which may comprise polymer in solvent.

[0097] After at least partial drying or curing, the masking material may be removed from the contact areas (e.g., via manual scrapping with a hand scrapper).

[0098] A further preparation may include cleaning of the exposed contact areas (e.g., with a cleaner such as acetone or isopropyl alcohol) to remove any mask residue. This may be followed by an alkaline dip to remove surface grease. An electric etch in acid may remove any passivated layer from the substrate surface at the contact areas.

[0099] A desmut in acid may remove common surface oxides associated with the substrate alloy (e.g., oxides of nickel, chromium, aluminum, titanium, and cobalt, among others).

[0100] A thin nickel strike may be applied to promote adhesion of subsequent plating layer(s). Example strike is a Wood’s nickel strike. Example strike thickness is about 2 micrometers, more broadly 1.0 micrometers to 5.0 micrometers or 1.5 micrometers to 3.0 micrometers.

[0101] Thereafter, the nickel-chromium plating may be performed (discussed in further detail below) to restore material at the contact areas. Example as-applied thickness is about 50 micrometers, more broadly 10 micrometers to 150 micrometers or 30 micrometers to 80 micrometers.

[0102] Excess Ni-Cr material may typically be applied which may then be machined down to a specified profile. The amount of material moved by the machining may be small. Thus, the machining may take the form of a simple abrasive polishing. For example, hand polishing with an abrasive-impregnated rubber wheel on an air-driven spindle or alternative automated abrasive brush methods. [0103] After any further cleaning, the restored segments may be reassembled on an engine including assembling with new or refurbished vanes.

[0104] A heat treatment, if performed may occur at any time post-plating. For example, heat treatment may be performed in an air furnace after removal of all masking. Example heat treat is at 600°C to 800°C for 2.0 to 10.0 hours, more particularly 650°C to 760 °C for 2.0 to 10.0 hours or an example about 700° for about 4 hours.

[0105] An example nickel sulfamate solution is formed from nickel sulfamate (H4N2NiOeS2), boric acid (H3BO3), chloride (e.g., from NiCh), and chromium. An example process for forming the solution comprises blending into water base (e.g., distilled or deionized) the nickel sulfamate (e.g., an amount effective to yield 90g/L Ni in the final Cr- containing solution) powder, boric acid powder (e.g., an amount effective to yield 30g/L in the final Cr-containing solution), a chlorine source (e.g., an amount effective to yield 8g/L in the final Cr-containing solution (e g., nickel chloride (NiCh)). Thereafter, the chromium powder is added (e.g., an amount effective to yield 30g/L in the final Cr-containing solution) and mixed together.

[0106] This is a basic formula and there may be variations. Some variations (as in prior art variations not including chromium) involve the source of chloride. A possible alternative or additional source is hydrochloric acid (HC1). Use of hydrochloric acid as the chlorine source provides an additional control input such as to achieve a given target pH while controlling other key elemental concentrations. The solution is acidic with an example pH of 3.5 to 4.5. Example compositions are shown in Table I below. Given the relatively low chlorine concentration and the 2: 1 atomic ratio relative to nickel in nickel chloride, the nickel chloride will make a small contribution to overall nickel content. In Table I below, obtaining 7.7 g/L CT from NiCh adds about 6.4 g/L Ni to the solution which may be an example about 5% to 10% of the amount of nickel from the nickel sulfamate. In use, there will be concentration variations due to plating of nickel from the solution to the part being plated and liberation of nickel from the anode to the solution.

[0107] The chromium is introduced as fine powder. The fineness of the powder helps facilitate its diffusion into the nickel upon heat treatment. The potential powder size is in the range from 1.0 micrometers to 20.0 micrometers, more particularly in the range from 1.0 micrometers to 12.0 micrometers, or in the range from 1.0 micrometers to 10.0 micrometers (e.g., all particles in that range or at least the specified concentration represents particles in that range). Example D50 is 10 micrometers or slightly less such as 5.0 micrometers to 10 micrometers or 3.0 micrometers to 10. micrometers although finer variations are discussed further below). Example substrates are shown in Table II below. The example NiCr material is up to 60% Cr by weight more particularly 10% to 60% or 15% to 40%, balance Ni exclusive of diffusion.

[0108] A further variation involves use of the nickel-chromium plating above as a matrix for an abrasive. An example component or part is a gas turbine engine blade wherein an abrasive tip coating is being applied. An example blade is a stage of blades on an integrally bladed rotor (IBR). An example location is a turbine section (e.g., a high pressure turbine (HPT) section of a two-spool engine also having a low pressure turbine (LPT) downstream/aft thereof). Slightly different preparation and coating steps may be involved relative to the example case segment above. For example, in an original manufacture situation of the blade, less (if any) or at least different cleaning may be appropriate to the situation on the one hand. On the other hand, in a restoration/remanufacture situation of a worn or damaged blade, substantially more preparation would be involved. This may include, for example, grinding down the remnants of an existing tip. The grinding may be so significant that a replacement piece is applied (e.g., welded, brazed, or diffusion bonded) to replace lost substrate thickness. However, depending upon the nature of the wear or damage, the grinding may not be down to original substrate or may only be through a small enough amount of substrate that thickness can be made up via plating.

[0109] Additionally, the blade examples present issues of the timing of application of thermal barrier coating or the like either in the original manufacture situation or the restoration/remanufacture.

[0110] For simplicity, in the example blade abrasive tip application, it is assumed that the substrate has been prepared and is masked everywhere except the tip (such as via the process noted above for the case). The etch, desmut, nickel strike, and application of a first nickel-chromium plating may be as in the example above. There may, however, be a thickness difference. An example initial nickel-chromium layer for the abrasive coating is approximately 10 micrometers to 25 micrometers thick, more broadly, 2.0 micrometers to 50 micrometers. It is likely to be relatively thin in original manufacture situations but may be substantially thicker in restoration/remanufacture situations if making up for lost substrate. [0111] Abrasive may then be tacked to the initial nickel-chromium plating. An example abrasive is cubic boron nitride (cBN). An example tacking is by gravity feeding of abrasive grit onto the surface followed by a thin layer of nickel sulfamate plating, such as 10 micrometers (more broadly 5.0 micrometers to 15.0 micrometers), which retains the grit to the surface. Example tacking may comprise the same sulfamate plating used for the NiCr but lacking Cr. It is also acceptable to use a Woods nickel strike.

[0112] After the tacking, there may be a second nickel-chromium plating to form a matrix top coat embedding the abrasive particles. An example thickness for the matrix top coat is 75 micrometers to 150 micrometers, more broadly, 25 micrometers to 300 micrometers. This similar heat treatment may follow to that of the case example.

[0113] The chromium powder can be diffused into the pure nickel deposit at relatively low diffusion temperatures (e.g., 600°C to 760°C) which has the benefit of staying below heat treatment temperatures for the nickel superalloy substrate, thereby avoiding microstructural changes to the alloy. The resulting Ni-Cr alloy layer is relatively corrosion resistant (e.g., compared with a pure nickel deposit such as a conventional nickel sulfamate plating). The NiCr coating is highly uniform and, based on observed hardness, believed to have low stress and good ductility (e.g., similar to a pure nickel deposit). Relative to pure Ni, it is also relatively stable with lower tendency to draw substrate elements into the coating. It also has higher temperature capability due to the ability to resist oxidation (by the mechanism of forming a protective chromium oxide passive layer). The high temperature capability makes the plating and process particularly relevant to turbine section components and the more downstream (higher temperature) compressor section components.

[0114] A baseline pure nickel sulfamate plating has a hardness of approximately 300 (HVIOOg). For pure nickel, hardness does not vary much with heat treatment. In contrast, the Example 1 has hardness of 350 HV 100g before heat treatment and 250 HV 100g after heat treatment (1300°F (704°C) for four hours). This shows good ductility of a NiCr alloy formed after the heat treatment.

Table I

Nickel Sulfamate-Cr Plating Solution

[0115] As noted above, overall nickel content may be greater than that from the nickel sulfamate due to nickel originating in nickel chloride. Thus, as an approximation, example overall nickel content for the three ranges are 60-135, 70-110, and 80-108 g/L.

Table II

Substrate Composition [0116] IN718 is UNS N07718/W.Nr. 2.4668, Inconel® alloy 718 Huntington Alloys

Corp., Huntington, West Virginia). Notable substrate alloy components that it is desirable to limit diffusing into the coating are Co, Al, and Ti. Example combined contents of these are 10.0% to 40.0% by weight, more narrowly 15.0% to 35.0% or 20.0% to 35.0%. Considering Cr, example combined Co, Cr, Al, and Ti is 20.0% to 55.0%, more particularly 25.0% to 50.0%.

[0117] Two further groups of combinations involve nickel-cobalt sulfate plating solutions with chromium powder. Otherwise, apparatus and methods may be as above. In one such group, the chromium is essentially the only particulate. In another group, there also is an oxide ceramic particulate such as alumina. As is discussed below, the oxide filler is particularly relevant for abrasive coatings. The chromium-only may be used for abrasive or non-abrasive (e.g., wear coating) applications.

[0118] As with the first group there may be a Wood’s nickel strike (e.g., preceded by conventional masking, cleaning, electrolytic etch, de- smut, and acid pickle).

[0119] As with the first group, in abrasive embodiments, a subsequent cBN tack (for abrasive applications) is also performed but by nickel sulfate plating. An example pre-tack (post-strike) base layer NiCo sulfate-Cr plating is about 25 micrometers, more broadly 10 micrometers to 40 micrometers. An example nickel sulfate plating in the cBN tack has 250 g/L (more broadly, 200 to 300 g/L) nickel sulfate, 26 g/L (more broadly, 20 to 30 g/L) nickel chloride, 30 g/L boric acid (more broadly, 25 to 45g/L), and pH 4.5 to 5.5. The cBN tack may be again followed by a second stage of the NiCo sulfate-Cr plating (e.g., about 115 micrometers, more broadly 75 micrometers to 155 micrometers).

[0120] Table III below provides examples and ranges for the NiCo sulfate-Cr plating solution.

Table III

NiCo Sulfate-Cr Plating Solution

* from N1C12-6H2O (26g/L)

[0121] In general, variations may exist by recombining the different chromium and alumina ranges, particularly and other ranges generally. Example combined nickel content (from the sulfate/sulfamate and nickel chloride) is 48 to 135 g/L, For the sulfate, a narrower combined range is range 48 to 100 g/L or 48 to 93 g/L or 55 to 70 g/L.

[0122] In general, there may be a combined content for the particulate filler (Cr and alumina in the example). In particular, examples combined particulate filler is 1.0-100.0 g/L, more narrowly, 5.0-50.0 or 10.0-50.0 or 15.0-50.0 or 20.0-45.0.

[0123] The chromium powder and the alumina powder each have example powder size in the range from 1.0 micrometers to 20.0 micrometers, more particularly in the range from 1.0 micrometers to 12.0 micrometers, or in the range from 1.0 micrometers to 10.0 micrometers (e.g., all particles are in that range or at least the specified concentration represents particles in that range) which is particularly relevant for even distribution post-cBN tack. Example D50 is 10 micrometers or slightly less such as 5.0 micrometers to 10 micrometers or 3.0 micrometers to 10. micrometers although finer Cr variations are discussed further below).

[0124] The alumina addition serves to impart wear resistance. A mixture such that the ratio of alumina to chromium is about 1 : 1 may provide beneficial wear resistance without overwhelming the alloying effect of the chromium. More broadly, an example upper limit on the alumina to chromium ratio is 1.5:1 or 1.2:1 (too much alumina will physically block diffusion and prevent uniformity of Cr diffusion into the Ni). Thus, particular example ranges wherein significant alumina is present include either of those upper limits and lower limits of 2:1 chromium to alumina or 3:1 chromium to alumina.

[0125] Example chromium powder is at least 90% pure (by weight), or at least 95 or 99% pure. Example alumina powder is at least 90% pure (by weight), or at least 95 or 99% pure.

[0126] A test sample was made of the Example 2 composition (as a pre-tack and posttack plating for cBN) on an IN100 substrate. Prior to any heat treat, the strike was 0.0001 inches (2.5 micrometers) thick. The Example 2 pre-tack layer was 29 micrometers thick. The tack was 15 micrometers thick. The post-tack second layer was 84 micrometers thick.

[0127] A test sample was made of the Example 3 composition (as a pre-tack and posttack plating for cBN) on an IN100 substrate. Prior to any heat treat, the strike was 0.0001 inches (2.5 micrometers) thick. The Example 3 pre-tack layer was 35 micrometers thick. The tack was 14 micrometers thick. The post-tack second layer was 83 micrometers thick.

[0128] As-deposited, large particles of chromium (or chromium and alumina for Ex. 3) are disproportionately above the initial plating layer. The CBN may have helped cause a gradation in the distribution of particles. Specifically, in the initial layer before the tack, a certain fraction of larger particles will adhere to the plate. With constant agitation, some of the larger particles will be driven off before they can adhere. However, after the CBN tack, the spaces between CBN particles may help trap the larger chromium (and alumina when present) particles. This would yield a greater fraction of large particles in the post-tack layer than in the pre-tack layer.

[0129] As deposited, an average hardness measurement (HV 100g) for the Example 2 composition was 283. After the four-hour heat treatment, the average was 188. This evidences stress reduction via the Cr diffusion and heat treat which is beneficial to for less fatigue debit.

[0130] After heat treatment of Example 2 at 1300°F for four hours in a vacuum was observed that the Cr particles from the initial pre-tack plating layer were well diffused within that layer, with only larger particles not diffused. The generally larger particles of the second layer were not.

[0131] After maintaining such heat treatment for 192 hours, it was observed that there may be slight diffusion of Cr from the first layer into the substrate, but the Cr band formed by the first layer remains visible and large Cr particles in the second layer remain.

[0132] Relative to the Cr in nickel sulfamate plating, the Cr in NiCo sulfate plating may be particularly beneficial when used with Co-containing substrates (e.g., at least 10 weight percent Co) and, particularly such Co-containing substrates that operate at higher temperature (e.g., turbine section components vs. HPC components).

[0133] The failure of the chromium particles to diffuse into the nickel in the NiCo sulfate Example 2 and Example 3 embodiments (see FIG. 13 for Example 3) relative to Ni sulfamate plating is believed due to cobalt hindering chromium diffusion. This remains the case after heat treat in/exposure to air.

[0134] This lack of chromium diffusion suggests further embodiments being created that would involve some combination of yet smaller chromium particulate size and/or lower chromium content than what was effective to diffuse in the nickel sulfamate plating. For example, any of the Table III ranges or other variations thereon described could be modified to a lower 1.0-20.0 g/L Cr content or 1.0-15.0 g/L, or 1.0-10.0 g/L or 4.0-10.0 g//L. Similarly, the Cr size distribution could be limited to a range of 1.0 micrometer to 5.0 micrometers or 1.0 micrometer to 2.0 micrometers (e.g., all particles are in that range or at least the specified concentration represents particles in that range). Example D50 is thus also within 1.0 micrometer to 4.0 micrometers or 1.2 micrometers to 3.0micrometers for such finer material. [0135] A specimen according to Cr-alumina Example 3 was similarly tested. It was observed a similar trend in that the smaller particles, particularly of the initial plating, were well diffused after heat treatment at 1300°F for four hours in a vacuum, with the exception of the largest particles in the coating. That Example 3 strike was similar to Example 2. The pretack layer was 28 micrometers thick. The tack was 13 micrometers thick. The post-tack second layer was 76 micrometers thick.

[0136] Heat treatments in air were performed for Examples 2 and 3. FIG. 14A is an SEM/EDX map of the Example 2 cBN abrasive coating with a chromium-containing nickelcobalt sulfate plating matrix after 1300°F (~704°C) for 192 hours in air. FIGs. 14B-14F correspond to the FIG. 14A map but respectively targeting chromium, nickel, aluminum, oxygen, and cobalt. For this tested specimen, the pre-tack layer was 25 micrometers thick. The tack was 16 micrometers thick. The post-tack second layer was 87 micrometers thick. [0137] FIG. 14B shows a slight diffusion of chromium from the first layer to the substrate. A relatively chromium-rich band above the substrate is left by the pre-tack layer. In the post-tack layer, there is substantially more chromium including bright spots reflecting undiffused chromium particles. A slightly more chromium-rich surface oxide is evidenced and suggested by the correlation with oxygen in FIG. 14E.

[0138] In FIG. 14C, there is a band between the two layers reflecting preservation of the nickel tack.

[0139] In FIG. 14D, the presence of a clear boundary in aluminum content between the substrate and coating indicates minimal aluminum depletion from the substrate.

[0140] FIG. 14F shows cobalt in the substrate and a first band of cobalt-rich material generally throughout the pre-tack layer and a second band of cobalt -rich material in an upper/outer portion of the post-tack layer.

[0141] FIG. 15A is an SEM/EDX map of an-Example 3 cBN abrasive coating with a chromium- and alumina-containing nickel-cobalt sulfate plating matrix after 1300°F (~704°C) for 192 hours in air. FIGs. 15B-15F correspond to the FIG. 15A map but respectively targeting chromium, nickel, aluminum, oxygen, and cobalt. For this tested specimen, the pre-tack layer was 27 micrometers thick. The tack was 12 micrometers thick. The post-tack second layer was 91 micrometers thick.

[0142] As with FIGs. 14B and 14E, FIGs. 15B and 15E evidence a surface chromium oxide. In FIG. 15B, the pre-tack layer being clearly slightly richer in Cr than the substrate is still visible. Additionally, contrasted with FIG. 14B, there are few if any larger undiffused chromium particles. It is believed that their complete diffusion within the post-tack layer occurred at the expense of complete aluminum diffusion. This is at least partially due to the lower chromium content in FIG. 15/Example 3 relative to FIG. 14/Example 2.

[0143] FIG. 15C again shows the diffused vestige of a nickel strike at the substrate surface and shows more visible remnant of the nickel tack at the interface between pre-tack and post-tack layers.

[0144] FIG. 15D shows larger alumina particles remain undiffused in both the pre-tack and post-tack layers. FIG. 15D shows a clear substrate boundary in aluminum content associated with the minimal alloy depletion of the substrate. Specifically, the substrate appears slightly brighter than the pre-tack layer portions that are not artifacts of the alumina particles. This suggests only limited, if any, out-diffusion of aluminum from the substrate. [0145] FIG. 15F shows bands of cobalt similar to those of FIG. 14F.

[0146] For this mixed particulate Example 3, as-applied average hardness (HV 100g) was 301. The four-hour vacuum heat treatment average hardness was 189.

[0147] Relative to the Cr-only filler, the Cr-alumina combination will be more wear resistant. In abrasive contexts the alumina will add additional abrasive capability beyond that of the primary abrasive (cBN in the example).

[0148] In the final coating layer (exclusive of cBN or other tacked abrasive, if any), example remaining Cr particle content after heat treatment or equivalent in-service heating is at least 1.0% by volume (e.g., more particularly 1.0% to 20% or 2.0% to 15.0% or 4.0% to 12.0%) and example alumina content (when present) is at least 5.0% by volume (more particularly 5.0% to 40.0% or 10.0% to 30% or 20.0% to 30%). In addition to or alternative to alumina, other candidate fillers include zirconia.

[0149] Among possible further variations is NiCo sulfamate plating for Cr or Cr with additional filler. These may be applied using the FIG. 7 apparatus discussed above.

Similarly, the nickel sulfamate may be used with the additional alumina or tother filler in addition to Cr. Such sulfamate plating may offer stress reduction benefits relative to sulfate. And as noted above, either the sulfate or sulfamate plating may be used in non-abrasive applications without the cBN.

[0150] Also, there may be additional or alternative layers. In examples with two Cr-filled sulfate or sulfamate layers (e.g., pre- and post-tack), one layer may be replaced by something different.

[0151] 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.

[0152] 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 component configuration and material, details of such baseline may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.

Claims

CLAIMS What is claimed is:

1. A method comprising: providing a nickel sulfamate plating solution; immersing a metallic substrate in the plating solution; and applying a voltage between the substrate and an anode to apply a plating, wherein: the providing comprises blending chromium powder with a precursor of said plating solution so that the plating solution is a Cr-containing plating solution; and the as-applied plating forms a layer containing chromium particles from said powder.

2. The method of claim 1 further comprising forming the precursor by adding to water: H₄N₂NiO₆S₂; boric acid; and nickel chloride.

3. The method of claim 1 wherein the plating solution comprises:

1.0 to 100.0 g/L Cr; and

60 to 135 g/L Ni;

20 to 80 g/L boric acid;

4.0 to 20.0 g/L Cl; and a pH of 3.5 to 5.5.

4. The method of claim 3 wherein the plating solution has one or more of:

15.0 g/L to 50.0 g/L Cr;

70 to 110 g/L Ni;

20 to 60 g/L boric acid;

6.0 to 12.0 g/L Cl; and a pH of 3.5 to 5.0.

5. The method of claim 1 wherein the substrate comprises Ni as a largest by weight component.

6. The method of claim 1 further comprising: a cBN tack, wherein the applied plating forms a matrix for particles of the cBN.

7. The method of claim 6 wherein the applying of the plating is in: a first stage before the cBN tack; and a second stage after the cBN tack, the two stages in the same said plating solution or separate said plating solutions.

8. The method of claim 6 wherein: the metallic substrate forms a gas turbine engine blade airfoil; and the plating is applied to a tip of the airfoil.

9. The method of claim 1 further comprising: a nickel strike, wherein the plating is atop the nickel strike.

10. The method of claim 1 wherein: the metallic substrate forms a gas turbine engine case segment and the plating is applied to a vane-mounting hook section.

11. The method of claim 10 further comprising: mounting a vane to the vane-mounting hook section to contact the plating.

12. The method of claim 11 wherein: the vane-mounting hook section has: an axially-extending portion having distal axial end surface and an outer diameter surface; and a flange extending radially outward from a junction with the axially-extending portion to a body of the case segment and having an axially-facing surface; and a channel for receiving a mounting projection of the vane is formed by: the axially-extending portion outer diameter surface; the flange axially-facing surface; and a portion of an inner diameter surface of the body.

13. The method of claim 1 further comprising heat treating: at a temperature of 600°C to 760°C for a time of 2.0 to 10.0 hours.

14. The method of claim 13 wherein: the heat treating diffuses a majority of the chromium powder with the nickel.

15. The method of claim 13 further comprising: machining of the plating after the heat treating.

16. A plating method comprising: a nickel strike; and after the nickel strike, nickel sulfamate plating, wherein: the nickel sulfamate plating comprises plating in a plating solution having a chromium concentration of at least 1.0 g/L.

17. The plating method of claim 16 wherein one or more of: the chromium is in particulate form; the nickel strike is a Wood’s nickel strike; the nickel strike is directly or indirectly to a nickel-based alloy substrate; and the plating solution has a chromium concentration of 1.0 g/L to 100.0 g/L.

18. The plating method of claim 17 wherein one or more of: the chromium particulate has a size distribution of 1.0 micrometers to 12.0 micrometers; the nickel-based alloy substrate comprises, by weight, at least 10.0% to 40.0% combined Co, Al, and Ti; the nickel-based alloy substrate comprises, by weight, at least 20.0% combined Co, Cr, Al, and Ti; and the plating solution has a chromium concentration of 15.0 g/L to 50.0 g/L.

19. The method of claim 16 further comprising: a cBN tack.

20. The method of claim 16 further comprising: a heat treatment.

21. A method comprising: providing a plating solution; immersing a metallic substrate in the plating solution; and applying a voltage between the substrate and an anode to apply a plating, wherein: the providing comprises blending chromium powder with a precursor of said plating solution so that the plating solution is a Cr-containing plating solution; and the as-applied plating forms a layer containing chromium particles from said powder.

22. The method of claim 21 wherein: the blending further comprises blending alumina powder so that the plating solution is an alumina-containing plating solution; and the as-applied plating forms said layer containing alumina particles.

23. The method of claim 21 wherein one or more of: the plating solution has 1.0 to 100.0 g/L combined chromium particulate and alumina particulate; the plating solution has at least 15.0 g/L each chromium particulate and alumina particulate; and the chromium particulate and alumina particulate each have sizes of 1.0 micrometers to 12.0 micrometers.

24. The method of claim 21 wherein: the plating solution has at least 15.0 g/L chromium particulate in a size range of 1.0 micrometers to 12.0 micrometers.

25. The method of claim 21 further comprising forming the precursor by adding to water: nickel sulfate; cobalt sulfate; boric acid; and nickel chloride.

26. The method of claim 21 wherein the plating solution comprises:

1.0 to 100.0 g/L Cr and, if any, alumina, combined;

48 to 93 g/L Ni;

1.2 to 3.6 g/L Co;

10 to 80 g/L boric acid;

4.0 to 20.0 g/L Cl; and a pH of 4.3 to 5.7.

27. The method of claim 21 further comprising forming the precursor by adding to water: H₄N₂NiO₆S₂; boric acid; and nickel chloride.

28. The method of claim 21 wherein the plating solution comprises:

1.0 to 100.0 g/L Cr; and

60 to 135 g/L Ni;

20 to 80 g/L boric acid;

4.0 to 20.0 g/L Cl; and a pH of 3.5 to 5.5.

29. The method of claim 28 wherein the plating solution has one or more of: 15.0 g/L to 50.0 g/L Cr;

70 to 110 g/L Ni;

20 to 60 g/L boric acid;

6.0 to 12.0 g/L Cl; and a pH of 3.5 to 5.0.

30. The method of claim 21 wherein the substrate comprises Ni as a largest by weight component.

31. The method of claim 21 further comprising: a cBN tack, wherein the applied plating forms a matrix for particles of the cBN.

32. The method of claim 31 wherein the applying of the plating is in: 1 a first stage before the cBN tack; and a second stage after the cBN tack, the two stages in the same said plating solution or separate said plating solutions.

33. The method of claim 31 wherein: the metallic substrate forms a gas turbine engine blade airfoil; and the plating is applied to a tip of the airfoil.

34. The method of claim 21 further comprising: a nickel strike, wherein the plating is atop the nickel strike.

35. The method of claim 21 wherein: the metallic substrate forms a gas turbine engine case segment and the plating is applied to a vane-mounting hook section.

36. The method of claim 35 further comprising: mounting a vane to the vane-mounting hook section to contact the plating.

37. The method of claim 36 wherein: the vane-mounting hook section has: an axially-extending portion having distal axial end surface and an outer diameter surface; and a flange extending radially outward from a junction with the axially-extending portion to a body of the case segment and having an axially-facing surface; and a channel for receiving a mounting projection of the vane is formed by: the axially-extending portion outer diameter surface; the flange axially-facing surface; and a portion of an inner diameter surface of the body.

38. The method of claim 21 further comprising heat treating: at a temperature of 600°C to 760°C for a time of 2.0 to 10.0 hours.

39. The method of claim 38 wherein: the heat treating diffuses a majority of the chromium powder with the nickel.

40. The method of claim 38 further comprising: machining of the plating after the heat treating.

41. A plating method comprising: a nickel strike; and after the nickel strike, plating, wherein: the plating comprises plating in a plating solution having a chromium particulate concentration of at least 1.0 g/L.

42. The plating method of claim 41 wherein one or more of: the plating is a nickel or nickel-cobalt plating; the chromium particulate is at least 95% pure Cr by weight; the nickel strike is a Wood’s nickel strike; the nickel strike is directly or indirectly to a nickel-based alloy substrate; and the plating solution has a chromium particulate concentration of 1.0 g/L to 100.0 g/L in a size range of 1.0 micrometers to 12.0 micrometers.

43. The plating method of claim 42 wherein one or more of: the chromium particulate has a size distribution of 1.0 micrometers to 12.0 micrometers; the nickel-based alloy substrate comprises, by weight, at least 10.0% to 40.0% combined Co, Al, and Ti; the nickel-based alloy substrate comprises, by weight, at least 20.0% combined Co, Cr, Al, and Ti; and the plating solution has a chromium particulate concentration of 15.0 g/L to 50.0 g/L.

44. The plating method of claim 42 wherein one or more of: the chromium particulate has a size distribution of 1.0 micrometers to 4.0 micrometers; the nickel-based alloy substrate comprises, by weight, at least 10.0% to 40.0% combined Co, Al, and Ti; the nickel-based alloy substrate comprises, by weight, at least 20.0% combined Co, Cr, Al, and Ti; and the plating solution has a chromium particulate concentration of 1.0 g/L to 15.0 g/L.

45. The method of claim 41 further comprising: after the plating, a cBN tack.

46. The method of claim 45 further comprising: a further plating in a plating solution having a chromium particulate concentration of at least 1.0 g/L.

47. The method of claim 41 further comprising: a heat treatment.

48. A coated article comprising: a metallic substrate; and a plating layer on a surface of the metallic substrate comprising: chromium particulate.

49. The coated article of claim 48 wherein: the plating layer is a matrix for an abrasive.

50. The coated article of claim 48 wherein: the plating layer further comprises alumina particulate.

51. The coated article of claim 48 wherein: the chromium particulate is at least 1.0% of the layer by volume.