174, 175.

Principal contact between the seal and the contacting members is between the seal OD surface 162 and the runner ID surface 171. Additional contact may be between the seal axial end surfaces and the adjacent groove wall surface. Wear and damage may occur at any of these. Typically, the counterface members nay be uncoated alloy at the interfaces (e.g., uncoated at the surfaces 171, 174, 175).

Another example for repair is a component interfacing with a spring compression static seal. For example, as in the '122 publication baseline, stainless steel or nickel- or cobalt-based superalloy or other seal substrates may be formed by deforming sheetmetal or may be cast or otherwise formed. Example seals include axial compression seals such as a bellows seal or a W-seal, or for radial compression seals, such as C-seals or E-seals. For example, seal 220 (FIG. 1B) is a bellows or similar type seal with convoluted cross-section effective to be deformed under compression to self-spring-bias engagement with the counterface members. The cross-section generally has a generally inner diameter (ID) surface 221, a generally outer diameter (OD) surface 222 generally parallel and spaced apart from the ID surface by a material thickness T_S, and end surfaces 224 and 225. In an installed axially compressed state, axial ends 226, 227 of the seal are formed by portions of one of the surfaces 221, 222 (both 221 in the example). The illustrated seal is a W-seal although other configurations are possible (e.g., more or fewer cycles of the cross-sectional wave form) as are radial seals (e.g., an E-seal).

For the example seal 220, forward counterface members engaging the axial end 226 are a radially extending end surface portions 230 of a circumferential array of blade outer air seals (BOAS) 232. BOAS ID surfaces closely surround tips of airfoils 240 of a stage of blades 242. For the example seal 220, aft counterface members engaging the axial end are a radially extending end surface portions 250 of the OD shrouds 254 of a circumferential array of vanes 252. Example vanes are in clusters with multiple airfoils 253 per cluster. Alternatives include singlets.

In these example embodiments, wear or damage may notably occur to counterface surfaces 171, 174, 175, 230, and 250. Each example counterface member (including others discussed below to be repaired) may be formed of a nickel- or cobalt-based based (e.g., largest by weight component Ni or Cr, respectively) alloy or superalloy (e.g., uncoated), such as Inconel® 718 (IN-718; UNS N07718; AMS 5662), Inconel® 100 (IN-100; UNS N13100; AMS 5397)), and Inconel® 713C (IN-713C; Alloy 713C) each of (Huntington Alloys Corp., Huntington, West Virginia), Mar-M-247 and Haynes® 188 (UNS R30188) of Haynes International, Kokomo, Indiana.

Either of the wear areas, the component contacting the seal 160, 220 may receive local damage. FIG. 2 generically shows a damage site 300 in a surface 302 of a substrate 304. The surface 302 (generically representing any of counterface surfaces 171, 174, 175, 230, and 250 above and others discussed below) is in contact with the contacting seal surface. Example damage depth is shown as H₁.

FIG. 3 shows the damage site 300′ after disengaging from the seal and locally machining (e.g., abrasive grinding) to a depth H₂. FIG. 4 shows a buildup of HEA repair material 310 applied by HVOF to a peak thickness T₁which is greater than H₂. In the FIG. 4 the buildup leaves the surface 312 of the as-applied repair material proud of the adjacent portion of the surface 302. Thus, a finishing (e.g., ASTM E-3) (e.g., abrasive belting, grinding, polishing, and/or peening) may reduce the repair material to leave a finished surface 312′ (FIG. 5—shown reassembled with a replacement seal 160, 220) essentially flush to the adjacent portion of the surface 302. Example machining depth H₂and final coating/repair thickness T₂are at least 0.30 mm or at least 0.50 mm or at least 1.0 mm (e.g., with optional upper limits in any combination with said lower limits of 3.00 mm, or 2.50 mm or 2.00 mm or 1.50 mm). An example angular span of the repair material of any single repair is small (e.g., 1° to 5°.

In one example of repair of the surface 174 or 175, an axially-open and radially outwardly open recess (not shown) is machined (e.g., abrasively ground) in the opposite wall section 173 or 172, respectively. The recess may allow access to machine the damaged surface 174 or 175 (and then machine the sprayed repair) and allows spray gun access for normal/orthogonal spray. After the repair is machined, the recess may be filled. Example filling is via the same HVOF gun and material used in the repair. The filled recess may itself be machined back to nominal contour. As a practical matter, the seal 160 may have wearing contact only with one of the two surfaces 174, 175 thus, imperfection of the other created by machining and then repairing the other is not significant and the structural weakening from filling the recess is not significant.

Because the self-sprung seal 220 is held between two different members, disassembly of the two members from each other may allow easy access to the damage site for the repair (as distinguished from the groove of FIG. 1B wherein both opposite surfaces are in a single piece).

Although these examples involve a seal as the contacting element to a repaired member, others may lack seals such as where two members other than deals directly engage.

Table 1 below shows HVOF deposition parameters for nominal FeCoCrMnNi HEA coating (using a Diamond Jet™ 2700 gun of Oerlikon Metco, Pfaeffikon, Switzerland):

TABLE 1

Feed rate
50
g/min

Oxygen
151.75
LPM

Propylene
86.48
LPM

Air
331.90
LPM

Spraying distance
150
mm

Transverse speed′
1.0
m/s

Deposition efficiency achieved
~76%

Thickness
1.3 mm (after 30 passes)

Substrate temperature
250-300° C. (with IR camera)

Relative to the Parameters in Patel et al., this is fuel rich. We have determined that the use of fuel rich deposition parameters is beneficial in producing thicker coatings (e.g., 1.3 mm in the example) with reduced formation of oxides and porosity after 30 passes. In contrast, the use of oxygen rich deposition parameters in the Patel et al. publication, resulted in the formation of a significant amount of oxides during spraying and a final coating thickness of only 300 micrometers. To mitigate oxide formation and achieve a lower amount of oxides in the coating, relative to the parameters in the Patel et al. article, we recommend making the oxygen/fuel ratio more fuel rich and increasing the powder feed rate

For example, feed rate is increased from the Patel et al. 23 g/min. to a value of at least 40 g/min. (e.g., to 50 g/min.). Similarly, the Patel et al. oxygen to fuel ratio is almost 4:1 but is reduced to a bit less than 2:1 (more broadly the amount of oxygen (not from the air) is up to 300% of the amount of fuel, more narrowly up to 250% or 200%, with optional lower limits of 100% and 150% for any of those upper limits). Although advantageous feed rate may be relatively gun-specific, the oxygen-fuel balance is relatively insensitive to the particular gun.

Table 2 below shows feedstock blends of elemental powders for the HEA:

TABLE 2

HEA Powder

Element (Atomic Percent)

Fe
Co
Cr
Mn
Ni
Other

Ex. 1
20
20
20
20
20
†

nominal

†

Ex. 2
20.36
19.46
20.85
20.27
19.06
††

Range 1
16.0 to 25.0
16.0 to 25.0
16.0 to 25.0
16.0 to 25.0
16.0 to 25.0
††

Range 2
17.0 to 23.0
17.0 to 23.0
17.0 to 23.0
17.0 to 23.0
17.0 to 23.0
††

Range 3
18.0 to 22.0
18.0 to 22.0
18.0 to 22.0
18.0 to 22.0
18.0 to 22.0
††

Range 3
18.5 to 21.5
18.5 to 21.5
18.5 to 21.5
18.5 to 21.5
18.5 to 21.5
††

† Impurities only

†† ≤5.0 other elements total; ≤1.0 other elements individually

Example 1 corresponds to nominal FeCoCrNiMn. Example 2 corresponds to the vendor-sourced powder composition and was estimated as the average value of the three readings (one EDS area analysis and two-point analyses) and is shown truncated to two decimal places although measurement precision is much coarser. Although, below the table, dagger symbols are used to provide two examples of non-listed components other values are possible. Thus, any of the examples or ranges could be multiplied by substituting the listed option for the other of the two listed options. Yet alternatively, for each of these, further alternative ranges may be provided such as ≤3.0 other elements total and ≤1.0 other elements individually; ≤2.0 other elements total and ≤1.0 other elements individually; ≤3.0 other elements total and ≤0.50 other elements individually. Additionally, the examples such as given above assume very little attrition of individual elements during the spray process. Thus, the as-sprayed coating may be characterized by any of those same examples and ranges. However, there may be attrition situations in which a source material outside one or more of the ranges is used to deposit as-deposited material within said one or more ranges (and vice-versa). The Ex. 2 feedstock powder was obtained from Eutectic Canada Inc. (of Vaudreuil-Dorion, QC, Canada) and is believed to be a single alloy powder with FCC single solid solution.

Although a single HEA was tested for the target thicknesses, other HEA may be useful. More broadly example HEA has 12.0 to 35.0 atomic percent each of at least four main metallic elements (e.g., typically four to seven or four to six main elements with no more than a 10.0 percentage points difference between the lowest content of said four and the highest content of said four (or highest and lowest contents of all main elements).

A particularly significant main element is Co in that it generates a lubricious cobalt oxide layer upon initial sliding. The remaining main HEA elements Fe, Cr, Ni, Mn, provide the basic HEA strength. The manganese stabilizes the FCC to make it more ductile to compensate for the hardness. It also forms Mn-containing oxide layer for lubricity but less significant than the Co for lubricity.

FIG. 6 shows an article 20 having an FeCoCrMnNi HEA coating 26 HVOF sprayed on a surface 24 of a substrate 22. The example FIG. 1 substrate is 304L stainless steel. The coating 26 was deposited by HVOF and the deposition parameters of Table 1. As discussed below, the substrate may be a component interfacing with a seal and the coating surface