Patent Description:
Marks are created on the surface of metal machine parts for a number of reasons. In one application, lasers etch a surface of a metal part to create an identification mark, e.g., an identifying bar code. In another application, wire free creep measurement test structures are permanently formed, e.g., cut or printed, onto or into the metal part's surface so the part can be scanned for creep assessment after use. By identifying changes in the test structure created over time, e.g., by comparison to a baseline twin test structure, creep can be measured. Each test structure may be unique and include its own identifier, e.g., bar code. Repairs or replacement may be identified based on the strain measurements.

The processes of creating the marks suffer from a number of drawbacks. For example, the metal parts are oftentimes protected from harsh operational environments, e.g., heat, corrosive gases, etc., by one or more protective coatings including a ceramic that cover the surface of the metal part. Current methods to create the marks in the surface of the metal part are not applicable to the protective coatings, e.g., ceramic coatings. For example, electronic discharge machining (EDM) may be used to create relatively deep marks in the metal part, e.g., a cut, but cannot be used on protective coatings. Other methods that create marks such as photolithography-based chemical etching, grit blasting and laser ablation, are also inapplicable to protective coatings because the processing cannot be controlled relative to the more brittle ceramic coating leading to penetration of the protective coating and exposing the metal or cracking of the coating and the metal. Both situations render the coating useless or shorten the life of the coating, and eventually shorten the life of the part by initiating cracks in the bond coat and/or base metal. Precision is also very hard to achieve when machining ceramics. Chemical etching has been applied to both metal and ceramic coatings to create marks, but it requires precise control of the chemicals and duration, and cannot be readily applied in a selective fashion. Thus, the process is typically untenable, except perhaps in a highly controlled, factory setting. Indeed, current processes for creating marks are always performed in a factory setting with highly controlled equipment, and are incapable of precise reproduction in an on-site location, e.g., at a power plant for a turbomachine part. Consequently, most current mark creating processes cannot be used on-site for used metal parts having a protective coating including a ceramic thereon.

Where parts do not include a ceramic coating, a ceramic marking may be added, but this process cannot be completed outside of highly controlled, factory setting. Further, the ceramic mark is typically very brittle and not erosion resistant.

<CIT> and <CIT> each disclose a method for creating a three-dimensional (3D) mark in a protective coating over a metal part, the method comprising the steps defined in the preamble of independent claim <NUM>.

<CIT> discloses a method to mark the coating of a workpiece using a blasting process in order to engrave a machine-readable marking such as a bar code.

<CIT> discloses a method of manufacturing a body with a slot as a test crevice based on an abrasive water jet process and using a mask which is placed on a reference body and may be magnetically or adhesively attached thereto before applying the abrasive water jet process.

The invention provides a method for creating a three-dimensional (3D) mark in a protective coating over a metal part, the method comprising: positioning a first mask over the protective coating, the first mask including a first opening pattern therein; performing a first abrasive waterjet process on the protective coating using the first mask, the first abrasive waterjet at least eroding a first portion of the protective coating exposed through the first opening pattern to create the 3D mark, the mark penetrating only partially through the protective coating; and removing the first mask, leaving the 3D mark in the protective coating. The 3D mark in the protective coating includes an opening having a width between <NUM> and <NUM> micrometers and a depth less than <NUM> micrometers.

The illustrative aspects of the present disclosure are designed to solve the problems herein described.

It is noted that the drawings of the disclosure are not to scale.

As an initial matter, in order to clearly describe the current disclosure it will become necessary to select certain terminology when referring to and describing relevant machine components within an industrial machine. When doing this, if possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a metal particular component may be referred to using several different or overlapping terms. What may be described herein as being a single metal part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single metal part.

Several descriptive terms may be used regularly herein, as described below.

Where an element or layer is referred to as being "on," "engaged to," "disengaged from," "connected to" or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to" or "directly coupled to" another element or layer, there may be no intervening elements or layers present.

As indicated above, the disclosure provides embodiments of a method for creating a three-dimensional (3D) mark in a protective coating over a metal part. The method includes positioning a mask over the protective coating, the mask including an opening pattern therein; and performing an abrasive waterjet process on the protective coating using the mask. The abrasive waterjet at least erodes a first portion of the protective coating exposed through the first opening pattern to create the 3D mark. The 3D mark only partially penetrates through the protective coating, thus preventing damage to the coating and/or exposure of the underlying metal. The mask is removed, leaving the 3D mark in the protective coating. The use of the mask and abrasive water jetting allow the 3D mark to include an opening having a width between <NUM> and <NUM> micrometers, in a preferred embodiment between <NUM> and <NUM> micrometers, and in a more preferred embodiment, between <NUM> and <NUM> micrometers. The methods allow formation of a 3D mark on a protective coating where normally marks could not be formed and/or with an opening size that is impossible with current processing. The process can be advantageously carried out in a factory setting or on-site. "On-site" may include any situation that does not include the highly controlled environment of a factory such as but not limited to: an aircraft hangar, a power plant, an oil rig, a ship, a bridge, or a metal structure of a building. Formation of the 3D mark in the protective coating allows mark applications such as strain measurements, identification, etc., to be added to metal parts that already have a protective coating thereon.

Referring to the drawings, methods for creating a three-dimensional (3D) mark in a protective coating over a metal part will now be described. <FIG> shows a cross-sectional view of a metal part <NUM> including a protective coating <NUM> over at least a portion of the metal part. Metal part <NUM> may include any now known developed part upon which protective coating <NUM> may be desired. In one non-limiting example, metal part <NUM> may include a turbomachine blade or nozzle, or a part thereof, that is exposed to hot combustion gases. Metal part <NUM> may include a metal body <NUM> made of any metal or metal alloy. In one non-limiting example, metal body <NUM> may be made of a superalloy, which may include any alloy having numerous excellent physical characteristics compared to conventional alloys, such as but not limited to: high mechanical strength, high thermal creep deformation resistance. Examples include but are not limited to: Rene <NUM>, CM247, Haynes alloys, Incalloy, MP98T, TMS alloys, CMSX single crystal alloys, IN738, Hast X, stainless steel e.g., ST13, ST70. While shown as having a planar exterior surface <NUM>, metal body <NUM> can be planar and/or curved (see e.g., <FIG>), and may include any variety of exterior surface structure, e.g., dimples, ridges, trenches, etc..

Protective coating <NUM> may include a ceramic thermal barrier coating (TBC) <NUM> over a bond coating <NUM>, as shown in <FIG>, or a bond coating <NUM> alone (see e.g., <FIG>). TBC <NUM> may include any now known developed ceramic TBC material such as but not limited to yttria-stabilized zirconia (YSZ), mullite and alumina. TBC <NUM> may also include additional layers (not shown) such as a thermally grown oxide. TBC <NUM> may have a variety of porosities and/or densities. TBC <NUM> may be dense vertically cracked. TBC <NUM> may have a thickness < <NUM> millimeters (mm), preferable < <NUM> micrometers (microns) with a manufacturing tolerance preferable < <NUM> microns. Bond coating <NUM> may include any now known developed bond coat material such as but not limited to: nickel or platinum aluminides, nickel chromium aluminum yttrium (NiCrAlY) or nickel cobalt chromium aluminum yttrium (NiCoCrAlY). Bond coating <NUM> may have a thickness, for example, < <NUM> microns. Where necessary, bond coating <NUM> and TBC <NUM> may be used together. Protective coating <NUM> may be over all of an exterior surface <NUM> of metal body <NUM> or over just a portion of exterior surface <NUM>. Protective coating <NUM> may be formed on metal body <NUM> using any now known developed manner, e.g., plasma spraying.

<FIG> shows a cross-sectional view of positioning a mask <NUM> over protective coating <NUM>. As shown in <FIG>, mask <NUM> includes an opening pattern <NUM> therein. Opening pattern <NUM> has any number of openings <NUM> having any shape or dimensions desired. In one embodiment, opening pattern <NUM> may have a smallest opening 124X having a width W between <NUM> and <NUM> micrometers, in a preferred embodiment between <NUM> and <NUM> micrometers, and in a more preferred embodiment, between <NUM> and <NUM> micrometers. Mask <NUM> may be made of any material capable of having opening pattern <NUM> formed therein, e.g., by a waterjet cutting process, EDM, etc., and capable of withstanding an abrasive waterjet process, described herein. In one embodiment, mask <NUM> may include, for example, a stainless steel sheet. Mask <NUM> may be positioned over protective coating <NUM> in any number of ways. For example, it can be simply laid over protective coating <NUM>, or the process may include attaching mask <NUM> to protective coating <NUM> and/or metal body <NUM>, e.g., by clamps (see e.g., <NUM> in <FIG>), fasteners, adhesive, etc. Mask <NUM> may be in contact with protective coating <NUM> or spaced therefrom. Opening pattern <NUM> may be made in mask <NUM> material using a waterjet process; however, any now known developed metal cutting process capable of the desired precision may also be employed such as but not limited to: EDM, laser cutting, drilling, mechanical cutting. In the example shown, mask <NUM> is a positive mask, but it can also be a negative mask (see e.g., <FIG>).

<FIG> shows a cross-sectional view of performing an abrasive waterjet process <NUM> on protective coating <NUM> using mask <NUM>. As shown in <FIG>, abrasive waterjet process <NUM> erodes a first portion of protective coating <NUM>, e.g., TBC <NUM> without damaging bond coating <NUM>, exposed through opening pattern <NUM> to create a 3D mark <NUM>. 3D mark <NUM> may include any number, shape and size of openings <NUM> commensurate with opening pattern <NUM> in mask <NUM>. A second portion of protective coating <NUM> under mask <NUM> is protected by the mask and is not eroded. As shown in <FIG>, abrasive waterjet process <NUM> is controlled such that 3D mark <NUM> penetrates only partially through protective coating <NUM>. The extent to which openings <NUM> penetrate protective coating <NUM> can be controlled by, for example, the waterjet pressure. The width of opening <NUM> (i.e., in X-Y plane) may depend on a number of factors such as but not limited to: abrasive particle size, density, velocity (based on waterjet pressure and nozzle distance from material), and/or hardness (e.g., HRB if measured on the Rockwell scale using any conventional process); hardness of the material to be opened; machining accuracy of mask <NUM> (e.g., <NUM> for precision waterjet cutting, <NUM> for laser cutting); and/or the width of the mask machining tool (e.g., drill, mill, waterjet, laser (e.g., <NUM> for waterjet and laser). A depth of openings <NUM> (i.e., in Z direction) may be controlled based on the duration of the process. Openings <NUM> may extend partly through TBC <NUM>, completely through TBC <NUM> to bond coating <NUM>, or less preferably completely through TBC <NUM> and partly through bond coating <NUM>. In the latter case, metal body <NUM> is not abraded, i.e., it remains completely preserved from the abrasion. Metal body <NUM> remains completely preserved from the abrasion.

In another embodiment, when there is no TBC <NUM>, openings <NUM> may extend partly through bond coating <NUM>, or completely through bond coating <NUM> to a surface of metal body <NUM>. However, metal body <NUM> is not abraded, i.e., it remains completely preserved from the abrasion. The precision in the depth of abrasive waterjet process can be controlled to not abrade the surface - no abrasion or crack is created on metal body <NUM>.

The abrasive waterjet process <NUM> can be performed using any now known developed abrasive waterjet system. Abrasives used can be selected for the materials being abraded and the desired duration of the process. The opening <NUM> has a width between <NUM> and <NUM> micrometers. In a preferred embodiment, opening <NUM> may have a width between <NUM> and <NUM> micrometers, and in a more preferred embodiment, between <NUM> and <NUM> micrometers. The width may be produced with a precision/tolerance of +/-<NUM>%, and preferably +/-<NUM>%. In one embodiment, abrasive waterjet process <NUM> occurs at a water pressure of between <NUM> bars and <NUM> bars. It has been discovered that this pressure range allows creation of structures such that 3D mark <NUM> can create openings <NUM> of a width described herein, even on metal parts <NUM> with curved surfaces and with metal parts <NUM> installed on other equipment.

As shown in the cross-sectional view of <FIG> and the plan view of <FIG>, after the abrasive waterjet process <NUM>, mask <NUM> may be removed, leaving 3D mark <NUM> in protective coating <NUM>. 3D mark <NUM> may include any variety of opening <NUM> capable of being created by an abrasive waterjet process <NUM> (<FIG>) including but not limited to: holes <NUM> (partially through coating <NUM>) and channels <NUM>. Groups of holes may be closely clustered to form a dimple pattern <NUM>. Opening <NUM>, after removing mask <NUM>, has a depth less than <NUM> microns, and a maximum depth at or near the thickness of protective coating <NUM>.

In one embodiment, after removing mask <NUM>, protective coating <NUM> may be optionally machined <NUM> to a desired depth less than a depth of protective coating <NUM> prior to the machining.

Referring to <FIG> and <FIG>, some embodiments of the disclosure may include repeating the masking and abrasive waterjet process to create a 3D mark <NUM> having openings <NUM> not possible with just one masking and waterjet process. The process may also repeat more than twice, if desired. As shown in the cross-sectional view of <FIG>, after removing mask <NUM>, the process may include positioning another mask <NUM> over protective coating <NUM>. Mask <NUM> includes another opening pattern <NUM> therein. Opening pattern <NUM> may have any number of openings <NUM> having any shape or dimensions desired. In one embodiment, opening pattern <NUM> may have a smallest opening 224X having a width W between <NUM> and <NUM> micrometers, in a preferred embodiment between <NUM> and <NUM> micrometers, and in a more preferred embodiment, between <NUM> and <NUM> micrometers. The width may be produced with a precision/tolerance of +/-<NUM>%, and preferably +/-<NUM>%. <FIG> also shows performing a second abrasive waterjet process <NUM> on protective coating <NUM> using mask <NUM>. The second abrasive waterjet <NUM> erodes an additional amount of the first portion of protective coating <NUM>, i.e., where openings <NUM> exist, and/or a second portion of protective coating <NUM>, i.e., where openings <NUM> do not exist, exposed through second opening pattern <NUM> to create 3D mark <NUM> with the first eroded portion of protective coating <NUM>. 3D mark <NUM> penetrates only partially through protective coating <NUM> after the second abrasive waterjet process <NUM>.

Opening pattern <NUM> may be the same as opening pattern <NUM>, allowing deepening of openings <NUM>, but may be different. As observed in the cross-sectional view of <FIG> and the plan view of <FIG> shows examples of how a different opening pattern <NUM> may create openings <NUM> from the second mask/waterjet process that interact with openings <NUM> from the first mask/waterjet process. For example, openings <NUM> may: be independent of openings <NUM> (see e.g., opening <NUM>), add to the depth, length or width of openings <NUM> (see e.g., openings <NUM>), and/or allow for creation of openings that cross paths (see e.g., crossed openings <NUM>). <FIG> shows the structure after removing second mask <NUM>, leaving 3D mark <NUM> in protective coating <NUM>. Second abrasive waterjet process <NUM> may be the same as first abrasive waterjet process <NUM> (<FIG>). In some embodiments, second abrasive waterjet process <NUM> may be different than first abrasive waterjet process <NUM> (<FIG>). For example, second abrasive waterjet process <NUM> may use a different water pressure than first abrasive waterjet process <NUM> (<FIG>). Second abrasive waterjet process <NUM> may be controlled in any manner described relative to the first abrasive waterjet process <NUM>. Mask <NUM> may be made of any of the materials and may be made in any manner described herein for mask <NUM>. Openings <NUM> may have any dimensions as described relative to openings <NUM>.

3D mark <NUM>, <NUM> can take any variety of form of mark typically applied to a metal part. <FIG> show examples of 3D marks. It will be recognized that where a single mask/waterjet process is used for forming the 3D marks in <FIG>, the masks may have opening patterns <NUM> having openings <NUM> therein that are identical or nearly identical to the openings (<NUM> or <NUM>) shown. Further, where more than one mask/waterjet process is used, the masks may have openings <NUM>, <NUM> that collectively create the openings (<NUM> and <NUM>) shown. <FIG> shows a 3D mark <NUM> in the form of an identifier for a metal part, e.g., a bar code (traditional, quick response or other form) and/or an alphanumeric identifier. As observed, the process can achieve sharp edges and/or round edges without cracks. <FIG> shows a mask for creating a 3D mark <NUM> in the form of a creep sensor in protective coating <NUM>. In this regard, a method according to embodiments of the disclosure may include performing a creep analysis based on 3D mark <NUM> in the protective coating. While any now known developed creep sensor measurement may be employed, the creep sensor may be, for example, in any form of a creep sensor for use in a LifeSight® creep measurement system, available from General Electric Co. In any event, in contrast to conventional creep analysis, the creep sensor is in an existing protective coating <NUM>, not in a ceramic added to the metal for the purpose of the sensor exclusively. Further, this process can be performed on-site rather than in a factory, eliminating costs for, for example, part transportation, coating removal and it can be performed on larger parts which would not be considered possible otherwise.

<FIG> shows a 3D mark <NUM> with an array of openings for use, for example, as dynamic cooling openings for cooling passages in metal part <NUM>. <FIG> shows a 3D mark <NUM> with various linear openings. <FIG> shows a 3D mask <NUM> exemplifying structure formed with a negative mask such that openings <NUM>, <NUM> are the larger parts removed, leaving raised elements <NUM> in protective coating <NUM>.

<FIG> illustrates a metal part <NUM> with a curved exterior surface <NUM> such as an airfoil for a turbomachine blade or nozzle. Protective coating <NUM> here includes only bond coating <NUM> over metal body <NUM>. A curved mask <NUM>, <NUM> is shown over protective coating <NUM>, prior to any abrasive waterjet process. The methodology, as described herein, can be applied to the metal part of <FIG>.

Referring again to <FIG>, there is shown a metal part <NUM>. Metal part <NUM> may include metal body <NUM>. Metal body <NUM> may include any material as described herein and may constitute any form of structure upon which a protective coating <NUM> may be advantageous, e.g., a turbomachine airfoil. Metal body <NUM> may be solid or hollow and may include any variety of internal structure (not shown), e.g., cooling passages, supports, etc. While shown as having a planar exterior surface <NUM> (<FIG>), metal body <NUM> can be planar and/or curved (see e.g., <FIG>), and may include any variety of exterior surface structure, e.g., dimples, ridges, trenches, etc. Metal part <NUM> may also include protective coating <NUM> over at least a portion of metal body <NUM>, as described herein. A 3D mark is in protective coating <NUM> and may include an opening <NUM>, <NUM> having a width between <NUM> and <NUM> micrometers, in a preferred embodiment between <NUM> and <NUM> micrometers, and in a more preferred embodiment, between <NUM> and <NUM> micrometers. The width may be produced with a precision/tolerance of +/-<NUM>%, and preferably +/-<NUM>%. Protective coating <NUM> may include TBC <NUM> and bond coating <NUM>, or just bond coating <NUM> alone. The 3D mark extends only partially through protective coating <NUM>, i.e., partially through TBC <NUM>, completely through TBC and partially through bond coating <NUM>, or where bond coating <NUM> is used alone, partially through bond coating <NUM>. The width has an influence on the performance of the 3D mark and TBC <NUM> and/or bond coating <NUM>. For example, a large mark is easier to produce and to measure. However, protective coating <NUM> may be weakened in the region of a large 3D mark. The suggested ranges allow a production with high quality measurement while not affecting protective coating <NUM> (i.e., if the 3D mark is too wide, metal body <NUM> below the coating might overheat and the part life time may be affected). The precision/tolerance should be kept to ensure quality measurements with no or negligible influence on the protective coating performance.

Embodiments of the disclosure provide methods of forming a 3D mark in a protective coating over a metal part with high precision even though the method may not be performed in a factory setting. Accordingly, the methods can be applied on-site to a used metal part with a protective coating. The methods are not destructive of the protective coating, and will not form cracks or other damage in the coating or in the metal part. Since the 3D mark does not penetrate through the protective coating, the underlying metal body remains protected. No cracks are initiated and propagated in the protective coating or the metal body. The mask can be applied as a negative or a positive marks of the pattern desired. 3D mask allows performance of a creep analysis to metal parts having protective coatings where the analysis would normally not be possible. The methods provide cost effective production of various structures, e.g., creep sensors, bar codes, etc., in a factory or on-site, on any metal part. Currently creep sensors have high production cost and can only be created in the factory. In addition, the material currently applied for creating a creep sensor has a limited lifetime in an eroding environment. A creep sensor made in the protective coating has much longer lifespan.

The foregoing drawings show some of the processing associated according to several embodiments of this disclosure. In this regard, each drawing represents a process associated with embodiments of the method described. It should also be noted that in some alternative implementations, the acts noted in the drawings may occur out of the order noted or, for example, may in fact be executed substantially concurrently or in the reverse order, depending upon the act involved. Also, one of ordinary skill in the art will recognize that additional steps that describe the processing may be added.

Claim 1:
A method for creating a three-dimensional (3D) mark (<NUM>; <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; <NUM>) in a protective coating (<NUM>) over a metal part (<NUM>), the method comprising:
positioning a first mask (<NUM>) over the protective coating (<NUM>), the first mask (<NUM>) including a first opening pattern (<NUM>) therein;
performing a first abrasive waterjet process (<NUM>) on the protective coating (<NUM>) using the first mask (<NUM>), the first abrasive waterjet process (<NUM>) eroding a first portion of the protective coating (<NUM>) exposed through the first opening pattern (<NUM>) to create the 3D mark (<NUM>), the 3D mark (<NUM>) penetrating only partially through the protective coating (<NUM>); and
removing the first mask (<NUM>), leaving the 3D mark (<NUM>) in the protective coating (<NUM>);
characterized in that the 3D mark (<NUM>) in the protective coating (<NUM>) includes an opening (<NUM>) having a width between <NUM> and <NUM> micrometers and a depth less than <NUM> micrometers.