The present disclosure relates to a method for applying electroplated coatings, and more specifically to a method for applying abrasive grit to gas turbine airfoil blade tips via pulse plating.
Oftentimes, a gas turbine blade tip includes a coating with abrasive particles embedded in a matrix, the tip being intended to run against the surface of a shroud of a material which is softer than the abrasive particles. The codeposition of matrix material and particles is typically accomplished from an electrodeposition bath in which there are suspended abrasive particles formed from aluminum oxide, cubic boron nitride (CBN), or other abrasive carbides, oxides, silicides, or nitrides.
Although effective, the electrolytic application of the CBN abrasive may result in a fatigue life reduction to allow the airfoils to withstand interactions with abradable air seals, but could benefit from increased wear resistance and fatigue strengthening.
A method for forming an abrasive surface according to one disclosed non-limiting embodiment of the present disclosure can include applying an electric current through a plating solution so as to cause an abrasive grit to be deposited onto a workpiece; and varying a waveform of the electric current while building up a matrix material at least partially around the abrasive grit.
A further embodiment of the present disclosure may include that the abrasive grit includes cubic boron nitride (CBN).
A further embodiment of the present disclosure may include that varying the waveform includes pulse reverse current plating.
A further embodiment of the present disclosure may include performing a low bake for bond optimization after build-up of the matrix material around the grit
A further embodiment of the present disclosure may include building up the matrix material around the abrasive grit with pulsed current nickel plating.
A further embodiment of the present disclosure may include that building up the matrix material around the abrasive grit includes building up a nickel layer.
A further embodiment of the present disclosure may include performing a bake for stress relief subsequent to building up the matrix material around the abrasive grit.
A further embodiment of the present disclosure may include that varying the waveform of the electric current includes pulsing of the electric current to cause new nucleation of nickel crystals.
A further embodiment of the present disclosure may include that the workpiece is a rotor blade.
A further embodiment of the present disclosure may include that the workpiece is a tip of a rotor blade.
A method for forming an abrasive surface according to one disclosed non-limiting embodiment of the present disclosure can include pulse plating a workpiece to build up a matrix material around an abrasive grit.
A further embodiment of the present disclosure may include that the abrasive grit includes cubic boron nitride (CBN).
A further embodiment of the present disclosure may include that the pulse plating causes new nucleation of nickel crystals.
A further embodiment of the present disclosure may include that the pulse plating includes tacking on the abrasive grit.
A further embodiment of the present disclosure may include that the pulse plating includes building up a nickel layer as the matrix material around the abrasive grit.
A further embodiment of the present disclosure may include performing a bake for stress relief subsequent to building up the matrix material around the abrasive grit.
A rotor blade according to one disclosed non-limiting embodiment of the present disclosure can include an abrader that includes an abrasive grit with a grain size between 10-100 nm and a hardness between 250-400 HV.
A further embodiment of the present disclosure may include that rotor blade is a turbine blade.
A further embodiment of the present disclosure may include that the abrader is applied to a tip of the rotor blade.
A further embodiment of the present disclosure may include that the abrasive grit includes cubic boron nitride (CBN) that is pulse plated on the tip of the rotor blade.
The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting.
Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiments. The drawings that accompany the detailed description can be briefly described as follows:
The engine 20 generally includes a low spool 30 and a high spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing structures 38. The low spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor (LPC) 44 and a low pressure turbine (“LPT”) 46. The inner shaft 40 drives the fan 42 directly or through a geared architecture 48 to drive the fan 42 at a lower speed than the low spool 30. An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system.
The high spool 32 includes an outer shaft 50 that interconnects a high pressure compressor (HPC) 52 and high pressure turbine (HPT) 54. A combustor 56 is arranged between the HPC 52 and the HPT 54. The inner shaft 40 and the outer shaft 50 are concentric and rotate about the engine central longitudinal axis A.
Core airflow is compressed by the LPC 44 then the HPC 52, mixed with the fuel and burned in the combustor 56, then expanded over the HPT 54 and the LPT 46. The turbines 54, 46 rotationally drive the respective low spool 30 and high spool 32 in response to the expansion. The main engine shafts 40, 50 are supported at a plurality of points by bearing structures 38 within the static structure 36. Various bearing structures 38 at various locations may alternatively or additionally be provided.
With reference to
The full ring shroud assembly 60 and the BOAS assembly 62 are axially disposed between a forward stationary vane ring 68 and an aft stationary vane ring 70. Each vane ring 68, 70 include an array of vanes 72, 74 that extend between a respective inner vane platform 76, 78 and an outer vane platform 80, 82. The outer vane platforms 80, 82 are attached to the engine case structure 36.
The rotor assembly 66 includes an array of blades 84 circumferentially disposed around a disk 86. Each blade 84 includes a root 88, a platform 90 and an airfoil 92 (also shown in
With reference to
With reference to
The method 300 is herein directed to tipping blades in the cold section and need not specifically utilize Ni/Co—Cr—Al—Y/Hf powder or a nickel and/or cobalt (Ni/Co) matrix. The Cr—Al—Y/Hf powder refers to a mixture of chromium, aluminum, yttrium and/or hafnium elements in powder forms that are added into the bath (
The agitation of the plating bath causes the powder to land on the blade tip 96. One example metal is a nickel/cobalt combination. The nickel/cobalt combination is plated at the same time that the Cr—Al—Y/Hf powder is landing on the blade tip, causing the powder to be encapsulated within the plating. When the plating is fully built up, what's left is a matrix 411 surrounding the abrasive grit 412, including the nickel/cobalt metal dispersed with Cr—Al—Y/Hf powder. At that point, the coating is diffusion heat treated, causing the Cr—Al—Y/Hf powder to diffuse into the nickel/cobalt forming a homogenous Ni—Co—Cr—Al—Y/Hf matrix around the abrasive grit 412. Pulse plating can be applied to Ni/Co—Cr—Al—Y/Hf powder or a Ni/Co matrix as well as for the high temperature capability requirements in the hot section as this coating may utilize a Ni/Co—Cr—Al—Y/Hf powder which is pulse plated into the Ni/Co matrix then heat treated to diffuse the Ni/Co—Cr—Al—Y/Hf into the Ni/Co matrix.
In the cold section, for example, the abrader 400 may include a nickel or a nickel-cobalt layer within which is disposed the abrasive grit 412 such as cubic boron nitride (CBN). The nickel or the nickel-cobalt is essentially the matrix 411 in which the abrasive grit 412 is disposed. In the hot section, the abrader 400 may include a nickel or a nickel-cobalt layer that contains the abrasive grit 412 in addition to a Ni/Co—Cr—Al—Y/Hf powder, then be heat treated to diffuse the Ni/Co—Cr—Al—Y/Hf into the nickel or a nickel-cobalt layer.
Pulse plating (
Pulsing the current supply causes new nucleation of nickel crystals every time the current is turned on, resulting in a relatively finer grain size, and lower coating porosity. Pulse plating is operable to increase the strength of the nickel or nickel-cobalt matrix. For example, the hardness and fatigue of the abrader 400 produced by the pulse plating method 300 is greater than the hardness and fatigue of the abrader 400 produced by other plating methods that do not involve pulse plating. This increase in hardness and fatigue resistance is primarily due to the reduced grain size of the nickel or nickel-cobalt matrix that occurs during pulse plating as compared with the grain size produced in a matrix having an identical chemical composition during the constant current process (
Initially, and with continued reference to
Next, the electrolytic nickel strike/flash layer 402 (
The strike/flash layer 402 is a relatively thin layer whose function is to reduce imperfections in the surface of the tip 96. In the strike/flash layer 402 layer, the tip 96 may be plated in a pulse plating process for a total time period of 1 minute to 10 minutes, or more specifically 2 to 5 minutes. While the strike/flash layer 402 detailed herein includes nickel, the strike/flash layer 402 may also include a combination of nickel and cobalt. The strike/flash layer 402 forms a very strong bond with other nickel plating, and this layer ensures that subsequent plating layers will also have a relatively strong bond to the substrate.
Next an electrolytic base layer 404 (
Next, the matrix material 411, which may be in slurry form, tacks the abrasive grit 412 (
In one embodiment, a nickel sulfamate plating bath is used to deposit a nickel matrix as the abrasive grit 412 is pressed against the “bond layer” from step 310 (
Next, after the co-deposition tacking step is completed, the abrasive grit 412 is further overplated with the matrix material 411 (Step 314) to form an overplate layer 408 (
The overplate layer 408 may include nickel or nickel-cobalt. When the overplate layer 408 utilizes only nickel, it may also be produced in a nickel sulfamate bath by conducting the plating operation for 3 to 4 hours to produce a layer that has a thickness of 75 to 175 micrometers, or more specifically in one example, 90 to 150 micrometers. The total thickness of the nickel or nickel-cobalt layer may be about 100 to 200 micrometers.
Next, a bake for bond optimization and stress relief may be performed (Step 316).
With reference to
With reference to
In one example, each blade tip 96 may be pulse plating (
In this example, the blade tip 96 has the abrader 400 that includes a grit with a grain size between 10-100 nm and a hardness between 250-400 HV.
Pulse plating for electroplated abrasive coatings can provide a relatively finer grain size on the scale of tens of nanometers per grain, reduced coating porosity, and increased hardness. According to the Hall-Petch relation, materials with smaller grain sizes generally benefit from grain-boundary strengthening, which increases the coating's fatigue strength, and also the fatigue life of the entire airfoil. Reduced coating porosity and increased hardness improves the wear resistance of the coating, and therefore the coating's durability and life. This reduces the frequency of required repair and overhaul of these coatings, which saves money and time. Additionally, pulse plating has been shown to improve the uniformity of the coating, as far as plating thickness and distribution, which could positively affect the overall quality of the coating and reduce production defects. Furthermore, pulse plating could also allow for higher currents to be utilized when depositing the coating, which would allow for the coating to be applied faster and thereby increasing production rate.
The use of the terms “a,” “an,” “the,” and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to normal operational attitude and should not be considered otherwise limiting.
Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.
It should be appreciated that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be appreciated that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.
The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.