The disclosure relates to suspension plasma spray. More particularly, the disclosure relates to liquid feedstock suspension and solution plasma spray guns.
Suspension plasma spray (SPS) is a form of plasma spray wherein a particulate suspended in a carrier liquid is delivered to the plasma spray gun. In solution plasma spray, a solution is delivered to the gun. These liquid feedstock methods may be distinguished, for example, from other systems wherein powder is fed directly into the gun to interact with plasma and any residual carrier gas or from non-powder systems (e.g., wire systems).
One recent SPS proposal is in U.S. patent application Ser. No. 14/735,211, filed Jun. 10, 2015, and entitled “Suspension Plasma Spray Apparatus and Use Methods”, the disclosure of which is incorporated by reference in its entirety herein as if set forth at length.
One aspect of the disclosure involves a plasma spray gun comprising: a plasma outlet having an axis; and a plurality of liquid feedstock outlets having a non-uniform distribution about said axis.
In one or more embodiments of any of the foregoing embodiments, the plurality of liquid feedstock outlets have a distribution that averages off the axis.
In one or more embodiments of any of the foregoing embodiments, the plurality of liquid feedstock outlets have a distribution that averages along the axis.
In one or more embodiments of any of the foregoing embodiments, the plurality of liquid feedstock outlets are each configured to dispense a suspension in a direction toward the axis.
In one or more embodiments of any of the foregoing embodiments, the plurality of liquid feedstock outlets comprises a pair of liquid feedstock outlets spaced by a nonzero angle of less than 45° about said axis.
In one or more embodiments of any of the foregoing embodiments, the pair of liquid feedstock outlets are formed by respective orifice pieces mounted in a shared body.
In one or more embodiments of any of the foregoing embodiments, the pair of liquid feedstock outlets have respective axes intersecting beyond the plasma outlet axis.
In one or more embodiments of any of the foregoing embodiments, the pair of liquid feedstock outlets have respective axes at an angle to each other smaller than said nonzero angle when viewed parallel to the axis.
In one or more embodiments of any of the foregoing embodiments, the pair of liquid feedstock outlets are at a single axial position relative to the plasma outlet.
In one or more embodiments of any of the foregoing embodiments: the pair is a first pair; and the plasma spray gun further comprises a second pair of liquid feedstock outlets wherein each liquid feedstock outlet of the second pair is diametrically opposite a corresponding liquid feedstock outlet of the first pair.
In one or more embodiments of any of the foregoing embodiments, the only liquid feedstock outlets are the first pair and the second pair.
In one or more embodiments of any of the foregoing embodiments, the angle is 10° to 45°.
In one or more embodiments of any of the foregoing embodiments, the angle is 20° to 35°.
In one or more embodiments of any of the foregoing embodiments, the only liquid feedstock outlets are the pair.
In one or more embodiments of any of the foregoing embodiments, plasma spray gun further comprises a third liquid feedstock outlet a nonzero angle from the pair of liquid feedstock outlets.
In one or more embodiments of any of the foregoing embodiments, plasma spray apparatus includes the plasma spray gun and further comprises a suspension or solution line coupled to the plasma spray gun.
In one or more embodiments of any of the foregoing embodiments, a suspension or solution supply coupled to the suspension or solution supply line.
In one or more embodiments of any of the foregoing embodiments, the suspension supply comprises ceramic particulate in an alcohol-based carrier.
In one or more embodiments of any of the foregoing embodiments, a carrier gas supply is coupled to the plasma spray gun.
In one or more embodiments of any of the foregoing embodiments, a power line is coupled to the plasma spray gun.
Another aspect of the disclosure involves a method for using the plasma spray gun. The method comprises: discharging a plasma from the plasma spray gun; and discharging suspension or solution flows from the plurality of liquid feedstock outlets to intersect the plasma.
In one or more embodiments of any of the foregoing embodiments, the method being used to apply a coating to a part wherein the part comprises a nickel-based superalloy substrate.
In one or more embodiments of any of the foregoing embodiments, the method is used to apply a coating to a part wherein: the part is a gas turbine engine component.
In one or more embodiments of any of the foregoing embodiments, the method is used to apply a coating to a part wherein: the coating is a stabilized zirconia.
Another aspect of the disclosure involves a plasma spray method using a plasma spray gun. The method comprises: discharging a plasma from a plasma outlet; and discharging a pair of liquid feedstock streams from a pair of liquid feedstock outlets, the liquid feedstock streams having a non-uniform distribution about an axis of the plasma.
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.
Like reference numbers and designations in the various drawings indicate like elements.
The exemplary outlets 24A and 24B of
Regarding the initial fragmenting, coating microstructure is strongly correlated to the initial contact of the liquid feedstock with the edge of the plasma plume, also known as the fragmentation event. A continuous liquid feedstock moving on the order of tens of m/s impinging on the edge of the plasma plume moving at hundreds of m/s creates primary liquid droplet fragments on the order of tens to hundreds of micrometers. As previous studies have shown (P. Fauchais, G. Montavon, R. S. Lima, B. R. Marple, “Engineering a new class of thermal spray nano-based microstructures from agglomerated nanostructured particles, suspensions and solutions: An invited review”, Journal of Physics D: Applied Physics, Volume 44, Issue 9, pages 1-53, IOP Publishing, Ltd., London, England, Feb. 15, 2011), optimal fragmentation is reached when the liquid momentum is slightly larger than momentum at the edge of the plasma. Geometrically, the liquid stream is then only in initial contact with a fraction of the surface area on the edge of the plasma (e.g., with the plasma represented by a cylindrical volume).
Regarding fragment penetration and entrainment, subsequently, liquid fragments with enough remaining momentum penetrate the plasma and are entrained which allows further fragmentation down to the size of a few micrometers or smaller during transit to the part. As is discussed below, both too much penetration and too little penetration are detrimental.
Regarding particle melting, also during transit, evaporation of the liquid fragments in the feedstock and melting of the spray particles occur.
The foregoing may be contrasted with merely increasing flow rate of a single injection point 24 of
The use of two spaced-apart streams 522A and 522B versus a single stream of 522 twice the flow rate may decrease the liquid momentum of each stream (contrasted with a single larger stream) 522 relative to the plasma at their respective contact locations and allows optimal fragmentation to occur. Also, the spacing between liquid feedstock streams exposes the liquid feedstock to two different sectors of the plasma and increases the available amount of enthalpy for evaporation and particle softening or melting to occur.
Closely spacing the streams 522A and 522B may have a further benefit that is not otherwise immediately apparent. If two streams are close together, the streams will have an additive component to their momentum. This will result in deeper radial penetration into the plasma than might be achieved by diametrically opposed streams. Specifically, when two smaller mass flow rates are injected in close proximity of one another, such as in
Aside from the poor fragmentation that results from having one high flow rate injection point, having a single injection point may result in over-penetration of the plasma as is noted above. A two-stream configuration may offer one or both of: 1) the increased surface area exposure described above; and 2) preventing or eliminating over-penetration into the plasma.
Compared to (contrasted with) a diametrically opposed injection (
As mentioned above, the cooperation of the two flows may lead to other embodiments wherein the centerlines 502A and 502B do not intersect the axis 500 but intersect each other at a point away from the axis 500.
Additionally, the possibility exists for adding further suspension outlets. In general, these may be characterized as being at a non-uniform spacing about the plasma axis 500. In the
An even distribution or uniform distribution would include an exactly even or exactly uniform distribution plus those substantially even or substantially uniform such as within typical manufacturing and assembly tolerances of exactly even or uniform. A non-even or non-uniform distribution would be beyond this. For example, a non-even distribution might be associated with variation in outlet-to-outlet spacing of more than 5° or more than 10° or more than 20°. Similarly, a clearly off-center average would be associated with at least as great a departure as one would find if one eliminated an outlet from an otherwise evenly/uniformly distributed group of four outlets.
In one example of a gun 70
The injection setup is not limited simply to a co-planar radially inward suspension stream and nozzle orientation. For example, another embodiment utilizing the effect in the plasma can be achieved with staggered injection points along the plasma axis (e.g., along axis 500). This may allow for more injection points than just placing injectors around the gun face 27. In one configuration, the injector axes 502A and 502B are pointed towards the axis 500. Yet other embodiments (not shown) may have the injector axes 502A and 502B pointed partially axially (i.e., with a component parallel to the axis 500) inward towards or outwards away from the gun face opening 22. Additional embodiments (not shown) that utilize the effect can combine elements of staggered, non-planar and radially inward injection. The features of the various embodiments may be recombined in other combinations. For example, the difference between θ and α of
The system 200 includes a suspension source 234. The exemplary source 234 may contain a reservoir of a mixture of coating particles and a liquid carrier suspending the particles. Other variations may involve mixing the particles and the carrier at the source 234. The suspension source 234 may include items such as: one or more pumps and/or gas sources (e.g., air, Ar, and/or N2) for pressurizing the suspension to drive suspension flow from the suspension source to the plasma gun 21; meters; sensors; valves; diagnostic hardware; and the like. As noted above, exemplary particles are of a ceramic such as a zirconia-based ceramic (e.g., at least 50% zirconia by weight). Exemplary liquid carrier is alcohol-based (e.g., at least 50% alcohol by weight).
A flowpath (suspension supply flowpath) 236 extends from an outlet 238 of the suspension source 34 to the suspension outlets 24A and 24B (and any others—not shown). The exemplary outlets 24A and 24B are external to the plasma gun 21 outlet 22. Thus, the suspension flow discharged from the outlets may mix with the plasma 242 and its carrier gas to be propelled as the spray 240.
Alternative plasma gun configurations (not shown) may integrate the suspension supply line 270 into a gun body such that the mixing of the suspension with the plasma and carrier gas is internal to the gun (e.g., via internal outlets of each).
This represents a basic system for performing SPS. Various other components (not shown), including one or more filters and/or vibrators may be located along the flowpath 236 to prevent agglomerates/large particles from plugging the orifices of the nozzles or building up in undesirable locations. Additional possible features include: a recirculation line/flowpath to recirculate suspension back to the source 234 to prevent stagnation of the suspension and associated clogging; vibrators along the line 270/flowpath 236 to prevent settling of suspended particulate; a water or solution source for purging; and an air or additional gas source for various functions including purging, powering vibrators, and the like. Examples of such features are seen in the aforementioned U.S. patent application Ser. No. 14/735,211.
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.
Where a measure is given in English units followed by a parenthetical containing SI or other units, the parenthetical's units are a conversion and should not imply a degree of precision not found in the English units.
One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing baseline configuration, details of such baseline may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.
This is a divisional application of U.S. patent application Ser. No. 14/993,582, filed Jan. 12, 2016, and entitled “Suspension Plasma Spray Apparatus and Use Methods”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length.
Number | Date | Country | |
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Parent | 14993582 | Jan 2016 | US |
Child | 16773098 | US |