Method for making high lubricity abradable material and abradable coating

Abstract

An abradable powder composition is includes a metal component, a lubricant component, and a polymer component. A portion of the metal component is wrapped in the lubricant component to achieve high lubricity and abradability. The abradable powder composition can be used to form an abradable seal coating provided for use in a turbo machinery having a housing and a wheel having multiple blades. The housing houses the wheel which rotates therein. The seal coating is formed on the inner walls of housing adjacent where the wheel blades pass during their rotation. When the wheel is rotated such that, the blades contact the seal coating, it is abraded to form a close fit gap. The abradable seal coating preferably does not produce significant wear of the blade tips or transfer abradable material significantly to the blade tips upon being abraded.

Claims

1. A method of making an abradable coating, comprising the steps of: providing a powder composition comprising particles of a metal component, a lubricant component, and particles of a polymer component; and thermal spraying the powder composition onto a substrate; wherein the metal component is at least 50% by weight of the powder composition and the lubricant component is 1% to 10% by weight of the powder composition; wherein each particle within a first subset of the particles of the metal component of the powder composition consists of the metal component wrapped in the lubricant component and each particle within a second subset of the particles of the metal component of the powder composition consists of the metal component free of the lubricant component; and wherein the powder composition is produced by mixing the first subset with the second subset and then mixing therewith the particles of the polymer component which consist entirely of the polymer component.

2. A method of making a seal for turbo machinery having a housing with inner walls that define an open interior suitable for containing a rotatable component, the method comprising the steps of: providing a powder composition comprising particles of a metal component, a lubricant component, and particles of a polymer component; and spraying the powder composition onto at least a portion of the inner walls of the housing of the turbo machinery to form an abradable coating thereon; wherein the metal component is at least 50% by weight of the powder composition and the lubricant component is 1% to 10% by weight of the powder composition; wherein each particle within a first subset of the particles of the metal component of the powder composition is consists of the metal component wrapped in the lubricant component and each particle within a second subset of the particles of the metal component of the powder composition consists of the metal component free of the lubricant component; and wherein the powder composition is produced by mixing the first subset with the second subset and then mixing therewith the particles of the polymer component which consist entirely of the polymer component.

3. The method according to claim 2, wherein the turbo machinery is a turbocharger.

4. The method according to claim 2, wherein the abradable coating has a hardness R15Y of less than 70.

5. The method according to claim 2, wherein the abradable coating has a hardness R15Y of less than 50.

6. The method according to claim 2, wherein the metal component is aluminum or an aluminum alloy.

7. The method according to claim 2, wherein the metal component is an aluminum alloy comprising aluminum and silicon or copper.

8. The method according to claim 2, wherein the metal component is a metal or an alloy comprising iron, nickel, cobalt, manganese, silicon, tin or zinc.

9. The method according to claim 2, wherein the lubricant component comprises hexagonal boron nitride, molybdenum disulfide, graphite, tungsten disulfide, molybdenum diselenide, or mixtures thereof.

10. The method according to claim 2, wherein the polymer component is 5 to 40% by weight of the composition.

11. The method according to claim 2, wherein the polymer component comprises a polyester.

12. The method according to claim 1, wherein the coating has a hardness R15Y of less than 70.

13. The method according to claim 1, wherein the coating has a hardness R15Y of less than 60.

14. The method according to claim 1, wherein the coating has a hardness R15Y of less than 50.

15. The method according to claim 1, wherein the metal component is aluminum or an aluminum alloy.

16. The method according to claim 1, wherein the metal component is an aluminum alloy comprising aluminum and silicon or copper.

17. The method according to claim 1, wherein the metal component is a metal or an alloy comprising iron, nickel, cobalt, manganese, silicon, tin or zinc.

18. The method according to claim 1, wherein the lubricant component comprises hexagonal boron nitride, molybdenum disulfide, graphite, tungsten disulfide, molybdenum diselenide, or mixtures thereof.

19. The method according to claim 1, wherein the polymer component is 5 to 40% by weight of the composition.

20. The method according to claim 1, wherein the polymer component comprises a polyester.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a schematic representation of a composite powder material for high lubricity and abradability in accordance with the present disclosure.

(2) FIG. 2 is a perspective view of a turbocharger compressor housing with an abradable seal coating formed on inner surface of thereof in accordance with the present disclosure.

DETAILED DESCRIPTION

(3) In a first preferred embodiment, an abradable powder composition is provided that includes a metal component, a lubricant component, and a polyester component, wherein a portion of the metal component is wrapped in the lubricant component. That is, some, but not all, of the metal is wrapped in the lubricant. The composition thus generally includes three components: polyester, lubricant-wrapped metal, and unwrapped metal. This lubricant-wrapped metal component can be produced using a mechanical milling, chemical deposition, chemical vapor deposition (CVD), or physical vapor deposition (PVD) process.

(4) The metal component can be a metal or a metal alloy. Preferred metal components include aluminum or an aluminum alloy, such as aluminum silicon alloy (silumin) or aluminum bronze alloy. The metal component in the powder composition is preferably in the form of metal particles, and are preferably aluminum particles or aluminum alloy particles. In addition to aluminum and silicon, silumin can also contain other metals, such as magnesium and copper. Similarly, in addition to aluminum and copper, aluminum bronze can also contain other metals, such as iron, nickel, cobalt, manganese, silicon, tin, and zinc. Other metal alloys can also include iron, nickel, cobalt, manganese, silicon, tin, or zinc. The metal components are preferably present as at least 50 by weight of the total powder composition.

(5) The lubricant component can be any suitable dry lubricant. Preferably lubricant materials include boron nitride such as hexagonal boron nitride, molybdenum disulfide, graphite, tungsten disulfide, or molybdenum diselenide. Mixtures of multiple lubricant materials, including but not limited to the preferred lubricants above, can be used as the lubricant component. The lubricant component is preferably present as at least 1 wt. % of the total powder composition.

(6) The polymer component can be any suitable polymer, include copolymers. Preferred polymers include polyester. The preferred polyester is poly(oxy-1,4-phenylenecarbonyl). The polymer component is preferably present as at least 5 wt. % of the total powder composition.

(7) To provide advantageous properties for coatings produced therefrom, the powder composition is preferably made up of a portion of the metal component wrapped in the lubricant component, the remaining portion of the metal component unwrapped, and the polyester component. Preferably, the powder composition includes 50 to 94 wt. % of the metal component, 1 to 10 wt. % of the lubricant component, and 5 to 40 wt. % of the polymer component. Preferably, at least 20% by weight of the metal component is wrapped in the lubricant component. More preferably, at least 20% by weight of the metal component is wrapped with lubricant and has less than 30% by surface of exposed metal component.

(8) A coating produced from the powder composition described above has numerous properties that are advantageous to use as an abradable seal coating. For example, the hardness is relatively low of the powder material and thus abradable seals produced therefrom, which prevents significant wear of a moving component that engages seals, such as the blade tips of a turbo machinery. By preventing significant wear, it is meant that the moving component is not damaged in a way that materially affects its performance or performance lifetime. Weak bonding between the individual lubricant-wrapped metal component particles contributes to the relatively low hardness. The powder material and abradable seal coatings produced therefrom also have good lubricity, which also helps to prevent significant wear of the moving component and reduces material to transfer to the moving component. The powder material and abradable seal coatings produced therefrom also have a good balance between coating integrity and abradability, resulting in the seal abrading easily when contacted with the moving component while at the same time being held together with strong enough bonds such that the seal maintains its structure, particularly in harsh environments. The balance between coating integrity and abradability is achieved by the bonding between the materials. The polymer material particularly contributes to the abradability while the unwrapped metal component contributes to the coating integrity.

(9) To form the powder material, particles of the metal component are wrapped in a phase of the lubricant component using a mechanical or chemical process in a first step. The lubricant phase/film on metal or its alloy particles will provide a non-stick or weak bonding between the particles, and also provide lubricity property into the material. The first property will aim to improve abradable property, and the second property to lubricity. In a second step, additional particles of the metal component are mixed with the lubricant-wrapped metal component particles to create a mixture of wrapped metal and unwrapped metal. This mixture of material will ensure the resultant coating has good mechanical properties, abradable properties and coating integrity. In a third step, to further improve abradability, particles of the polymer component are added to the mixture of lubricant-wrapped metal particles and unwrapped metal particles by a blending process to produce the powder composition. In a fourth step, the powder can be sprayed with conventional thermal spray techniques, such as by air plasma or flame, onto a surface to produce a coating thereon.

(10) An example of a powder composition 1 is shown schematically in FIG. 1 that includes a metal component 10, a lubricant component 20, and a polymer component 30. A portion of the metal component 10 is formed as unwrapped metal component 10a, whereas the remainder of the metal component 10 is wrapped with lubricant 20 to form wrapped metal component 10b.

(11) The powder material is suitable to be used as an abradable seal coating for maximizing the efficiency of an axial or centrifugal turbo machinery. FIG. 2 depicts an example turbo machinery, specifically a turbocharger, 100 that includes a housing 101 having inner walls that define an open interior 102 designed to contain a wheel having blades (not pictured) that rotates therein. An abradable seal coating 103 is formed on the inner walls of the housing 101. The abradable seal coating is prepared from the powder composition 1 discussed above. The powder composition 1 is applied as a coating to the inner walls of the housing 101 adjacent where the wheel blades pass during their rotation to form the abradable seal coating 103. Conventional thermal spray techniques can be used to produce the coating in the turbo machinery housing to form the abradable seal coating. Air plasma or flame spray are examples of spray techniques to produce the coatings. Upon rotation, the blades of the wheel contact the abradable seal coating 103 such that it is abraded to form a seal having close fit gap. The close fit gap reduces backflow in the turbo machinery.

(12) The abradable seal coating 103 preferably does not produce significant wear of the blade tips. To achieve this, the hardness of the abradable seal coating 103 on the R15Y scale is preferably less than 70, more preferably less than 60, and most preferably less than 50. Preferably, a minimal portion of the abradable seal that abrades adheres to the blade tips upon abrading. Preferably 3%, more preferably 2%, and even more preferably 1% of the abraded portion of the seal adheres to the blade tips after it is abraded.

(13) When ranges are expressed herein, it is to be appreciated that other embodiments include any subranges and values encompassed therein. For example, the range of 10 to 20% encompasses 10 to 15%, 12 to 17%, 13 to 20%, and so forth.