Patent ID: 12252793

DETAILED DESCRIPTION

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.

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.

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.

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.

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.

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.

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.

An example of a powder composition1is shown schematically inFIG.1that includes a metal component10, a lubricant component20, and a polymer component30. A portion of the metal component10is formed as unwrapped metal component10a, whereas the remainder of the metal component10is wrapped with lubricant20to form wrapped metal component10b.

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.2depicts an example turbo machinery, specifically a turbocharger,100that includes a housing101having inner walls that define an open interior102designed to contain a wheel having blades (not pictured) that rotates therein. An abradable seal coating103is formed on the inner walls of the housing101. The abradable seal coating is prepared from the powder composition1discussed above. The powder composition1is applied as a coating to the inner walls of the housing101adjacent where the wheel blades pass during their rotation to form the abradable seal coating103. 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 coating103such that it is abraded to form a seal having close fit gap. The close fit gap reduces backflow in the turbo machinery.

The abradable seal coating103preferably does not produce significant wear of the blade tips. To achieve this, the hardness of the abradable seal coating103on 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.

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.