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Patent Issued for Oxidation Resistant Nanocrystalline MCrAl(Y) Coatings and Methods of Forming Such Coatings

August 13, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Cheruvu, Narayana S. (San Antonio, TX); Wei, Ronghua (San Antonio, TX), filed on April 15, 2010, was published online on July 29, 2014.

The assignee for this patent, patent number 8790791, is Southwest Research Institute (San Antonio, TX).

Reporters obtained the following quote from the background information supplied by the inventors: "Several components such as those used in land-based and aero gas turbines, steam turbine boilers, and chemical processing equipment operate in severe oxidizing and hot corrosion environments. These components may operate in frequent on-off mode. As a result the components may be exposed to high temperatures and experience thermal cycling between the operating temperatures (relatively high temperatures) and room temperature, which may result in relatively high thermal stresses in the coating and the protective oxide scale.

"MCrAl(Y) coatings have been applied to these components via low pressure plasma spray, plasma vacuum spray or high velocity oxy flame processes. Upon exposure to high temperature environments (700.degree. C. to 1200.degree. C.) the aluminum present in the coating proximate to the outer surface reacts with oxygen in the environment, forming an Al.sub.2O.sub.3 oxide layer, which protects the component from further oxidation. However, during thermal cycling, the high thermal stresses may cause spallation of the Al.sub.2O.sub.3 coating, which may be accelerated by the presence and formation of mixed oxides including NiO, Cr.sub.2O.sub.3 and spinels that may form with the Al.sub.2O.sub.3. As spallation occurs, aluminum in the coating may diffuse towards the surface to replenish the Al.sub.2O.sub.3 coating. It may be appreciated that the aluminum may diffuse not only towards the surface of the coating, but also into the substrate. Thus, the coating service life may be dependent upon the amount of aluminum present and the potential rate of aluminum consumption."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "An aspect of the present disclosure relates to a method of forming an oxidation resistant nanocrystalline coating. The method may include depositing an oxidation resistant coating comprising an MCrAl(Y) alloy on a substrate, wherein M, includes iron, nickel, cobalt, or combinations thereof present greater than 50 wt % of the MCrAl(Y) alloy, chromium is present in the range of 15 wt % to 30 wt % of the MCrAl(Y) alloy, aluminum is present in the range of 6 wt % to 12 wt % of the MCrAl(Y) alloy and yttrium, is optionally present in the range of 0.1 wt % to 0.5 wt % of the MCrAl(Y) alloy. In addition, the coating may exhibit a grain size of 200 nm or less as deposited.

"In a further aspect, the coating may include a surface and exhibit a usable aluminum content (Al.sub.usable) for diffusing into the substrate or to the coating surface, wherein the usable aluminum content may be equal to 5.5 wt % to 11.5 wt %. In yet a further aspect, the coating may exhibit an overall increase in weight of 0.000 grams/cm.sup.2 to 0.0010 grams/cm.sup.2 over an initial weight value when thermally cycled to peak temperatures of 1010.degree. C. for 50 minutes per cycle and cooled to room temperature in 10 minutes per cycle over 1500 cycles.

"Another aspect of the present disclosure relates to an oxidation resistant nanocrystalline coating. The coating may include an MCrAl(Y) alloy, wherein M, includes iron, nickel, cobalt, or combinations thereof present greater than 50 wt % of the MCrAl(Y) alloy, chromium is present in the range of 15 wt % to 30 wt % of the MCrAl(Y) alloy, aluminum is present in the range of 6 wt % to 12 wt % of the MCrAl(Y) alloy and yttrium, is optionally present in the range of 0.1 wt % to 0.5 wt % of the MCrAl(Y) alloy. The coating may exhibit a grain size of 200 nm or less as deposited on a substrate."

For more information, see this patent: Cheruvu, Narayana S.; Wei, Ronghua. Oxidation Resistant Nanocrystalline MCrAl(Y) Coatings and Methods of Forming Such Coatings. U.S. Patent Number 8790791, filed April 15, 2010, and published online on July 29, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8790791.PN.&OS=PN/8790791RS=PN/8790791

Keywords for this news article include: Aluminum, Light Metals, Nanotechnology, Nanocrystalline, Emerging Technologies, Southwest Research Institute.

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Source: Journal of Engineering


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