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China's DD6 nickel-based single-crystal superalloy for WS-15 turbofan engine

Discussion in 'China & Asia Pacific' started by Martian, Jan 1, 2017.

  1. Martian

    Martian Captain SENIOR MEMBER

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    China's first indigenous WS-10A turbofan engine uses the first-generation Chinese DD3 nickel-based single-crystal superalloy.

    China's superior second-generation DD6 nickel-based single-crystal superalloy is used in the second-generation WS-15 turbofan engine, which is equivalent to the American Pratt & Whitney F119 engine for the F-22.

    The obvious question: what is the difference between the performance of DD3 and DD6?

    In the picture (shown in the citation below), you can see the DD6 is smooth and displays "hot corrosion resistance...tested by burner rig method at 9OO’C for 100 hours, in uncoated condition at 0.002% salt content."

    Physics is pretty straightforward. Higher temperature and pressure mean more efficient compression. This leads to higher thrust. Thus, a WS-15 turbofan engine built with DD6 will allow the Chengdu J-20 stealth fighter to supercruise.

    The WS-15 engine is expected to be publicly unveiled between 2018 and 2020.

    A Low-Cost Second Generation Single Crystal Superalloy DD6 - TMS

    [​IMG]
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    Elemental Composition Differences Between DD6 and DD3

    DD3 is 9.5% Chromium (by weight), 5% Cobalt, 4% Molybdenum, 5.5% Tungsten, 5.8% Aluminum, 2% Titanium, and the rest is Nickel plus secret trace elements.

    DD6 is 4.3% Chromium (by weight), 9% Cobalt, 2% Molybdenum, 8% Tungsten, 7.5% Tantalum, 2% Rhenium, 0.5% Niobium, 5.6% Aluminum, 0.1% Hafnium, and the rest is Nickel plus secret trace elements.

    "Casting trials on DD6 alloy have been conducted involving a great number of slabs, bars and some complex shaped hollow turbine blades. These trials demonstrated that DD6 alloy is not prone to the formation of single crystal process defects such as tieckles and slivers, and possesses excellent single crystal castability. The MCrAlX coating has been applied to DD6 alloy successfully."

    The process of growing the single crystal is a secret process. The temperature, pressure gradient, and environment (vacuum, partial vacuum, Argon atmosphere, etc.) necessary to create the DD6 single-crystal superalloy has to be exact. All of these parameters are necessary to control crystal structure, size, and growth of the final product.

    A Low-Cost Second Generation Single Crystal Superalloy DD6 - TMS

    [​IMG]
     
    HariPrasad, R!CK and Inactive like this.
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