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Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

  • US 6,296,909 B1
  • Filed: 05/11/2000
  • Issued: 10/02/2001
  • Est. Priority Date: 12/22/1998
  • Status: Expired due to Fees
First Claim
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1. A method comprising the steps of:

  • thermal spraying a mullite powder to form a mullite layer on a substrate, the thermal spraying step being performed so that the mullite powder is heated to a deposition temperature between the peritectic and liquidus temperatures of mullite, by which the mullite powder melts to form a silica-rich liquid phase and solid alumina phases, and the mullite layer is deposited to contain alumina phases in a silica-rich mullite matrix;

    following deposition of the mullite layer but before the mullite layer cools from the deposition temperature to a temperature at which cracks form in the mullite layer, heating the mullite layer in-situ for a duration and at a temperature sufficient to convert the alumina phases to mullite and thereby substantially achieve phase equilibrium within the mullite layer; and

    then cooling the mullite layer to room temperature, the mullite layer being substantially free of alumina phases and silica-rich phases and free of through-thickness cracks.

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