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  • 1.  HVOF spray of Aluminum oxide over Silicon carbide

    Posted 9 days ago

    Hi Guys

    I have an application for a thermal spray of Alumina (Aluminum oxide 99% purity) over Silicon carbide base. Please share your experiences and knowledge on this topic. The points like thickness of coating for optimal properties, High temperature application, Fatigue requirements for silicon carbide, etc. Please help me with your input and do the needful. 

    Prasad Rao
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  • 2.  RE: HVOF spray of Aluminum oxide over Silicon carbide

    Posted 6 days ago

    There is just not enough information here to offer meaningful comments. In general, silicon carbide and alumina are not compatible due to a large difference in coefficient of thermal expansion. So the application has to be better defined to come up with a viable solution:

    1. What grade of silicon carbide is being considered? Hot-pressed, sintered or reaction sintered and why?
    2. Why alumina?
    3. What are the service conditions? Temperature (steady state, transient, cycling), atmosphere (oxidizing, vacuum or reducing), contact with other materials, friction or wear requirements, electrical conductivity requirements, etc
    4. Is an interlayer allowed or acceptable?

    FYI, the high strength silicon carbide has no "endurance" limit like high strength steels. The tensile strength is is not a strong function of number of cycles. However, tensile strength is a strong function of surface finish and notch strength and fracture toughness should be the primary design parameters. Further, most suppliers will publish three-point or four-point rupture strength. Unfortunately, these parameters are not precise and are lower than the tensile strength.

    As a first step, I would recommend that you review the past literature published by The American Ceramic Society and public reports from US Department of Energy and US Department of Defense.


    Dr. Ratnesh Dwivedi

    President, RKD ENGG, LLC

    [Ratnesh] [Dwivedi]

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