Chemical Vapor Deposition

Chemical Vapor Deposition

Chemical vapor deposition (CVD) results from the chemical reaction of gaseous precursor(s) at a heated substrate to yield a fully dense deposit. Ultramet uses CVD to apply refractory metals and ceramics as thin coatings on various substrates and to produce freestanding thick-walled structures.

Thermodynamics and kinetics drive both precursor generation and decomposition. Control of thermodynamics and kinetics through temperature, pressure, and concentrations yields the desired deposit.

CVD reaction

CVD reaction

Metal deposition

metal halide (g) → metal(s) + byproduct (g)

Ceramic deposition

metal halide (g) + oxygen/carbon/nitrogen/boron source (g) → ceramic(s) + byproduct (g)

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Advantages of CVD

  • Can be used for a wide range of metals and ceramics
  • Can be used for coatings or freestanding structures
  • Fabricates net or near-net complex shapes
  • Is self-cleaning—extremely high purity deposits (>99.995% purity)
  • Conforms homogeneously to contours of substrate surface
  • Has near-theoretical as-deposited density
  • Has controllable thickness and morphology
  • Forms alloys
  • Infiltrates fiber preforms and foam structures
  • Coats internal passages with high length-to-diameter ratios
  • Can simultaneously coat multiple components
  • Coats powders

Hot-wall CVD reactor in process. Parts heated and coated within graphite furnace.

Cold-wall CVD reactor in process. Part heated directly and coated.

Microstructure of high-emittance black rhenium coating showing pyramidal dendrites formed by CVD

Layered CVD ceramic coating (top) conforms closely to underlying substrate to create a robust bond at the interface.

Left, large freestanding solid rhenium thruster (19″ high × 10″ diameter at base) fabricated by CVD, demonstrating Ultramet’s scale-up expertise; top right, freestanding parts of solid rhenium, tantalum, and tungsten formed by CVD; bottom right, monolithic CVD rhenium thrust chambers for tactical propulsion applications.

Top left, mirror fabricated entirely by CVD of silicon carbide foam with a polished silicon carbide facesheet; bottom left, rhenium-coated graphite spheres; right, iridium-lined rhenium thrust chamber with niobium flanges, all fabricated by CVD.

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CVI and UVCVD

Materials Deposited by CVD

Inside-out Processing

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