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Silica thin films applied to Ni-20Cr alloy via combustion chemical vapor deposition

Surface and Coatings Technology
Publication Date
DOI: 10.1016/s0257-8972(97)00469-6
  • Silica Thin Films
  • Combustion Chemical Vapor Deposition
  • Ni-20Cr
  • Chemistry


Abstract Amorphous silica thin films (<0.5 μm) have been deposited onto Ni-20Cr via combustion chemical vapor deposition (CVD) using two different nozzle assemblies, an oscillating capillary nebulizer (OCN) and a simple nebulizing needle. The deposition conditions were similar for the two different nozzles, although slightly different coating morphologies were observed. The OCN-deposited material was deposited onto rotating samples (4 rpm), and showed a morphology striated in thickness, presumed to be a result of thermal gradients present across the rotating sample. The samples deposited with a nebulizing needle did not show these striations, but rather, showed a nodular morphology. Protection to Ni-20Cr from the flame during deposition is reported, in addition to isothermal oxidation kinetic measurements which quantify the degree of protection provided by silica. Silica reduces the oxidation rate of Ni-20Cr, with less transient oxidation of Ni reported for silica-coated samples, as well as the rate constants of Ni-20Cr being reduced at all test temperatures by more than an order of magnitude. These reductions are attributed to the deposited oxides serving as reactive elements in the chromia scale.

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