Abstract
A modified triode sputtering technique was used to deposit nickel-chromium alloys on pure nickel substrates maintained at temperatures varying from 550 to 1050 °C by controlled, low energy electron bombardment heating. The coatings (110–200 μ thick), deposited at rates between 960 and 1400 Å/min, were evaluated utilizing metallographic, chemical analysis, electron microprobe, x-ray diffraction, and electron diffraction techniques. A new phase, designated ε, was found when Ni-22 at.% Cr was deposited at temperatures above 750 °C. The volume fraction of the new phase increased from 10% at 750 °C to 13% at 1050 °C. Heat treatment for 200 h at 1050 °C showed no change in volume fraction of ε previously deposited at that temperature, indicating that ε is the equilibrium phase. The ε phase containing 87 at.% chromium had a tetragonal structure with a c/a=0.55, and a columnar-plate habit and grew perpendicular to the interface. The alloy target containing 12 at.% chromium condensed as ε+γ between 750 ° and 950 °C but only γ at 1050 °C. A tentative phase diagram section has been proposed showing the relationship between ε and γ, and α phases.
Published Version
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