Zirconium vacuum arc operation in a mixture of Ar and O 2 gases: Ar effect on the arcing characteristics, deposition rate and coating properties

O. Goldberg, E. Goldenberg, V. N. Zhitomirsky, S. R. Cohen, R. L. Boxman

Research output: Contribution to journalArticlepeer-review

Abstract

The effect of oxygen and argon partial pressures (P O2, P Ar) in a Zr vacuum arc on plasma ion current density J p, arc voltage V arc, deposition rate v d, and selected coating properties was determined. A d.c. arc current of I arc=100A was initiated between a Zr cathode and a grounded anode. Cathode spots produced a plasma jet, which entered a 1/8 torus macroparticle (MP) filter. The plasma was guided by a d.c. magnetic field through an aperture to a glass substrate or a flat disk probe, mounted on a rotatable holder. J p was measured with the probe, negatively biased to V b=-60V. Coating thickness was measured using a profilometer, and coating properties were investigated using optical microscopy, energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nano-indentation and optical analysis. The discharge electrical characteristics and the coating deposition rate were found to be significantly influenced by P O2 and P Ar. J p and v d increased with P Ar until a maximum at P Ar=0.27Pa and decreased with P O2. V arc decreased with both P Ar and P O2. The changes in J p, V arc, and v d, with P Ar were larger at larger P O2. The J p, V arc, and v d dependencies suggest that addition of Argon increased the Zr ion emission from the cathode, possibly because Ar ion bombardment reduced Zr surface oxidation and improved plasma conductivity. Zirconium Oxide (ZrO 2) coatings were transparent and had colored interference rings. Well adhered, MP-free ZrO 2 coatings were deposited with P O2≥1.07Pa. Coatings deposited with P O2=1.07Pa+P Ar=0 were amorphous, whereas those deposited with P O2=1.07Pa+P Ar=0.27Pa had some degree of a monoclinic phase. Furthermore, the refractive index (n) and extinction coefficient (k) slightly decreased, from 2.22 to 2.17, and from 0.03 to 0.01, respectively and coating hardness (H) and Young's Modulus (E) decreased from ~12.9 to ~11.6GPa and from ~153 to ~136GPa respectively when P Ar=0.27Pa was added to a P O2=1.07Pa environment.

Original languageEnglish
Pages (from-to)4417-4424
Number of pages8
JournalSurface and Coatings Technology
Volume206
Issue number21
DOIs
StatePublished - 15 Jun 2012

Keywords

  • Arc voltage
  • Argon
  • Deposition rate
  • Filtered vacuum arc deposition
  • Ion current
  • Zirconium dioxide

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