Microstructure, mechanical, and corrosion properties of Zr1-xCrxBy diboride alloy thin films grown by hybrid high power impulse/DC magnetron co-sputtering

Babak Bakhit*, Samira Dorri, Ali Kosari, Arjan Mol, Ivan Petrov, Jens Birch, Lars Hultman, Grzegorz Greczynski

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

We study microstructure, mechanical, and corrosion properties of Zr1-xCrxBy coatings deposited by hybrid high-power impulse/DC magnetron co-sputtering (CrB2-HiPIMS/ZrB2-DCMS). Cr/(Zr + Cr) ratio, x, increases from 0.13 to 0.9, while B/(Zr + Cr) ratio, y, decreases from 2.92 to 1.81. As reference, ZrB2.18 and CrB1.81 layers are grown at 4000 W DCMS. ZrB2.18 and CrB1.81 columns are continual from near substrate toward the surface with open column boundaries. We find that the critical growth parameter to achieve dense films is the ratio of Cr+-dominated ion flux and the (Zr + B) neutral flux from the ZrB2 target. Thus, the alloys are categorized in two groups: films with x < 0.32 (low Cr+/(Zr + B) ratios) that have continuous columnar growth, rough surfaces, and open column boundaries, and films with x ≥ 0.32 (high Cr+/(Zr + B) ratios) that Cr+-dominated ion fluxes are sufficient to interrupt continuous columns, resulting in smooth surface and dense fine-grain microstructure. The pulsed metal-ion irradiation is more effective in film densification than continuous Ar+ bombardment. Dense Zr0.46Cr0.54B2.40 and Zr0.10Cr0.90B1.81 alloys are hard (>30 GPa) and almost stress-free with relative nanoindentation toughness of 1.3 MPa√m and 2.3 MPa√m, respectively, and remarkedly low corrosion rates (∼1.0 × 10-6 mA/cm2 for Zr0.46Cr0.54B2.40 and ∼ 2.1 × 10-6 mA/cm2 for Zr0.10Cr0.90B1.81).

Original languageEnglish
Article number153164
Number of pages12
JournalApplied Surface Science
Volume591
DOIs
Publication statusPublished - 2022

Keywords

  • Corrosion protection
  • Diboride alloys
  • Mechanical properties
  • Microstructure
  • Thin films
  • Zirconium diborides

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