We study microstructure, mechanical, and corrosion properties of Zr_1-xCr_xB_y 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, ZrB_2.18 and CrB_1.81 layers are grown at 4000 W DCMS. ZrB_2.18 and CrB_1.81 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 Zr_0.46Cr_0.54B_2.40 and Zr_0.10Cr_0.90B_1.81 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 Zr_0.46Cr_0.54B_2.40 and ∼ 2.1 × 10^-6 mA/cm² for Zr_0.10Cr_0.90B_1.81).

Refractory transition-metal (TM) diborides have high melting points, excellent hardness, and good chemical stability. However, these properties are not sufficient for applications involving extreme environments that require high mechanical strength as well as oxidation and corrosion resistance. Here, we study the effect of Cr addition on the properties of ZrB₂-rich Zr_1-xCr_xB_y thin films grown by hybrid high-power impulse and dc magnetron co-sputtering (Cr-HiPIMS/ZrB₂-DCMS) with a 100-V Cr-metal-ion synchronized bias. Cr metal fraction, x = Cr/(Zr + Cr), is increased from 0.23 to 0.44 by decreasing the power P_ZrB2 applied to the DCMS ZrB₂ target from 4000 to 2000 W, while the average power, pulse width, and frequency applied to the HiPIMS Cr target are maintained constant. In addition, y decreases from 2.18 to 1.11 as a function of P_ZrB2, as a result of supplying Cr to the growing film and preferential B resputtering caused by the pulsed Cr-ion flux. ZrB_2.18, Zr_0·77Cr_0·23B_1.52, Zr_0·71Cr_0·29B_1.42, and Zr_0·68Cr_0·32B_1.38 films have hexagonal AlB₂ crystal structure with a columnar nanostructure, while Zr_0·64Cr_0·36B_1.30 and Zr_0·56Cr_0·44B_1.11 are amorphous. All films show hardness above 30 GPa. Zr_0.56Cr_0.44B_1.11 alloys exhibit much better toughness, wear, oxidation, and corrosion resistance than ZrB_2.18. This combination of properties makes Zr_0·56Cr_0·44B_1.11 ideal candidates for numerous strategic applications.