Phase evolution of radio frequency magnetron sputtered Cr-rich (Cr,Zr)2O3 coatings studied by in situ synchrotron X-ray diffraction during annealing in air or vacuum

The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr 0.28 Zr 0.10 O 0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO 2 formation starting at ∼ 750–800 °C, followed by decomposition of the α-Cr 2 O 3 structure in conjunction with bcc-Cr formation, starting at ∼ 950 °C. The resulting coating after annealing to 1140 °C is a mixture of t-ZrO 2 , m-ZrO 2 , and bcc-Cr. The air-annealed sample shows t-ZrO 2 formation starting at ∼ 750 °C. The resulting coating after annealing to 975 °C is a mixture of t-ZrO 2 and α-Cr 2 O 3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO 2 fraction compared with α-Cr 2 O 3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 °C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.