Microstructure and mechanical properties of Al 2O 3–Cr 2O 3 composite coatings produced by atmospheric plasma spraying

Abstract

Al 2O 3, Al 2O 3–Cr 2O 3 and Cr 2O 3 coatings were deposited by atmospheric plasma spraying. Phase composition of powders and as-sprayed coatings was determined by X-ray diffraction. Electron probe microanalyzer was employed to investigate the polished and fractured surface morphologies of the coatings. Mechanical properties including microhardness, fracture toughness and bending strength were evaluated. The results indicate that the addition of Cr 2O 3 is conducive to the stabilization of α-Al 2O 3. Compared with the pure Al 2O 3 and Cr 2O 3 coatings, Al 2O 3–Cr 2O 3 composite coatings show lower porosities and denser structures. Heterogeneous nucleation of α-Al 2O 3 occurs over the isostructural Cr 2O 3 lamellae and partial solid solution of Al 2O 3 and Cr 2O 3 might be occurring as well. Furthermore, grain refining and solid solution strengthening facilitate the mechanical property enhancement of Al 2O 3–Cr 2O 3 composite coatings.