In situ (Al,Cr)2O3-Cr composite coating fabricated by reactive plasma spraying

In situ (Al,Cr)2O3-Cr composite coating was fabricated by reactive plasma spraying Al-Cr2O3 composite powder. Phase composition and microstructure of the as-sprayed coating was characterized by X-ray diffractometer, scanning electron microscope and transmission electron microscope. Indentation fracture behavior of the coating was investigated. It is found that the microstructure of the coating consists of [(Al,Cr)2O3+Cr] eutectic and Cr+[(Al,Cr)2O3+Cr] hypoeutectic. The eutectic microstructure of the coating shows the characteristic of nano structure, in which Cr particles with size less than 40 nm distribute in (Al,Cr)2O3 solid solution matrix. The hypoeutectic microstructure of the coating consists of Cr particles with size larger than 1 µm and [(Al,Cr)2O3+Cr] divorced eutectic. The toughness of the (Al,Cr)2O3-Cr composite coating is significantly improved compared with that of the conventional Al2O3 coating.