Microstructure and wear resistance of Al2O3–TiB2 composite coating deposited by axial plasma spraying

Two Al 2 O 3 –TiB 2 composite coatings were deposited by axial plasma spray using two types of feedstocks. One of the feedstocks was a conventional micrometre sized Al 2 O 3 –30 wt-%TiB 2 composite powder from a self-propagating high temperature synthesis (SHS) process. The second was fabricated by spray drying SHSed Al 2 O 3 –30 wt-%TiB 2 composite powder doped with 10 mass-% nanosized Al 2 O 3 powder. The microstructure of the feedstocks and as sprayed coatings were comparatively investigated by scanning electron microscope and X-ray diffraction. Wear resistance of as sprayed coatings were assessed using block on ring wear test at room temperature. Results showed that Al 2 O 3 –TiB 2 composite coatings were composed of α-Al 2 O 3 , γ-Al 2 O 3 , TiB 2 and a small amount of TiO 2 . TiB 2 that mostly remained in the shape of undeformed particle were dispersedly distributed in the matrix of the composite coatings. The coating from spray dried powder exhibited finer and denser microstructure and demonstrated better wear resistance than the coating from the SHSed powder under the same sliding conditions.