Microstructure and wear resistance of Al_2O_3 TiB_2 composite coating deposited by axial plasma spraying

摘要

Two Al_2O_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_2O_3-30 wt- percent TiB_2 composite powder from a self-propagating high temperature synthesis (SHS) process. The second was fabricated by spray drying SHSed Al2O_3-30 wt- percent TiB_2 composite powder doped with 10 mass- percent nanosized AI_2O_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_2O_3-TiB_2 composite coatings were composed of alpha-Al_2O_3, gamma-Al_2O_3, TiB2 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.