Abstract
Chromium oxide coatings are used in gas turbine engines in anti-wear applications. Ultrafine YPSZ and WC/Co feedstock powders have already been widely used to prepare the ultrafine structured YPSZ and WC/Co coatings, which exhibited improved mechanical properties when compared to those of conventional coatings. Ultrafine chromium oxide powders, prepared by the method of solution precipitation, can not be directly used as plasma spray feedstock powder, because of its low mass of individual ultrafine particle and not good flowability. In this paper, spray drying and heat treatment are used to reprocess the ultrafine chromium oxide powder. The chromium oxide coating is prepared by plasma spraying. X-ray diffraction (XRD) is used to analyze the phase constituents of the feedstock powder and coatings. Scanning electron microscopy (SEM) is used to observe the morphology and particle size of ultrafine powder feedstock powder as well as to examine the microstructure of the chromium oxide coating. In addition, loose density and flowability of the feedstock powder and hardness and bond strength of the ultrafine chromium oxide coating are measured. Experimental results show that the large agglomerated ultrafine chromium oxide feedstock powder after being reprocessed are spherical, have good flowability and high loose density, which are suitable for plasma spraying. The wear properties and microstructure of the ultrafine chromium oxide coatings are improved when compared to the ones of the conventional coatings.
