Abstract
Al2O3–Y2O3 nano- and micro-composite coatings have been deposited on boiler steel substrates using sol–gel composite coating technology. The processes include dipping samples in a sol–gel solution dispersed with fine ceramic powders, which is prepared by high-energy ball milling. Scanning electron microscopy (SEM) and XRD analyses show that the one-layer coating (i.e. dipping for one time) has a thickness of more than 2 μm. The coating is mainly composed of α-Al2O3 and γ-Al2O3, and is relatively dense without cracking after drying and sintering treatments. The oxidation tests performed in air at 600°C show that the coatings possess much improved resistance to high temperature oxidation and scale spallation. It is believed that the nano-structured composite particles and reactive elements are integrated into the coatings, which played an important role in improving their oxidation resistance.
