Thermally sprayed coatings for protection of fretting wear in land-based gas-turbine engine

Wear is one of the major causes of failure in many parts and components in gas-turbine engines. The fuel nozzle and its collar are two of the components that suffer rapid wear, in particular fretting wear at elevated temperature due to the vibration of the engine. The reported work was carried out to study the wear-resistant coatings for this application. Four types of coating, namely WC–17% Co, Cr3C2–25% NiCr, AlSi graphite and CoMoCrSi, were deposited on stainless steel substrates by thermal spraying technique. Physical properties of the coatings, such as adhesion strength, porosity and microstructure, were measured for comparison. Wear properties of the coatings were obtained using an in-house, flat-on-flat wear tester, which was designed to simulate the vibrating condition of the nozzle. The tester was positioned inside a furnace to obtain an operating condition of 500 °C. Wear tests were performed for various time duration for each set of specimen. The wear behaviors of each type of coating was also studied.