Effect of the Impurities Contained in Fuel and Air on the Sulfide Corrosion of Gas Turbine Engines Blades

The working fluid temperature and pressure increase constantly in the process of improving gas turbine engines (GTE) and increasing their service life and performance. Turbine elements are subjected to high thermomechanical loads and a continuous action of an aggressive environment. These actions are especially significant for the working blades of the first stages of a GTE turbine located in a region of the highest temperatures. One of the most serious types of damage in this case is the corrosive effect on a working blade from the combustion gases entering the flow part of the turbine. The TS-1 fuel used in an aircraft contains sulfur compounds, namely, elemental sulfur and mercaptans, which leads to an aggressive effect on the GTE turbine blade material together with sodium and potassium from the air during combustion. To ensure long-term operation of GTE turbine blades at a gas temperature of up to 800–850°C at the turbine inlet, the content of these products in both fuel and air is limited according to regulatory and technical documentation. However, it is not yet possible to completely exclude them. The presence of sulfur compounds on GTE turbine blades causes sulfide corrosion. Therefore, we consider the influence of impurities in the fuel and air on the sulfide corrosion of the GTE turbine blade material and present a mechanism for sulfur dissolution in metal oxides or protective coating and the diffusion of sulfur oxide from the coating surface into depth. The cause of the influence of sodium chloride contained in the air on the corrosion of a nickel alloy or a protective coating applied on it has been established. The influence of vanadium in the fuel on the corrosion rate is presented. To increase the performance of GTE turbine blades under the influence of such an aggressive environment, we propose to use a new coating formed from an aqueous suspension and to introduce chromium into the coating, which provides a longer durability of this coating compared to serial aluminide coatings. The introduction of chromium is ensured due to an exothermic reaction during coating formation in the course of heat treatment.