Influence of impurities contained in fuel and air on sulfide corrosion of turbine blades of the gas turbine engine

Abstract

In the process of improving gas turbine engines (GTE), increasing the resource and efficiency, there is a constant increase in temperature and pressure of the working fluid. Turbine elements are subjected to high thermomechanical loads and continuous exposure from the aggressive environment. These impacts are especially significant for the working blades of the first stages of the turbine, located in the area of the highest temperatures. One of the most serious types of damage in this case is the corrosive effect on the working blade from the combustion gases entering the flow part of the turbine. The TS-1 fuel used on an aircraft contains sulfur compounds in its composition – elemental sulfur and mercaptans, which in the combustion process, together with sodium and potassium in the air, leads to an aggressive effect on the material of the turbine blade. To ensure the long-term operation of the turbine blades of the turbine at the gas temperature at the turbine inlet up to 800...850 ℃, the content of these products in both fuel and air is limited according to the regulatory and technical documentation. However, it is not yet possible to exclude them completely. The presence of sulfur compounds on the turbine blades of the GTE causes sulfide corrosion. Therefore, the article considers the influence of impurities in fuel and air on the process of sulfide corrosion of the turbine blades material of the turbine. The mechanism of sulfur dissolution in metal oxides or protective coating is presented, as well as the diffusion of sulfur oxide from the coating surface into its depth. The reason for the influence of sodium chloride contained in the air on the corrosion of nickel alloy or the protective coating applied on it has been established. The influence of vanadium in the fuel on the corrosion rate is given. In order to increase the efficiency of the turbine blades when exposed to such an aggressive environment, it is proposed to use a new coating formed from an aqueous suspension and allowing the introduction of chromium into the coating, which provides a higher durability of such a coating in comparison with serial aluminide coatings. The introduction of chromium is ensured by an exothermic reaction occurring during the formation of the coating during heat treatment.