Yuanzineng kexue jishu (Sep 2023)
Corrosion Behavior of Typical Materials for Key Components of Steam Turbines in Supercritical CO2 Environment
Abstract
The turbine system is an indispensable part of power cycle or power generation system using supercritical CO2 as the working fluid. The safety for high-temperature component directly affects the long-term safe operation of the entire power cycle or power generation system. For the turbine in supercritical CO2 power cycle, the corrosion of materials for key high-temperature components was less studied, so to ensure that heat-resistant materials Co3W3, 1Cr10Mo1NiWVNbN and high temperature nickel based alloy 718 can be used to build key components of the turbine, it is necessary to study the corrosion behavior of three heat-resistant materials in supercritical CO2 environment. The corrosion behavior of three typical high-temperature component materials for turbines in supercritical CO2 environment at 600 ℃ and 20 MPa for 3 000 h was studied in this paper. The formation and variation of corrosion products on the surface of 1Cr10Mo, Co3W3 and IN718 were obtained by combining corrosion weight gain of materials, microscopic characterization of corrosion products and corrosion thermodynamic calculations. The scanning electron microscopes, energy spectrometers, X-ray diffractometer and glow discharge spectrometers were used to analyze the morphology, composition and elemental distribution of corrosion products formed on the three materials. The results show that the weight gain of IN718 in supercritical CO2 environment was much lower than that of two heatresistant steels Co3W3 and 1Cr10Mo1NiWVNbN. The corrosion weight gain curves of the two heat-resistant steels Co3W3 and 1Cr10Mo1NiWVNbN were conformed to be the parabolic corrosion law, indicating that the corrosion process was controlled by ion diffusion. Based on the in-depth element distribution, it can be inferred that the three materials underwent simultaneous oxidation and carbonization reactions in this environment. The corrosion products formed on IN718 were mainly composed of Cr2O3, while the corrosion products formed on heat-resistant steels Co3W3 and 1Cr10Mo1NiWVNbN were Fe2O3, Fe3O4 and (Fe,Cr)3O4. Moreover, the carbonization reaction of heat-resistant steels was serious, forming Fe and Cr carbides. According to the corrosion weight gain, corrosion product and carbide product thickness, the corrosion resistance of the three materials in the supercritical CO2 environment is in the following order: IN718>Co3W3>1Cr10Mo1NiWVNbN.
