A Comparison of Stress Corrosion Cracking Susceptibility of Steam Turbine Blade Materials for Geothermal Plants

作者：Wu Lianlian^*; Takeda Yoichi; Morita Hiroki; Shoji Tetsuo

来源：Corrosion, 2017, 73(2): 125-137.

DOI：10.5006/2058

• condensed geothermal steam environment
• corrosion fatigue
• environmentally assisted cracking
• geothermal
• turbine blade materials
• pitting susceptibility
• stress corrosion cracking susceptibility

In order to evaluate the environmentally assisted cracking (EAC) susceptibility of three possible alloys, 16Cr-4Ni, 12Cr, and 13Cr, to be used as turbine blade materials for a geothermal power plants, corrosion fatigue tests were performed in simulated condensed geothermal environment without H2S. EAC includes an environmental fatigue crack growth under a cyclic stress and stress corrosion cracking (SCC) under a constant load, where a unique time domain analysis (TDA) can plot all of the data on a single figure. Based upon the analysis by TDA, it was found that 16Cr-4Ni had the highest SCC resistance, as well as best performance in environmental fatigue, but no conclusive difference in EAC susceptibility between 12Cr and 13Cr was observed. Intergranular cracking was observed in 13Cr at the testing condition of high frequency and high stress intensity range. The lower EAC resistance of 12Cr than 16Cr-4Ni might be attributable to its lower pitting resistance, and the local environment built up inside of the pits as well as its surrounding can be more aggressive with lower pH and higher Cl- concentration, which could accelerate the EAC growth.

• 出版日期2017-2