Stress corrosion cracking and corrosion fatigue of steam-turbine rotor and blade materials. M. O. Speidel, J. Denk and B. Scarlin. COST-Berichte EUR 13186, Physical Science Series; Bezug über Bundesanzeiger-Verlag, Postfach 10 80 60, 5000 Köln 1

1991 ◽  
Vol 42 (8) ◽  
pp. 446-446
Author(s):  
K. Schleithoff
Keyword(s):  
Stress Corrosion ◽  
Steam Turbine ◽  
Corrosion Fatigue ◽  
Stress Corrosion Cracking ◽  
Physical Science ◽  
Turbine Rotor ◽  
Corrosion Cracking ◽  
Steam Turbine Rotor

Study on Stress Corrosion Cracking Sensitivity of CrNiMoV Steam Turbine Rotor Steels

2019 ◽  
Vol 795 ◽  
pp. 102-108 ◽  
Author(s):  
Shu Xian Lin ◽  
Yu Hui Huang ◽  
Fu Zhen Xuan ◽  
Shan Tung Tu
Keyword(s):  
Stress Corrosion ◽  
Steam Turbine ◽  
Stress Corrosion Cracking ◽  
Turbine Rotor ◽  
Optical Microscope ◽  
Corrosion Cracking ◽  
Slow Strain Rate Test ◽  
Operation Condition ◽  
Steam Turbine Rotor ◽  
Rate Test

The stress corrosion sensitivities of 25Cr2Ni2MoV, 26NiCrMoV10-10 and 30Cr2Ni4MoV low-pressure rotor steels in simulated nuclear steam turbine operation condition were investigated by slow strain rate test (SSRT), and the stress corrosion cracking (SCC) mechanisms were studied by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Results revealed that the SCC sensitivity of 25Cr2Ni2MoV steel was highest in 3.5wt.%NaCl solution at 180°C, while the SCC sensitivity of 26NiCrMoV10-10 steel and 30Cr2Ni4MoV steel are similar. The SCC sensitivity of CrNiMoV steam turbine rotor steels could be decreased by the increase of Ni element and the decline of mechanical intensity. Cracks initiate from metal surface and then propagate to the inner metal, which showed a form of transgranular cracking.

Stress Corrosion Cracking of Low-Pressure Steam Turbine Rotor

2011 ◽  
Author(s):  
Liang Yan ◽  
Kazuyoshi Nakajima ◽  
Shuichi Inagaki ◽  
Masao Arimura ◽  
Shigeo Hosoi
Keyword(s):  
Stress Corrosion ◽  
Steam Turbine ◽  
Stress Corrosion Cracking ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Corrosion Cracking ◽  
Sulfur Concentration ◽  
X Ray ◽  
Steam Turbine Rotor ◽  
Pressure Steam

Corrosion cracks were found at the bottom of the first hook of the L-4 stage of a low-pressure steam turbine rotor after about 230,000 hours operation with about 300 times of starts and stops of a thermal power plant. They developed in the circumferential direction, showing a groove line on the bottom surface of the first hook. Cross sectional observation showed that they had branched and blunted shapes, and X-ray cartography analysis results showed that they filled with corrosion products, and sulfur concentration was detected. In order to verify that they were caused by stress corrosion cracking (SCC), bent-beam stress-corrosion tests with four-point loaded specimens (ASTM G40 method) were performed in a 0.25wt%H2SO4+NH4OH solution with a pH controlled at 9.8 to simulate the corrosion environment of the steam turbine, and the test temperature was set at 80°C. After 6,000-hour and 10,000-hour tests, the cross sections of SCC specimens were inspected with a scanning electron microscope (SEM). Branched and blunted cracks were observed and the crack shapes were similar to those of the corrosion cracks occurred in the steam turbine. Sulfur concentration was also observed in the blunted cracks of the specimens by X-ray cartography analysis. Based on the test results, it can be assumed that the corrosion cracks developed from stress corrosion cracking (SCC) in the low-pressure steam turbine. It is thus necessary to periodically inspect not only the L-1, 2 stages of the wet and corrosion zone, but also the L-3, 4 stages of dry and salt zone in low-pressure steam turbines.

Stress Corrosion Cracking and Corrosion Fatigue Analysis of Nuclear Steam Turbine Rotor

2014 ◽  
Author(s):  
Gang Chen ◽  
Puning Jiang ◽  
Xingzhu Ye ◽  
Junhui Zhang ◽  
Yifeng Hu ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Steam Turbine ◽  
Corrosion Fatigue ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Power Plants ◽  
Fatigue Cracking ◽  
Corrosion Cracking ◽  
Major Influence ◽  
Steam Turbines

Although stress corrosion cracking (SCC) and corrosion fatigue cracking can occur in many locations of nuclear steam turbines, most of them initiate at low pressure disc rim, rotor groove and keyway of the shrunk-on disc. For nuclear steam turbine components, long life endurance and high availability are very important factors in the operation. Usually nuclear power plants operating more than sixty years are susceptible to this failure mechanism. If SCC or corrosion fatigue happens, especially in rotor groove or keyway, it has a major influence on nuclear steam turbine life. In this paper, established methods for the SCC and corrosion fatigue-controlled life prediction of steam turbine components were applied to evaluating a new shrunk-on disc that had suffered local keyway surface damage during manufacture and loss of residual compressive stress.

A New Generalized Nonlinear Superposition Theory and its Applications in Modeling Corrosion-Fatigue

2013 ◽  
Author(s):  
Zhigang Wei ◽  
Limin Luo ◽  
Marek Rybarz ◽  
Kamran Nikbin
Keyword(s):  
Synergistic Effect ◽  
Stress Corrosion ◽  
Corrosion Fatigue ◽  
Stress Corrosion Cracking ◽  
Failure Mechanisms ◽  
Corrosion Cracking ◽  
Time Dependent ◽  
Linear Superposition ◽  
Nonlinear Superposition ◽  
Cycle Dependent

Corrosion-fatigue and stress corrosion cracking have long been recognized as the principal degradation and failure mechanisms of materials under combined corrosive environment and sustained/cyclic loading conditions. These phenomena are strongly material and environment dependent, and cycle-dependent fatigue and time-dependent matter diffusion/chemical reaction at the crack tip can be operational simultaneously. How to include these cycle-dependent and time-dependent phenomena in a single model and how to study the failure mechanisms interaction are big challenges posed to material scientists and engineers. In this paper the current linear superposition theories for modeling cycle-dependent and time-dependent corrosion-fatigue and stress corrosion cracking phenomena are reviewed first. Subsequently, a generalized nonlinear superposition theory is proposed to incorporate possible nonlinear interaction or synergistic effect among the underlying mechanisms. The unified model derived from the new theory, depending on the specific materials and loading condition and environment, can be reduced to pure corrosion, pure fatigue, stress corrosion cracking and corrosion-fatigue. Finally, for the first time, a new breakthrough parameter is defined in this paper to quantitatively describe the interaction or synergistic effect between two different operating mechanisms, such as time- and cycle-dependent mechanisms.

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