In geothermal power plants materials, e.g. pumps are exposed to extreme corrosive thermal water. This results in corrosion fatigue and so inevitably the reduction of the lifetime of these components. Also in the field of the carbon dioxide storage technology (carbon capture and storage, CCS) components are exposed to a corrosive environment and mechanical stress. In order to gain knowledge upon the corrosion fatigue strength of materials, a corrosion chamber for "in situ" conditions was designed and successfully tested. Two different steels, X46Cr13 and X5CrNiCuNb16-4, have been tested in the corrosion chamber and their corrosion behavior was investigated and compared. To simulate the frequency of operating pumps (30 - 40 Hz) a resonant testing machine has been used. In addition technical CO2 was introduced into the closed system at a rate close to 9 L/h to keep stable environmental conditions. The samples have a surface roughness of Rz = 4, to simulate technically machined surfaces. X46Cr13 reached the maximum number of cycles (12.5 x 106) at a stress amplitude of 173 MPa. X5CrNiCuNb16-4 reached the maximum number of cycles (10 x 106) at a stress amplitude at 150 MPa. The scatter range of X5CrNiCuNb16-4 is very high (1:34); by comparison the scatter range of X46Cr13 is only 1:3.5.

Subject
Pits, Test methods, Geothermal energy, Corrosion fatigue, Water, Materials, Machinery, Corrosion cracking, Stress cracking, Stress, Scatter, Mechanical failure, Steel
Keywords:
steel, corrosion chamber, geothermal power, CCS, corrosion fatigue
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2014
Association for Materials Protection and Performance (AMPP)
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