Papers by Author: Janusz Cwiek

Abstract: The paper presents results of research and failure analysis undertaken to determine failure causes of a steam turbine casing. After 130,000 hours of service the crack in a outer shell of the turbine casing was found. The inner shell of the casing was made of cast steel grade G21CrMoV5-7, and the outer shell of grade G20CrMo4-5. Following research were performed in order to determine causes of the casing failure: chemical analysis; microstructure examinations with the use of light microscope, scanning electron microscope (SEM); mechanical properties examinations using the Charpy impact test, and Vickers hardness test; fracture mode evaluation with SEM.

Abstract: Purpose of this paper is presentation of forms of hydrogen degradation in steel along with pointing out methods for hydrogen degradation prevention. The paper outlines influence of nitrided layer on 34CrAlNi7-10 steel to its susceptibility to hydrogen degradation. Investigation was carried out with the use of slow strain tensile rate test (SSRT). Fracture surfaces after SSRT test were examined with scanning electron microscope (SEM) to reveal a mode and mechanism of cracking.