Failure Mechanisms on Exhaust Systems of Naval Gas Turbines

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Citations (Scopus)

Abstract

Some exhaust systems of naval gas turbines have been periodically repaired due to thermal-fatigue crack propagation after entering into service. Those structures were made of austenitic stainless steel grade AISI 316L in thin wall plates, which were bent in rolling machines and welded with longitudinal and circumferential joints by means of shielded metal arc, TIG or MIG/MAG welding processes. The plate thickness is about 3.7 mm and the temperature on the exhaust system is approximately 500°C and 350°C in the critical zones, which are located in the lower and intermediate regions of the exhaust system.Several cracks were detected at the critical regions, near the weld toe of butt and T-welded joints. The stress concentration factors induced by the weld angle, toe radius and rolled surface finishing diminishes the fatigue life strength. Some cracked material samples were taken out from the exhaust system structure and were analysed with a Scanning Electron Microscope (SEM/EDS), in order to determine the failure mechanisms involved in the crack propagation process. Those results are presented in the paper. Several high temperature fatigue and creep tests were performed with CT specimens. The mechanisms of crack propagation on the CT specimens were studied by SEM and compared with the fracture surfaces obtained from the samples taken out from the structure. The carbide precipitation on the grain boundaries was also studied.
Original languageEnglish
Title of host publicationAdvanced Materials Forum IV
Subtitle of host publicationSelected, peer reviewed papers from the 4th International Materials Symposium Materiais 2007
EditorsAT Marques, AF Silva, APM Baptista, C Sa, F Alves, LF Malheiros, M Vieira
Place of PublicationSwitzerland
PublisherTrans Tech Publications Ltd
Pages946-950
Number of pages5
Volume587-588
ISBN (Print)978-0-87849-373-9
DOIs
Publication statusPublished - 1 Jan 2008
EventAdvanced Materials Forum IV - Selected, peer reviewed papers from the 4th International Materials Symposium Materiais 2007 and 8th Encontro da Sociedade Portuguesa de Materiais - SPM - Porto, Portugal
Duration: 1 Apr 20074 Apr 2007

Publication series

NameAdvanced Materials Forum
PublisherTrans Tech Publications
Volume587-588
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Conference

ConferenceAdvanced Materials Forum IV - Selected, peer reviewed papers from the 4th International Materials Symposium Materiais 2007 and 8th Encontro da Sociedade Portuguesa de Materiais - SPM
CountryPortugal
CityPorto
Period1/04/074/04/07

Keywords

  • AISI 316L austenitic stainless steel grade
  • Creep
  • Failure mechanisms
  • Fatigue

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