Characterization of pre- and post-service grain boundary phases in a cast austenitic steel

Raymond R. Unocic, Kinga A. Unocic, Bruce A. Pint, Mark D. Lipschutz

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

Abstract

Austenitic steel castings are currently being used in components for industrial gas turbine engines. Service experience has indicated a degradation of mechanical properties with extended exposures at elevated temperature. The purpose of this study was to characterize the grain boundary phases that develop during the casting processes as a likely explanation for the observed performance. In order to isolate these precipitates, a variety of electron microscopy characterization techniques were used to characterize their composition after various heat treatments and service exposure. In the baseline, ascast and annealed condition, a discontinuous network of grain boundary metal carbides was observed. These precipitates coarsened during short-term annealing at 649°C and a denuded zone formed in the adjacent matrix. When the 38,600 h service-exposed material was analyzed, the grain boundaries were highly decorated with a more continuous film of grain boundary carbides as well as voids attributed to creep cavitation. In addition to carbides, acicular AlN precipitates were identified on the grain boundaries of the casting examined after service exposure.

Original languageEnglish
Title of host publicationASME 2011 Turbo Expo
Subtitle of host publicationTurbine Technical Conference and Exposition, GT2011
Pages755-760
Number of pages6
DOIs
StatePublished - 2011
EventASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011 - Vancouver, BC, Canada
Duration: Jun 6 2011Jun 10 2011

Publication series

NameProceedings of the ASME Turbo Expo
Volume4

Conference

ConferenceASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011
Country/TerritoryCanada
CityVancouver, BC
Period06/6/1106/10/11

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