TY - GEN
T1 - Characterization of pre- and post-service grain boundary phases in a cast austenitic steel
AU - Unocic, Raymond R.
AU - Unocic, Kinga A.
AU - Pint, Bruce A.
AU - Lipschutz, Mark D.
PY - 2011
Y1 - 2011
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84865481476&partnerID=8YFLogxK
U2 - 10.1115/GT2011-46710
DO - 10.1115/GT2011-46710
M3 - Conference contribution
AN - SCOPUS:84865481476
SN - 9780791854648
T3 - Proceedings of the ASME Turbo Expo
SP - 755
EP - 760
BT - ASME 2011 Turbo Expo
T2 - ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011
Y2 - 6 June 2011 through 10 June 2011
ER -