Phase Transformation in Cast Superaustenitic Stainless Steels

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 2006

DOI:https://doi.org/10.2172/897374· OSTI ID:897374

Lee Phillips, Nathaniel Steven ^[1]

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1. Iowa State Univ., Ames, IA (United States)

Superaustenitic stainless steels constitute a group of Fe-based alloys that are compositionally balanced to have a purely austenitic matrix and exhibit favorable pitting and crevice corrosion resistant properties and mechanical strength. However, intermetallic precipitates such as sigma and Laves can form during casting or exposure to high-temperature processing, which degrade the corrosion and mechanical properties of the material. The goal of this study was to accurately characterize the solid-solid phase transformations seen in cast superaustenitic stainless steels. Heat treatments were performed to understand the time and temperature ranges for intermetallic phase formations in alloys CN3MN and CK3MCuN. Microstructures were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy and wavelength dispersive spectroscopy (EDS, WDS). The equilibrium microstructures, composed primarily of sigma and Laves within purely austenitic matrices, showed slow transformation kinetics. Factors that determine the extent of transformation, including diffusion, nucleation, and growth, are discussed.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-07CH11358; W-7405-ENG-82
• OSTI ID: 897374
• Report Number(s): IS--T 2662
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALLOYS
CASTING
CORROSION
CREVICE CORROSION
DIFFUSION
HEAT TREATMENTS
KINETICS
MATRICES
MECHANICAL PROPERTIES
NUCLEATION
PHASE TRANSFORMATIONS
SCANNING ELECTRON MICROSCOPY
SPECTROSCOPY
STAINLESS STEELS
TRANSFORMATIONS
TRANSMISSION ELECTRON MICROSCOPY
WAVELENGTHS