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Title: Microstructure characterization of heat affected zone after welding in Mod.9Cr–1Mo steel

The microstructure of the heat affected zone after welding was investigated in Mod.9Cr–1Mo steel, using TEM and STEM-EDX. The microstructure of thin foil was observed at the fusion line, and at the positions of 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm and 3.5 mm to the base metal side of the fusion line. Martensite structure with very fine lath and high dislocation density was confirmed at all positions. Twins with a twin plane of (112) were locally observed at all positions. Elemental mapping was obtained for all positions by means of STEM-EDX. Inclusions of mainly Si were formed at the fusion line but not at the other positions. No precipitates could be detected at the fusion line or at the position of 0.5 mm. On the other hand, MX particles were observed at the positions of 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm and 3.5 mm even after welding. M{sub 23}C{sub 6} particles were also confirmed at the positions of 2.0 mm, 2.5 mm, 3.0 mm and 3.5 mm. Very fine equiaxed grains were locally observed at the positions of 2.0 mm and 2.5 mm. The Cr content of the equiaxed grainsmore » was about 12 mass%, although the martensite area included about 8 mass% Cr. - Graphical abstract: Display Omitted - Highlights: • Nonequilibrium microstructure of heat affected zone was observed after welding in Mod.9Cr–1Mo steel. • Inclusions containing Si were detected at the fusion line. • Undissolved M{sub 23}C{sub 6} and MX particles were confirmed in heat affected zone. • Twins with a twin plane of (112) were locally observed at all positions. • Very fine ferrite grains with high Cr content were observed in fine grained heat affected zone.« less
Authors:
 [1] ;  [2] ; ;  [1] ;  [3]
  1. Materials Reliability Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)
  2. Surface Physics and Structure Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)
  3. IHI Corporation, 1, Shin-nakahara-cho, Isogo-ku, Yokohama 235-8501 (Japan)
Publication Date:
OSTI Identifier:
22476056
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 101; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CHROMIUM ALLOYS; DENSITY; DISLOCATIONS; FERRITES; FOILS; HEAT AFFECTED ZONE; INCLUSIONS; MARTENSITE; METALS; MICROSTRUCTURE; MOLYBDENUM ALLOYS; PRECIPITATION; STEELS; TRANSMISSION ELECTRON MICROSCOPY; WELDING