Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment

Journal Article · Mon Jan 15 04:00:00 EST 2018 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2017.11.045· OSTI ID:22832949

Wang, Wanxia ^[1]; Li, Chaowen ^[1]; Jiang, Li ^[1]; Ye, Xiang-Xi ^[1]; Yu, Kun; Chen, Shuangjian ^[1]; Li, Zhijun; Zhou, Xingtai ^[1]

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1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

Highlights: • The formation and spheroidization of the eutectic-like carbides are found in the Hastelloy N alloy during welding and PWHT. • All precipitates in the joints before and after the PWHT are identified as a M{sub 6}C type carbide with different morphology. • The diffusion of main element of Mo leads to the decrease of lattice parameter of the carbide during the welding and PWHT. - Abstract: The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M{sub 6}C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M{sub 6}C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M{sub 6}C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M{sub 6}C carbides, which results in a decrease of the lattice parameter.

• OSTI ID: 22832949
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 135; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBIDES
CONCENTRATION RATIO
DIFFUSION
EUTECTICS
GAS TUNGSTEN-ARC WELDING
HASTELLOY N
HEAT AFFECTED ZONE
HEAT TREATMENTS
LATTICE PARAMETERS
PRECIPITATION
SOLID SOLUTIONS
WELDED JOINTS