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- Title
Effects of MC on the High-Temperature Performance of Ni-Based Welding Material NiCrFe-7.
- Authors
Mo, Wenlin; Lu, Shanping; Li, Dianzhong; Li, Yiyi
- Abstract
The effects of MC ( M = Cr, Fe) on the high-temperature performance of the NiCrFe-7 welding rods and weld metals were studied by high-temperature tensile tests and microstructure analysis. MC at the grain boundaries (GBs) has a cube-on-cube coherence with one grain in the NiCrFe-7 weld metals, and the adjacent MC has the coherence relationship with the same grain. The grain with a coherent MC has a Cr-depletion region. The number and size of MC particles can be adjusted by heat treatment and alloying. There are two temperatures [ T: 923 K to 1083 K (650 °C to 810 °C) and T: 1143 K to 1203 K (870 °C to 930 °C)] at which the GBs and grains of the NiCrFe-7 welding rod have equal strength during the high-temperature tensile test. When the temperatures are between T and T, the strength of the GBs is lower than that of the grains, and the tensile fractures are intergranular. When the temperatures are below T or over T, the strength of the GBs is higher than that of the grains, and the tensile fractures are dimples. MC precipitates at the GBs, which deteriorates the ductility of the welding rods at temperature between T and T. MC aggravates ductility-dip-cracking (DDC) in the weld metals. The addition of Nb and Ti can form MX ( M = Ti, Nb, X = C, N), fix C in grain, decrease the initial precipitation temperature of MC, and mitigate the precipitation of MC, which is helpful for minimizing DDC in the weld.
- Subjects
NICKEL welding; CRYSTAL grain boundaries; TENSILE strength; EFFECT of temperature on nickel alloys; HEAT-resistant chromium-iron-nickel alloys
- Publication
Metallurgical & Materials Transactions. Part A, 2014, Vol 45, Issue 11, p5114
- ISSN
1073-5623
- Publication type
Article
- DOI
10.1007/s11661-014-2439-2