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The role of phosphorus in precipitation behavior and its effect on the creep properties of alumina-forming austenitic heat-resistant steels

Title
The role of phosphorus in precipitation behavior and its effect on the creep properties of alumina-forming austenitic heat-resistant steels
Author
이창희
Keywords
Phosphorous; Creep test; Precipitation behavior; Alumina-forming austenitic heat-resistant (AFA) steel
Issue Date
2017-01
Publisher
ELSEVIER SCIENCE SA
Citation
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, v. 684, page. 14-21
Abstract
The precipitation behavior and creep properties of lower phosphorus (P) alumina-forming austenitic (AFA(LP)) heat-resistant steel were investigated and compared to those of AFA. The creep rupture time and hardness of the investigated steels were improved with the decrease of the P content. The TEM and EELS analyses confirmed an enhanced P concentration in the M23C6 precipitates along the grain bolindaries. The P promoted the precipitation of M23C6 and also suppressed the precipitation of secondary NbC in the earlier stage of aging. The creep rupture time of AFA became shorter compared to AFA(LP) due to the reduction in the fraction of secondary NbC which acts as a dominant strengthening phase during creep. The suppression of secondary NbC precipitation by P increased the Nb content in the austenite matrix and accelerated the precipitation of the Laves phase in the intermediate stage. However, the difference in Vickers hardness caused by Laves phase was not large in both alloys because the volume fraction of Laves phase strongly depended on the nominal content of Mo rather than Nb. The Vickers hardness at the earlier stage is determined by the precipitation of secondary NbC and the difference of the hardness maintained at the final stage. Thus, it is found that P degrades the creep rupture time and P is a detrimental element in terms of creep and precipitation hardening in AFA steels.
URI
https://www.sciencedirect.com/science/article/abs/pii/S0921509316315052?via%3Dihubhttps://repository.hanyang.ac.kr/handle/20.500.11754/105120
ISSN
0921-5093; 1873-4936
DOI
10.1016/j.msea.2016.12.021
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > MATERIALS SCIENCE AND ENGINEERING(신소재공학부) > Articles
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