서지주요정보
475 ℃ 시효처리와 W 첨가가 이상 스테인리스강의 기계적 성질 및 부식특성에 미치는 영향 = Effects of aging at 475 ℃ and W addition on the mechanical properties and the corrosion characteristics of duplex stainless steels
서명 / 저자 475 ℃ 시효처리와 W 첨가가 이상 스테인리스강의 기계적 성질 및 부식특성에 미치는 영향 = Effects of aging at 475 ℃ and W addition on the mechanical properties and the corrosion characteristics of duplex stainless steels / 박찬진.
저자명 박찬진 ; Park, Chan-Jin
발행사항 [대전 : 한국과학기술원, 1999].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8009363

소장위치/청구기호

학술문화관(문화관) 보존서고

MMS 99022

SMS전송

도서상태

이용가능

대출가능

반납예정일

초록정보

Duplex austenitic/ferritic stainless steels(DSS) are known to undergo 475℃ Embrittlement' similar to ferritic stainless steels, which affects the mechanical properties of ferritic phase, when exposed to temperature range of 300~550℃ This embrittlement is caused by the formation of Cr-rich α phase. This leads to a subsequent loss of impact toughness because of the restriction of dislocation movement and also a degradation of corrosion resistance owing to Cr-depleted regions around it. In this study, effects of thermal aging at 475℃ and W addition on the mechanical properties and corrosion characteristics of duplex stainless steels were investigated by destructive and nondestructive, electrochemical method. To evaluate the effects of Mo and W, Fe-25Cr-7Ni-xMo-yW-0.25N (3Mo, 2Mo-2W, 1.5Mo-3W, 6W) were designed to have same PREw value by varying the content of Mo and W. After solution annealing at 1050℃, DSS were aged at 475℃ for 1hr, 10hr, 100hr, and 300hr. A mechanical degradation of the designed alloys with aging were investigated by tensile and Charpy-impact tests. And electrochemical anodic polarization tests were done in NaCl and in HCl solution to evaluate localized corrosion resistance and passivity characteristics of DSS with aging. Also a modified DL-EPR method were used to detect Cr-depleted regions of the aged sample. Finally, gavanic corrosion behaviors between austenitic and ferritic phases in acidic solution were investigated by AFM (atomic force microscope). A mechanical degradation with aging was measured for the designed alloys. However, W-containing alloys still remained high impact energy after aging. In the anodic polarization responses, it showed that the pitting potentials decreased in NaCl solution and the critical current density and the passivation current density increased in HCl solution with aging. For the sample aged for 300 hr showed second anodic current peak in the passivation range during polarization tests. The degradation of corrosion resistance was retarded as W/Mo (wt%/wt%) ratio increased. Modified EPR test results showed that a recativation current was detected for the aged alloys. Finally, AFM analysis after immersion tests for the aged samples in HCl sol. showed that galvanic corrosion occurred in the countless local cells consisted of the Cr-rich and the Cr-depleted regions within the ferrite matrix as well as in the ferrite-austenite phase boundaries. The dissolution depth of the ferritic phase of the 1.5Mo-3W alloy at the vicinity of phase boundaries was lager than that of 3Mo alloy. It means that the 1.5Mo-3W alloy have more resistance to the precipitation of α' phase than the 3Mo alloy. A detrimental effect of the precipitation of Cr-rich α' phase on the corrosion characteristics as well as on the mechanical properties of DSS were made clear in this study. And it is made manifest that a substitution of W for Mo in DSS can retard the precipitation of α' phase.

서지기타정보

서지기타정보
청구기호 {MMS 99022
형태사항 viii, 99 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Chan-Jin Park
지도교수의 한글표기 : 권혁상
지도교수의 영문표기 : Hyuk-Sang Kwon
학위논문 학위논문(석사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 : p. 97-99
주제 475 ℃ 취성
이상 스테인리스강
alpha 상
W 첨가효과
475 ℃ embrittlement
Duplex stainless steels
Cr-rich alpha phase
W addition
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