서지주요정보
니켈기 초내열합금에서 피막처리가 고온 기계적 성질및 미세조직에 미치는 영향 = A study on the effects of a coating treatment on the high temperature mechanical properties and microstructure in a nickel-base superalloy
서명 / 저자 니켈기 초내열합금에서 피막처리가 고온 기계적 성질및 미세조직에 미치는 영향 = A study on the effects of a coating treatment on the high temperature mechanical properties and microstructure in a nickel-base superalloy / 강석봉.
발행사항 [서울 : 한국과학기술원, 1986].
Online Access 원문보기 원문인쇄

소장정보

등록번호

4104022

소장위치/청구기호

학술문화관(문화관) 보존서고

DMS 8607

휴대폰 전송

도서상태

이용가능

대출가능

반납예정일

리뷰정보

초록정보

The effects of an aluminide coating treatment on creep-rupture properties of a directionally and conventionally solidified nickel-base superalloy Rene 80 were investigated. The secondary creep rates and rupture lives of the coated/uncoated conventionally solidified nickel-base superalloy Rene 80 were determined at 871℃ under the stress range of 245 to 345 MPa. The coating treatment resulted in a significant decrease in rupture lives for both the directionally and conventionally solidified materials. No reductions in rupture ductilities were observed. The activation energy for creep in the temperature range of 870℃ to 910℃ at 245 MPa was approximately 300 KJ/mole, which was comparable to the measured activation energy for Oswald ripening of the gamma prime precipitates. The influence of the hot corrosion due to a 75 wt% $Na_2SO_4-25wt%$ NaCl coating on the creep properties of coated/uncoated conventionally solidified alloy was also evaluated. For the uncoated alloy, creep crackings were initiated at the oxidized surfaces, while for the coated alloy, the creep cracks were nucleated at grain boundaries in the subcoated layer beneath the coating/substrate interfacial zone. In the coated condition, there were two mechanisms of creep crack initiations with varying applied stress and temperature ranges. At the higher stresses and/or lower temperatures, creep fractures were essentially controlled by the crack nuclei in the coated layer. A number of coating surface cracks occurred during the creep tests, due to the high hardness of the diffusion zone in the coated layer. The formation of the sharp microcracks in the coated layer was attributed to the higher hardness of the diffusion zone relative to the substrate. Elimination of transverse grain boundaries by directional solidification did not have any advantage in extending the rupture life of the directionally solidified material over that of conventionally cast material after the coating treatment. At the lower stresses and/or higher temperatures, the subcoat cavities provided large subsurface defects. Under the applied stress, the ductile coating layer flew readily into the windening crack, allowing the development of high local stress at the crack tip, resulting in the further cracking along the grain boundary. This mechanism may explain the result of improved creep life obtained at 982℃/156.9 MPa$ under the conditions of the hot corrosion by a 75wt% $Na_2SO_4-25wt%$ NaCl. The effect of stress aging on the creep rupture properties and microstructure under the condition of 982℃/156.9 MPa was studied with and without an isothermal aging at 982℃. The creep rupture life decreased drastically due to the degeneration of gamma prime precipitates and cavitation along grain boundaries. It was found that the deteriorated creep strength could be restored by applying the regenerative heat treatment.

서지기타정보

서지기타정보
청구기호 {DMS 8607
형태사항 [vi], 153 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Suck-Bong Kang
지도교수의 한글표기 : 김영길
지도교수의 영문표기 : Young-Gil Kim
학위논문 학위논문(박사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 : p. 145-153
주제 Creep.
Microstructure.
Alumium coatings.
Metals --Mechanical properties.
기계적 성질. --과학기술용어시소러스
미세 조직. --과학기술용어시소러스
크리프. --과학기술용어시소러스
초내열 합금. --과학기술용어시소러스
Heat resistant alloys.
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