Defect Formation During High Power Laser Welding of a Creep Resistant Nickel Alloy- [electronic resource]
Defect Formation During High Power Laser Welding of a Creep Resistant Nickel Alloy- [electronic resource]
- 자료유형
- 학위논문파일 국외
- 최종처리일시
- 20240214101930
- ISBN
- 9798380735599
- DDC
- 621
- 저자명
- Gao, Mingze.
- 서명/저자
- Defect Formation During High Power Laser Welding of a Creep Resistant Nickel Alloy - [electronic resource]
- 발행사항
- [S.l.]: : The Pennsylvania State University., 2023
- 발행사항
- Ann Arbor : : ProQuest Dissertations & Theses,, 2023
- 형태사항
- 1 online resource(191 p.)
- 주기사항
- Source: Dissertations Abstracts International, Volume: 85-05, Section: B.
- 주기사항
- Advisor: Debroy, Tarasankar;Palmer, Todd A.
- 학위논문주기
- Thesis (Ph.D.)--The Pennsylvania State University, 2023.
- 사용제한주기
- This item must not be sold to any third party vendors.
- 초록/해제
- 요약High power laser welding, with powers on the order of 10 kW, represents an attractive pathway for improving productivity in the single pass joining of thick section structures. During high power laser welding of Inconel 740H, a candidate material for the steam pipes in advanced ultra supercritical power plants, defects were observed, including keyhole collapse porosity, liquation cracking in the heat affected zone, and solidification cracking in the fusion zone, which displayed variations with processing conditions. Although liquation cracks and keyhole porosity were observed for all these high power laser welding conditions due to the high heat input and keyhole instability, horizontal solidification cracks across the fusion zones were observed at depths of around 70% to 80% of the weld depths, while the same material does not display similar solidification cracking during arc welding and low power laser welding conditions. A similar crack was not observed in another nickel alloy, Inconel 690, under the same welding conditions.To capture the complex interactions between alloy composition and processing conditions leading to the appearance of these cracks, well-tested heat transfer and fluid flow and thermomechanical models were integrated to calculate temperature histories, solidification conditions, and the resulting stresses and strain rates across the solidifying mushy zone. The coupling of these powerful models provided a means for evaluating horizontal solidification cracking susceptibility and predicting crack locations by identifying the simultaneous appearance of critical strain rate and tensile stress levels across different processing conditions and alloys.Since alloy composition is usually fixed within a specified range, the prevention of these defects requires tight control of the processing conditions. Wobble head laser welding, as an emerging tool in high power laser welding, was employed, which provides new opportunities to alter process conditions and produce defect free welds. Due to the additional transverse and backward motions with the laser beam oscillation, the laser energy density distribution across the weldment was altered, leading to variations in weld pool dimensions, solidification conditions, and stress state across the welds. The application of beam oscillation led to shorter, wider, and shallower weld pools. Due to these changes in weld profiles, the solidification rate was reduced while the temperature gradient was increased compared with the linear welds. These changes in the process conditions also impacted the stress state, which provide opportunities to prevent solidification cracking during high power laser welding process.
- 일반주제명
- Heat transfer.
- 일반주제명
- Solidification.
- 일반주제명
- Single crystals.
- 일반주제명
- Lasers.
- 일반주제명
- Grain boundaries.
- 일반주제명
- Nickel alloys.
- 일반주제명
- Aluminum alloys.
- 일반주제명
- Pressure distribution.
- 일반주제명
- Energy.
- 일반주제명
- Cracks.
- 일반주제명
- Alloys.
- 일반주제명
- Geometry.
- 일반주제명
- Morphology.
- 일반주제명
- Solids.
- 일반주제명
- Materials science.
- 키워드
- Laser welding
- 키워드
- Keyhole porosity
- 키워드
- Nickel alloy
- 기본자료저록
- Dissertations Abstracts International. 85-05B.
- 기본자료저록
- Dissertation Abstract International
- 전자적 위치 및 접속
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