초록 ▼

합금설계
○ 선행기술조사(국내외 특허 732건 상세분석)
○ 열역학, 실험계획법 기반 합금설계
-TCP 상 0.1% 이하
-Cr, Co, Mo, Ta, Zr, Hf, W 합금원소 영향 고려하여 설계
-특허 분석결과 고려

모델합금 제조
○ 용해기술 분석 및 선정
-VIM 이용 50kg 급 용해
○ 모델합금 용해 및 제조
-Cr 22, Co 11.5, Mo 10, C 0.08, B 0.003, Mn 0.1 합금 제조
-압연, 열처리 조건 등 기본 제조조건 확립
○

합금설계
○ 선행기술조사(국내외 특허 732건 상세분석)
○ 열역학, 실험계획법 기반 합금설계
-TCP 상 0.1% 이하
-Cr, Co, Mo, Ta, Zr, Hf, W 합금원소 영향 고려하여 설계
-특허 분석결과 고려

모델합금 제조
○ 용해기술 분석 및 선정
-VIM 이용 50kg 급 용해
○ 모델합금 용해 및 제조
-Cr 22, Co 11.5, Mo 10, C 0.08, B 0.003, Mn 0.1 합금 제조
-압연, 열처리 조건 등 기본 제조조건 확립
○ 성분분석
-합금에 대해 35군데 성분분석을 통한 조성균일성과 0.5%p 정확성 검증

합금원소 영향평가
○ 기계적 특성평가
-입계강화제, Cr, Co, Mo 함량에 따른 합금제조
-상온, 950oC 인장시험 및 분석
○ 단기고온특성평가
-제조된 합금에 대해 950oC, 공기중 환경에서 부식시험 및 결과분석
○ 미세조직 분석
-광학, SEM, TEM 이용한 미세조직 분석

제조공정 영향평가
○ 공정조건에 따른 기계적 특성평가(고온 강도, 연신특성)
-탄화물 안정 온도영역 도출
-열처리 조건에 따른 기계적 특성평가
○ 단기고온특성평가
-열처리 적용 합금에 대한 부식시험

초고온환경 특성평가
○ 초고온로 환경 부식특성평가
-초고온로 냉각재 환경을 모사한 조건에서 합금조성, 제조조건에 따른 부식시험 및 분석
○ 단기 크리프 특성평가
-30MPa, 950oC 조건에서 합금조성, 제조조건에 따른 크리프 평가 및 분석

초고온 환경저항성 니켈-크롬계 합금 요소기술 개발
○ 합금원소 및 제조공정과 합금특성 상관관계 분석
-실험계획법을 이용한 결과의 통계적 분석, 상관관계 분석
○ 후보모델 합금 도출
-인장특성, 크리프 특성, 부식특성의 입체적 분석
-최적의 후보모델합금 도출과 방향성 제시

Abstract ▼

IV. Results of the Project
1. Alloy design
A. Survey of previous patents
The 732 domestic and international patents were investigated for overview of chemical composition and post processing for nickel based alloy and to decide direction to alloy development. State of the art of commercial

IV. Results of the Project
1. Alloy design
A. Survey of previous patents
The 732 domestic and international patents were investigated for overview of chemical composition and post processing for nickel based alloy and to decide direction to alloy development. State of the art of commercial alloy at 950oC was surveyed.

B. Thermodynamics and design of experiment based alloy design
Analysis of thermodynamically stable phase and its equilibrium fraction at 900 and 950oC was carried out as a function of the alloying element. Alloy design was tried based on design of experiment using the analyzed thermodynamic equilibrium phase fraction results.

2. Model alloy manufacturing
A. Melting technology analysis and selection
Through considering various melting techniques, VIM (vacuum induction melting) was selected as melting technique useful for laboratory scale wrought alloy melting.

B. Model alloy melting and manufacturing
Ni based alloy (Cr 22, Co 11.5, Mo 10, C 0.08) was melted. Basic processing parameter was determined through tensile test at room temperature and 950oC and microstructure analysis as a function of the hot rolling temperature, reheat number and cooling method. This was performed using design of experiment. Solution annealing temperature and additional heat treatment effect was investigated through mechanical property and microstructure analysis.

C. Composition analysis
Chemical comosition was analyzed using ICP (inductively coupled plasma) for 35 points per 1 alloy. Target composition could be controlled to 0.5%p difference. Harmful elements such as S and P could be controlled to 10ppm.

3. Alloy assessment with alloying element
A. Assessment of mechanical property
Alloys adding Zr and Hf as alloying elements which are known as grain boundary strengthener and with various Cr, Mo and Co contents were fabricated. Tensile test were performed at room temperature and 950oC. Elongation to rupture, yield strength and tensile strength were compared.

B. Assessment of short term high temperature property
Alloys with various Cr, Mo and Co contents were tested at 950oC up to 250hr in air. Corrosion property was analyzed through weight gain method and microstructure analysis.

C. Microstructure analysis
Microstructure of alloys were investigated using optical microscope, SEM (scanning electron microscope) and TEM (transmission electron microscope) as a function of the alloying elements. By comparing tensile test results, effect of alloying element on mechanical property was analyzed.

4. Alloy assessment with process variable
A. Assessment of mechanical property with process variable
Precipitate distribution and high temperature tensile property was investigated as a function of the additional heat treatment in the range of 1020 ∼1140oC. Optimum heat treatment condition was determined. Additional heat treatment effect on tensile property and microstructure was evaluated for alloys with various Cr, Mo and Co contents. Tensile property can be controlled varying heat treatment condition and alloying elements. Precipitate distribution was investigated as a function of the alloying element. Serrated boundary for grain boundary strengthening and then high temperature tensile property improvement was suggested and controlled.

B. Assessment of short tem high temperature property
Corrosion property was assessed for alloys with/without additional heat treatment. Corrosion property was analyzed through weight gain method and microstructure analysis. Way to improve corrosion property was deduced.

5. Alloy assessment in very high temperature environment
A. Corrosion property under VHTR environment
Corrosion test for alloys with various alloying elements were performed in impure helium ambient as well as air at 950oC considering VHTR environment. Effect of heat treatment on corrosion property was also viewed. Corrosion property was analyzed through weight gain method and microstructure analysis. Corrosion property was compared with that of Alloy 617.

B. Assessment of short term creep property
Creep property was investigated at 30MPa, 950oC as a function of the alloying element and post processing parameter such as additional heat treatment. Creep properties of laboratory made alloys were compared with that of Alloy 617.

6. Development of essential technology of nickel-chrome model alloy for very high temperature reactor
A. Relation analysis of alloy property as a function of alloying element and processing parameter
Tensile property, corrosion property and creep property were investigated as a function of the alloying element (Cr, Co, Mo, Zr, Hf, Ta, W, Al, Ti), processing parameter (heat treatment temperature, time, cooling rate). Using testing results, multi-dimensional analyses based on design of experiment were performed in view of yield strength, tensile strength, elongation to rupture, weight gain, surface oxide, internal oxide, carbide depleted layer, creep rate, creep strain and creep strength.

B. Suggestion of potential model alloy
Optimum potential model alloy was suggested considering tensile property, corrosion property and creep property. Direction to alloy development beyond commercial alloy such as Alloy 617 was mentioned.

목차 Contents

• 표 지 ... 1
• 제 출 문 ... 2
• 보고서 요약서 ... 3
• 요 약 문 ... 5
• SUMMARY ... 10
• CONTENTS ... 15
• 목 차 ... 17
• List of Tables ... 19
• List of Figures ... 20
• 제 1 장 연구개발 과제의 개요 ... 23
• 제 2 장 국내외 기술개발 현황 ... 24
• 제 1 절 합금설계 ... 24
• 제 2 절 모델합금제조 ... 24
• 제 3 절 합금원소 영향평가 ... 25
• 제 4 절 제조공정 영향평가 ... 25
• 제 5 절 초고온환경특성평가 ... 26
• 제 6 절 초고온환경저항성 니켈-크롬계 합금요소기술개발 ... 27
• 제 3 장 연구개발 수행내용 및 결과 ... 28
• 제 1 절 합금설계 ... 28
• 1. 선행기술조사 ... 28
• 2. 열역학, 실험계획법 기반 합금설계 ... 31
• 제 2 절 모델합금제조 ... 35
• 1. 용해기술 분석 및 선정 ... 35
• 2. 모델합금 용해 및 제조 ... 35
• 3. 성분분석 ... 44
• 제 3 절 합금원소 영향평가 ... 45
• 1. 기계적 특성평가 ... 45
• 2. 단기고온특성평가 ... 50
• 3. 미세조직 분석 ... 53
• 제 4 절 제조공정 영향평가 ... 70
• 1. 공정조건에 따른 기계적 특성평가 ... 70
• 2. 단기고온특성평가 ... 75
• 제 5 절 초고온환경 특성평가 ... 77
• 1. 초고온로 환경 부식특성평가 ... 77
• 2. 단기 크리프 특성 평가 ... 79
• 제 6 절 초고온환경 저항성 니켈-크롬계 합금요소기술개발 ... 96
• 1. 합금원소 및 제조공정과 합금특성 상관관계 분석 ... 96
• 2. 후보모델 합금 도출 ... 102
• 제 4 장 목표 달성도 및 관련 분야에의 기여도 ... 104
• 제 5 장 연구개발결과의 활용계획 ... 107
• 제 6 장 연구개발과정에서 수집한 해외과학기술정보 ... 108
• 제 7 장 연구시설∙장비 현황 ... 108
• 제 8 장 참고문헌 ... 109
• 끝페이지 ... 113