표제지
목차
Abstract 7
제1장 서론 18
제2장 이론적 배경 21
2.1. 내열강 21
2.1.1. Heat-resistant ferritic steel 21
2.1.2. Heat-resistant austenitic steels 22
2.2. 고온열화(high temperature degradation) 26
2.2.1. 크립 26
2.2.2. 열화에 따른 오스테나이트 스테인리스강의 석출 29
2.2.3. Larson Miller Parameter(LMP) 32
2.2.4. 석출경화(precipitation hardening) 34
2.3. 고온산화(high temperature oxidation) 37
2.3.1. 금속산화물의 형성 37
2.3.2. 엘링감 도표 39
2.3.3. 산화 속도론 41
2.4. 황화 부식(sulfidation corrosion) 47
2.4.1. 고온 황화 부식(high temperature sulfidation corrosion) 47
2.4.2. 합금원소의 효과(effect of the alloy elements) 48
제3장 실험방법 50
3.1. 시험편 및 시험 조건 선정 50
3.1.1. 시험편 선정 50
3.1.2. 연소가스 선정 53
3.2. 강도저하 평가 56
3.2.1. 열화 시험편 제작(대기 분위기) 56
3.2.2. 부식 시험편 제작(연소가스 분위기) 56
3.2.3. 미세조직 관찰 59
3.2.4. 인장시험 59
3.2.5. 경도측정 60
3.2.6. 파단면 관찰 60
3.3. 고온부식 특성 평가 65
3.3.1. 시험편 전처리 65
3.3.2. 부식특성 평가 65
제4장 실험 결과 및 고찰 66
4.1. 열화 전 내열강의 강도 평가 66
4.2. 온도 변수에 따른 9Cr-1MoVNb 강의 산화 특성 평가 71
4.3. 온도 변수에 따른 9Cr-1MoVNb 강의 강도 저하 특성 평가 82
4.4. 열화 분위기에 따른 9Cr-1MoVNb의 부식 및 강도 저하 특성 평가 112
4.5. 열화 온도에 따른 AISI 304의 산화 특성 평가 124
4.6. 열화 온도에 따른 AISI 304의 강도 저하 특성 평가 134
4.7. 열화 분위기에 따른 AISI 304의 강도 저하 특성 평가 162
4.8. 열화 온도에 따른 Inconel 600의 산화 특성 평가 174
4.9. 열화 온도에 따른 Inconel 600의 강도 저하 특성 평가 184
4.10. 열화 분위기에 따른 Inconel 600의 부식 및 강도 저하 특성 평가 211
제5장 결론 223
참고문헌 226
Table 3.2.1. Estimation of the serviced time at 550 ℃ with accelerated... 58
Table 3.2.2. Etchant for each material 61
Table 4.1.1. Vickers hardness of each material deteriorated at 550 ℃ and... 69
Fig. 2.1.1. Schematic diagram of (a) the typical microstructure of the... 24
Fig. 2.1.2. General concept of alloy design for austenitic heat resistant... 25
Fig. 2.2.1. Tensile strength with temperature for various superalloy 27
Fig. 2.2.2. A typical creep curve 28
Fig. 2.2.3. Schematic representation of carbide precipitation at a grain... 31
Fig. 2.2.4. Time- Temperature- Transformation diagram of AISI 316L 33
Fig. 2.2.5. Representation of a dislocation bypassing particles 35
Fig. 2.3.1. The initial formation of an oxide scale by adsorption of oxygen,... 38
Fig. 2.3.2. Ellingham diagram showing free energies of formation for selected... 40
Fig, 2.3.3. Different oxidation kinetics 42
Fig. 2.3.4. Typical weight gain curve for high temperature alloys suffering... 46
Fig. 3.1.1. Microstructure(a), chemical composition(b), and mechanical... 51
Fig. 3.1.2. Microstructure(a), chemical composition(b), and mechanical... 54
Fig. 3.1.3. Microstructure(a), chemical composition(b), and mechanical... 55
Fig. 3.2.1. Photograph of the electric furnace for high- temperature corrosion 57
Fig. 3.2.2. Schematic diagram of the tensile test specimen 62
Fig. 3.2.3. Photograph of tensile tester 63
Fig. 3.2.4. Photograph of Vivkers hardness instrument 64
Fig. 4.1.1. Stress- strain curves of each material 67
Fig. 4.1.2. Fractography of the each material 70
Fig. 4.2.1. Weight gain of the isothermally oxidized 9Cr- 1MoVNb at 550 and... 72
Fig. 4.2.2. Surface morphologies of the isothermally oxidized 9Cr- 1MoVNb at... 74
Fig. 4.2.3. Surface morphologies of the isothermally oxidized 9Cr- 1MoVNb at... 77
Fig. 4.2.4. XRD diffraction pattern of the isothermally oxidized 9Cr- 1MoVNb... 78
Fig. 4.2.5. (a) SEM image of the surface of oxidized 9Cr- 1MoVNb at 650 ℃... 79
Fig. 4.3.1. Analysis of microstructure for 9Cr- 1MoVNb deteriorated at 650 ℃... 84
Fig. 4.3.2. Analysis of microstructure for 9Cr- 1MoVNb deteriorated at 650 ℃ 86
Fig. 4.3.3. Spot EDS analysis for carbide of 9Cr- 1MoVNb deteriorated at 650 ℃... 88
Fig. 4.3.4. Vickers hardness of 9Cr- 1MoVNb deteriorated at 550 and 650 ℃... 89
Fig. 4.3.5. Stress- strain curves of 9Cr- 1MoVNb deteriorated at 650 ℃ with... 91
Fig. 4.3.6. Detailed mechanical property of 9Cr- 1MoVNb deteriorated at 550 ℃... 93
Fig. 4.3.7. Stress- strain curves of 9Cr- 1MoVNb deteriorated at 650 ℃ with... 95
Fig. 4.3.8. Detailed mechanical property of 9Cr- 1MoVNb deteriorated at 650 ℃... 97
Fig. 4.3.9. Comparison of tensile strength change rate of 9Cr- 1MoVNb with... 98
Fig. 4.3.10. Comparison of yield strength change rate of 9Cr- 1MoVNb with... 100
Fig. 4.3.11. Comparison of elongation change rate of 9Cr- 1MoVNb with... 101
Fig. 4.3.12. Fractography of 9Cr- 1MoVNb deteriorated at 550 ℃ with time 103
Fig. 4.3.13. Fractography of 9Cr- 1MoVNb deteriorated at 650 ℃ with time 106
Fig. 4.3.14. Microstructure of fracture plane 9Cr- 1MoVNb deteriorated at 650 ℃ 107
Fig. 4.3.15. Spot EDS analysis for second phase at fracture plane of... 108
Fig. 4.4.1. Weight gain of the 9Cr- 1MoVNb corroded at SO₂ gas condition... 113
Fig. 4.4.2. Surface morphologies of the isothermally 9Cr- 1MoVNb corroded at... 114
Fig. 4.4.3. EDS mapping analysis for 9Cr- 1MoVNb corroded at SO₂ gas... 115
Fig. 4.4.4. Stress- strain curves of 9Cr- 1MoVNb deteriorated at 650 ℃ - SO₂... 117
Fig. 4.4.5. Detailed mechanical property of 9Cr- 1MoVNb deteriorated at 650 ℃... 119
Fig. 4.4.6. Fractography of 9Cr- 1MoVNb deteriorated at 650 ℃ - SO2 gas with... 122
Fig. 4.5.1. Weight gain of the isotermally oxidized AISI 304 at 550 and 650 ℃ 125
Fig. 4.5.2. Surface morphologies of the isothermally oxidized AISI 304 at 550 ℃ 127
Fig. 4.5.3. Surface morphologies of the isothermally oxidized AISI 304 at... 130
Fig. 4.5.4. XRD diffraction pattern of the isothermally oxidized AISI 304 at... 131
Fig. 4.5.5. (a) SEM image of the surface of oxidized AISI 304 at 650 ℃... 132
Fig. 4.6.1. Microstructure of AISI 304 deteriorated at 650 ℃... 136
Fig. 4.6.2. Microstructure of AISI 304 deteriorated at 650 ℃... 138
Fig. 4.6.3. EDS spot analysis of AISI 304 deteriorated 650 ℃ during 1,000... 140
Fig. 4.6.4. Vickers hardness of AISI 304 deteriorated at 550 ℃ and 650 ℃... 141
Fig. 4.6.5. Stress- strain curves of AISI 304 deteriorated at 550 ℃ with time 142
Fig. 4.6.6. Detailed mechanical property of AISI 304 deteriorated at 550 ℃... 144
Fig. 4.6.7. Stress- strain curves of AISI 304 deteriorated at 650 ℃ with time 145
Fig. 4.6.8. Detailed mechanical property of AISI 304 deteriorated at 650 ℃... 149
Fig. 4.6.9. Comparison of tensile strength change rate of AISI 304 with... 150
Fig. 4.6.10. Comparison of yield strength change rate of AISI 304 with... 152
Fig. 4.6.11. Comparison of elongation change rate of AISI 304 with... 153
Fig. 4.6.12. Fractography of AISI 304 deteriorated at 550 ℃ with time 156
Fig. 4.6.13 .Fractography of AISI 304 deteriorated at 650 ℃ with time 159
Fig. 4.7.1. Weight gain of the isothermally AISI 304 corroded under SO₂ gas... 163
Fig. 4.7.2. Surface morphologies of the AISI 304 corroded at SO₂ gas... 164
Fig. 4.7.3. EDS mapping analysis for AISI 304 corroded at SO₂ gas... 165
Fig. 4.7.4. Stress- strain curves of AISI 304 deteriorated at 650 ℃- SO₂ gas... 168
Fig. 4.7.5. Detailed mechanical property of AISI 304 deteriorated at 650 ℃ -... 170
Fig. 4.7.6. Fractography of AISI 304 deteriorated at 650 ℃ - SO₂ gas with... 172
Fig. 4.8.1. Weight gain of the isotermally oxidized Inconel 600 at 550 and... 175
Fig. 4.8.2. Surface morphologies of the isothermally oxidized Inconel 600 at... 177
Fig. 4.8.3. Surface morphologies of the isothermally oxidized Inconel 600 at... 179
Fig. 4.8.4. XRD diffraction pattern of the isothermally oxidized Inconel 600 at... 181
Fig. 4.8.5. (a) SEM image of the surface of oxidized Inconel 600 at 650 ℃... 182
Fig. 4.9.1. Analysis of microstructure for Inconel 600 deteriorated at 650 ℃... 186
Fig. 4.9.2. Microstructure of AISI 304 deteriorated at 650 188
Fig. 4.9.3. EDS mapping analysis for Inconel 600 deteriorated at 650 ℃... 190
Fig. 4.9.4. Vickers hardness of Inconel 600 deteriorated at 550 and 650 ℃... 191
Fig. 4.9.5. Stress- strain curves of Inconel 600 deteriorated at 550 ℃ with... 192
Fig. 4.9.6. Detailed mechanical property of Inconel 600 deteriorated at 550 ℃... 194
Fig. 4.9.7. Stress- strain curves of Inconel 600 deteriorated at 650 ℃ with... 196
Fig. 4.9.8. Detailed mechanical property of Inconel 600 deteriorated at 650... 198
Fig. 4.9.9. Comparison of tensile strength change rate of Inconel 600 with... 200
Fig. 4.9.10. Comparison of yield strength change rate of Inconel 600 with... 202
Fig. 4.9.11. Comparison of elongation change rate of Inconel 600 with... 203
Fig. 4.9.12. Fractography of Inconel 600 deteriorated at 550 ℃ with time 206
Fig. 4.9.13. Fractography of Inconel 600 deteriorated at 650 ℃ with time 208
Fig. 4.10.1. Weight gain of the isothermally Inconel 600 corroded at SO₂... 212
Fig. 4.10.2. Surface morphologies of the Inconel 600 corroded at SO₂ gas... 213
Fig. 4.10.3. EDS mapping analysis for 9Cr- 1MoVNb corroded at SO₂ gas... 214
Fig. 4.10.4. Stress- strain curves of Inconel 600 deteriorated at 650 ℃ - SO₂... 216
Fig. 4.10.5. Detailed mechanical property of Inconel 600 deteriorated at 650 ℃... 218
Fig. 4.10.6. Fractography of Inconel 600 deteriorated at 650 ℃ - SO₂ gas... 220