MEMOIRS OF SHONAN INSTITUTE OF TECHNOLOGY Vol. 41, No. 1, 2007 * Effects of Element Additions on High-Temperature Corrosion of Heat-Resisting Alloys Tadaaki AMANO* Adherence of oxide scale formed on Fe 20Cr 4Al (Standard: 4 ppm S), Fe 20Cr 4Al (FZ: 1 ppm S) purified by floating zone melting, Fe 20Cr 4Al (0.05, 0.1, 0.3, 0.5)Pd(Pt) and Fe 20Cr 4Al (0.01 0.5)Y alloys was studied in oxygen for 18 ks at 1373 1673 K, by mass gain measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Spalling of oxide scale on the standard alloy occurred along the alloy grain boundaries after oxidation at 1373 K, and was found to spall over the entire surface after oxidation at 1473 and 1573 K. However, the standard alloy showed good oxide adherence after oxidation at 1673 K. Mass gains of all the alloys, except Y-containing alloys, showed almost the same values, however, those of Y-containing alloys decreased with increasing yttrium up to 0.1%, and then increased with increasing yttrium content after oxidation for 18 ks at 1473 K. High-temperature corrosion behavior of Fe 20Cr 4Al, Fe 20Cr 4Al (FZ) and Fe 20Cr 4Al X (X 0.5Pd, 0.5Pt, 0.5Au, 0.1Lu) alloys was studied in an oxygen-water vapor (dew point: 313 K) environment for 18 ks at 1473, 1573 and 1673 K. FZ, 0.5Pd, 0.5Pt and 0.1Lu alloys showed good oxide adherence. After oxidation at 1673 K, the mass gain of 0.5Pt alloy showed the smallest value compared with those of the other alloys. This result suggested that 0.5Pt alloy has an outstanding corrosion resistance in an water-vapor environment. 1 1273 K * 18 10 16 1) 2) 3) 4) Y 2 50 g 4 ppm Fe 20Cr 4Al FZ Pd, Pt, Au, Lu Y Pt Y 0.5 mm 0.5 10 20 mm 3 (#1500) 5 5 0.5 mm 3 63
41 1 Table 1. Chemical composition of alloys (mass%). Alloy Fe Cr Al S Pd Pt Fe 20Cr 4Al (Standard) Bal. 20 4 0.0004 Fe 20Cr 4Al (FZ) Bal. 20 4 0.0001 Fe 20Cr 4Al 0.05Pd Bal. 20 4 0.0001 0.049 Fe 20Cr 4Al 0.1Pd Bal. 20 4 0.0001 0.099 Fe 20Cr 4Al 0.3Pd Bal. 20 4 0.0001 0.299 Fe 20Cr 4Al 0.5Pd Bal. 20 4 0.0001 0.498 Fe 20Cr 4Al 0.05Pt Bal. 20 4 0.0001 0.050 Fe 20Cr 4Al 0.1Pt Bal. 20 4 0.0001 0.100 Fe 20Cr 4Al 0.3Pt Bal. 20 4 0.0001 0.300 Fe 20Cr 4Al 0.5Pt Bal. 20 4 0.0001 0.499 (3 mm) X SEM EPMA 3 FeCrAl(Pd, Pt) 3.1 Table 1 1373, 1473, 1573 1673 K 18 ks 3.2 3.2.1 Fig. 1 1373, 1473, 1573 1673 K 18 ks Standard, FZ Pd Pt Standard Standard 1473 1573 K 3.2.2 Fig. 2 Standard 1473 1573 K Fig. 1. Mass change of Fe 20Cr 4Al (Standard, FZ, Pd, Pt) alloys exposed to oxygen for 18 ks at 1373, 1473, 1573 and 1673 K; (a) Standard, (b) FZ, (c) 0.05Pd, (d) 0.1Pd, (e) 0.3Pd, (f) 0.5Pd, (g) 0.05Pt, (h) 0.1Pt, (i) 0.3Pt, (j) 0.5Pt. Table 1 Standard 4 ppm FZ H 2 H 2 S (Pd, Pt) SO SO 2 Standard 64
Fig. 2. Surface appearance of Fe 20Cr 4Al (Standard, FZ, Pd, Pt) alloys exposed to oxygen for 18 ks at 1373, 1473, 1573 and 1673 K; (a) Standard, (b) FZ, (c) 0.05Pd, (d) 0.1Pd, (e) 0.3Pd, (f) 0.5Pd, (g) 0.05Pt, (h) 0.1Pt, (i) 0.3Pt, (j) 0.5Pt. Fig. 3. SEM micrographs of oxide scale on Fe 20Cr 4Al (Standard, FZ, Pd, Pt) alloys exposed to oxygen for 18 ks at 1373 K. Fig. 4. SEM micrographs of oxide scale on Fe 20Cr 4Al (Standard) alloy exposed to oxygen for 18 ks at 1373 K. 1673 K 1673 K X a-al 2 O 3 3.2.3 SEM Fig. 3 1373 K Standard Fig. 4 Standard 1373 K Fig. 5 1373 K Fig. 5. SEM micrographs of oxide scale on Fe 20Cr 4Al (Pt, Pd) alloys exposed to oxygen for 18 ks at 1373 K; (a) 0.05Pd, (b) 0.3Pt. 0.05Pd 0.3Pt 1673 K standard FZ 90 Fig. 65
41 1 Fig. 6. SEM micrographs of spalled area of the alloy surface after bending test of (a) Fe 20Cr 4Al (Standard) and (b) Fe 20Cr 4Al (FZ) alloys exposed to oxygen for 18 ks at 1673 K. 6 Standard FZ Table 2 Standard, FZ Pd Pt 3.3 Fe 20Cr 4Al Fe 20Cr 4Al Pd Pt 1373, 1473, 1573 1673 K 18 ks Table 2. Summary of scale feature on Fe 20Cr 4Al (Standard, FZ, Pd, Pt) alloys exposed to oxygen for 18 ks at 1373, 1473, 1573 and 1673 K. Alloy Temperature (K) 1373 1473 1573 1673 Fe 20Cr 4Al (Standard) partially saplled wrinkled entirely saplled wrinkled, cavities entirely spalled planar, reticular, cavities no spalled planar, reticular Fe 20Cr 4Al (FZ) slightly spalled slightly spalled slightly spalled no spalled slightly wrinkled planar planar, reticular planar, reticular Fe 20Cr 4Al 0.05Pd no spalled slightly spalled slightly spalled no spalled slightly wrinkled slightly wrinkled planar, reticular planar, reticular Fe 20Cr 4Al 0.1Pd no spalled slightly spalled slightly spalled no spalled slightly wrinkled planar planar, reticular planar, reticular Fe 20Cr 4Al 0.3Pd slightly spalled slightly spalled slightly spalled no spalled slightly wrinkled planar planar, reticular planar, reticular Fe 20Cr 4Al 0.5Pd slightly spalled slightly spalled slightly spalled no spalled slightly wrinkled planar planar, reticular planar, reticular Fe 20Cr 4Al 0.05Pt slightly spalled slightly spalled no spalled no spalled slightly wrinkled slightly wrinkled planar, reticular planar, reticular Fe 20Cr 4Al 0.1Pt no spalled slighly spalled no spalled no spalled slightly wrinkled planar planar, reticular planar, reticular Fe 20Cr 4Al 0.3Pt slightly spalled slightly spalled no spalled nospalled planar planar planar, reticular planar, reticular Fe 20Cr 4Al 0.5Pt slightly spalled slightly spalled slightly spalled no spalled planar planar planar, reticular planar, reticular 66
Table 3. Chemical composition of alloys (mass%). Alloy Fe Cr Al S Pd Pt Y Fe 20Cr 4Al (Standard) Bal. 20 4 0.0004 Fe 20Cr 4Al (FZ) Bal. 20 4 0.0001 Fe 20Cr 4Al 0.5Pd Bal. 20 4 0.0001 0.498 Fe 20Cr 4Al 0.5Pt Bal. 20 4 0.0001 0.499 Fe 20Cr 4Al 0.01Y Bal. 20 4 0.0001 0.0001 Fe 20Cr 4Al 0.02Y Bal. 20 4 0.0001 0.0002 Fe 20Cr 4Al 0.05Y Bal. 20 4 0.0001 0.0023 Fe 20Cr 4Al 0.1Y Bal. 20 4 0.0001 0.0382 Fe 20Cr 4Al 0.2Y Bal. 20 4 0.0001 0.0980 Fe 20Cr 4Al 0.5Y Bal. 20 4 0.0001 0.3449 1 Fe 20Cr 4Al (4 ppm) 1373 K 1473 1573 K 1673 K 2 1373, 1473 1573 K 3 1673 K Standard FZ FZ Standard FZ 4 FeCrAl(Pd, Pt, Y) 4.1 1273 K a- 1) 12) 13) 23) 2) 4),7),11),17) 23) (Pd, Rh, Pt) 24) 27) FeCrAl (Standard, FZ, Pd, Pt, Y) 1273 1673 K 0.6 18 ks 4.2 Table 3 1473 K 18 ks SEM 1273 K 7.2 18 ks 1373 K 1.8 18 ks 1473 K 0.6, 7.2 18 ks 1573 K 1.8 7.2 ks 1673 K 18 ks 4.3 4.3.1 Fig. 7 FeCrAl (Standard, FZ, 0.5Pd, 0.5Pt) 1473 K, 18 ks 0.50 0.52 10 2 kg/m 2 Pd Pt Standard Standard 67
41 1 Fig. 7. Mass gain of Fe 20Cr 4Al (Standard, FZ, 0.5Pd, 0.5Pt) alloys exposed to oxygen for 18 ks at 1473 K. Fig. 9. Surface appearance of Fe 20Cr 4Al (Standard, FZ, 0.5Pd, 0.5Pt, 0.01 0.5Y) alloys exposed to oxygen for 18 ks at 1473 K; (a) Standard, (b) FZ, (c) 0.5Pd, (d) 0.5Pt, (e) 0.01Y, (f) 0.02Y, (g) 0.05Y, (h) 0.1Y, (j) 0.5Y. Table 4. Oxides determined by X-ray diffraction of Fe 20Cr 4Al (Standard, FZ, 0.5Pd, 0.5Pt, 0.01 0.5Y) alloys exposed to oxygen for 18 ks at 1473 K. Alloy Oxides Fig. 8. Mass gain of Fe 20Cr 4Al (0.01 0.5Y) alloys exposed to oxygen for 18 ks at 1473 K. Fig. 8 FeCrAl Y 1473 K, 18 ks Standard 0.1Y Y Y 4.3.2 Fig. 9 FeCrAl (Standard, FZ, 0.5Pd, 0.5Pt, 0.01 0.5Y) 1473 K, 18 ks Standard, FZ, 0.5Pd 0.5Pt Standard FZ, 0.5Pd 0.5Pt Y 0.01Y Table 3 FCA a-al 2 O 3 (w) FZ a-al 2 O 3 (s) 0.5Pd a-al 2 O 3 (s) 0.5Pt a-al 2 O 3 (s) 0.01Y a-al 2 O 3 (s) 0.05Y a-al 2 O 3 (s) 0.1Y a-al 2 O 3 (s) 0.2Y a-al 2 O 3 (s) Y 3 Al 5 O 12 (vw) 0.5Y a-al 2 O 3 (s) Y 3 Al 5 O 12 (w) s: strong, w: weak, vw: very weak. Standard 4 ppm Standard Y Y, 0.5Pd brown, 0.1Y, 0.2Y 0.5Y glossy gray gray Table 4 FeCrAl (Standard, FZ, 0.5Pd, 0.5Pt, 0.01Y 0.5Y) 1473 K, 18 ks 68
Fig. 10. SEM micrographs of oxide scale on Fe 20Cr 4Al (Standard, FZ, 0.5Pd, 0.5Pt, 0.01 0.5Y) alloys exposed to oxygen for 18 ks at 1473 K; (a) Standard, (b) FZ, (c) 0.5Pd, (d) 0.5Pt, (e) 0.01Y, (f) 0.02Y, (g) 0.05Y, (h) 0.1Y, (j) 0.5Y. X a-al 2 O 3 0.2Y 0.5Y Y 3 Al 5 O 12 0.2Y 0.5Y Fig. 10 FeCrAl (Standard, FZ, 0.5Pd, 0.5Pt, 0.01Y 0.5Y) 1473 K, 18 ks Standard FZ, 0.5Pd 0.5Pt Y Y 0.1Y, 0.2Y 0.5Y Standard, FZ, 0.5Pd, 0.5Pt, 0.01Y, 0.02Y 0.05Y 1000 SEM Standard, FZ, 0.5Pd 0.5Pt 1.0 mm 0.01Y, 0.02Y 0.05Y 0.5, 0.5 0.4 mm Y 0.1Y, 0.2Y 0.5Y 3000 SEM 0.1Y 0.2Y 0.13 0.07 mm 0.5Y 0.1Y, 0.2Y 0.5Y, 1, 2 4 mm Y 3 Al 5 O 12 (Table 4) 4.3.4 SEM 1273 K a-al 2 O 3 q-al 2 O 3 Standard 1273 K, 7.2 ks q-al 2 O 3 Fig. 11 Standard 1273 K, 7.2 ks a- Al 2 O 3 q-al 2 O 3 1273 K 7.2 18 ks, 1373 K 1.8 18 ks, 1473 K 0.6, 7.2 18 ks, 1573 K 1.8 7.2 ks 1673 K 18 ks 1273 K, 7.2 ks q-al 2 O 3 4.1 mm 1473 K, 7.2 ks 1473 K, 18 ks 3.8 mm 1573 K, 1.8 7.2 ks 3.5 2.9 mm 1573 K, 7.2 ks 1273 K, 7.2 ks q-al 2 O 3 1373 K, 18 ks 1673 K, 18 ks 69
41 1 Fig. 11. SEM micrographs of oxide scale on Fe 20Cr 4Al (Standard) alloy exposed to oxygen for 0.6 18 ks at 1273 1673 K; (a) 1273 K, 7.2 ks. (b) 1273 K, 18 ks. (c) 1373 K, 1.8 ks. (d) 1373 K, 18 ks. (e) 1473 K, 0.6 ks. (f) 1473 K, 7.2 ks. (g) 1473 K, 18 ks. (h) 1573 K, 1.8 ks. (i) 1573 K, 7.2 ks. (j) 1673 K, 18 ks. Fig. 12. SEM micrographs of oxide scale on Fe 20Cr 4Al (FZ, 0.5Pd, 0.5Pt) alloys exposed to oxygen at 1273 1673 K. 1473 K, 7.2 ks 1473 K, 7.2 ks 18 ks 0.3 0.5 mm 1573 K, 1.8 7.2 ks 0.6 1.0 mm 1673 K, 18 ks 7 mm Fig. 12 FZ, 0.5Pd 0.5Pt 1273 K 7.2 ks, 1473 K 7.2 ks, 1573 K 7.2 ks 1673 K 18 ks 1273 K, 7.2 ks 1473 K 7.2 ks, 1573 K 7.2 ks 1673 K 18 ks 0.2, 1.0 2.0 mm Fig. 13 0.05Y, 0.1Y 0.5Y 1473 K 7.2 ks, 1573 K 7.2 ks 1673 K 18 ks 0.05Y 0.1Y 0.5Y 1673 K, 7.2 ks 0.05Y 1473 K 7.2 ks, 1573 K 7.2 ks 1673 K 18 ks 0.5, 1.5 2 mm 0.1Y 0.5Y 70
Fig. 13. SEM micrographs of oxide scale on Fe 20Cr 4Al (0.05Y, 0.1Y, 0.5Y) alloys exposed to oxygen at 1473 1673 K. Fig. 14. SEM micrographs of oxide scale on Fe 20Cr 4Al (Standard) alloy exposed to oxygen (a) for 7.2 ks at 1573 K and then (b) for 18 ks at 1673 K. 2 mm 0.1Y 0.5Y Y 3 Al 5 O 12 Y Y 3 Al 5 O 12 1673 K, 18 ks 1 mm Fig. 14 Standard (a) 1573 K, 7.2 ks (b) 1673 K, 18 ks (a) 1673 K, 18 ks (a) (b) (b) (a) 4.4 1473 K, 18 ks Standard, FZ, 0.5Pd 0.5Pt Y 0.1% Y Y FeCrAl Pd Pt 0.1% Y Al 2 O 3 Al Y Y 1473 K Al 28) 0.01% Y Y Fe Y Y 2 O 3 Y 2 O 3 Al 2 O 3 Y 3 Al 5 O 12 Y 1) 2) Y Y 3 Al 5 O 12 Al 1) 2) Y 3 Al 5 O 12 0.1Y, 0.2Y 0.5Y 71
41 1 Table 5. Summary of scale feature on Fe 20Cr 4Al (Standard, FZ, 0.5Pd, 0.5Pt, 0.01 0.5Y) alloys exposed to oxygen for 18 ks at 1473 K. Alloy Fe 20Cr 4Al (Standard) Fe 20Cr 4Al (FZ) Fe 20Cr 4Al 0.5Pd Fe 20Cr 4Al 0.5Pt Fe 20Cr 4Al 0.01Y Fe 20Cr 4Al 0.02Y Fe 20Cr 4Al 0.05Y Fe 20Cr 4Al 0.1Y Fe 20Cr 4Al 0.2Y Fe 20Cr 4Al 0.5Y Scale feature entirely spalled, wavy, fine reticular facial cavity (1 mm), gray faintly spalled, planar, fine reticular facial cavity (1 mm), gray faintly spalled, planar, fine reticular facial cavity (1 mm), brown faintly spalled, planar, fine reticular facial cavity (1 mm), gray slightly spalled, wavy, fine reticular facial cavity (0.5 mm), gray faintly spalled, slightly wavy, fine reticular facial cavity (0.5 mm), gray faintly spalled, slightly wavy, fine reticular facial cavity (0.4 mm), gray no spalled, planar, dense, facial cavity (0.13 mm) glossy gray, fine Y 3 Al 5 O 12 particle (1 mm g.b.) no spalled, planar, dense, facial cavity (0.07 mm) glossy gray, fine Y 3 Al 5 O 12 particle (3 mm g.b.) no spalled, planar, dense, glossy gray fine Y 3 Al 5 O 12 particle (5 mm g.b., g.) no faintly slightly entirely, g.b.; grain boundary, g.; grain. Y 11),13),6),19),29) Table 5 FeCrAl (Standard, FZ, 0.5Pd, 0.5Pt, 0.01 0.5Y) 1473 K 18 ks Standard Standard 4 ppm Forest Davidson 30) 4 ppm 12) 1 3 ppm FeCrAl 4, 7, 35 53 ppm 1) 12) 1 ppm 3),5),9) 12),30) 1473 K, 18 ks 0.5Y 31) Y Y 0.1Y, 0.2Y 0.5Y gray 0.1Y, 0.2Y 0.5Y glossy gray (porous) (dense) 1473 K a-al 2 O 3 3),6),9) 16),18),19),21),22),29) 31) 1273 K g-al 2 O 3 q-al 2 O 3 29),32),33) 32),33) a-al 2 O 3 1 2 34) 35) 1273 K, 7.2 ks a-al 2 O 3 q-al 2 O 3 32) q-al 2 O 3 a-al 2 O 3 29),32),33) 12% 32) q- Al 2 O 3 1273 K, 7.2 ks q-al 2 O 3 4.1 mm 1473 K, 7.2 ks 1473 K, 18 ks 3.8 mm 1573 K, 1.8 ks 7.2 ks 3.5 2.9 mm 1573 K, 7.2 ks 1573 K, 7.2 ks 72
Table 6. Chemical composition of alloys (mass%). Alloy Fe Cr Al S Pd Pt Au Lu Fe 20Cr 4Al (Standard) Bal. 20 4 0.0004 Fe 20Cr 4Al (FZ) Bal. 20 4 0.0001 Fe 20Cr 4Al 0.5Pd Bal. 20 4 0.0001 0.498 Fe 20Cr 4Al 0.5Pt Bal. 20 4 0.0001 0.499 Fe 20Cr 4Al 0.5Au Bal. 20 4 0.0001 0.499 Fe 20Cr 4Al 0.1Lu Bal. 20 4 0.0001 0.04 1673 K, 18 ks 36) 4.5 Fe 20Cr 4Al (Standard: 4 ppms), Fe 20Cr 4Al (FZ: 1 ppm), Fe 20Cr 4Al 0.5Pd, Fe 20Cr 4Al 0.5Pt Fe 20Cr 4Al (0.01 0.5)Y 1273 1673K 0.6 18ks 1 1473 K, 18 ks Standard Y 0.1Y, 0.2Y, 0.5Y, FZ, 0.5Pd 0.5Pt 2 1473 K, 18 ks Standard, FZ, 0.5Pd, 0.5Pt, 0.01Y, 0.02Y 0.05Y 0.1Y, 0.2Y 0.5Y 3 Fe 20Cr 4Al 1273 K, 7.2 ks 1473 K 7.2 ks 1573 K, 7.2 ks 1673 K, 18 ks Standard 7 mm FZ, 0.5Pd, 0.5Pt, 0.05Y 2 mm, 0.1Y 0.5Y 1 mm 4 1673 K, 18 ks 0.1Y, 0.2Y 0.5Y Y 3 Al 5 O 12 2 mm Fig. 15. Mass change of Fe 20Cr 4Al (Standard, FZ, 0.5Pd, 0.5Pt, 0.5Au, 0.1Lu) alloys exposed to an oxygen-water vapor (dew point: 313 K) environment for 18 ks at 1473, 1573 and 1673 K; (a) Standard, (b) FZ, (c) 0.5Pd, (d) 0.5Pt, (e) 0.5Au, (f) 0.1Lu. Y 5 FeCrAl(Pd, Pt, Au, Lu) 5.1 Table 6 10 20 0.5 mm 3 313 K (40 C) (100 cc/min) 1473, 1573 1673 K 18 ks X SEM 5.2 4 ppm 1 ppm Fig. 15 73
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