Further investigations into alloy induced acidic fluxing

Figures & data

Figure 1. (a) MarM 509 exposed at 700 °C in air for 100 hours with no deposit. (b) MarM 509 exposed at 700 °C for 100 hours in 8.5 vol.% O₂, 10.5 vol.% CO₂, 5 vol.% H₂O and 90 ppm SO_x with 80/20 Na₂SO₄/K₂SO₄ at 1.5 µg/cm²/h [4].

Figure 2. Test furnace apparatus [8].

Table 1. Nominal alloy elemental compositions wt.% (at.%) [11].

Alloy	Ni	Co	Cr	Ti	W	Al	Ta	Mo	C	Zr
PWA 1483	Bal	9	12.2	4.1	3.8	3.6	5	1.9	0.07
	(60.2)	(8.9)	(13.7)	(5)	(1.2)	(7.8)	(1.6)	(1.2)	(0.3)
MarM 509	10	Bal	23.5	0.2	7		3.5		0.6	0.5
	(10.2)	(55.7)	(27.1)	(0.3)	(2.3)		(1.2)		(3)	(0.3)

Figure 3. Cumulative probability of change in good metal plots for PWA 1483 (top) and MarM 509 (bottom). Exposure carried out at 700 °C in an air atmosphere with 300 ppm SO₂. The deposit flux was 1.5 µg/cm²/h of 80/20 (Na/K)₂SO₄ modified with additions of 1.5 µg/cm²/h of Mo.

Figure 4. Median (top) and 4% (bottom) probability of metal loss exceedance plots. Exposure carried out at 700 °C in an air atmosphere with 300 ppm SO₂. The deposit flux was 1.5 µg/cm²/h of 80/20 (Na/K)₂SO₄ either modified with 1.5 µg/cm²/h of molybdenum or unmodified [8].

Figure 5. BSE images for PWA 1483 (left) and MarM 509 (right) showing areas both representative of the majority of the sample and also extreme corrosion features.

Figure 6. BSE image with point analysis and EDX element map of a corrosion feature on PWA 1483 after 500 hours of exposure at 700 °C in an air atmosphere with 300 ppm SO₂. The deposit flux was 1.5 µg/cm²/h each of 80/20 (Na/K)₂SO₄ and Mo..

Figure 7. BSE image with point analysis and EDX element map of a corrosion feature on MarM 509 after 500 hours of exposure at 700 °C in an air atmosphere with 300 ppm SO₂. The deposit flux was 1.5 µg/cm²/h each of 80/20 (Na/K)₂SO₄ and Mo..

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