High temperature corrosion of hot-dip aluminized steel in Ar/1%SO2 gas

Microstructural Changes of Al Hot-Dipped P91 Steel during High-Temperature Oxidation

“…Hence, the Al 5 Fe 2 layer (spots [11][12][13][14][15][16][17][18][19] was thicker than the Al 13 Fe 4 layer (spots 7-10 inside the alloy layer) [10,11]. On the other hand, in the case of low-alloyed carbon steels, the characteristic finger-or tongue-like morphology that oriented along the c-axis of Al 5 Fe 2 generally developed at the coating/substrate interface [4][5][6]9,10,12,13]. Such a morphology however was not noticeable around the spots 19-20 shown in Figure 2a, because vacancies in Al 5 Fe 2 were occupied more by substrate elements in the current high-alloyed Cr steel, resulting in the flattening of the coating/substrate interface and narrowing of the alloy layer.…”

“…Hence, the α-Al 2 O 3 peak was weak in Figure 3a. Unequal mass flow and volume change due to the transformation of the topcoat and the alloy layer to Al 13 Fe 4 and Al 5 Fe 2 generated cracks and numerous voids in the coating [5][6][7]9,14,15] ( Figure 3c). The loosely adherent α-Al 2 O 3 scale was partially broken (see the Al map of Figure 3d).…”

“…Hence, the high-temperature oxidation resistance of 9Cr-1Mo steels needs to be improved through surface modification techniques. Aluminum hot-dipping is a simple, cost-effective coating technique that could form the compact, slow growing, protective alumina scale in reaction with oxygen at high temperatures [4][5][6][7][8][9][10][11][12][13][14][15]. It also improves the surface hardness by forming Al-Fe intermetallics [5,7,9,13].…”

“…Aluminum hot-dipping is a simple, cost-effective coating technique that could form the compact, slow growing, protective alumina scale in reaction with oxygen at high temperatures [4][5][6][7][8][9][10][11][12][13][14][15]. It also improves the surface hardness by forming Al-Fe intermetallics [5,7,9,13]. Diverse aluminized coatings have been obtained by hot-dipping carbon steels in Al [5,7,12,13] and Al-Si molten baths [5,9], 5Cr-0.5Mo steels in Al [14] and Al-Si molten baths [16], and 9Cr-1Mo steels in Al-Si [17] and Al-Si-Mg molten baths [15].…”

“…Diverse aluminized coatings have been obtained by hot-dipping carbon steels in Al [5,7,12,13] and Al-Si molten baths [5,9], 5Cr-0.5Mo steels in Al [14] and Al-Si molten baths [16], and 9Cr-1Mo steels in Al-Si [17] and Al-Si-Mg molten baths [15]. They significantly enhanced the high-temperature oxidation and corrosion resistance of the underlying steels through forming α-Al 2 O 3 [5,7,9,[12][13][14]17,18], α-Al 2 O 3 + FeAl [6,15], and FeAl [16] layers. However, microstructural changes during high-temperature oxidation and the oxidation resistance of 9Cr-1Mo steels that were hot-dipped in the Al molten bath have not been adequately investigated before.…”