High temperature performance of materials for the energy sector exposed to water steam

In this work, issues regarding the energy sector in Poland are described in terms of subcritical technology which is commonly used and plays the most important role in electric power production. In such technology steam temperature reaches 500-530°C with 14-16 MPa pressure. In addition, in this study the mechanism of high temperature corrosion of Fe and Ni- based materials with a different content of Cr considered for construction of new coal power plants will be discussed. The study clearly shows that at high temperatures (675°C and 725°C) in a pure steam atmosphere the Fe based alloy with 18 wt.% of Cr creates the formation of Fe-Cr spinel, the phase indicates poorer corrosion resistance than Cr₂O₃, however better than magnetite (Fe₃O₄) or hematite (Fe₂O₃). It was also shown that Fe based alloys were characterised by the development of islands rich in Fe₃O₄. The formation of such islands is related to an unequal distribution of iron concentration and its activity within the matrix, and the inability to create a thin protective layer of spinel or an independent layer of Cr₂O₃. The Ni based alloy 718+ developed a layer of Ni-Cr spinel (NiCr₂O₄) with a thickness of 2 μm.

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