Progress of high temperature corrosion-resistant materials for superheaters

4 Progress of high temperature corrosion-resistant materials for superheaters 

The alloy design of seamless tubes for use as SHTs takes into consideration both corrosion resistance and heat-resistant characteristics. Furthermore, excellent weldability, plastic workability, etc. are required for fabrication of the boilers. Generally, at temperatures of approximately 350°C or lower, carbon steel is used. In the high temperature region of 400°C or higher where high corrosion resistance is required, Fe base and Ni base austeiutic materials (Tables 19.1 and 19.2) are tested and used. Field corrosion tests have shown that the addition of alloying elements such as Mo, Nb and Si to Ni-Cr-Fe alloys is effective for corrosion resistance. The main corrosion-resistant alloys currently developed and applied are described below. 

Alloy 825 Solid wall, (SB423) composite (ASME) 

HR11N Solid wall, composite (Sumitomo Metal) 

Trade name Shape of tubes (maker) Chemical composition (mass%) Tensile properties (RT)  

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