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The article deals with the first results from the so-called laboratory exposure loop after 10,000 h operation. This loop is an experimental setup that allows the selected material to be exposed to the conditions that prevail in the boiler of a coal-fired power plant or incineration site. Among these conditions are elevated temperature, corrosive environment, and internal pressure of water steam. In this case, the loop (consisting of two bends and six weld joints) was made from SUPER 304H (X10CrNiCuNb18-9-3) superheater tubes. Before the experiment, the welded loop was filled with water, so steam with a pressure of 23 MPa was generated when heated to 550 °C. In addition, small-scale, stripe-shaped specimens were placed inside the loop and then exposed to steam during exposure. The loop was placed partly out of the furnace, thus not fully heated, and covered up with the power plant ash. At weekly intervals, the cooler part of the loop (the one covered up with the ash) was sprayed with water to induce thermal shock. After exposure of both loops (one for 5000 h, the other for 10,000 h), their bodies were cut, and mechanical tests (i.e. tensile and Charpy impact tests) were performed. The microstructure of the straight parts bends and weld joints of the loop tubes was investigated 1and documented using light optical microscopy (LOM) and scanning electron microscopy (SEM).
Keywords: Exposure loop, austenitic steel, SUPER 304H, superheater, microstructure© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.