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One of the approaches to simulate creep testing conditions as close as possible to the real service conditions of boiler tubes is the use of internal pressure creep tests (burst tests). This paper describes the implementation and results of such creep tests performed on welded joints of superheater tubes ø 44 × 6.3 mm made of HR3C steel, welded by the TIG process using a filler material based on the nickel superalloy Inconel 617. The tests were carried out at two temperatures, 730 °C and 760 °C, under internal pressures up to 29 MPa. The experimentally obtained times to failure exceeded the values predicted by parametric calculations based on available material data. Significant tube bulging was observed, and failure was mainly located in the HR3C base material in the vicinity of the weld. Metallographic analysis confirmed a dominant intergranular creep damage mechanism characterized by the formation of chains of cavities and microcracks initiated from the outer surface. Close to the weldment, the presence of δ-ferrite and precipitates of σ-phase were also detected along grain boundaries in HR3C steel.
Keywords: creeep, internal pressure, burst test, HR3C, weldment, cavitation damage, sigma phase© 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.