This paper describes the influence of technological treatments (i.e., bending or welding) on the structural stability of SUPER304H austenitic steel used in reheaters and superheaters in fossil fuel power plants. Although the worldwide trend is transitioning to green power sources, the lifetime of existing power plants has to be prolonged until the transition is complete. Experimental material was tested in as-received state (straight tubes), bends, and homogeneous weld joints. Part of the specimens was solution-annealed after the technological operation. Afterwards, all the samples were thermally aged in furnace (650, 675 and 700 °C) for 7560–20,000 h. For comparison, bent specimens were placed at experimental sites on an operating powerplant for 10,000+ h. The long-term aging causes the formation of Cr-based carbides on the grain boundaries along with the Fe-Cr sigma phase. Combination of elevated temperature and residual stress accelerates formation of the sigma phase. This can be prevented by solution-annealing after bending. Mechanical properties were evaluated by Vickers hardness and tensile tests. The microstructure was observed using light optical microscopy (LOM) and scanning electron microscopy (SEM) with the energy-dispersive X-ray detector (EDXS). Electron backscatter diffraction (EBSD) and X-ray powder diffraction (XRPD) were used to characterize the brittle phases.

Aim of the article is to provide properties comparison between initial state and two thermally exposed states of creep resistant steel SUPER 304H by usage of conventional and miniaturised tensile test specimens. Tests were performed at room temperature. Thermally exposed material was aged by 15 and 30 thousand hours at 675°C. This exposition which simulated accelerated operation exposition caused precipitation of intermetallic phases which affect mechanical properties like ultimate strength and elongation. The performed tests showed a decrease in elongation and ultimate strength between the first exposed state and initial state followed by partial increase of both tested values for the second exposed state. Sigma phase precipitation was confirmed for the exposed samples. The presence of the sigma phase also led to a change in the fracture morphology from full ductile (initial state) to combined ductile with the presence of brittle particle cleavage (exposed states). A comparison of the tests performed on classical and miniaturized test samples proved the possibilities of using miniaturized samples both for the basic material and for the exposed ones.

In this work, a TiNbCr alloy is proposed for solid-state hydrogen storage applications. The design of the alloy is based on the Hume-Rothery rules and the thermodynamic parameters ΔH _mix and Ω , while the alloy was conceived as single-phase with a BCC lattice. Samples were synthesized from alloy powder using additive technology and the DED method. The prepared samples were printed with different parameters and their structure and phase composition were subsequently analyzed. The possible influence of these printing parameters on the properties of hydrogen storage alloys is discussed.