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Inconel 625 flux-cored wire is widely used in the repair of solar energy storage pipelines because of its excellent corrosion resistance. In the application environment of molten salt pipeline containing high-temperature chloride, the surface of the repaired pipeline is easy to deposit salt film, which leads to high-temperature hot corrosion. In this paper, in order to study the hot corrosion mechanism of Inconel 625 cladding metal. Inconel 625 cladding metal was prepared by MAG welding. The corrosion behavior of Inconel 625 cladding metal under isothermal (800 °C) and thermal cycle (600–800 °C) conditions in KCl-MgCl2 (60–40 mol %) molten salt environment was investigated. The results showed that the corrosion rate of Inconel 625 cladding metal was 12.39 μm/year under 72-h isothermal conditions, and the corrosion products mainly included MgO and NiCr2O4. Under the condition of 3 thermal cycles, the corrosion rate of the sample was 11.21 μm/year, and the corrosion products mainly included MgO, NiCr2O4 and Cr2O3. This was because the Cr2O3 protective shell dissolved and fell off under isothermal conditions. Besides, the hot corrosion path penetrated along the random HAGBs. The larger number of HAGBs increased the diffusion path of Cr element, which led to increased corrosion under isothermal conditions. Under the condition of thermal cycle, there was an intermittent cooling effect, and the corrosion time was less at the highest temperature, which improved the stability of the Cr2O3 protective shell. At the same time, it reduced the number of HAGBs and reduced the penetration path of hot corrosion. The diffusion coefficient of Cr element was reduced by 55.6%, which reduced the corrosion rate. [ABSTRACT FROM AUTHOR]

With rapid developments in industry, the unique design of high-entropy alloys (HEAs) has become a research hotspot in the field of corrosion. In this work, AlCrCuFeNiNb0.2Tix HEAs were prepared through flux-cored wire and deposited on the surface of low-carbon steel by gas metal arc welding (GMAW). The effect of Ti on the phase structure and corrosion resistance of AlCrCuFeNiNb0.2Tix HEA surfacing layer is discussed in detail. The results demonstrate that the microstructure of the surfacing layer was mainly composed of BCC solid solution with Fe-Cr phase and FCC solid solution with tiny amounts of MC phase. The microstructure presents the typical dendritic (DR) and interdendritic (ID) structures. It indicates that the addition of Ti can significantly promote the corrosion resistance of the surfacing layer. The corrosion resistance effect is stronger than that of 304 stainless steel. With the continuous addition of Ti, the self-corrosion current density of polarization curve decreases, the capacitance impedance radius of electrochemical impedance spectroscopy (EIS) increases, and the corrosion resistance of the surfacing layer improves. In the low-frequency region of EIS, there is an inductance component with pitting tendency. When the addition was Ti0.8, the corresponding corrosion resistance value of the surfacing layer impedance was the smallest. [ABSTRACT FROM AUTHOR]

Barium strontium titanate glass-ceramics with different La2O3 contents (0, 0.5, 1.0, and 1.5 mol. %) were prepared by the melt-quenching technique. The phase developments, microstructures, and impedance behavior of these glass-ceramics have been investigated as a function of La2O3 content. By the X-ray diffraction study, a gradual change with increasing La2O3 content was observed. X-ray photoelectron spectroscopy indicated that the oxygen vacancy concentration decreases with the increase of La2O3 content. Lanthanum substitution resulted in an initial increase and then a decrease in the value of dielectric constant. From impedance spectroscopy, there are two electrical responses occurring: a low frequency response, which is related to the crystal-glass interface, and a high frequency response corresponding to the crystal phase. The low frequency peak shifts to lower frequencies and the high frequency peak shifts to higher frequencies with increasing lanthanum content. Both the temperature sensitivity of impedance and the value of ac conductivity decrease with the increase of La2O3 content. [ABSTRACT FROM AUTHOR]

In this paper, the element nitrogen (N) is used to partially replace the element nickel (Ni) in flux-cored wire. A 44%Ni-24%Cr-0.18N nitrogen-containing low-nickel flux-cored wire with excellent corrosion resistance is prepared. The corrosion behavior of nitrogen-containing low-nickel weld cladding and Inconel 625 weld cladding in 40 KCl + 60 MgCl2 (wt%) molten salt at 900 °C is studied. The results show that the selective dissolution of Cr occurs in both weld claddings. The corrosion resistance of the 44%Ni-24%Cr-0.18N nitrogen-containing low-nickel weld cladding is better than that of the Inconel 625 weld cladding. The reason is that added N can react with H+ in molten salt to generate NH 4 + , remove corrosive impurities of MgOH+ in molten salt and change the corrosion environment. N preferentially combines with Cr to form Cr2N, reduces the diffusion precipitation of Cr and improves the corrosion resistance. [ABSTRACT FROM AUTHOR]