PSI - Issue 72

Aleksandra Krstevska et al. / Procedia Structural Integrity 72 (2025) 172–180

174

Figure 1 Microstructure of X10CrMoVNb9-1

Figure 2 Type IV cracking (Lee & Maruyama, 2015)

In addition to its applications in power industry, X10CrMoVNb9-1 steel is also being considered for future technologies, such as fusion reactors and latent heat storage systems, due to its excellent thermal properties and resistance to hydrogen diffusion (Rahim et al., 2023; Rhode et al., 2019, 2021). The ongoing research into the mechanical properties, microstructural stability, and welding technology for X10CrMoVNb9-1 steel continues to expand its potential applications in advanced engineering applications, highlighting its importance as a material of

choice for high-performance structural components. 3. Welding technology for X10CrMoVNb9-1 steel

Gas Tungsten Arc Welding (GTAW) is one of the most used techniques for welding X10CrMoVNb9-1 steel to other materials, such as Incoloy 800HT and austenitic stainless steels, such as 304H. This method allows precise control over the heat input and results in high-quality welds. Investigations have shown that using GTAW with appropriate filler materials, such as ERNiCr-3, can result with excellent mechanical properties in dissimilar welds, achieving ultimate tensile strengths and good impact toughness. The ability to control the heat affected zone (HAZ) is particularly important in maintaining the mechanical properties of X10CrMoVNb9-1 steel during the welding process (Sauraw et al., 2021). Creating dissimilar metal welds between X10CrMoVNb9-1 martensitic steel and austenitic stainless steels, presents several challenges that can significantly impact the integrity and performance of the welded joints. One of the primary challenges is the difference in thermal expansion coefficients, this mismatch can lead to residual stresses and cracking at the weld interface due to the thermal cycling during welding and subsequent cooling (Akram et al., 2017b; M. M. A. Khan et al., 2012). The high thermal expansion of austenitic stainless steels compared to X10CrMoVNb9-1 can cause significant stress concentrations, particularly in the heat affected zone (HAZ), leading to potential failure of the weld. Another significant issue is the formation of brittle intermetallic phases at the weld interface. The interaction between the different alloying elements in X10CrMoVNb9-1 and austenitic stainless steels can lead to the development of hard, brittle zones, which are prone to cracking under stress and this is particularly problematic in high-temperature applications where the mechanical properties of the weld are critical for long-term performance. The presence of these intermetallic phases can also affect the ductility and toughness of the weld joint, making it less reliable under operational conditions (Akram et al., 2017b; M. M. A. Khan et al., 2012). The different chemical compositions of X10CrMoVNb9-1 and austenitic stainless steels can lead to localized corrosion phenomena, such as pitting, particularly in aggressive environments (Kemény & Kovács, 2022; Varbai et al., 2022). Corrosion can be more pronounced by the presence of residual stresses and microstructural differences, allowing corrosion to penetrate the material (Varbai et al., 2022; Zong et al., 2022). The selection of appropriate filler material is crucial in mitigating these challenges. The filler metal must be compatible with both X10CrMoVNb9-1 and austenitic stainless steel to ensure a quality welded joint. Improper selection can lead to poor mechanical properties or increased susceptibility to cracking and corrosion (Akram et al., 2017b; Varbai et al., 2022). The use of interlayers, such as ERNiCr-3, has been proposed to improve the performance of dissimilar welds by providing a buffer that compensates the differences in thermal expansion and mechanical properties (Abburi Venkata et al., 2016; Akram et al., 2017b). The challenges associated with welding dissimilar metals between X10CrMoVNb9-1 steel and austenitic stainless steel include differences in thermal expansion, the formation of brittle intermetallic phases, microstructural differences, corrosion resistance, and the need for careful filler material selection. Addressing these challenges is