No abstract

No abstract

The microstructure development and mechanical behaviour of dissimilar metal welds between ferritic and austenitic steel, as well as their application in nuclear power plants, are discussed in this review paper. Nuclear reactor components, such as steam generators and pressure vessels, consist primarily of SA508 due to their low cost and high operating temperatures and pressures. The welding of dissimilar metals is crucial due to variations in physical characteristics such as thermal conductivity, thermal expansion coefficient, mechanical properties and chemical compositions. The principal challenges of dissimilar ferritic and austenitic steel welding are the subject of this review work. Weldability issues include a sharp change in mechanical and metallurgical characterization across the fusion line, carbon migration, cyclic thermal stresses and residual stresses, which necessitate a thorough investigation of the welded joint. Generally, austenitic steel and nickel-based fillers are used to join austenitic and ferritic steel materials; however, owing to many weldability concerns, nickel-based consumables are replacing austenitic consumables. Another critical issue in the weld joint is the selection of appropriate welding consumables, and detailed explanations of the benefits of employing a buttering layer on the ferritic side are provided. The effect of heat treatment on the metallurgical and mechanical characteristics of the weld joint, as well as the formation of residual stress, has also been thoroughly explored.

This study investigates electrode coatings designed for use in nuclear power plant weld joints, particularly their electrical, thermophysical and physicochemical properties. The Al2O3-CaF2-CaO-SrO-based shielded metal arc welding electrodes were developed using the extreme vertices design technique. The coating composition's structure and phases were analyzed using X-ray diffraction, while Fourier transform infrared spectroscopy analysis was used to identify the types of bonds present. Advanced characterization methods were utilized to assess the coating formulations’ physicochemical, thermophysical and structural aspects. Thermal properties, including specific heat, thermal diffusivity and conductivity, were evaluated using a hot disk apparatus, while thermogravimetric analysis was employed to determine the enthalpy change and thermal stability of the flux coating. The electrical properties of the flux coatings were examined using a precision LCR instrument. Statistical analysis was employed to create regression models for each coating property to investigate the influence of mineral constituents on the flux coating properties. Regression analysis is a statistical method used to establish a relationship between mineral interactions. In flux composition selection, it can help determine the physical significance of each factor and its relationship with the coating's performance. The results indicate that the mineral constituents’ individual elements, binary and tertiary interactions, significantly impact the flux composition's physicochemical, electrical and thermophysical properties.

This study investigated the thermophysical, physicochemical, and electrical characteristics of electrode coatings developed for application in the weld joint of nuclear power plants (NPPs).The extreme vertices design technique has been used in this work to develop the Al2O3-SiO2-CaO-Na3AlF6-based SMAW electrodes. Twenty-six electrode coating compositions were formulated, and flux coatings were milled into a fine powder for further characterization. XRD technique was utilized to investigate the structure and phases of the coating composition, and the FTIR analysis technique was employed to determine the nature of bonds. The coating's thermal characteristics, including conductivity, diffusivity, and specific heat, were evaluated using hot disk equipment. Enthalpy change and thermal stability of flux coating were determined using the TGA technique. The precision LCR instrument was used further to examine the electrical characteristics of the flux coatings. In addition, a regression model has been developed for each coating property using statistical analysis and investigated a correlation between the properties and mineral interactions. Results reveal that the individual elements and their binary and tertiary interaction significantly influence the physicochemical, thermophysical, and electrical properties of the flux coatings.