Research status and future perspectives on superalloy fusion welding

Owing to their unique high-temperature mechanical properties and outstanding high-temperature oxidation resistance, superalloys have become key materials in aviation, aerospace, petrochemical, metallurgy, electric power, automotive, and other industrial fields. Due to the structural complexity and high manufacturing cost of the hot sections of aeroengines, vessel engines, and gas turbines, the development and practicality of superalloy welding technology are critical to satisfying the design and maintenance requirements of hot sections. In this work, the research progress of superalloy fusion welding is described. Its advantages and application scope, such as arc welding, electron beam welding, and laser welding, are elaborated. Common types of welding cracks are introduced, and the mechanisms and influencing factors of solidification cracks, liquation cracks, strain-age cracks, and ductility-dip cracks are summarized. The primary techniques to enhance the weldability of fusion welding are also examined in terms of heat input, material composition, microstructure, and welding residual stress. The requirements for the temperature-bearing level of superalloys in industrial development are constantly increasing; thus, the types of superalloys are also being iteratively updated. They have evolved from deformed superalloys to ordinary cast polycrystalline superalloys to novel superalloy materials such as directional solidification and single-crystal superalloys. Thus, continuously conducting welding research on emerging superalloys, traditional nonweldable superalloys, and dissimilar materials that are extremely incompatible with metallurgy is necessary. Because the composition and microstructure of the base material have an important bearing on weldability, it is necessary to strengthen the composition design of emerging superalloys and conventional nonweldable superalloys in future works. Moreover, it is critical to pay attention to the improvement of welding process technology and pre- and post-weld treatment methods. In particular, research on detection and elimination measures of welding residual stress should be strengthened, which is one of the most effective approaches for lowering the weld crack-sensitivity of superalloys. This is of great importance for synergistically enhancing the welding performance of superalloys. Moreover, monitoring and simulation techniques for the welding process can be used to perform in-depth research on scientific issues such as molten pool flow and welding heat and mass transfer during the fusion welding process. This is of great scientific value for promoting the development of fusion welding technology. Based on the foundation of enhancing welding processes, future work on automation and intelligence of welding processes should also gradually deepen, which is one of the important directions to improve welding stability and reliability and promote the widespread application of superalloy fusion welding.