As a candidate material for turbine blades in aerospace engines, Nb-Si-based alloys have attracted significant research attention due to their high melting point and low density. However, their poor high-temperature oxidation resistance limits practical applications. Different alloying elements, including Ti, Mo, and Hf, were added to Nb-Si-based alloys to study the microstructural evolution of alloys. Additionally, the oxidation behavior and the oxidation kinetics of different alloys, as well as the morphology and microstructure of oxide scale and interior alloys at 1523 K from 1 h to 20 h were analyzed systematically. The current findings indicated that the Mo element is more conducive to promoting the formation of high-temperature precipitates of β-Nb₅Si₃ than the Ti and Hf elements. Inversely, the Ti element tends to cause the transition from high-temperature-phase β-Nb₅Si₃ to low-temperature-phase α-Nb₅Si₃, while the Hf element improves the appearance of the γ-Nb₅Si₃ phase but inhibits the other phases and refines the primary Nbss effectively. Noteworthily, compared with the oxidation weight gain of different alloys, Nb-16Si-20Ti-5Mo-3Hf-2Al-2Cr alloy has excellent high-temperature oxidation resistance, in which the oxidation products are TiNb₂O₇, Nb₂O₅, SiO₂, TiO₂, and HfO₂. It can be determined that in the oxidation process, the Ti element will preferentially form an oxide film of TiO₂, thereby wrapping around the matrix phases, protecting the matrix, and improving the antioxidant capacity, while the Hf element can form an infinite solid solution with the matrix and consume the small number of oxygen atoms entering the matrix, so as to achieve the effect of improving the oxidation resistance.

Basic research on and the industrial development of zirconium alloys in China started relatively late, with insufficient domestic production capacity for zirconium alloy castings; especially for large-sized zirconium alloy castings, there is little production experience and significant challenges in quality control. Therefore, the production and research and development of zirconium alloy castings have received widespread attention from academia and industrial production sectors. This article analyzes the production status of domestic zirconium alloy castings, examines the casting process characteristics of valve body castings, and optimizes the casting process based on ProCAST simulation analysis results, using a lost foam precision casting process to cast a large-sized, high-pressure zirconium alloy casting for chemical use. The phase composition and microstructure were tested and analyzed, and the results showed the following: there is a certain thickness of the diffusion contamination layer on the surface of the castings. Finally, key points regarding zirconium alloy casting surface quality control and welding quality control were proposed, effectively improving the quality of the castings.