Synthesis, microstructure, growth kinetics and oxidation performance of complex concentrated silicide coatings on Nb₇Ti₇Al₁Cr₁ via hot-dip siliconizing

Abstract

For different types of materials, particularly those exposed to high-temperatures, applying protective coatings significantly increases their resistance to oxidation. In this study, for the first time, the hot-dip method was used to synthetize silicides-based coatings on a refractory complex concentrated alloy substrate Nb₇Ti₇Cr₁Al₁. Coatings were applied by dipping the substrates in molten Al-30Si alloy at 850 °C for different time periods. Using XRD and SEM/EDS methods aphase, microstructure, and chemical composition of the coatings were analyzed, revealing a primary M(Si,Al)₂ layer. The coating thickness increased linearly with deposition time, indicating interfacial reaction-controlled growth. Notably, a 10-minute coating synthesis significantly improved oxidation performance. Short-term oxidation tests at 1200 °C for 20 h in synthetic air showed linear kinetics for the base alloy, while the coated sample exhibited parabolic behavior and 87 % reduced mass gain. These findings demonstrate the potential of liquid-assisted siliconizing for producing oxidation-resistant coatings.