China's Refractories

Abstract: To develop specific lining materials for rare earth steel nozzles, LaAlO₃ powder was first synthesized by high-temperature solid-phase synthesis at 1 400 °C for 3 h using La₂O₃ and Al₂O₃ powders as raw materials. Then BN, AlN, Si₃N₄ and TiN powders were pressed into φ 30 mm× 7 mm substrate samples under 120 MPa with PVA as the binder. Equal amounts of La₂O₃ and LaAlO₃ powders were placed on their surfaces, reacting at 1 550 °C for 3 h in different atmospheres (reducing and argon conditions). The interfacial reactions of the four nitride (BN, Si₃N₄, AlN, and TiN) substrate samples with La₂O₃ and LaAlO₃ in different atmospheres were studied, respectively. The results show that in reducing and argon atmospheres, the intensity order of the reactions between the four nitrides and La₂O₃ is Si₃N₄>BN>AlN>TiN. In the reducing atmosphere, the reaction intensity order of the four nitrides with LaAlO₃ is Si₃N₄>AlN≈TiN>BN. However, in the argon atmosphere, the order is Si₃N₄>BN>AlN≈TiN. TiN has good structural stability in both reducing and argon atmospheres, and shows weak reactivity with La₂O₃ and LaAlO₃. It is a relatively good anti-clogging lining material for rare earth steel nozzles.

Key words: nitrogen-based refractories, interfacial reaction, rare earth steel, anti-clogging lining