Abstract: Effect of Ti on microstructure and mechanical properties of 9Cr-3Si-Al ferritic heat-resistant steel was studied. The results show that a large number of carbide particles which are fine and even, are distributed in the grains of the forged tested steel, and some of them are dissolved into the matrix after solution treatment. Combined with XRD and EDS tests, it is shown that the carbide particles are mainly Ti(C,N) phase which is MX phase on the specimen surface, while a small amount of Cr₂₃C₆ phase is detected on the grain boundary. The tensile strength and yield strength of the tested steel specimens aged at 600 ℃are higher than those of the solid solution specimens. Through the observation of the fracture morphology at room temperature and 650 ℃, it is found that the fracture at room temperature is brittle fracture with a small amount of micropores, which is a quasi-cleavage fracture. While the fracture at high temperature is microporous aggregation features, the density of dimples is higher and the toughness is better.

Key words: Ti-containing ferritic heat-resistant steel, microstructure, mechanical properties, fracture behavior