Research Progress on the Combined CVI+PIP Densification Process for SiC_f/SiC Composites for Aero-Engine Hot-Section Components

The next-generation aero-engines impose increasingly stringent demands on the high-temperature resistance, lightweight nature, and long service life of hot-section components. Continuous silicon carbide fiber-reinforced silicon carbide (SiC_f/SiC) ceramic matrix composites have emerged as core candidate materials owing to their excellent comprehensive performance. However, the efficient densification of complex-shaped components remains a critical bottleneck restricting their engineering applications. The combined chemical vapor infiltration (CVI) and precursor infiltration and pyrolysis (PIP) process, by synergistically leveraging the advantages of CVI in fabricating a SiC matrix with high crystallinity and few defects and the characteristics of PIP in efficient pore filling and near-net shaping, provides an optimal technical pathway to address the issues of low densification efficiency, high cost, and unbalanced performance associated with single processes. This paper focuses on the synergistic mechanism of the CVI+PIP combined process. It systematically analyzes the parameter optimization strategies for key processing steps, including fiber preform fabrication, interphase tailoring, initial CVI densification, deep PIP filling, and post-treatment. The core advantages of this combined process in enhancing material density, optimizing microstructure, shortening the fabrication cycle, and reducing cost are elaborated in depth. Furthermore, the application examples and performance of the process in typical hot-section components such as combustor liners, turbine guide vanes, and exhaust nozzles are reviewed in detail. Finally, considering current technical challenges including process optimization, precise microstructural control, and the development of durable environmental barrier coatings, future research directions are proposed. This paper provides important theoretical support and technical references for the scale-up fabrication of high-performance SiC_f/SiC composite hot-section components and the performance leap of aero-engines.