Tensile Creep Properties and Damage Mechanisms of 2d-Woven C/Hfc-Sic Composites in High-Temperature Oxidizing Atmosphere

Abstract

2D-C/HfC-SiC composites were prepared by a combination of precursor impregnation pyrolysis (PIP) and chemical vapor infiltration (CVI). Creep tests were performed at 1100 °C in air under different stress conditions. Unlike most of C/SiC and SiC/SiC ceramic matrix composites only underwent deceleration and steady-state stages, the C/HfC-SiC composites also underwent acceleration stage in the creep process. The reason was that the mechanical properties of C/HfC-SiC materials prepared by PIP+CVI methods were different from those prepared by traditional methods. The microscopic morphological analysis of the sample fracture showed that the oxidation products SiO 2 and Hf-Si-O glass phases of the HfC-SiC matrix played a filling role in the sample cracks during creep. In turn, it provided effective protection to the internal fibers of the sample. The creep failure of C/HfC-SiC composites in high-temperature oxidizing atmosphere was caused by the oxidation of the fibers. The total creep process was dominated by the oxidation of carbon fibers. It was noteworthy that there was the generation of Hf x Si y O z nanowires in the samples after high-temperature creep. The analysis of the experimental data showed that the creep stress had a linear negative correlation with the creep life.

Keywords: High-temperature creep, Ultra-high temperature ceramics, SiO2 and Hf-Si-O glass phases, Nanowires