Creep of Hi-Nicalon(tm) S Ceramic Fiber Tows at 700 degrees C in Air and in Silicic Acid-Saturated Steam
Abstract
Aircraft structural and engine components are subjected to elevated temperature and steam environments during operation. Ceramic matrix composites (CMCs) are prime candidates to replace superalloys as turbine blade materials. This research investigated a silicon carbide (SiC) fiber, Hi-Nicalon S, which is a candidate for reinforcement of CMCs with SiC-based matrices. Hi-Nicalon Sfiber tows were creep tested at 700C in air and in silicic acid-saturated steam. The steam was saturated with silicic acid in order to simulate the interaction that would occur in a SiC-SiC CMG as the steam environment enters through matrix cracks and leaches Si from the matrix while moving towards the fibers. Creep stresses ranged from 2.96 to 1256 MPa in air and from 2.96 to 798 MPa in silicic acid-saturated steam. Creep strains were measured and steady-state creep rates were determined. In air, creep runout was achieved at stresses as high as 1023 MPa, while in saturated steam creep runout was achieved only at 750 MPa. Creep rates were approximately an order of magnitude greater in saturated steam than in air. Post-test fiber microstructure analysis revealed the presence of a passive oxidation layer on the fibers tested in both environments but no evidence of active oxidation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 04, 2016
- Accession Number
- AD1054830
Entities
People
- Matthew W. Piper
Organizations
- Air Force Institute of Technology