High-Temperature, High-Speed Testing of Silicon Carbide

Author(s):

Natasha Bradley, Andrew J. Wright, David Lee, Kristopher D. Behler, Michael J. Presby, Todd Henry, and John Hrynuk

Abstract:

This work presents an assessment of using temperature and jet velocity as metrics for repeatable high-temperature, high-speed testing of silicon carbide. In order to better understand the variability between different experimental setups, mounting, and boundary conditions, two different erosion setups were used. Tests were conducted at NASA Glenn Research Center, where erosion was observed. Testing was also conducted in a similar test facility at ARL with different sample mounting conditions. Silicon carbide test samples were fabricated in combination with boron carbide and alumina into 38.1-mm-diameter disks at thicknesses of 3.33 and 9.91 mm. Samples were then exposed to a high-temperature (∼1371 ℃), high-speed (150 m/s) flow for at least 60 min. To induce erosion of the silicon carbide, 50-µm alumina particles were added to the flow, while particle image velocimetry was used to characterize the flow speed and direction. Erosion was observed to be highly sensitive to the flow boundary conditions and test setup. When the erosion jet exit was extremely close to the sample, like in the High Velocity Burner Test Rig at NASA Glenn, the surface of the silicon carbide was worn smooth revealing void content from the manufacturing process inside the sample. In the ARL Jet Burner Test setup, the silicon carbide did not erode, despite similar jet velocities and temperatures. Particle image velocimetry data showed that jet expansion with distance and sample mounting condition is critical to the erosion process. The results of this report clearly demonstrate that jet velocity and temperature are insufficient variables to define erosion conditions, and boundary conditions play a critical role in the process. The results shown here highlight the need for the research community to develop a set of highly repeatable boundary conditions, and other experimental conditions, to accurately assess ablation and erosion processes of materials.