  High entropy carbides (HECs) are a promising new class of ultra-high
temperature ceramics that could provide novel material solutions for leading
edges of hypersonic vehicles, which can reach temperatures above 3500C and
experience extreme thermal gradients. Although the mechanical and thermal
properties of HECs have been studied extensively at room temperature, few works
have examined HEC properties at high temperatures or considered these
materials' responses to thermal shock. In this work, we measure the thermal
conductivity of a five-cation HEC up to 1200C. We find that thermal
conductivity increases with temperature, consistent with trends demonstrated in
single-metal carbides. We also measure thermal conductivity of an HEC deposited
with varying CH4 flow rate, and find that although thermal conductivity is
reduced when carbon content surpasses stoichiometric concentrations, the films
all exhibited the same temperature dependent trends regardless of carbon
content. To compare the thermal shock resistance of HECs with a refractory
carbide, we conduct pulsed laser ablation measurements to determine the fluence
threshold the HECs can withstand before damaging. We find that this metric for
the average bond strength trends with the theoretical hardness of the HECs as
expected.
