Additive Manufacture of Porous ZrC for NTP In-Core Insulators

View Video Presentation: https://doi.org/10.2514/6.2021-3229.vid Nuclear Thermal Propulsion requires high temperature insulators to manage to thermal environment between high temperature fuel elements and structure. The unforgiving in-core operating conditions limit potential material candidates. Zirconium Carbide (ZrC) is a promising candidate due to a high melting temperature, hydrogen compatibility, and low neutron absorption cross sections. However, fully dense ZrC is not an insulator but it has been found that the thermal conductivity of ZrC decreases by increasing porosity to approximately 60 percent theoretical density (%TD). Previous methods for generating porous ZrC were difficult, expensive, and time consuming. Binder jet additive manufacture can print ceramic materials to near net shape. Binder jet is not utilized in many aerospace applications due to a low post-sintering density of 60 %TD. For this application the inherent lower density is leveraged as an advantage in production porous ZrC in order to control the thermal conductivity. A feasibility study was conducted to investigate binder jet parameter development for ZrC, heat treatment optimization (burn-out and sinter), microstructural characterization, mechanical testing, and thermal testing to generate near-net shape ZrC components with ~60 %TD with the desired thermal conductivity and mechanical strength.