A Reaction Synthesis Approach to Additively Manufacture Net-Shape Chromium Carbide and Non-Oxide Refractory Ceramics

Abstract

A net-shape synthesis process has been used to convert different isovolumetric precursor mixtures composed of either 100 vol% 86/14 molar Cr/Cr2O3 or 50 vol% 86/14 molar Cr/Cr2O3 with 50 vol% Cr3C2 to form multilayer chromium carbide materials suitable for reactive powder bed fusion additive manufacturing. Selective deposition was performed by patterning precursor layers using a masked high-volume, low-pressure slurry spray deposition technique. Following deposition, each layer was thermochemically converted to Cr3C2 at 950 °C in a gas atmosphere containing 76 vol.% Ar, 4 vol.% H2, 20% vol.% CH4. This process was repeated multiple times to construct layered structures representative of additively manufactured refractory ceramics. X-ray diffraction characterization and quantitative phase analysis of each converted layer indicated that the average phase fraction of Cr3C2 present in the multi-layered samples following conversion from Cr/Cr2O3 and Cr3C2/Cr/Cr2O3 precursors was 94.5 wt% (SD = 0.92) and 98.8 wt% (SD = 0.21) respectively. Despite the higher phase fraction of Cr3C2 produced by the three-component precursor system, SEM imaging of the sample microstructures and fracture analysis indicated that increased bonding occurred in Cr3C2 produced by conversion of Cr/Cr2O3. This reaction-induced bonding enhanced the interlayer mechanical integrity. The results in this work demonstrate the use of isovolumetric reaction synthesis techniques that are broadly applicable for non-oxide ceramic production using reactive additive manufacturing methods.