Reactive laser synthesis of ultra-high-temperature ceramics HfC, ZrC, TiC, HfN, ZrN, and TiN for additive manufacturing

Ultra-high-temperature ceramics (UHTCs) are optimal structural materials for applications that require extreme high temperature resilience (Mp > 3000 °C), resistance to chemically aggressive environments, wear, and mechanical stress. Processing UHTCs with laser-based additive manufacturing (AM) has not been fully realized due a variety of obstacles. In this work, selective laser reaction sintering techniques (SLRS) were investigated the production near net-shape UHTC such as HfC, ZrC, TiC, HfN, ZrN, TiN. Specifically, group IV transition metal oxide precursor (<44 μm) converted reaction-bonded into layers using single-step processing in 100 vol% CH4 or NH3 gas might be compatible prevailing powder bed fusion techniques. Conversion either metals (Hf, Zr Ti) oxides (HfO2, ZrO2, TiO2) particles was first examine mechanisms volume changes associated SLRS single-component systems. alone produced stoichiometric phases yields up >99.9 wt% total carbides nitrides during rapid reactive in-situ scheme. However, single-phase feedstocks, gas-solid reactivity induced volumetric (correlated stochiometry rocksalt-type carbide nitride products) resulted residual stresses cracking model-AM product layer. To mitigate conversion-induced precursors, composite metal/metal precursors employed compensate (which expands conversion) contracts). While conversion optimized HfC little +0.9% change, results indicated interparticle adhesion must obtain robust UHTC-AM layers. Computational models carbon nitrogen diffusion host lattices corroborated experimental where progressive particle inhibit unless parameters carefully favor bonding over discrete conversion. method presents considerations, we demonstrate how approach may viable AM numerous readily current methods.