Synthesis, crystal growth, structure, and micro-hardness of W9Al3CoC3—First single crystal studies on an ordered hexagonal κ-carbide

Single crystals of the new carbides W9Al3CoC3 were synthesized from a metallic melt and characterised by XRD and EDXS measurements. The crystal structure of W9Al3CoC3 was refined on the basis of single crystal data (hP32, P63/mmc, a = 7.9051(11) Å, c = 7.7869(16) Å, Z = 2, 304 reflections, 20 parameters, R1(F) = 0.0272, wR2(F2) = 0.0562). W9Al3CoC3 belongs to the family of κ-carbide M9M3′C3 or M10M3′C3 which are important components for cermets. Its crystal structure is characterised by CW6-octahedra which are connected to 6.3.6.3 Kagomé-net. Co and Al have no contacts to C-atoms. The metal atoms are ordered and all positions show full occupation. W9Al3CoC3 represents the first κ-carbide with a complete structure refinement on the basis of single crystal data. Micro-hardness measurement on single crystals yield values of HV = 15.5 GPa and HK = 12.5 GPa.