Thermal and chemical stability of the ß-W2N nitride phase

Pure Be, W and Be:W mixed coatings with nominal compositions of (5:5) and (1:9) were deposited on silicon plates and implanted at room temperature with 30 keV N ⁺ ions with fluences up to 5e17 ions/cm ². Ion beam and X-ray diffraction analysis evidenced the formation of the α-Be ₃N ₂ and β-W ₂N nitrides. The identified tungsten nitride phase evolves from a BCC W lattice to a BCC W(N) solid solution after irradiating at a fluence of 1e17 N ⁺/cm ² and to the compact FCC β-W ₂N structure at 5e17 N ⁺/cm ². Thermal stability of β-W ₂N was investigated by annealing the coatings for 1 h up to 1073 K. The results point to the release of non-bonded nitrogen solute in β-W ₂N over the annealing range and to the thermal stability of the nitride phase up to 1073 K.