Hard amorphous nanocomposite coatings with oxidation resistance above 1000°C

Abstract

This article reports on two classes of novel hard amorphous coatings: (a) Si₃N₄/MeN_x coatings with high (≥50 vol.-%) content of Si₃N₄ phase; here Me=Zr, Ta, Ti, Mo, W, etc. and x=N/Me is the stoichiometry of MeN_x metal nitride phase, and (b) Si–B–C–N coatings with strong covalent bonds. These nanocomposites exhibit high thermal stability against crystallisation and high oxidation resistance, both at temperatures considerably exceeding 1000°C. Hard amorphous coatings were prepared using reactive magnetron sputtering. Properties of sputtered coatings were characterised using the following techniques: X-ray diffraction, electron probe microanalysis, Rutherford backscattering spectrometry, elastic recoil detection, high resolution transmission electron microscopy, selected area electron diffraction, atomic force microscopy, microhardness tester Fischerscope H 100, differential scanning calorimetry and thermogravimetric analysis. It was found that hard amorphous coatings of both new systems exhibit excellent oxidation resistance at high temperatures about 1500 and 1700°C for amorphous Si₃N₄/MeN_x and Si–B–C–N coatings respectively.