Oxidation behaviour of W-N-M (M = Ni, Ti) sputtered films

In this research work we studied the influence of metal (Ni or Ti) addition on the oxidation behaviour of W-N coatings at different temperatures. For this purpose steel substrates were coated by reactive (N(2)) sputtering composite W-10 wt.%Ti or Ni targets. The highest oxidation resistance was found for W-N-Ni, followed by W-N-Ti and finally by W-N. This behaviour is explained as a function of the as-deposited structure and morphologies of the coatings and of the compactness and type of the oxide formed. W-N-Ni films give rise to denser oxide scales than W-N films and to different types of oxide in comparison with W-N-Ti films. This behaviour is verified only up to 750 degrees C. Afterwards, the oxidation behaviour of W-N-Ni coatings is similar to the other films. This temperature corresponds to the crystallization onset of the as-deposited amorphous structure of W-N-Ni.