Influence of sputtering conditions on corrosion of sputtered W-Ti-N thin film hard coatings: salt spray tests and image analysis

The corrosion resistance of sputter-coated W-Ti-N films on high speed steel substrates prepared under different deposition conditions has been compared by varying the film surface roughness, the film thickness and depositing a first W-Ti layer. Salt spray tests have been carried out and the resulting pitting corrosion evaluated by image analysis and by microscopy and X-ray diffraction. The results show that the most important factors influencing corrosion are film compactness and thickness. The detailed mechanism of corrosion is discussed, involving electrolyte penetration with substrate corrosion, the corrosion products either blocking further corrosion or leading to localised film rupture. (C) 2000 Elsevier Science Ltd. All rights reserved.