Interface characterization of combination hard/solid lubricant coatings by specific methods

• Published in: Surface & coatings technology 2002-05, Vol.154 (2), p.194-203
• Main Authors: Navinšek, B., Panjan, P., Čekada, M., Quinto, D.T.
• Format: Article
• Language: English
• Subjects: Cathodic arc evaporation; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Exact sciences and technology; Hard/solid lubricant; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; PVD coating
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/S0257-8972(02)00002-6

Double or combination coatings and multilayered coatings were recently developed as a new generation of protective PVD coating for cutting tools. Some of these have already been applied in selected cases in modern machining techniques such as dry high-speed milling, turning, tapping and drilling, or when using a minimum quantity of lubricant (MQL). In this work we studied details of the combination of two coatings, one a solid lubricant (WC/C) coating sputtered onto a hard, wear- and temperature-resistant (TiAlN) coating, deposited onto high-speed steel and cemented carbide substrates. Using specific analytical methods, we focused our investigation on interface (interlayer) characterization between individual layers and the substrate. A detailed knowledge of the interlayer properties is the basis for understanding and interpretation of the macroscopic properties of WC/C–TiAlN combination coatings in a given tribological system. Depth profiles of Vickers microhardness, as determined on low-angle cross-sections of test samples, showed that the TiAlN layer had approximately 3000 HV 0.05, the W-rich interlayer approximately 2500 HV 0.05 and the WC/C solid lubricant approximately 1000 HV 0.05. High adhesion strength was proved by the REVETEST scratch test and by additional SEM+EDS analyses and depth profiles of the scratch tracks. Total delamination L c was observed at critical loads from 80 to 115 N. A low scratching coefficient μ* (0.05–0.20) was typical of thin (3 μm) and also of thick (10.8 μm) coatings. The width of the WC/C–TiAlN interlayer (0.15–0.20 μm) was measured from the SEM image of the kalotest ball crater and from fracture cross-sections. This narrow transient area was also detected and analysed by AES depth profile analysis and by EDS linescan and SEM microanalysis at low-angle cross-sections of the coated samples. All the results were correlated successfully with the declared basic macroscopic properties of the WC/C–TiAlN combination layer.