| AVS 54th International Symposium | |
| Advanced Surface Engineering | Tuesday Sessions |
| Session SE-TuP |
| Session: | Advanced Surface Engineering Poster Session |
| Presenter: | M. Nose, University of Toyama, Japan |
| Authors: | M. Nose, University of Toyama, Japan T. Kawabata, University of Toyama, Japan S. Khamthe, Graduate School of Science and Engineering, Japan K. Matsuda, University of Toyama, Japan T. Nagae, University of Toyama, Japan S. Ikeno, University of Toyama, Japan K. Nogi, Osaka University, Japan |
| Correspondent: | Click to Email |
Aluminum/magnesium pressure die-casting needs protective coatings to the molding dies in order to extend die life. When applied to cast liquid aluminum or magnesium alloy into molding parts, die surface faced harsh conditions such as soldering and erosion at temperatures over 600 oC. DLC (diamond like carbon) or a-C (amorphous carbon) coating has been widely applied to machine-tools for aluminum, due to enhanced tribological properties in terms of low friction, high hardness and non-affinity to aluminum. However, DLC or a-C becomes thermally unstable at temperatures higher than 300 oC when coating hardness drastically drops with temperature. Nanocomposite coatings consisting of transition metal nitride/carbide and amorphous carbon are expected to be stable at higher temperatures and to reduce adhesion of nonferrous alloy. In this study, TiAlN/C nano-composite coatings synthesized by PVD process were examined the effects of sputtering conditions on the microstructure and mechanical properties, and evaluated as potential applications in molding dies. Coating films were synthesized by the co-sputtering of TiAl (pulsed-d.c. sputtering) and C (d.c. sputtering) targets using a Facing Target-type Sputtering system (FTR-2, Osaka Vacuum Co., Ltd.) under an environment with a mixture of Ar and N2 on square plates of Si and high speed steel (ANSI M2). The structure of the films was investigated by means of XRD, XPS and HRTEM with GIF (Gatan Imaging Filter). Mechanical properties of coating films were measured in detail by a submicron indentation system (H-100, Fischer). Although TiAlN or a-C films showed hardness of about 30 or 10 GPa, one of TiAlN/a-C films containing several % of a-C showed higher hardness of 43 GPa. The Zero-loss image indicated that a change of contrast accompanies the change of composition of Ti and Al. Nanometer-size of Al agglomerates were observed and Ti distribution corresponded to that of Al. XPS analysis of C1s spectrum revealed that carbon in the films bound almost as C-C with a few bondings of Ti-C or Al-C and C-N. Ti2p and Al2p spectrum indicated that these transition metals bound mostly with nitrogen. These results indicated that nano-composite structure consisting of complicated mixture of nanocrystalline Ti-Al-N phase and a-C phase (with a small amount of C:N phase and metal carbide phase) existed in the TiAlN/a-C films.