Selbstheilende verschleißbeständige Presswerkzeuge zur Herstellung von Diamant-Verbundwerkstoffen
Materials in Sintering Processes and Generative Manufacturing Processes
Final Report Abstract
NiTi SMA thin film is used as the main part of the self-heling composite coating system due to its excellent load bearing capacity. The development of the self-healing composite coatings was performed in four steps. In the first step, NiTi SMA coatings were developed and optimized by finding the most suitable: 1) annealing technique 2) annealing temperature 3) sputtering targets 4) Composition (near equiatomic and Ti-rich). It was found that in-situ annealing technique is more prominent than post-annealing one because, post annealing method results in poor coating-to-substrate adhesion, weak wear performance and low quality SME (large hysteresis).The NiTi thin films in-situ annealed at 80°C are completely amorphous while they are at 305°C partially amorphous, at 425°C mostly crystallized and at 525°C completely crystallized. Mechanical and tribological performance of the in-situ annealed coating at 305°C was better than the other coatings due to the presence of nanocrystalline NiTi embedded in the brittle NiTi amorphous matrix. However, these coatings did not present sufficient SME and SE since they were not completely crystallized. The in-situ annealed NiTi thin films at 425°C and 525°C possess inherent SME and SE. Since in-situ annealing at 525°C could result in the diffusion of TiCN protective coating layer into NiTi interlayer, a lower in-situ annealing temperature of 425°C was chosen. Equiatomic NiTi thin films in-situ annealed at 425°C were sputtered from Ti-rich NiTi alloy targets and separate elemental Ni and Ti targets. It was found that employing alloy targets is more suitable since it results in a faster crystallization of NiTi coatings with a better SME, SE and wear resistance capability. Near equiatomic NiTi coatings were compared with Tirich NiTi coatings. It was observed that the existence of Ti2Ni precipitations in Ti-rich coatings results in poor wear performance and lower degree of crystallization within the coating materials. In the second step, TiCN coatings were developed by adjusting the flowing rate of C2H2 reactive gases and consequently carbon content of the coatings. It was observed that mechanical and tribological performance of the coatings can be tailored by adjusting the flowing rate of C2H2 reactive gases. The best mechanical and tribological performance was observed in the TiCN coatings which were deposited under the maximum C2H2 flowing rate of 65mln. For the third step, the developed TiCN coating system was developed on the developed NiTi interlayer coatings under different thickness ratio. The goal was to find the optimum thickness ratio in which SME and SE effect of NiTi interlayers is maintained after deposition of TiCN protective coating layers. It was found that the maximum NiTi/TiCN thickness ratio can be 1/3 to present self-healing capability in the composite NiTi based coating system.
Publications
- Deposition of Superelastic Composite NiTi based Films, Vacuum, Volume 104, 2014, 41–46
Wolfgang Tillmann, Soroush Momeni
(See online at https://doi.org/10.1016/j.vacuum.2013.12.010) - Comparison of depositing NiTi thin films sputtered from NiTi alloy targets and separated elemental Ni and Ti targets Journal of Materials Processing Technology, Volume 220, 2015, 184–190
Wolfgang Tillmann, Soroush Momeni
(See online at https://doi.org/10.1016/j.jmatprotec.2015.01.014) - Effect of annealing techniques on tribological performance of NiTi SMA thin films, Surface & Coatings Technology, Volume 276, 2015, 286–295
Wolfgang Tillmann, Soroush Momeni
(See online at https://doi.org/10.1016/j.surfcoat.2015.07.012) - In-situ annealing of NiTi thin films at different temperatures, Sensors and Actuators: A Physical, Volume 221,2015, 9–14
Wolfgang Tillmann, Soroush Momeni
(See online at https://doi.org/10.1016/j.sna.2014.10.034) - Tribological performance of near equiatomic and Ti-rich NiTi shape memory alloy thin films, Acta Materialia, Volume 92, 15, 2015, 189–196
Wolfgang Tillmann, Soroush Momeni
(See online at https://doi.org/10.1016/j.actamat.2015.04.006)
