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Preparation and characterization of CVD-TiN-coated carbon fibers for applications in metal matrix composites

: Abidin, Alfaferi Zainal; Kozera, Rafał; Höhn, Mandy; Endler, Ingolf; Knaut, Martin; Boczkowska, Anna; Czulak, Andrzej; Malczyk, Piotr; Sobczak, Natalia; Michaelis, Alexander


Thin solid films 589 (2015), S.479–486
ISSN: 0040-6090
Fraunhofer IKTS ()
CF / Al-MMC; lightweight; CVD; TiN; 3D-textile preform and GPI

Preparation and characterization of CVD-TiN-coated carbon fibers for applications in metal matrix composites (MMC) are promising materials for lightweight applications. So far the application has been hindered by a lack wettability of carbon fibers by aluminum alloys and detrimental reactions like aluminum carbide (Al4C3) formation. Protective coatings prepared by chemical vapor deposition (CVD) could be a suitable way to overcome these problems. In this work carbon fiber based 3D-textile preforms were coated with titanium nitride (TiN). Coating thickness, homogeneity, layer structure and composition were determined. Furthermore oxidation resistance and tensile strength of coated fibers were investigated. The wettability by molten aluminum combined with an interface analysis is examined on TiN-coated graphite substrates. Finally the quality of MMC parts prepared by gas pressure infiltration (GPI) method are evaluated. The CVD process was performed with a gas mixture of TiCl4, N2 and H2. A homogeneous coating was achieved at moderate deposition temperatures in the range from 800° to 850°C and by proper adjustment of further process parameters as TiCl4 concentration and total pressure. A very thin TiN layer with a thickness between 30 nm and 35 nm improves the oxidation resistance and results in a moderate decrease of the tensile strength from 3.9 GPa to 2.2 GPa. TiN improves the wettability and acts as a protective coating. However because of the long infiltration time in the GPI process, interface reactions occur. SEM investigations of TiN coated 3D-textile preforms infiltrated with AlSi9Cu3 alloy (226D) showa completely dense composite with a strong reduction of the Al4C3 formation. TiN offers a good protective effect if the contact time with the melt is not too long.