Interaction between Ti-6%Al-4%V Alloys and Hardmetals Coated by Cathodic-Arc Technology
At present, milling of titanium based alloys for aerospace applications is mainly carried out with un-coated WC-Co carbide tools. The present work evaluates the chemical interaction of the Ti-6%Al-4%V alloy with these WC-Co commercial hardmetals. Strong decarburation induced by carbon diffusion to the Ti based alloy is observed at temperatures ranging from 750-1000°C. This reaction is responsible for the high adhesion found at the alloy-carbide interface. Different cathodic arc coatings have proved efficient in inhibiting such reaction and the associated adhesion to the Ti-6%Al-4%V alloy. Delamination induced by reaction between the Ti6Al4V alloy and AlTiN and TiAlCN coatings increases with the hot pressing temperature, being more severe for the AlTiN material. A lower bound of 44 J/m2 has been obtained for the interfacial fracture energy of cathodic arc PVD TiAlCN coatings on hardmetal substrates, this value being significantly higher than those previously reported for TiAlN materials.
Omer Van der Biest, Michael Gasik, Jozef Vleugels
C.M. Moreno et al., "Interaction between Ti-6%Al-4%V Alloys and Hardmetals Coated by Cathodic-Arc Technology", Materials Science Forum, Vols. 492-493, pp. 353-358, 2005