Deposition of Ti–Al–N coatings by thermal CVD

This study investigates the feasibility to deposit metastable Ti1–xAlxN coatings by thermal chemical vapour deposition (CVD) from the TiCl4–AlCl3–NH3–Ar system in an industrial CVD unit. The chemical composition and phase constitution was altered using different AlCl3 contents and deposition temperatures. According to X-ray diffraction analysis, single-phase face-centered cubic (fcc) structures have been obtained up to 19 at.% Al, where the incorporation of Al decreases grain size and micro-hardness. In addition, fcc-AlN has been detected between 20 and 24 at.% Al causing an enhanced micro-hardness and extremely fine structures. High temperatures and Al-contents produce coatings of poor mechanical properties consisting of TiN and hexagonal close-packed AlN.