Structure and properties of TiB2 coatings produced by dynamic ion mixing

TiB2 ceramic coatings have been produced at room temperature by dynamic ion mixing (DIM) using two deposition methods: either electron beam coevaporation or ion sputtering of a TiB2 target. The bombardment during deposition was performed with high energy heavy ions: 100 keV Ar+, 320 keV Ar+, 320 keV Xe+. It is demonstrated that thick coatings up to 1 μm of homogeneous composition and controlled structure can be produced by this method. Cross-sectional transmission electron microscopy observations (XTEM) show that the ion mixing of growing films induces crystallization of the TiB2 hexagonal phase whereas the coatings are amorphous without mixing. The analysis of experimental results indicates that a critical damage level of about 1 dpa (displacement per atom) is necessary before detecting a significant crystallization effect. The intrinsic film hardness was estimated in the range 2200-2800 kgf/mm2. Substantial adhesion improvement is also observed in cases where an efficient interface mixing was achieved. (orig.)