Structural study of a titanium–titanium boride cermet coating formed upon laser fusion of boron on a titanium foil

Abstract

The laser melting conditions of boron and titanium on the surface of a titanium foil have been determined. Both fusions induce a chemical reaction resulting in the formation of a cermet (ceramic–metal composite) coating on the surface of the titanium sample. This coating, the hardness of which lies between 300 and 500 Hv (whereas its thickness lies between 100 and 160 µm) is made of an intimate mixture of α-Ti, TiB₂ and TiB, the metallic phase being the major one. Underlying, α-Ti is only heat affected with, just beneath the cermet layer, acicular looking grains. Crystallographic analyses of TiB₂ indicate that the phase presents rather large crystallites with sizes of about 0.07 µm and 1 µm along the [00l] and [h00] directions, respectively. This phase presents no preferred orientation and almost no network strains.