Optical microscopy and microhardness characterisation of some biovitroceramics used as coatings on titanium

Some vitroceramics belonging to the oxidic system SiO2-CaO-P2O5-B2O3-Na2O-K2O-Li2O-MgO-TiO2 were prepared and then characterised by optical microscopy and microhardness trials. The frits from the above mixture were turned into composite materials by reinforcing them with 0.1-0.8% in weight Ti powder. Both simple and composite frits were used for coating the titanium plates by enamelling. The vitroceramic layer-titanium couples were characterised by means of optical microscopy and microhardness trials. From hardness tests made at vitroceramic layer-metallic substrate interface adherence of the layer to the substrate was determined. By reinforcing the vitroceramic frits with titanium powder we tried to increase the fracture toughness and decrease the brittleness of the coating layers. These quantities were computed from Vickers microhardness values, indentation forces, measurements of the microhardness imprint diagonals and cracks that propagate from the imprint corners.