a coated cutting tool comprises a substrate having an outer coating of refractory material with an interfacial layer intermediate the substrate and outer coating for enhancing the adherence of the layer of refractory material to the substrate . the interfacial layer is provided by reacting titanium halide with a layer of alpha - silicon nitride to form a smooth and uniform layer of titanium nitride . the cutting tool may also comprise the intermediate products of alpha - coated silicon nitride or the titanium nitride coated tool formed by reacting the alpha - silicon nitride coating .