Study on the preparation of hard and wear-resistant titanium nitride films on silicon nitride ceramic cutting tools

Hard and wear-resistant titanium nitride coatings were deposited by pulsed high energy density plasma technique on silicon nitride ceramic cutting tools at ambient temperature. The coating thickness was measured by an optical profiler and surface Auger microprobe. The elemental composition and depth concentration profiles, phase compositions and elemental binding states of the coatings were determined by Auger microprobe, x-ray photon-electron spectroscope, and X-ray diffractometer. The microstructures of the coatings were observed by scan electron microscope and the roughness of the sample surface was measured by an optical profiler. The mechanical properties of the coatings were determined by nanoindentation and nanoscratch tests. The tribological properties were evaluated by the cutting performances of the coated tools applied in turning of HT250 steel under industrial conditions. The structural and mechanical properties of the coatings were found to depend, strongly on synthetic conditions. Under optimized deposition conditions, the adhesive strength of TiN film to the substrate was satisfactory with the highest critical load up to more than 80 mN. The TiN films possess very high nanohardness and Young's modulus, which are near to 28 GPa and 350 GPa, respectively. The wear resistance and edge life of the silicon nitride ceramic tools were improved dramatically because of the deposition of titanium nitride coatings.