Study of hard and wear-resistant films onto silicon nitride ceramic cutting tools by pulsed high energy density plasma

Hard and wear-resistant TiN, TiCN and TiAlN coatings were deposited onto silicon nitride ceramic cutting tools at ambient temperature by pulsed high energy density plasma technique. Under optimum conditions, the maximum nanohardness of the as-deposited TiN, TiCN and TiAlN coatings were more than 27 GPa, 53 GPa and 40 GPa, respectively; the maximum Young's modulus were more than 350 GPa, 550 GPa and 680 GPa, respectively; the maximum critical loads measured by nanoscratch tests were more than 80 mN, 100 mN and 90 mN, respectively. Compared with the uncoated Si3N4 ceramic cutting tools, the flank wears of the tools coated with TiN, TiCN and TiAlN, evaluated by the cutting performance under industrial conditions, were reduced by a factor of 2-3, 6-8 and 5-7, respectively. The improvement in mechanical properties of the coated tools was attributed to the deposition of TiN, TiCN and TiAlN coatings.