TiAlN/TiAlZrN multilayered hard coatings for enhanced performance of HSS drilling tools

Alternate TiAlN/TiAlZrN multilayered hard coatings with bilayer periods ranging from 6.7 to 600 nm were prepared by cathodic arc method on steel substrates and 8 mm HSS drills. The elemental composition of the composing layers was determined. A thoroughly investigation of the characteristics of multilayers and of the TiN, TiAlN and TiAlZrN single layer coatings was done, concerning the phase composition, texture, microhardness, adhesion and dry drilling performance. The highest microhardness values, of about 49 GPa, were measured for the multilayers with Λ ≈ 13 nm, while the coatings with large Λ values (~ 600 nm) were found to have the best adhesion (critical load Lc = 63 N). The dry drilling tests revealed that the nanometer scale multilayered TiAlN/TiAlZrN coatings exhibited superior drilling performance as compared with commonly used single layer coatings (TiN, TiAlN).