Deposition of TiAlSiN nanocomposite coatings using four-cathode reactive direct current unbalanced magnetron sputtering system

Surface engineering approaches are being increasingly employed for enhancing the effective life of cutting tools with a view to reduce machining costs. The ever increasing demands for high precision machining and increased cutting performance in terms of cutting speed and lifetime require wear resistant tools of large dimensional accuracy having very sharp cutting edges. In this study TiAlSiN nanocomposite coatings were deposited on high speed drill bits, mild steel, silicon substrates and tungsten carbide cutting tool inserts using a four cathode reactive direct current unbalanced magnetron sputtering system. TiAlSiN nanocomposite coatings were deposited using Ti, Al, and Si, targets in the presence of Ar and N2 plasma. Various treatments were given to the substrates to improve adhesion of TiAlSiN coatings. The coatings were characterized and tested for their tribological properties. The morphology of the as-deposited coatings was characterized using FESEM and AFM. The mechanical and the thermal stabilities were also evaluated. These coatings exhibited hardness in the range of 30-35 GPa. For the performance evaluation, the TiAlSiN coated drills were tested under accelerated machining conditions. With a drill speed 800 r.p.m and feed rate 0.08 mm/rev. the uncoated drill failed after drilling 50 holes in a 12 mm thick 304 stainless steel plate. Under the same conditions the TiAlSiN coated drills averaged 714 holes before failure. Results indicated that for TiAlSiN coated drill the tool life can be increased by a factor of more than 14