The performance of TiAlSiN coated cemented carbide tools enhanced by inserting Ti interlayers

To enhance the cutting performance of TiAlSiN coated cemented carbide tools by inserting Ti interlayers and to explore their mechanism, TiAlSiN/Ti multilayer coatings with different Ti thicknesses, including 0 nm, 25 nm, 50 nm, 100 nm, and 150 nm, were deposited onto cemented carbide (WC-10 wt%, Co) substrates by high power impulse magnetron sputtering (HiPIMS). The microstructure, hardness, grain orientation, residual stress, adhesion, and toughness of those coatings were measured, and the cutting performance against Inconel 718 was analyzed. Meanwhile, finite element method (FEM) indentation simulations were performed to gain detailed insight into the effects of Ti interlayer thickness on mechanical properties of TiAlSiN/Ti multilayer coatings. Results demonstrated that mechanical properties of TiAlSiN multilayer coatings were significantly changed after the Ti interlayer was introduced, and the multilayer coating #M2 with 25 nm Ti layer showed the excellent toughness and adhesion without sacrificing hardness too much. As Ti interlayer thickness increased, both toughness and adhesion decrease owing to the plastic mismatch between individual layers, and these changes were discussed detailedly with finite element method. Moreover, the result of the cutting experiment also revealed that the tool flank wear Vb can be reduced by the multilayer structure. This improvement is believed to be due to the increasing toughness, which alleviated the damage caused by the continuous impact load of hard phases generated by Inconel 718 during cutting.