This paper reports on the optimization of (Ti,Si,Al)Nx coatings to improve the performance of coated tools in dry cutting applications. The performance and the wear mechanisms of (Ti,Si,Al)Nx tungsten carbide coated tools were investigated. Tool life and tool failure modes were thoroughly examined by scanning electron microscopy (SEM) complemented with energy dispersive spectroscopy (EDS) in order to study the wear mechanisms. After 15 min at high cutting speed (200 m/min), the cutting edges of almost all the coatings still remained in good conditions. The results presented on this paper confirmed that nc-(Ti1−xAlx)/a-SiNx nanocomposite coatings offer a significant potential to operate in extreme environments, since this coating outperformed one of the best solutions actually available in the market for high speed turning. An improvement on the tribological behaviour of (Ti,Si,Al)Nx films was also observed with thermal annealing before the turning tests, due to a self hardening effect as consequence of the spinodal segregation of the (Ti,Al,Si)N metastable phase. On the other hand, no significative increase on the performance of the coated tools was observed with depositing an amorphous Al2O3 interlayer.