Properties analysis of gradient CrAlTiN coated high-speed steel tools

The cutting tools coated with physical vapor deposition are extensively used in global manufacturing for reducing production costs and improving productivity in metal cutting operations. In this paper, a new gradient CrAlTiN coating was deposited on high speed steel substrates using closed field unbalanced magnetron sputter ion plating system with Cr, Al and Ti metal targets. The coatings were characterized using the following techniques: the thickness with a spherical crack tester, the microhardness with a Vickers hardness tester, the adhesion with a scratch tester, the wear rate and friction coefficient with a pin on disc tester, the chemical composition with an energy spectrometer, the phase composition with a X-ray diffractometer and micrographs with a scanning electron microscope and transmission electron microscope. The properties of the coatings were found to depend strongly on substrate bias voltages. Under optimized substrate bias voltages conditions, the gradient CrAlTiN coatings have the desired properties of high hardness, good adhesion, exceptional wear resistance and high thermal stability for cutting tools. Drilling tests showed that the performance of the gradient CrAlTiN coated HSS twist drills is remarkably improved as compared with that of TiN coated drills, and it will be one of the most perspective coatings for HSS cutting tools.