DEPOSITION OF ARC TIALN COATINGS WITH PULSED BIAS

It is a well-known fact that tire aluminium content of TiAlN coatings deposited with the arc physical vapour deposition (PVD) process depend s mainly on substrate potential and source-to-substrate distance. To a chieve good results in cutting operations with TiAlN-coated tools with a low aluminium content in the film, it is necessary to deposit TiAlN with a relatively high bias voltage which raises the substrate temper ature to a level which can cause some damage to the structure of even high speed steel substrates. For high performance cutting operations w ith TiAlN thin films a high and homogeneous aluminium content in the f ilms, especially on cutting edges, is necessary. Higher aluminium cont ent in are PVD thin films is achieved with lower bias voltage during d eposition which in turn lowers the deposition temperature and conseque ntly enables heat-sensitive substrates to be coated; however, for good adhesion of the deposited films a high bias voltage is required. The application of a pulse bias generator instead of a d.c. bias offers th e possibility to decrease the deposition temperature and to obtain mor e aluminium in the coating. In this paper we compare coating propertie s of TiAlN deposited with d.c. and pulsed bias source. With pulsed bia s it is possible to achieve higher aluminium content in the coating, e specially on cutting edges. Analysis of increase in aluminium on cutti ng edges was carried out by energy-dispersive X-ray analysis.