Modified TiAlN coatings prepared by d.c. pulsed magnetron sputtering

Abstract

Coatings like TiN or TiAlN are well established as hard and wear resistant tool coatings. These coatings often are prepared by PVD techniques like arc evaporation or d.c. magnetron sputtering. Typical micro hardness values of such hard coatings are in the range of 30 GPa. Compared to d.c. magnetron sputtering processes the pulsed magnetron sputter deposition technique could be shown as a clear advancement. Furthermore pure TiAlN hard coatings as well as TiAlN coatings modified by addition of elements like Si and Cr were prepared in order to improve the coating properties using the pulsed magnetron sputter technique in a batch coater equipped with 4 targets. Coatings prepared with the pulsed sputter process showed both high hardness and high wear resistance. The application potential of pulsed sputtered TiAlN coatings is demonstrated by turning test results of coated cemented carbide cutting inserts. Beside hardness and wear, other properties like adhesion or high temperature stability were determined. Cross sectional SEM images revealed the growth structure in dependence of the applied substrate bias and of the added elements. The chemical composition of the coatings was investigated by electron microprobe analysis and the phase and crystal size were determined by X-ray diffraction. Using the pulsed magnetron sputter process the coating properties, especially the hardness and the morphology, could be significantly improved. With indentation hardness values in the range of 40 GPa the region of super hard materials could be reached.