The interface between TiAlN hard coatings and steel substrates generated by high energetic Cr+ bombardment

The microstructure of TiAlN coatings deposited by reactive unbalanced magne tron (UBM) sputtering after substrate bombardment with Cr ions, generated b y a cathodic are, and compositional changes of the ferritic steel substrate have been investigated for different bias voltages (U-b) during the Cr bom bardment. Analysis was carried out using cross-sectional transmission elect ron microscopy (XTEM) and conversion electron Mossbauer spectroscopy (CEMS) . The aim of the Cr bombardment is a substrate sputter cleaning effect. Thi s is achieved when a bias voltage of - 1200 V is applied. In this case subs equent UBM deposition of TiAlN leads to the growth of dense coatings exhibi ting local epitaxy. For lower bias voltages GEMS indicates Cr deposition re sulting in an open columnar structure of the subsequently grown TiAlN film, although small areas with oriented growth can still be observed. (C) 2000 Elsevier Science S.A. All rights reserved.