Structure and composition of ZrN and (Ti,Al)N coatings

Triode ion plated ZrN and (Ti,Al)N thin films were deposited on high-speed steel and stainless-steel substrates. The samples studied in this work were selected on the basis of their cutting performance in turning tests as reported earlier. In cutting tests (Ti,Al)N and ZrN both showed significantly increased wear life as compared to standard TiN. X-ray diffraction studies revealed for (Ti,Al)N a cubic B-1 NaCl structure with strong (200) orientation. The initial morphology was columnar, but by increasing the substrate current density the columnar growth could be suppressed and a finer structure resulted, while wear life in turning also increased. All ZrN coatings showed B-1 NaCl structure with a (111) preferred orientation. Their fracture surface was always noncolumnar and almost featureless as judged by scanning electron microscopy. However, cross-sectional transmission electron microscopy studies revealed a fine columnar structure also with these films. The ZrN coatings had a uniform through-thickness nuclear resonance broadening nitrogen depth profile, whereas irregularities were observed in the (Ti, Al)N coatings and an uneven aluminum distribution was revealed also by backscattering measurements