SURFACE AND INTERFACE ANALYSIS, zyxwvutsrqpo VOL. 18, 525-531 (1992) TiN, T i c and Ti(C, N) Film Characterization and its Relationship to Tribological Behaviour R. Bertoncello,'** A. Casagrande,' M. Casarin,' A. Glisenti,' E. Lanzoni,, L. Mirenghi3 and E. Tondello Italy Dipartimento di Chimica Inorganica, Metallorganica ed Analitica, Universita di Padova, via P. Loredan 4, 35131-Padova, Istituto di Metallurgia, Universita di Bologna, viale Risorgimento 4,40136-Bologna, Italy Centro Nazionale per la Ricerca e lo Sviluppo dei Materiali, via G. Marconi 147, 72023-Mesagne, Brindisi, Italy Scanning electron microscopy observations, energy dispersive spectroscopy, x-ray diffraction and x-ray photoelec- tron spectroscopy analyses have been employed to study the composition and the microstructure of titanium car- bonitride coatings deposited by a reactive ion-plating industrial system. Both TIN and TYC, N) coatings show a very fine and dense microstructure and consist of a NaCI-type single phase with a marked preferred orientation. X-ray photoelectron spectroscopy analysis of the characteristicTi, C and N lines establishes the extent of Ti(C, zy N) compound formation and the dependence of composition on the reactive gas flow ratio. Depth profiles obtained by XPS analyses after cycles of Ar zyxwvutsrq sputtering indicate chemical uniformity of the films. Microhardness measure- ments taken on coated HSS specimens show that Ti(C, N) are significantly harder than TIN and TIC films deposited under the same conditions. Ti(C, N) coatings have a lower coefficient of friction and a higher wear resistance than TiN coatings, irrespective of the mating material. INTRODUCTION Titanium nitride and carbide coatings are widely used in a variety of applications owing to their peculiar properties, such as high hardness, good corrosion resist- ance and excellent tribological behaviour.' Multi- component coatings, however, are believed to represent the most promising development in the field, owing to the benefits derived from solution- and/or dispersion- hardening effects, and hence the growing interest in systems such as TiAlN, TiN/TiC and TiC/TiB, ., A satisfactory method to deposite dense TiN coatings with good adhesion to steel substrates is reactive ion- plating (RIP), where Ti is vaporized into a Arm, gas plasma at 1 Pa residual pressure. This method can be extended to the deposition of ternary Ti(C, N) coatings by using Ar/N,/C,H, gas plasmas at different composi- tions. The aim of this work was to give a contribution to the development of multicomponent coatings by study- ing the microstructure and composition of Ti(C, N) coatings and by evaluating their tribological properties in comparison to those of conventional TiN coatings. EXPERIMENTAL Ti(C, N), T i c and TiN coatings were deposited onto HSS steel substrates using hollow cathode discharge- RIP. All substrates were carefully polished with a water-oil corundum suspension and cleaned in an ultra- sonic bath with l,l,l-trichloroethane. * Author to whom correspondence should be addressed. 0142-242 1/92/070525-07 $08.50 zyxwvutsrqp 0 1992 by John Wiley & Sons, Ltd. The specimens labelled SU1, SU2, SU3, SU6, SU7 and SUlO were mounted on a rotating barrel-jig, whereas those labelled SU4 and SU5 were clamped on a fixed rack facing the Ti source at a distance of 0.15 m. After introduction into the deposition chamber, the specimens were heated to the deposition temperature (763 & 10 K) at an Ar pressure of 0.1 or 0.2 Pa. In order to get a true 'metallic' surface, the specimens were finally ion-etched for 10 min in an Ar plasma at 1 Pa. The deposition was carried out in three steps. At first, Ti was deposited for 10 s. Thereafter, a controlled flow of Nz (99.99% purity) was admitted and a TiN film was deposited for 150 s. Finally, controlled flows of N, and C,H, (99.5% purity) were admitted and the Ti(C, N) coating was deposited for 20 min at a total pressure of 8 zyxwv x lo-' Pa. Owing to the greater distance from the Ti source and the less favourable average orientation to the vapour flux, the deposition rate on the rotating specimens was much lower than on the fixed specimens. After 20 min under the standard coating conditions, the average coating thickness was in the range 1.8-2.5 pm for the former and 5.6-7 pm for the latter. After the deposition, the specimens were cooled in an N, flow to 473 K and then brought up to atmosphere. The same procedure was adopted for the preparation of the TiN (SU5 and SUIO) and TIC (SU7) reference samples. The Ti(C, N) samples were deposited at three different C,H,/(N, + C,H,) flow ratios, 6 : 0.23, 0.33 and 0.58 (samples SU1, SU2 and SU3, respectively). The SU4 and SU6 specimens were coated at the same flow ratio as SU2. In all cases, the total flow of the reactive gases was between 400 and 450 ml min-'. Thickness and morphology were observed by SEM on the fracture sections. Phase constitution and texture were determined by x-ray diffraction (XRD) using Cu K, radiation, and composition was determined by zy Received 30 October zy 1991 Accepted 31 January 1992