Surface and Coatings Technology, 60 (1993) 549—555 5 The dependence of hardness and corrosion protection power of ion- beam-assisted deposition TiN coatings on the ion beam impact angle R. Hübler Inst it Ut 0 de InJ~rnthtica, Pontificia Universidade Catdlica do Rio Grande do Sul. Porto Alegre (Brazil) L. Alberts Lahoratoire ~I4etallurgiePhysique. Unirersité Poitiers, Poitiers (France) G. K. Wolf Physikalisch Chernisches Institut der Universität, In Neuenheimer Feld 500, W-6900 Heidelberg (Germany) Abstract Hard coatings such as titanium nitride are often porous and therefore not necessarily very corrosion resistant. Possibilities for reducing the film porosity are densification and multilayer structures. These methods are studied in our laboratories at present. Ion-beam-assisted deposition (IBAD) TiN films were deposited changing the angle between the substrate normal and the ion beam incidence direction. The films were characterized by transmission electron microscopy, scanning electron microscopy and X-ray diffraction analyses, the hardness was determined by means of a dynamic Vickers hardness tester and the corrosion behaviour was evaluated using current—potential measurements in a multicycle voltammogram mode. The results are strongly dependent on the changes in the crystal orientation induced by the ion flux under different angles. Careful optimization may lead to coatings with high hardness and excellent corrosion protection potential. These results are compared with TiTiN multilayers deposited by IBAD and magnetron sputtering and with a sputtered TiN single layer. 1. Introduction In this contribution the variations in the corrosi protection potential and hardness of thin TiN fir The success of TiN as a hard coating on steels under prepared by IBAD are reported as a function of t] tribocorrosive situations may be attributed to a number microstructural changes following ion beam inciden of exceptional properties of this material such as hard- angle variation. Ti/TiN multilayers prepared by magn ness, chemical stability, nobility, sufficient adhesion to tron sputtering and IBAD are included in this study f steel substrates and good wear and corrosion resis- comparison. The deposition parameters for the films a tance [1—3]. described in the next section together with the metho Several methods, e.g. chemical vapour deposition used to characterize the samples. Section 3 contains ti (CVD), magnetron sputtering, arc deposition and ion- experimental results obtained in the present work ai beam-assisted deposition (IBAD), have been used up to Section 4 the conclusions. now for the preparation of TiN thin films for corrosion and wear protection [3—5]. Unfortunately, most of these films have a columnar structure and are relatively porous. Recently, in our laboratories multilayered struc- 2. Experimental details tures of Ti/TiN were made succesfully in order to reduce the porosity [5, 6]. The IBAD system used for this study consists of The IBAD method offers a great flexibility for varia- deposition chamber operating at a base pressure tions in deposition parameters. An effect of ion bombard- 2x 10 ~ mbar equipped with a Duoplasmatron i ment during deposition can be the generation of films source and a 2 kW electron beam evaporator. It with preferred orientations [7, 8]. Among other proper- described in detail elsewhere [9]. ties, grain size, film stress, nucleation and defect density The samples serving as substrates were (I) cylinde may be optimized by ion-beam-assisted deposition. All of CK4S steel polished down to 1 i.tm diamond paste f these effects influence the hardness and corrosion protec- corrosion measurements, (2) silicon (Ill) for scannit tion properties of the coating. electron microscopy (SEM), X-ray diffraction (XRD) ai