Influence of nitrogen implantation on the properties of Ti and substoichiometric TiN x films deposited on high speed ste
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Influence of nitrogen implantation on the properties of Ti and substoichiometric TiNx films deposited on high speed steel M. T. Rodrigo and C. Jim´enez Universidad Aut´onoma de Madrid, 28049 Madrid, Spain
L. V´azquez Instituto Ciencia de Materiales, C.S.I.C., 28049 Madrid, Spain
F. Alonso INASMET-Camino de Portuetxe, 12-20009 San Sebasti´an, Spain
M. Fern´andez Instituto Ciencia de Materiales, C.S.I.C., 28049 Madrid, Spain
J. M. Mart´ınez-Duart Universidad Aut´onoma de Madrid, 28049 Madrid, Spain (Received 9 December 1996; accepted 29 September 1997)
Ti and TiNx (x , 1) thin films have been deposited on high speed steel (HSS) substrates by reactive sputtering and then N1 implanted. The increase of the NyTi ratio of the films during deposition is related to a decrease in their roughness, and N1 implantation produces another additional slight decrease of the roughness. The hardness of samples increases with the nitrogen content in the as-deposited samples; nevertheless, N1 -implanted Ti coatings show lower values of hardness than reactive sputtered TiNx films. a –Ti, e –Ti2 N, and d –TiN phases were identified by grazing x-ray diffraction.
I. INTRODUCTION
II. EXPERIMENTAL
Titanium nitride coatings have been largely applied in a variety of fields as diverse as, for example, medical prostheses1 or microelectronic devices.2 Their excellent mechanical and tribological properties have extended their application to protective coatings on mechanical parts and cutting tools. As it is well known, the deposition technique and, in particular, the deposition conditions, are closely related to the final properties of the TiN films. In the case of mechanical properties, there are mainly influences by the microstructure, morphology, density, crystal structure, and stoichiometry of the films.3,4 In particular, the strong influence of the roughness on the tribological properties (mainly friction and wear) has recently been pointed out.5 In the last few years, different surface treatments have been developed in order to modify the TiN coatings characteristics and to improve their mechanical behavior. Ion implantation has been shown to be especially promising for surface modification after deposition, without damaging the in-depth layers.6 Moreover, the complementary use of pulse vapor (PVD) techniques and ion implantation allows one to create hard coatings with gradual composition in depth. Our work has been specially focused on the influence of nitrogen implantation at energies of 100 keV on the properties of TiNx (0 , x , 1) hard coatings.
Two sets of TiNx samples (x , 1) were deposited on AISI M35 high speed steel (HSS) substrates. Disks of 5 mm height 3 15 mm f were cut from a cylindrical bar, machined, heat-treated, and polished. They were also degreased before deposition. The deposited films were obtained by reactive sputtering in an ION TECH system, with four different compositions, increasing in nitrogen content from pure titanium to TiN0.9 . The variation of the film compo
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