Tribological performance evidence on ternary and quaternary nitride coatings applied for industrial steel

Abstract

A diagnostic of mechanical and tribological behavior in ternary Ti-C-N and quaternary Ti-Nb-C-N films deposited onto Si~(100) and 4140 steel substrates by r.f. magnetron sputtering processvarying negative bias voltage from 0 to -100~V,was done in this work. Growth parameters as power density, Ar/N$_{2}$ flow rate, and substrate temperature were keptconstant at the moment of the deposition. Introduction of Nb in the ternary Ti-C-N film was evaluated by X-ray diffraction (XRD) analysis.Quantitative elemental concentration depth profile by glow discharge optical emission spectroscopy (GDOES) and the morphology via scanning electron microscopy (SEM) were observed for the layers before the tests. Mechanical and tribological properties for both coatings were obtained by mean of nanoindentation measurements throughload versus displacement method, and scratch test using the critical load criterion, respectively. The failure modes from scratch test were observed via optical microscopy. XRD results show as the amount of Nb is increased into the quaternary phase, the preferred orientation change in the film due to the modification in the strain and lattice parameter (Caicedo et al., 2007). EDX results from previous work show the TiCN and TiNbCN layers were stoichiometric (Caicedo et al., 2007). Nanoindentation results reaching the elastic-plastic behavior of the Ti{}C{}N and Ti{}C{}N films with inclusion of Nb (Ti{}Nb{}C{}N), indicate not only the hardness and elastic modulus but also the critical load for the adhesive failure increase when increasing r.f negative bias voltage. An improvement of hardness and critical load around 60% and 28% for Ti{}C{}N as well as 26% and 31%for Ti{}Nb{}C{}N, respectively, was associated to an increasing in the r.f negative bias voltage from 0 to~-100 V.