In Situ Studies of TiC1−x N x Hard Coating Tribology

Abstract

TiC 1-x N x hard coatings present time-dependent tribological behavior with an initial running-in period (500-2000 cycles) marked by an elevated friction coefficient, followed by [10000 cycles with low-friction and wear at room temperature (RT) in ambient air. The mechanisms behind this behavior are not completely understood. Tribological tests performed at RT and at different relative humidity (RH) levels revealed that a minimum value between 15 and 25% RH is needed to trigger the low-friction regime at a sliding speed of 100 mm s -1 . By in situ observations of transfer film growth, it could be observed that third body material is formed during this running-in period by plowing of the coating and shearing of the removed material. The appearance and thickening of the transfer film marks the beginning of the steady-state low-friction regime where the velocity is accommodated by interfacial sliding. At this stage in the tribological test, the recorded Raman spectra indicated the presence of C-H bonds in the wear track. Use of in situ analytical tools during wear tests provided insights with respect to tribological phenomena that were not available by conventional, post-mortem analysis methods.

Optical In Situ Micro Tribometer for Analysis of Real Contact Area for Contact Mechanics, Adhesion, and Sliding Experiments

“…There are various pathways for in situ analysis of a surface. In situ spectroscopies such as Raman spectroscopy have been used to analyze the chemical nature of the interactions by examining the wear surface or transfer films during sliding or just after it exits the contact without changing the environment [3,4]. In situ electron microscopy is increasingly popular; Varenberg used a scanning electron microscope to analyze the interaction at the interface from the side [5].…”

PVD and CVD Hard Coatings

“…These extremely different loading conditions, the necessity of increased performance and the demand to master difficult-to-machine materials, have driven the specific development of wear-resistant coatings within the last three decades to meet the individual requirements of the given application. This has recently been related to the in situ formation of self-lubricious reaction layers after a short running-in period in dry sliding contacts ( Figure 5), where the carbon released from the coating forms in humid environments an easy shearable, a few nanometer thick reaction layer characterized by weak C-H bonds (Rebelo de Figueiredo et al, 2010). In particular, TiC x N 1Àx is also of interest because of its excellent friction properties, where the friction coefficient of TiN in the order of 0.6-0.8 (Fateh, Fontalvo, Gassner, & Mitterer, 2007;Franklin & Beuger, 1992) against alumina is reduced to approximately 0.2 due to the formation of the TiC x N 1Àx solid solution (Rebelo de Figueiredo et al, 2008).…”

“…Coefficient of friction and transfer film thickness formed on a TiC x N 1Àx coating plotted versus the number of cycles for a reciprocating sliding test against an Al 2 O 3 counterbody performed in an atmosphere with 35-45% relative humidity (Rebelo deFigueiredo et al, 2010).…”

Tribological Properties of Arc-Evaporated NbAlN Hard Coatings

“…It is also possible that a major fraction of the counterpart wear occurred prior to the formation of the transfer film. In order to study the transfer Lines are a guide for the eye film formation in detail, in situ characterisation methods that monitor the tribological contact during sliding need to be used [25].…”