3 research outputs found
Fretting wear of TiN PVD coating under variable relative humidity conditions ā development of a ācompositeā wear law
Fretting is defined as a small oscillatory displacement between two contacting bodies. The
interface is damaged by debris generation and its ejection from the contact area. The
application of hard coatings is an established solution to protect against fretting wear. For this
study the TiN hard coating manufactured by a PVD method has been selected, and tested
against a polycrystalline alumina smooth ball. A fretting test programme has been carried out
at a frequency of 5 Hz, 100 N normal load, 100 Ī¼m displacement amplitude and at five values
of relative humidity: 10, 30, 50, 70 and 90% at a temperature of 296 K. The intensity of the
wear process is shown to be significantly dependent on the environmental conditions. A
dissipated energy approach has been employed in this study to quantify wear rates of the hard
coating. The approach predicts wear kinetics under constant medium relative humidity in a
stable manner. It has been shown that an increase of relative humidity promotes the formation
of hydrate structures at the interface and modifies the third body rheology. This phenomenon
has been characterised by the evolution of wear kinetics associated with a significant variation
of the corresponding energy wear coefficient. Hence, a ācompositeā wear law, integrating the
energy wear coefficient as a function of relative humidity, is introduced. It permits a
prediction of wear under variable relative humidity conditions from 10 to 90% within a single
fretting test. The stability of this approach is demonstrated by comparing various variable
relative humidity sequences