Tribological performance of TiN coatings deposited on 304 L stainless steel used for olive-oil extraction

Abstract

Titanium-nitride (TiN) coatings have been developed and used by industry in numerous tribological applications, including machining, manufacturing and transportation. However, they have not attracted any attention as a tribological coating to be used in olive-oil extraction devices. In fact, since the separation of vegetation water and solid phase of the olive is always made in a continuous process and in very short time, the wear damage of the metallic devices used in this process is still a serious problem. The purpose of this study is to investigate the mechanical and tribological behaviors of TiN coating under a wide range of deposition conditions. The results of this study have confirmed that the coatings deposited using direct current (DC) bias present several distinct changes compared to those produced with pulse bias, depending on the magnitude of the duty cycle applied with and without Argon gas. Besides, different grain orientations have been detected for both kinds of TiN coatings. Tribological performances for the obtained TiN coatings were investigated using different configurations namely reciprocating sliding and pin-on-disk tests. The responses of these coatings in terms of friction coefficient and wear depth were discussed. The main results when sliding against olive seed and alumina ball as counterbody have clearly revealed a significant improvement of tribological properties with the application of DC and pulse bias voltage. Moreover, the tribological behavior of TiN did not change much with the addition of Ar gas.