Harsh environment and changing work conditions (frequent start-stop, low/high speed, and boundary lubrication/dry friction) are the major factors causing the decrease of load carrying capacity, severe wear and poor reliability of friction pairs in mechanical seals. They are also the main challenge in the development of key parts for mechanical seals. Carbon-based coatings with diamond-like and graphite-like carbon coatings as representatives have attracted much attention in recent years.

Researchers at the State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences (CAS), have developed the key preparation technology of high hardness and low friction diamond-like and graphite-like carbon coatings for the surface of key parts in mechanical seals. They have also revealed the dependent relationship of tribopair between high hardness carbon-based coatings and various soft rubber and polymers. It has been proved that the new coatings can endure frequent start-stop tests and possess excellent antiwear property. The findings have been published in Tribology Letters (2012,47,67) .

Previously, in order to improve the triboligical property of diamond-like coatings under various gas and fluid environment, researchers have applied surface micro texturing and graded interface techniques to improve the performance of parts by making use of excellent performance and texturing effect of carbon-based coatings. They have provided physical description of triboligcal behavior of the coatings sliding against different counterparts as well. The findings have been published in Journal of Applied Physics (2011,109:013501), Journal of Applied Physics (2011,110:033521), Tribology Letters (2011,44:315) and Wear (2012,274-275:43).

Their work has received support from the National High-tech R&D Program of China (863 Program) and National Natural Science Foundation of China.

Schematic diagram of the results of the start–stop tests for diamond-like and graphite-like carbon coatings/soft rubber tribopair. (Image by WANG Liping et al.)

Structure and microstructure evolution mechanism of diamond-like coating during laser texturing process.(Image by WANG Liping et al.)