Tribological and mechanical properties of amorphous and semi-crystalline PEEK/SiO2 nanocomposite coatings deposited on the plain carbon steel by electrostatic powder spray technique

One of the main practical limitations of polymer coatings is dependency of their mechanical and physical properties on the crystallinity of polymer matrix. In this research, the effect of the presence of silica nanoparticles on microhardness, interfacial adhesion strength and tribological behavior of amorphous and semi-crystalline polyether–ether–ketone (PEEK) coatings were examined. The coatings were prepared by a combination of ball milling and electrostatic powder spraying methods. The results showed that the semi-crystalline pure PEEK coating had higher hardness, lower adhesion strength, coefficient of friction (COF) and wear rate than the amorphous one. However, the incorporating of PEEK with surface modified silica nanoparticles led to an increase in the coatings microhardness and interfacial adherence. The wear rates of both the semi-crystalline and amorphous nanocomposite coatings were lower than the pure ones but their COF were slightly higher. It was also found that, compared with the pure coatings, the sensitivity of the mechanical and tribological properties of the nanocomposite coatings to the crystalline structure of the PEEK matrix are less pronounced.