Investigation of Structural and Tribological Characteristics of TiN Composite Ceramic Coatings with Pb Additives

Abstract

Solid lubricating composite TiN coatings with Pb additives were obtained on steel and titanium substrates in the process of reactive magnetron sputtering of separate cathodes. Columnar, columnar nanostructured and composite nanostructured TiN coatings with different contents (3–13%) of a lubricating component (Pb) were obtained by deposition onto rotating and stationary substrates. It was found that deposition at a rotating substrate and 3% Pb content in the TiN matrix led to a columnar crystallite coating structure. With an increase in its content to 8%, columnar crystallites in the structure become less pronounced, and the coating becomes columnar nanostructured. In nanostructured composite coating with 12% Pb, the soft component is distributed both in the matrix and in the form of inclusions. XRD analysis of the composite nanostructured TiN–Pb coating indicates a textureless state. In this case, the diffraction lines of all present phases (Pb, PbO, TiN) are characterized by a significant broadening, indicating that the size of the subgrains are in range of 10–20 nm. Tribological tests of the coatings were carried out at room temperature and under conditions of stepwise heating. The nanostructured composite coating showed the best tribological characteristics due to a high Pb content, a relatively high microhardness (817 HV) and a textureless state with a low grain size. This coating had a low friction coefficient (~0.1) over 50,000 test cycles, both at room temperature and under conditions of stepwise heating up to 100 °C and 200 °C.