Preparation And Properties Of Solid Lubricating Coatings For WS ₂ - TiB ₂ Solid Lubricating Coatings

Coating has been widely used in the engineering components, especially, the solid self-lubricant coating has been found to elongate the lifetime of the components significantly, due to their low coefficient of friction and wear resistance.In this work, the WS2-TiB2 composite coatings, with different WS2 contents, were prepared by magnetron co-sputtering from independent WS2 and T1B2 targets. EDAX、XRD、AFM and SEM were used to characterize the element composition and the micro structure as a function of W content. Nanoindentation,Vickers indentation, and scratch test were used to investigate mechanical properties, such as hardness、cracking and deformation behaviors of the coatings with various W contents. Tribological performance was examined on a UMT-3 multifunctional tribometer. After the examinations, the wear rates, the coefficient of friction (CoF), and the morphology of wear tracks were investigated. The main results are as follows:1. With increasing the W content, transition of the structure from the crystalline to amorphous was identified. The increased WS2 addition caused an evolution of orientation and growth structure in our coatings. The coating with no W addition showed the TiB2 (001) texture. With increasing the W content (0< x≤ 13.4%), the coating exhibited TiB2 (001) and TiB2 (002) mixed texture. An the same time, the growth structure of the coating also changed with various WS2 content. With increasing the WS2 content, the growth structure evolves from columnar, through column-free and dense, to amorphous.2. Relative high hardness were obtained in all WS2-TiB2 coatings, the hardness of which are> 25GPa.3. The fracture toughness of the coating was significantly increased, with the WS2 addition, though the characterization by Vickers indentation.4. The samples with approprite amount of WS2 (0< x≤ 13.4%) have a low coefficient of friction,～0.18 in air (30% relative humidity), which is much better than that of the pure TiB2 coating and M2 steel substrate in dry friction 2N. The WS2-TiB2 coatings exhibited the adaptability to the humidity, which is reflected by the almost constant CoF in various relative humidity from 30%,50% to 70%. Under the 70% relative humidity and 2-5N load conditions, the coatings Wcontent (0< x≤ 13.4%) exhibited good resilience and wear rates on the order of 10-16 m3/N. The worn surface was very smooth and a small amount of reel-like debris was found in SEM. When the load was increased to 10N, the coating showed a rapid failure.5. The samples (S5、S6) with excessive WS2 addition (x≥ 13.9%) exhibited a rapid failure. Amounts of visible grooves and straight cracking or spalling were identified in the worn surface by SEM.