| Authors: | Deepthi, B.; Barshilia, Harish C.; Rajam, K. S.; Konchady, Manohar S.; Pai, Devdas M.; Sankar, Jagannathan. |
| Title: | Mechanical and tribological properties of sputter deposited nanostructured Cr-WS2 solid lubricant coatings. |
| Type: | Journal Article |
| Publisher: | Surf. Coat. Technol. |
| Year: | 2010 |
| Volume: | 205 |
| Issue: | 7 |
| Start Page: | 1937 |
| End Page: | 1946 |
| Abstract: | Solid lubricant coatings of WS2 and Cr-WS2 (15-50 at. % Cr) prepd. using an unbalanced magnetron sputtering system were evaluated for their mech. and tribol. properties. Nanoindentation results indicated that addn. of Cr helped in improving the mech. properties and the elastic recovery ability of Cr-WS2 coatings. The adhesive strengths of Cr-WS2 coatings were evaluated using a nanoscratch tester and from the nanoscratch profiles, crit. load values and optical images, it was evident that the adhesion of Cr-WS2 coatings increased with an increase in the Cr content. Further anal. of the nanoscratch data indicated that WS2 coatings exhibited large amt. of plastic deformation compared to Cr-WS2 coatings which showed a combination of elastic-plastic deformation. However, micro-tribometer measurements at a load of 2 N showed that the tribol. properties of Cr-WS2 coatings deteriorated with an increase in the Cr content. For example, Cr-WS2 coatings prepd. at Cr content >= 33 at.% failed after a sliding distance of 1 m. On the other hand, WS2 and Cr-WS2 coatings prepd. at low Cr contents (15-23 at. % Cr) exhibited a stable friction coeff. (50-60% relative humidity) in the range of 0.10-0.13 for a sliding distance of 14 m. Micro-Raman spectroscopy data of the worn films taken after a sliding distance of 14 m indicated the presence of WS2 transfer films for WS2 and Cr-WS2 coatings prepd. at low Cr contents. For Cr-WS2 coatings with Cr content >= 33 at.%, the worn films consisted predominantly of WO3. After an extended sliding distance of 50 m, Cr-WS2 coatings (15-23 at. % Cr) outperformed WS2 coating which failed after 20 m. Further, the coatings prepd. at low Cr contents did not show any failure even after a sliding distance of 200 m. At a higher load of 7 N, Cr-WS2 coating with 15 at. % Cr exhibited the best performance with a friction coeff. of 0.07 up to a sliding distance of 72 m. These results indicate that the amt. of Cr in the WS2 matrix needs to be controlled judiciously to obtain improved mech. and tribol. properties in Cr-WS2 solid lubricant coatings. [on SciFinder (R)] |
| Keywords: | Mechanical hardness (Vickers hardness; mech. and tribol. properties of sputter deposited nanostructured chromium-tungsten sulfide solid lubricant coatings); Adhesion; Coating materials; Friction; Magnetron sputtering; Nanostructures; Surface structure; Wear; Young's modulus (mech. and tribol. properties of sputter deposited nanostructured chromium-tungsten sulfide solid lubricant coatings); Humidity (relative; mech. and tribol. properties of sputter deposited nanostructured chromium-tungsten sulfide solid lubricant coatings) |
