Cold Spray Deposition of MoS[sub.2]- and WS[sub.2]-Based Solid Lubricant Coatings

• Published in: Lubricants 2024-07, Vol.12 (7)
• Main Authors: Lince, Jeffrey R, Woods, Peter, Woods, Eric, Mak, Wai H, Sitzman, Scott D, Clough, Andrew J
• Format: Article
• Language: English
• Subjects: Lubrication and lubricants; Powders; Tribology
• ISSN: 2075-4442; 2075-4442
• DOI: 10.3390/lubricants12070237

The cold spray deposition technique has been used to produce a new class of solid lubricant coatings using powder feedstocks of the metal disulfides WS[sub.2] or MoS[sub.2], either pure or mixed with Cu and Ni metal powders. Friction and cycle lives were obtained using ball-on-flat reciprocating tribometry of coated 304 SS flats in dry nitrogen and vacuum at higher Hertzian contact stresses (S[sub.max] = 1386 MPa (201 ksi)). The measured friction and thickness of the coatings were much lower than for previous studies (COF = 0.03 ± 0.01 and ≤1 µm, respectively), which is due to their high metal disulfide:metal ratios. Cu-containing metal sulfide coatings exhibited somewhat higher cycle lifetimes than the pure metal sulfide coatings, even though the Cu content was only ~1 wt%. Profiling of wear tracks for coatings tested to 3000 cycles (i.e., pre-failure) yielded specific wear rates in the range 3–7 × 10[sup.−6] mm[sup.3]N[sup.−1]m[sup.−1], similar to other solid lubricant coatings. When compared to other coating techniques, the cold spray method represents a niche that has heretofore been vacant. In particular, it will be useful in many precision ball-bearing applications that require higher throughput and lower costs than sputter-deposited MoS[sub.2]-based coatings.