Bi2S3 and MoS2 Soft Coatings: A Comparative Study of Their Frictional Behavior Under Different Humidity Levels, Normal Loads, and Sliding Speeds

Abstract

Bi 2 S 3 is a promising solid lubricant for demanding applications, such as oil extraction, heavy mining, and aerospace components. However, so far its tribological behavior has not been studied in depth. Bi 2 S 3 soft coatings were evaluated utilizing reciprocating sliding tests under different levels of relative humidity level, contact stress, and sliding speed and the results were benchmarked against MoS 2 coatings. In addition, ab initio calculations using density functional theory modeling were employed for studying the interaction between the sul des and the steel substrates and the effect of water intercalation at an atomic level. It was found that Bi 2 S 3 presents excellent environmental adaptability and substrate protection over a wide range of testing conditions, thanks to its characteristic crystal structure.

Enhancing the Tribological Performance of MoS$$_2$$ Coatings in Humid Environments with the Addition of Bi$$_2$$S$$_3$$

“…This explains the high COF values from the beginning of the tests, as the Bi 2 S 3 particles are being swept away by the steel ball. The adherence between Bi 2 S 3 and steel has been previously studied by Pilotti et al [19] using DFT modeling and it was found that it was significantly lower than the corresponding to MoS 2 .…”

“…Additionally, the dispersion in the average COF values between the different test runs was also lower for the composite coatings when compared to neat MoS 2 ones. Several studies have reported that the frictional behavior of MoS 2 coatings becomes higher and more unstable as the humidity level increases [24,[29][30][31] According to Pilotti et al [19], the behavior exhibited by the composite coatings can be explained by the crystal structure of Bi 2 S 3 , as it could accommodate a higher amount of water molecules between the layers. By doing so, it prevents the compromise of the Pauli repulsion effect between the S atoms of the different MoS 2 layers caused by the presence of water molecules.…”

“…From the work of Pilotti et al [19], bismuth sulfide (Bi 2 S 3 ) can be considered a good candidate for being mixed with MoS 2 to generate lubricating Fig. 1 Crystal structure of Bi 2 S 3 and MoS 2 , generated by VESTA [20] coatings that could operate over a wide range of ambient conditions.…”

Heterolamellar Bi2Se3/Bi2WO6 and Bi2Se3/N-Doped Bi2WO6 Nanosheet Composites as Potential Antifriction and Antiwear Agents

“…21 The frictional behavior of burnished Bi 2 S 3 soft coatings was evaluated utilizing reciprocating sliding tests. 22 On the other hand, Bi 2 Se 3 retains a rhombohedral crystal structure of the space group D 3d (R3m). 18 The quintuple layers of Bi 2 Se 3 containing Se−Bi−Se−Bi−Se atoms bonded covalently are fastened together by weak van der Waals forces.…”

“…The behavior of bismuth sulfide as a powder lubricant was studied at temperatures up to 580 °C . The frictional behavior of burnished Bi 2 S 3 soft coatings was evaluated utilizing reciprocating sliding tests …”