Microstructures and Properties of Nanostructured TiN/MoS 2 /Ag Composite Film Prepared by Pulsed Laser Deposition
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Microstructures and Properties of Nanostructured TiN/MoS2/Ag Composite Film Prepared by Pulsed Laser Deposition Hongjian Guo, Bo Li, Minmin Han, Wenyuan Chen, Zhenyu Zhang, and Junhong Jia (Submitted March 28, 2017; in revised form December 28, 2017) In this work, the structural and mechanical properties, tribological performance, and lubrication mechanism from room temperature to 900 °C of TiN/MoS2/Ag composite films were investigated in detail. Nanostructured TiN/MoS2/Ag composite film was obtained by assembling targets using pulsed laser deposition. The incorporation of lubricant layered MoS2 and soft metal Ag led to degraded mechanical properties, which could contribute to the lower friction coefficients at low temperatures. When the temperature increased to above 500 °C, the generated high-temperature lubricant MoO3 and silver molybdates played a critical synergetic lubrication effect, which formed a layer of lubricating film and reduced the friction coefficient. Thus, the cooperation of various lubrication phases contributed to improvement of tribological performance and resulted in continuous lubrication from room temperature to 900 °C. Keywords
composite film, lubrication mechanism, pulsed laser deposition (PLD), tribological property
1. Introduction With the development in aerospace engineering, the continuous lubricant materials operating under a wide range of temperature are in urgent demand. Chameleon solid lubricating films can reversibly adapt their surface chemistry and structure to maintain low friction while operating under a broad range of temperatures. These designed films not only exhibit the necessary hardness, wear resistance, and durability, but also could enable the self-release of the appropriate lubricant material for the anticipated operational environment and to form solid lubricating films in the contact area through wear processes. Since the ‘‘chameleon’’ lubrication is presented, various self-adaptive films have been reported elsewhere (Ref 1, 2). In the past decades, certain solid lubrication materials were developed to take advantage of molybdenum disulfide as a lubricant owing to its low friction coefficient in vacuum and low temperatures (Ref 3-5). Similar to graphite, MoS2 has a highly anisotropic crystal layer structure, which consists of a layer of molybdenum atoms arranged in a hexagonal array with each molybdenum atom surrounded at equal distance by six sulfur atoms placed at the corners of a triangular prism (Ref 6). Within the molecular structure of MoS2, there are strong covalent bonds among S or Mo atoms, but the S atomic layer Hongjian Guo, Lanzhou Institute of Technology, Lanzhou 730050, China; and State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China; Bo Li, Minmin Han, Wenyuan Chen, and Junhong Jia, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China; and Zhenyu Zhang, Lanzhou Institu
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