Evolution of the structure and tribological behavior of the organic coatings under gamma-ray irradiation

More reliable and long-term irradiation stability is essential for lubrication protection materials that served in nuclear energy equipment. In this paper, three typical commercially organic bonded solid lubricating coatings were chosen to investigate the influence of gamma (gamma)-ray irradiation on microstructure and tribological behaviors. The evolution of microstructure and the changes of tribological properties for these coatings after irradiation were comparatively studied in detail. The results revealed that the crystallinity of the molybdenum disulfide (MoS2) lubricating phase was improved and were partial oxidized in the coatings after gamma-ray irradiation, resulting in the surface roughness of the coating with MoS2 as the solid lubricating phase decreased significantly. The polytetrafluoroethylene (PTFE) lubricating phase was degraded from the long chains structure to smaller molecules after gamma-ray irradiation. The results of tribological properties of the three coatings after gamma-ray irradiation indicated that, for polyamide-imide-based lubricating coatings, the friction coefficient is decreased and the wear rate is increased after irradiation. For phenolic epoxy-based lubricating coating, the cross-linking effect of gamma-ray irradiation predominated to improve the wear resistance and prolong the wear life of the coating. But overall, the influence of irradiation on tribological properties of three polymer-based coatings could almost be neglected duo to the changes of the microstructure in nanoscale. This work provides path and direction for design and preparation of the lubricating coatings that served in a nuclear reactor.