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As the wear and tear effects of artificial joints disturb patients after joint replacement, techniques of new lubrication materials or methods are constantly being investigated. Hydrothermal method was adopted to produce carbon quantum dots (CDs), and physically cross-linked polyvinyl alcoholpolyethylene glycol hydrogel (PVA-PEG) to encapsulate CDs, which was evaluated as a lubricant for lubrication appraisal with their slow-release solution. Results of the friction experiment showed that the addition of CDs changed the structure of the gel and promoted the tribological properties of the gel. The structural characterization results show that the CDs are successfully wrapped in gel. The network cross-linked structure of the gel is improved due to the addition of CDs, which are shown by the results of thermogravimetric analysis (TGA) and differential scanning calorimetry analysis (DSC). At the same time, CDs can influence the thermal stability and crystallinity of the gel as well as the degree of cross-linking. These results of TGA and DSC suggest that the curled molecular chain will not be stretched during the gel cross-linking process. After 2 h of self-healing, the recovered gel did not break again under the pull of external force. All these contribute to the preparation and application of hydrogels which is worth looking forward to accelerate the development of polymer lubrication. K E Y W O R D S carbon quantum dots (CDs), polyethylene glycol hydrogel (PEG), polyvinyl alcohol (PVA), self-healing, tribological

Nanostructured super bainitic and quenching–partitioning (Q&P) martensitic steels with a significant amount of retained austenite obtained by low temperature bainitic transformation and Q&P respectively were studied to explore the effect of retained austenite on stirring wear resistance. The results suggest that the Q&P martensitic steel significantly enhanced the hardness of the worn surface (from 674 to 762 HV1) and increased the thickness of the deformed layer (∼3.3 μm), compared to the nanostructured bainitic steel. The underlying reason is that the Q&P martensitic steel has a higher stability of retained austenite thereby providing a superior transformation induced plasticity effect to increase surface hardness and reduce wear rate during the wear process.