冷热循环增韧非晶合金涂层的摩擦磨损机理研究

This proposal focuses on the friction and wear of amorphous alloy coating, which is suggested from the demand of the piston rod of the hydraulic cylinder. Aiming at the bottleneck problem of brittleness in amorphous coating application, the research idea of toughening and improving the tribological properties of coating is put forward based on the research of aging and rejuvenation of amorphous structure. To this end, after the analysis of the matching between the coating and the matrix, the fabrication with laser cladding and the tribology properties of amorphous coatings will be investigated. The effect of thermal cycling treatment on the properties of laser clad amorphous coatings, especially the variation of the toughness of the coating layer, will be analyzed. And the evolution of the structure of tribo-layer treated by thermal cycling will be paid more attention. At the same time, the corrosive wear behavior of amorphous coatings will be studied, and the thermal cycling effect on the friction coefficient, wear rate and friction-corrosion interaction will be analyzed. Then, the connection of friction condition, surface structure of tribo-layer, and properties of the coating will be built based on the inherent relationship between thermal cycling treatment and coating performance. Finally, it will reveal the corrosion wear mechanism of toughened amorphous coating. This proposal on the amorphous alloy coating treated by thermal cycling is expected to improve the toughness of amorphous coating and to obtain a protective amorphous coating with external hard internal toughening effect formed from the friction induced phase transition. It provides a new idea for the research on the tribological properties of amorphous coating, and is supposed to improve the equipment level of our country's water conservancy and marine engineering. So this work goes with an important scientific significance and an attractive application prospect.

本项目从水利枢纽启闭机液压缸活塞杆的需求出发，开展非晶合金表面涂层的摩擦磨损研究。针对非晶涂层脆性大的应用瓶颈问题，在非晶结构的老化与年轻化研究基础上，提出通过冷热循环处理增韧提升涂层摩擦学性能的研究思路。为此，在涂层与基体匹配性分析基础上，拟开展激光熔非晶涂层的制备及摩擦学性能研究，分析冷热循环处理对非晶涂层性能的影响，特别是涂层韧性的变化，并着重研究冷热循环前后摩擦表层的结构演变规律；同时，研究涂层的腐蚀磨损行为，深入分析冷热循环处理对摩擦系数、磨损量及摩擦-腐蚀交互作用的影响，构建摩擦条件、摩擦表层结构及摩擦学性能三者之间的联系，进而揭示增韧非晶涂层的腐蚀磨损机理。开展非晶合金涂层的冷热循环处理研究，可望提高涂层的韧性、并在摩擦过程中由摩擦诱导相变而形成外硬内韧的效果，为非晶涂层的摩擦学研究提供新思路，也为提高我国水利及海洋工程装备水平提供有力支撑，具有显著的科学意义和应用前景。

水利装备用液压启闭机的液压杆常年裸露在外，因偶然过载、磨损和腐蚀等原因，活塞杆的运行受阻，轻则导致闸门变形报废，重则引发泄洪困难而致水患风险。为此，水利装备中液压式启闭机的活塞杆常采用表面技术提高其耐磨、耐蚀及抗疲劳性能。电镀技术面临着废液污染、镀层种类有限及性能不高等问题。目前常用热喷涂技术制备活塞杆陶瓷涂层，但在含沙水流或者处于海洋潮间带等复杂环境下，陶瓷涂层存在着脆性大、容易被冲刷磨损及封孔缺陷等问题。由于非晶合金具有高硬度、高弹性、高断裂韧性及优异的耐蚀性，制备非晶涂层成为一种极具吸引力的活塞杆表面强化技术。然而，非晶合金由于脆性大的制约，常常没有表现出优异的摩擦学性能。本项目依据循环应力下双原子模型中的原子间距趋于扩大的理论以及非晶合金塑性增加的实验，提出通过液氮-室温的冷热循环处理方法，通过产生原子层面的循环应力，增大非晶合金体内的平均原子间距，即增加了自由体积的含量，造成原子在应力下有更多的活动空间，从而产生更多的滑移带，进而引起宏观上韧性的增加。又因材料硬度和韧性的增加有利于提高耐磨性，尽管非晶合金经冷热循环处理后的硬度略有下降，但由于韧性的提高，耐磨性总体有明显增强。冷热循环处理除了显著影响力学性能外，还明显提高了摩擦过程中形成保护性氧化层的能力和腐蚀环境下的耐蚀性，包括摩擦过程中的动态钝化能力。本项目实验条件下磨损率的提升幅度可以超过30%，摩擦系数也有显著降低。此外，在本项目还在非晶合金回春效应的基础上，进一步拓展其他涂层后处理技术，并证明超声冲击和碱溶液浸泡等技术也可以产生类似的显著提升效果。总之，本项目揭示了冷热循环处理提高非晶合金摩擦学性能的机理，必将促进液压杆表面优质防护涂层的发展。此外，由于液压缸也是海洋工程装备、采矿系统及海军船舶中各类执行机构的关键部件，所以研究活塞杆用非晶涂层在复杂工况条件下的可靠性及使用寿命也有重要的实际意义。