含B-O原位自生润滑膜形成的演进机制及其润滑机理研究

Cutting process plays an important role in manufacturing industry, but the tribological behaviors of current ceramic cutting tool are not stable during dry cutting processes, contributing to the quality and safety hidden trouble. Hence, Research on the forming and lubricating mechanism of In-situ reaction lubricating film forming on the wear surfaces of ceramic/metal pair has great signification in the academic and practical values. On the basis of tribo-chemical behavior of Si3N4-hBN ceramic composites, this research project devotes to the occurrence and lubrication mechanism of the surface film. The applicants quantitatively characterize tribological properties and formation situation of surface film through single factor method, and define the relationship among the test conditions, surface film and tribological characteristics. And, the interaction rules between B-O compound and Si-O compound were revealed by “segmentation analysis” method. The key lubricating substance was confirmed by the real-time temperature measurement system. Meanwhile, the forming conditions were further analyzed by thermodynamic calculation. Thus, it was obtained that the forming rules and lubricating nature of the surface film. Based on the above research, it was explored that the influence of metallographic structure and chemical composition for metal material on the formation and lubrication of surface film. The research results had an important theoretical significance on the revealing the tribological behavior, and provided the new test design methods and control approaches for analyzing the dynamic friction process and effectively controlling influence factors.

切削加工在机械制造行业占有重要的地位，而现有的陶瓷刀具材料在干式切削过程中摩擦性能不稳定，易造成质量和安全隐患，故研究陶瓷/金属摩擦面上原位自生润滑膜的形成机理和润滑机制具有重要的科学意义和实用价值。本项目基于Si3N4-hBN复相陶瓷能发生摩擦化学行为，以表面膜形成的演化机制及润滑机理为目标，采用单因素法对摩擦性能与表面膜形成情况定量表征，明确试验条件－表面膜－摩擦学性能之间的关联性；通过对摩擦表面的“分段分析”，揭示B-O化物和Si-O化物的交互作用规律，利用实时测温的手段，确认含B-O表面膜的核心润滑物质，辅以热力学计算进一步解析表面膜的形成条件，阐明表面膜形成的演化规律及润滑本质。基于上述研究结果，探索金属材料微观组织与化学成分对表面膜形成与润滑的影响效应。研究结果对揭示金属/陶瓷的摩擦学行为具有重要的理论意义，并为分析动态摩擦过程、有效控制影响因素提供新的试验设计方法与控制途径。

基于现有陶瓷刀具材料在干式切削加工中摩擦性能不稳定，易造成质量与安全隐患的事实，本项目针对陶瓷/金属摩擦副的摩擦学行为展开系统性研究，揭示摩擦表面膜的形成机理与润滑机制。通过热压烧结微米级与纳米级复合陶瓷，对比分析其物理、力学性能以及相应的微观组织，力图获得结构/润滑功能一体化复合陶瓷。通过单因素法探求载荷、速度、湿度、温度及配副材料对复合陶瓷/金属配副的摩擦磨损性能的影响效应，由此揭示含B-O、Si-O化物及金属氧化物的摩擦化学反应膜的润滑规律，确认表面膜的润滑物质，并辅以热力学计算以及减摩力学分析，阐明了表面膜的演化规律与润滑本质。.研究发现，干摩擦条件下，hBN的添加均有效地改善了陶瓷/金属摩擦副的摩擦磨损性能。尤其是，在特定试验条件下（10N，1.73m/s），Si3N4-hBN/不锈钢的干摩擦因数降至0.12，销、盘磨损率均不高于 10-5mm3/N•m。另一方面，随着湿度和温度的升高，Si3N4-hBN/不锈钢摩擦副呈现出较好的摩擦学行为，在湿度为RH60%时的摩擦因数低至0.03，磨损率低至10-6mm3/N•m数量级。摩擦过程中，hBN易于脱落形成剥落坑，剥落坑中的磨屑与水分子发生反应，反应产物（其中B2O3或H3BO3为核心物质）溢出剥落坑被拖曳成膜，该膜阻碍了陶瓷与金属的直接接触，保护并润滑摩擦表面，降低摩擦因数与磨损率。.项目组通过分段观测表面膜的形成过程，并利用热力学基本原理对摩擦化学反应的自发性进行了判定，进一步确定反应在室温（298K）下可自发发生的可能性。根据经典粘着摩擦理论和赫兹接触理论等对表面原位自生膜形成与润滑的相关因素进行了探讨，发现自润滑膜的润滑效应与接触材料的弹性模量、两体间直接接触面积占总接触面积的比率和界面间的剪切应力息息有关。