准晶碾磨诱导不锈钢增强钝化效应研究

It is widely known that the high corrosion resistance of stainless steels arises from surface passivation. It has been pointed out that abrasive polishing induces surface plastic deformation that accelerates Cr diffusion and the formation of dense passivation film, leading to a so-called enhanced passivation effect. We have found that, because of the unique low friction coefficient, high hardness/elasticity ratio, and proper hardness, quasicrystals as abrasive materials, in comparison with commonly-used hard ones, can realized the best surface flattening while maintaining a low level of surface removal, via a“smearing”-dominating wear mechanism. It is therefore anticipated that, if such quasicrystal abrasives are used to polish stainless steels, a new surface pretreatment can be obtained that combines good surface finishing with enhanced passivation, which has been indeed observed by us. The present project, based on electrochemical testing technology, systematically studies the essence mechanism of passivation enhancement on stainless steel by quasicrystal abrasive.Through a combination of simulation and experiment, investigate the abrasive properties such as hardness, elastic modulus, poisson's ratio, H/E, and the coefficient of friction, working on the influence to wear mechanism of stainless steel. Revealing the enhanced passivation effect induced by quasicrystal abrasive smearing on stainless steel, which process will be developed that leads to stainless steels with superior corrosion resistance.

不锈钢的高耐蚀性源于表面自钝化，而表面强烈塑性变形区会促进钝化元素的扩散，优先形成致密钝化膜，带来增强钝化效果。准晶材料具有低摩擦系数、高硬弹比以及合适的硬度等特性，作为磨料在包括不锈钢以内的多种软金属表面研磨，与常规的硬质磨料相比，能够以最小的表面去除率，通过 “碾磨”机制最大限度地实现表面光整化。申请人前期研究观察到准晶研磨所带来的明显增强钝化现象，因此，准晶磨料有望成为集表面光整化加工与增强钝化为一体的表面处理新方法。本项目利用电化学测试技术系统开展准晶碾磨不锈钢表面增强钝化机理研究，通过模拟仿真与实验相结合的方式，深度剖析准晶磨料的本质属性因素对不锈钢表面加工的特征，明晰磨料的硬度H、弹性模量E、泊松比ʋ、硬弹比H/E和摩擦系数µ等参数对不锈钢表面摩擦磨损作用机制的影响，并揭示准晶碾磨诱导不锈钢增强钝化效应的物理本质，发展一种快速优质钝化工艺，获得具有优异耐蚀性能的不锈钢材料.

在不锈钢生产中，首先对不锈钢表面进行预处理以获得洁净、光整的表面，为后续处理提供一个良好的表面性能。而不锈钢的高耐蚀性源于其表面原位生成致密稳定的富Cr钝化膜。然而，不锈钢表面加工状态对其钝化反应与耐腐蚀性能产生重要影响。因此，寻求一种集光整加工与增强钝化效应于一体的表面处理新方法具有广阔的工程应用前景。本项目取得的主要研究成果包括：（1）调控了准晶磨粒范围，优化了不锈钢光整加工工艺参数。（2）量化了准晶磨料对不锈钢表面塑性变形影响范围，建立了不锈钢表层硬度与等效塑性变形的关联性，明确了准晶磨料磨损机理，剖析了磨料与基体之间的摩擦系数对不锈钢表面的磨削特点，总结了磨料的硬度H、弹性模量E、硬弹比H/E对不锈钢表面塑形应变作用规律。（3）明晰了准晶磨料摩擦强化特性与不锈钢耐蚀能力的关联性。在碱性溶液中，准晶磨料处理的不锈钢内层膜电阻R2最大为2.57×105Ωcm2，其次是金刚石，Al2O3和SiO2内层膜电阻R2分别为8.10×104 Ωcm2、7.30×104Ωcm2和3.46×104Ωcm2，准晶磨料处理的不锈钢内层膜电阻比其他磨料处理的不锈钢表高高出一个数量级。动态磨蚀实验揭示了不同磨料处理对不锈钢表层纵向深度的塑性变形积累程度，是提高不锈钢表面钝化膜修复能力的关键。为高质量、表面强化及增强钝化于一体的不锈钢表面处理提供全新技术方法，对开辟准晶材料应用领域具有重要科学意义。