Study of run-in behaviour of laser-patterned surfaces underdry sliding conditions

本提案的主要目标是检查和了解激光纹理表面的演变，关于形貌和微观结构，在最初的滑动循环中，以定制摩擦和磨损性能。明确的表面形貌将由激光干涉冶金（LIMET）产生。该技术允许在一个加工步骤中生产高度控制的表面特征，其横向特征尺寸与相关工程尺度相比，可以通过连续激光纹理加工实现。传统技术表面的特征是随机的粗糙度分布，很难完整地描述。与此相反，LIMET允许精确定义的模型表面的可重复性形成，从而克服了随机粗糙度情况，这是该项目的主要优点之一。首先，将仔细检查与激光图案化基板摩擦的扁平球。在下一步中，还将对反体进行激光图案化，并对相互对准的作用和所得到的图案的横向特征尺寸进行详细研究。在这种情况下，将对具有不同晶体结构的技术相关材料（Ni， W, Ti）进行测试。此外，晶粒结构（准单晶和柱状生长的多晶样品）的影响将在项目中进行研究。此外，实验数据将被用作与伦敦帝国理工学院（A.V. Olver教授，D. Dini博士和S. Medina博士）直接合作的表面和微观结构演变建模的输入参数。我们在伦敦的合作伙伴提出的研究解决了在真实粗糙表面的接触分析中通常被忽视的表面相互作用的某些方面，特别是两个表面粗糙度的相互作用及其与法向切向载荷相互依赖关系和外部载荷机制的影响。虽然在没有考虑这些主题的情况下，接触建模已经取得了很大的进展，目前可以很好地预测载荷应力和接触条件，但现在有必要将这些细节引入建模系统，以达到摩擦和磨损的基本和预测建模所需的复杂水平。通过高分辨率技术结合我们在伦敦的科学合作伙伴最近开发的模型，可以生成定义良好的表面，并随后对制造样品进行表征，这将增强对干滑动下相互作用接触面的理解。此外，激光图案的微观结构退化将被广泛研究，这可以直接与模型相关。最后，所获得的结果将适用于其他材料和越来越重要的纳米级接触。

The main goal of this proposal is to examine and to understand the evolution of laser textured surfaces, regarding topography and microstructure, in the very first sliding cycles in order to tailor friction and wear properties. The well-defined surface topographies will be created by laser interference metallurgy (LIMET). This technique allows for the production of highly controlled surface features in one processing step with lateral feature sizes on relevant engineering scales compared to those achievable using sequential laser texturing processes. Conventional technical surfaces are characterized by a stochastic roughness distribution which is difficult to describe in its entirety. In contrast to that, LIMET permits the reproducible formation of precisely-defined model surfaces and thus overcomes the stochastic roughness situation which is one of the major benefits within the project. First of all, a flat ball rubbing against a laser-patterned substrate will be scrutinized. In a next step, also the counter body will be laser-patterned and the role of mutual alignment and the lateral features sizes of the resulting pattern studied in detail. In this context, tests will be performed on technologically relevant materials (Ni, W, Ti), all having different crystal structures. Furthermore, the influence of grain structure (quasi-single crystalline and columnar-grown polycrystalline samples) will be investigated within the project.In addition, the experimental data will be used as input parameters for modelling the surfaces and microstructural evolutions in a direct collaboration with the Imperial College London (Prof. A.V. Olver, Dr. D. Dini and Dr. S. Medina). The research proposed by our collaboration partners in London addresses some aspects of surface interaction that are commonly neglected in contact analysis of real rough surfaces, specifically the interaction of the roughness of both surfaces and its relationships with normal-tangential loading interdependency and the influences of external loading mechanisms. Whilst much progress has been made in contact modelling without consideration of these subjects, currently allowing good prediction of loading stresses and contact conditions, it has now become necessary to introduce such details into the modelling system in order to reach the level of sophistication needed for fundamental and predictive modelling of friction and wear.The possibility to generate well-defined surface and the subsequent characterisation of the as-fabricated specimens by high resolution techniques combined with recently developed models by our scientific partners in London will lead to an enhanced understanding of interacting contact surfaces under dry sliding. Moreover, the microstructural degradation of the laser pattern will be extensively studied which can be directly correlated with the models. Finally, the gained results will be applicable to other materials and increasingly important nanoscale contacts.