Fluid-free lubricant layers for the heavily loaded and unsynchronized operation of dry-running screw machines

该研究项目的目的是在宏观和微观尺度上了解MoSx（:X）固体润滑剂在干运转、非同步螺杆机械实际接触条件下的摩擦和磨损机理，并制定提高固体润滑剂寿命的策略。自行设计的螺杆机试验台通过设置可调的表面压力、温度、载荷持续时间和气氛，再现了实际接触的条件，并提供了一系列不同的参数集，用于滚动接触的情况。此外，HiPIMS溅射MoSx（:X）薄膜的调理调节了接触情况。在这种情况下，螺旋机的复杂几何形状对薄膜生长机制的阴影效应的影响进行了评估。薄膜厚度的变化与螺旋机的粗糙度有关，用Ag、W或C （X = Ag、W、C）对薄膜进行改性，以及将纯改性元件制成的薄膜涂在次级转子上，应控制滚动接触内的条件。根据这些接触参数，将详细阐述哪些化学、物理和结构表面特性决定了MoSx（:X）固体润滑剂的功能，并允许在微观尺度上预测材料的去除和失效。其功能是通过氧化、材料去除、表面应变重排、相变和材料混合等基本过程的影响和相互作用来描述的。基本过程的特征是在试验台建立的原位和操作方法，包括光和激光显微镜，拉曼散射和激光烧蚀选项，以及非原位技术。后者提供了对涂覆和未涂覆螺旋机表面的结构和化学物理特征的光谱和空间高分辨率见解。试验台上的测量技术动态地研究了螺杆副主、副转子的摩擦学基本过程。对结构和表面化学物理性质的了解，可以调整接触情况的参数，以控制旨在提高固体润滑剂寿命的基本过程，并在最小摩擦下减少能量输入。实验研究与机械模拟的相关性，其重点是依赖于载荷持续时间的材料去除和摩擦张力，将解释螺旋机的保护摩擦学层是如何以及在何种操作状态下形成的。知识最终将转移到固体润滑替代部件。

The aim of the research project is to understand friction and wear mechanisms of tailored MoSx(:X) solid lubricants under real contact conditions of dry-running, unsynchronized screw machines at the macro- and microscopic scale and to develop strategies for enhancing the lifetime of the solid lubricant. A self-designed screw-machine test bench reproduces the conditions of real contacts by setting an adjustable surface pressure, temperature, load duration and atmosphere and provides a range of distinct sets of parameters for the situation of the rolling contact. Additionally, the conditioning of HiPIMS sputtered MoSx(:X) thin films adjusts the contact situation. Within this context, the influence of the complex geometry of the screw machine regarding shadowing effects on film-growth mechanisms is evaluated. A variation in the thin film thickness with respect to the roughness of the screw machine, a modification of the thin film with Ag, W or C (X = Ag, W, C) as well as an application of films made from the pure modification element onto the secondary rotor shall control the conditions within the rolling contact.Depending on these contact parameters the question will be elaborated which chemical, physical and structural surface properties determine the functionality of the MoSx(:X) solid lubricants and allow for predicting the material removal and failure at the microscopic scale. The functionality is described by the effect and interaction of elementary processes which include oxidation, material removal, rearrangement of surface strain, phase transformations and material mixing. The elementary processes are characterized by in-situ and operando methods established at the test bench, which consist of light and laser microscopy as well as Raman scattering with an option of laser ablation, and ex-situ techniques. The latter provide spectrally and spatially high-resolved insights into structural and chemical-physical features of the coated and uncoated screw-machine surfaces. The measurement techniques at the test bench dynamically study the tribological elementary processes at the main and secondary rotor of a screw-machine pair.The understanding about the structural and chemical-physical surface properties allows for tailoring the parameters of the contact situation in order to control the elementary processes aiming at enhancing the lifetime of the solid lubricant and reducing the energy input at minimized friction. The correlation of the experimental investigations with a mechanical simulation, which focuses on the material removal and frictional tension in dependence on the duration of load, will explain how and in which operational states of the screw machines a protective tribological layer is formed. Knowledge shall finally be transferred to solid-lubricated alternative components.