Betrachtung der individuellen tribologischen Phänomene im Rahmen der Partikelerosion

The erosion of surfaces caused due to particle impact, for example through sand in desserts, leads to failure of technical equipment components up to the failure of whole technical facilities. This knowledge is an important argument to use scientific methods and experimental research to achieve a deeper insight into the mechanisms which cause these failures. Hence, a substantial aim is to gain an understanding of how such failures can be avoided in future.
This work demonstrates a basis by describing and characterizing the main interactions between particles and surfaces. For that purpose, surfaces of different materials are investigated after the impact of a particle collective to identify the individual wear mechanisms. The experimental tests on various surfaces (stainless steel, DLC-coating, copper) are conducted with different conditions of impact, whereby the velocity, the angle and the test duration are varied. Subsequently, methods are introduced which allow examining the interaction of single particles with the surfaces.
Various current works analyse the change in adhesion by the surface roughness, whereby the influence of the particle wear is not considered. In the present work, that topic was caught up on and the change of the particle surface due to wear is included in the investigations. The analysis of the results shows that only the consideration of the whole system of the worn surface in combination with the worn particle leads to a change in adhesion. Primarily, this context is based on the fact that every single contact situation differs from position to position and therefore, the particle wear can be neglected.
To describe the wear mechanism abrasion, the friction coefficient is determined by a scratch test conducted with the nanoindenter. These tests are implemented on surfaces which are impacted by erosion through particles and on not worn surfaces. Thereby the scratch tests are performed with a commercially available indenter as well as a self-built indenter on which an arbitrary particle can be glued on. The results show that the friction coefficient changes through particle impact and that the self-built indenter is suitable for the measurements.
As a further wear mechanism, the fatigue based on surface spalling is examined, which in the past was only possible with great effort. In this work the reference method of the nanoindenter is used which allows the indenter to oscillate with a frequency of 220 Hz and to fatigue the surface. As the obtained results are in good agreement with the “classic” fatigue research, the reference method opens up a new opportunity to investigate fatigue of material’s surfaces.
With the current work, a new basis and experimental methods to describe the single mechanisms of erosive wear are developed. On this basis, opportunities are offered to understand cause-effect relationships fundamentally between impacting particles and a surface, which help to make the right decision regarding the material selection for erosive applications.