Einfluss von unterschiedlich erzeugten Verschleißschutzschichten auf das Dauerschwingverhalten ausgewählter Werkstoffe und deren Verbesserung

• Applicant: Professor Dr.-Ing. Lothar Wagner
• Subject Area: Materials Engineering
• Term: from 2009 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 133263241

Whereas in general, the progress of wear damage can be quite well estimated, superposed mechanical loading and high temperatures can have catastrophic effects on the life time of coated components. For example, high cyclic bearing pressures can result from rolling forces. At the same time, shear stresses are induced with maximum values located some millimeters below the surface. Because of the cyclic nature of these compressive and shear stresses, the wear resistant coatings need to be designed and tested with regard to high cycle fatigue performance. In addition, the influence of temperature has to be taken into account. Tribological systems require surfaces with suitable microstructures that can achieve both high wear and fatigue resistances at high temperatures. Further life-determining factors are the nature and magnitude of the applied service loads. How the individual coating systems behave under axial or bending loads must be investigated by test series under quasi-static and cyclic loading as a function of temperature. The degree to which the interface morphology between substrate/coating or matrix/hardmetal phase must also be analyzed.This project will include MMC coatings that protect the substrate against dry abrasive wear. The abrasive wear resistance will be enhanced by particle reinforced Fe, Ni and Co base alloys. The wear protection is realized by hard metal particles of suitable geometry being embedded in the relatively soft matrix and vertically aligned to the surface. However, this particular structural morphology may detrimentally affect crack nucleation and crack propagation. At high pressure loads, the hard phases and the interfaces between the hard phase and the matrix may become crack nucleation sites. To what extent such fatigue progress may occur and to what extent this may contribute to premature failure of the multilayer system will be investigate.In case of intensive wear situations, the matrix must be strong enough to support the embedded hardmetal particles against the applied forces and to prevent brittle failure of the coating. Heat treatments will be performed for optimizing wear and fatigue resistances. This target can be realized by secondary hardening due to the precipitation of finely dispersed carbides. A precisely tuned heat treatment increases the strength of the matrix and thereby also the fatigue strength but in addition, can lead to an improved support of the embedded hardmetal particles.The increase in strength, however, often results in a loss of ductility. The research activities in this project aim to combine the material and material system properties in such a way that wear as well as HCF performance are optimized. The required heat treatments must take into account the microstructure changes of the substrate. In order to realize economic processes in the manufacturing of these components that are subjected to wear and fatigue loading, integrative process steps must be elaborated.

• DFG Programme: Research Grants
• Participating Person: Dr.-Ing. Manfred Wollmann