Synthesizing in situ Friction and Wear with ex situ Surface Metrology to Provide Post-mortem Tribological Analysis: Experiments and Modeling

Patrick Dougherty
2018
Surface wear is estimated to result in upwards of 70% of material failure in the US with costs of over 300 billion dollars per annum. Tribology is defined as the study of friction, lubrication, and wear, and while all three of these sub-disciplines stem from interactions at the asperity scale, studies involving the mechanics of industrial interfaces will often ignore their interdependence. This work makes use of a synthesis of in situ tribological data with ex situ surface characterization, in
more » ... aracterization, in order to elucidate the mechanics of friction and wear in a number of industrial interfaces each with its own objective. Section 1 focuses on using this technique to elucidate the mechanics of protective solid lubricants. Detailed experiments were conducted to study the formation and depletion of self-replenishing powder transfer films in both single component and composite forms. Based on the synthesis of ex situ and in situ findings, the primary wear mechanisms at each interface were described as abrasive and transfer film phenomena were described in a new way using a quasi-hydrodynamic approach. In addition to transfer films, hard tribological coatings were also studied for their ability to mitigate impact damage. Coefficient of restitution results were combined with investigations ex situ of the impact sites and compared to nanoindentation results of coating properties. Through synthesizing these results, it was found that more elastic coatings worked best on stiffer substrates, while harder, more brittle coatings worked best on soft substrates. In Section 2, the Section 1 findings were crucial in the development of a numerical model which was presented using abrasive formulations for the wear of soft surfaces and preferential patterning. Quantitative agreement for modeling friction and surface evolution, as well as qualitative agreement for wear trends were provided for experimental values from previous studies. In Section 3, this technique was used to study powder rheology as it applies to flows in the additive manufac [...]
doi:10.1184/r1/6723458 fatcat:b2f7uzmjj5hgxawgalzx2ehxd4