Process-Integrated Component Microtexturing for Tribologically Optimized Contacts Using the Example of the Cam Tappet—Numerical Design, Manufacturing, DLC-Coating and Experimental Analysis

Abstract

To meet the demand for energy-efficient and, at the same time, durable, functional components, the improvement of tribological behavior is playing an increasingly important role. One approach to reducing friction in lubricated tribological systems is the microtexturing of the surfaces tailored to the application, but in most cases, this leads to increased manufacturing costs and thus often makes their use in industry more difficult. In this work, we, therefore, present an approach for an efficient design and fully integrated production process using a cam tappet as an example. For the used cam tappet contact, we first determined the optimal texture geometries using two differently complex EHL (elastohydrodynamic lubrication) simulation models. Based on these, textured tappets were manufactured in a combined manner using sheet-bulk metal-forming and deposition with a diamond-like-carbon (DLC) coating for additional wear protection without further post-processing of the coating. We show that the simulation approach used has a rather subordinate influence on the optimization result. The combined forming of components with textured surfaces is limited by the local material flow, the resulting texture distortion, and tool wear. However, a targeted process design can help to exploit the potential of single-stage forming. The applied DLC coating has good adhesion and can completely prevent wear in subsequent reciprocal pin-on-disc tests, while the friction in the run-in behavior is initially higher due to the soothing effects of the coating. The experiments also show a tendency for shallow textures to exhibit lower friction compared to deeper ones, which corresponds to the expectations from the simulation.

Keywords

• EHL simulation
• microtextured surfaces
• optimization
• micro-coining
• sheet metal
• DLC-coating