Lubricating greases are used in various industrial fields ranging from food, transportation, aeronautical, construction, mining and steel industry. The aim is to decrease frictional forces and to protect industrial components from wear and/or corrosion damage. Their performance depends on interaction properties like adherence to the substrate, cohesion or consistency, and tackiness. However, up to date there is no established quantitative methodology that can be easily applied to efficiently and accurately evaluate the adhesion and tackiness of a grease.
A test procedure is established, based on approach-retraction curves, by using an upgraded TETRA Basalt-N2 micro-tribometer, with a Millinewton light load sensor. In this procedure a user selectable indenter body (ball, pin) gradually approaches the grease layer until they come into contact, then the indenter body keeps moving down until a pre-set contact load is reached. Then, the indenter body moves away from the greased substrate under well controlled conditions, until complete physical separation. During this approach-retraction cycle, the force on the load sensor is measured as a function of time and distance moved. This technique is the same as pull-off force experiments with an atomic force microscope for studying physical interactions.
- The approach-retraction methodology combined with the Basalt-N2 high precision sensor provide a useful tool that is capable of evaluating the pull-off force and tackiness of greases under variable conditions, depending on the industrial application.
- The ranking of different greases at variable conditions is possible. This will allow developers and end-users to differentiate between available greases and select the one that fits better to an application, whereas grease producing companies can quantitatively evaluate the quality of their products more easily.