Tool – Solid Lubricant – Workpiece Interactions in High Temperatures Applications

Abstract

Tribological research concerning sliding contacts operating at elevated temperatures has received very limited attention so far, despite its importance for reliable, safe and efficient operation of many tribological systems. Typical examples can be found in aerospace, power generation and metal working industry. Considerable differences induced by higher temperatures, when compared to lower temperature applications, are the increased rate of desired (tribochemical, oxidative) and undesired (adhesive, corrosive) reactions and changes in mechanical properties. The control of friction at the tool-workpiece interface and minimisation of tool wear is crucial to ensure the quality of formed parts. This can be achieved by spraying solid lubricant onto the surface of heated tools. The efficiency of high temperature industrial processes is strongly linked with the structure and thickness of the formed layer of oxides or/and applied solid lubricant onto the tools.The objective of this study is to verify the reliability of well-designed High Temperature Disc-on-Disc-Tribometer (HT-RRV) tests for providing accelerated data for friction and wear characterisation of several solid lubricants under forming conditions. Performed laboratory tests show that this test methodology can be used to carry out parametric studies with the aim to understand the tool – solid lubricant – workpiece interactions in high temperatures applications. The application of solid lubricant greatly changes the tribological performance by reducing the coefficient of friction, and adhesive and abrasive wear phenomena. Due to the in-situ formation in the tribocontact of a sacrificial layer, which is constantly formed and removed, the surface of the tool remains mostly unaffected in terms of damage.