Investigation of tribologically relevant surface layers formed on non-ferrous metals in oxygen-free conditions

Investigation of tribologically relevant surface layers formed on non-ferrous metals in oxygen-free conditions

Engineering under protective atmospheres or in vacuum allows the production of materials and components, where the absent of oxygen is an essential requirement for a succesful processing [1]. In the current study on non-ferrous metals it is revealed, that tribo-oxidation and the resulsting incread abrasive wear are the dominant wear mechanisms, which can be supressed by processing in an extrem high vacuum adequate environment (XHV-adequate) [2]. To investigate the wear mechanisms and the formation of surface layers of non-ferrous metals (aluminum, copper and titanium), an oxygen-free environment was created by using silane-doped inert gas (1,5% vol. SiH4 in argon). To analyse the inuence of the ambient atmosphere on the tribological properties, ball-on-disc tests were carried out on an universal tribometer (UMT). For the characterization of the microstructure and the chemical composition of the samples scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used. The techniques were supplemented by X-ray diraction (XRD), to identify the phase composition of the near-surface layers. The investigations have revealed that the ambient atmosphere has a signicant infuence on the tribological properties and thus on the friction/wear behavior. By suppressing the oxidation under full exclusion of oxygen, a reduction of the tribochemical wear could be shown, which is accompanied by a reduction of the wear volume. In XHV-adequate atmosphere, the investigations of the microstructure and the chemical composition showed that thermal exposure led to the formation of various silicides on the surface of the samples, resulting in novel friction-reducing layers (see Fig. 1). The oxygen-free production in XHV adequate atmosphere therefore offers a prosperity of innovation opportunities, from new processes to more efficient manufacturing processes and improved component properties.