Abstract
High hardness and good wear resistance have been revealed for the high-entropy alloy (HEA) system AlCoCrFeNiTi, confirming the potential for surface protection applications. Detailed studies to investigate the microstructure and phase formation have been carried out using different production routes. Powder metallurgical technologies allow for much higher flexibility in the customisation of materials compared to casting processes. Particularly, spark plasma sintering (SPS) enables the fast processing of the feedstock, the suppression of grain coarsening and the production of samples with a low porosity. Furthermore, solid lubricants can be incorporated for the improvement of wear resistance and the reduction of the coefficient of friction (COF). This study focuses on the production of AlCoCrFeNiTi composites comprising solid lubricants. Bulk materials with a MoS2 content of up to 15 wt % were produced. The wear resistance and COF were investigated in detail under sliding wear conditions in ball-on-disk tests at room temperature and elevated temperature. At least 10 wt % of MoS2 was required to improve the wear behaviour in both test conditions. Furthermore, the effects of the production route and the content of solid lubricant on microstructure formation and phase composition were investigated. Two major body-centred cubic (bcc) phases were detected in accordance with the feedstock. The formation of additional phases indicated the decomposition of MoS2.
Highlights
High-entropy alloys (HEAs) are gaining importance in current research
This study focused on enhancing the wear behaviour of the equimolar AlCoCrFeNiTi HEA by the addition of MoS2
The morphology and microstructure of the atomised AlCoCrFeNiTi powder was investigated in scanning electron microscope (SEM)
Summary
High-entropy alloys (HEAs) are gaining importance in current research. Regardless of their complex composition with at least five elements, the formation of simple cubic solid solutions can be achieved [1]. The high-entropy effect enables the formation of multi-element solid solutions due to the reduction of Gibbs free energy and thermodynamic stabilisation [6]. Improved high-temperature properties of AlCoCrFeNiTi are expected, the wear behaviour has not yet been investigated at increased temperature. The suitability of the SPS processing route for HEAs has already been mentioned [17,18], whereas the approach of incorporating solid lubricants has only been investigated for a few HEA systems [19,20]. The influence of the solid lubricant on microstructure and phase formation was investigated in detail
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