Study on self-lubricating properties of AlCoCrFeNi2.1 eutectic high entropy alloy with electrochemical boronizing

The boronizing treatment has been an effective way to strengthen and enhance the lubrication performance of alloys. However, the traditional power-pack boronizing method has been limited due to its time-consuming. Improving the boronizing efficiency is highly demanded for the strengthening and industry application of the high-entropy alloys (HEAs). In this study, the electrochemical boronizing strategy was applied to improve the surface hardness and self-lubrication performance of AlCoCrFeNi2.1 eutectic HEA (EHEA). The microstructure, phase formation and hardness of boronized alloys were studied. Results confirm the high efficiency of electro-chemical boronizing to form a boronized layer with a thickness of about 35 mu m in 30 min. The surface hardness of the boronized AlCoCrFeNi2.1 HEA reached to about 18 GPa due to the presence of NiB, FeB and Cr3B4 in the boronized layer. Tribological tests reveal that the self-lubrication property of AlCoCrFeNi2.1 HEA in water condition was significantly enhanced by the electrochemical boronizing treatment, e.g., the friction and wear reductions reach to about 25% and 80%, respectively. Lubrication mechanism investigation by X-ray photo-electron spectroscopy (XPS) analysis showed the formation of a H3BO3 tribofilm on the sliding surface during the friction process, which effectively reduce friction and wear. This study provided a novel and fast approach for surface hardening and self-lubrication enhancement of HEA systems using the electrochemical boronizing strategy.

Automated summary

Electrochemical boronizing was applied to improve the surface hardness and self-lubrication performance of AlCoCrFeNi2.1 HEA in this study. The results showed that electrochemical boronizing could efficiently form a boronized layer and reduce friction and wear.