Mo and boriding effect on microstructure, micro-nano mechanical properties and wear behavior of Al0.25CoCr1.5FeNi HEA

Abstract

CoCrFeNi-based high-entropy alloys exhibit promising properties under various stress conditions and are currently the subject of extensive research. However, they can be significantly strengthened by adding different alloying elements and even undergoing surface modifications. For this purpose, this study investigated the effects of Mo addition and boriding on the microstructure, mechanical properties, and wear behavior of Al0.25CoCr1.5FeNi alloy. The boriding process, applied at 950 degrees C, resulted in a dense, continuous, approximately 50 mu m thick borided zone on the surface. The phase changes in the alloy caused by the addition of Mo resulted in an increase in hardness from 6.7 GPa to 15.3 GPa. After the boriding process, surface hardness of 16.2-22.3 GPa was achieved. Elastic modulus values of 230 GPa were achieved with Mo and 295 GPa with boriding. Thanks to the increased mechanical properties, changes in alloy composition and boriding processes have reduced wear losses by up to 99 %. The coefficient of friction decreased from a range of 0.54-0.56 to a range of 0.31-0.34, depending on the applied load. This study includes a successful proposal for increasing the surface hardness and wear resistance of HEAs.