Effect of carbon on microstructure, mechanical properties and wear resistance of non-equiatomic Fe70Co7.5Cr7.5Ni7.5V7.5 medium-entropy alloys fabricated by powder metallurgy

In this study, non-equiatomic Fe 70 Co 7.5 Cr 7.5 Ni 7.5 V 7.5 medium-entropy alloys (MEAs) with different carbon contents were prepared via mechanical ball-milling, cold pressing and vacuum sintering. The microstructural evolution, mechanical properties and wear resistance of the MEAs were investigated Fe 70 Co 7.5 Cr 7.5 Ni 7.5 V 7.5 exhibited a body-centered cubic (bcc) structure with σ phase precipitation. After adding 4 at% and 8 at% carbon, the phase composition of the alloys was transformed to bcc+MC+ σ and bcc+MC+M 23 C 6 , respectively. The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides. Increasing the carbon content, the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4, respectively. Further, the dominant wear mechanism changed from the adhesion wear to the abrasion wear. Owing to the evenly distributed carbides and precipitated nanocarbides, Fe 64.4 Co 6.9 Cr 6.9 Ni 6.9 V 6.9 C 8 revealed an extremely low specific wear rate of 1.3×10 −6 mm 2 /(N·m) under a load of 10 N.