Optimization of (FeCrNi)100-xCx medium-entropy alloys via powder plasma arc additive manufacturing: microstructure and property regulation by carbon content

• PPA-AM successfully synthesizes (FeCrNi) 100-x C x MEAs with few defects. • Carbon addition induces carbide phases, altering microstructure. • Hardness and strength rise with carbon, but toughness drops. • Carbon tunes properties for optimal balance, validating PPA-AM. Multi-principal element medium-entropy alloys have recently garnered significant attention due to their stable single-phase solid solution structure and superior mechanical properties. Adding carbon can form Cr 23 C 6 carbide particles within single-phase face-centered cubic medium-entropy alloys, leading to second phase strengthening and, consequently, enhancing their strength. This study investigates the impact of carbon content in additive manufacturing on the microstructure and mechanical properties of FeCrNi medium-entropy alloys. (FeCrNi) 100-x C x medium-entropy alloys (x = 0, 2, 3, 4) were prepared using powder plasma arc additive manufacturing, and their structure and properties were characterized in detail. The sample without carbon addition displayed a single-phase face-centered cubic structure, but internal defects such as cracks and pores led to poor mechanical performance. With the addition of carbon, carbide precipitation gradually became evident in the samples, significantly improving their mechanical properties. The hardness increased from 140.59HV to 262.75HV, and the ultimate tensile strength increased from 273.73 MPa to 759.74 MPa. The results indicate that adding an appropriate amount of carbon forms carbides within the alloy, significantly enhancing its mechanical properties.