M. Włoczewski; K. Jasiewicz; P. Jenczyk; E. Gadalińska; K. Kulikowski; Y. Zhang; R.X. Li; D.M. Jarząbek
Metallurgical and Materials Transactions A 56 (2025) 1-17
In this study, theAlCoCrFeNiTi0.2 high-entropy alloy (HEA)was plasma nitrided to investigate the
microstructure andmechanical properties ofhigh-entropy nitrides formed in the surface layer ofthe
bulk sample. XRD measurements revealed a BCC fi FCC crystal structure transformation, with
the r phase disappearing and hexagonal aluminum nitride emerging. Further experimental studies
on the nitrided samples, including SEM, EDS, and EBSD, uncovered element segregation into
multiple FCC phases with similar lattice constants, such as the NaCl-type (AlCrCoFeNiTi0.2)N
high-entropy nitride. These observations align with theoretical analysis based on KKR-CPA
calculations. Additionally, plasma nitriding induced high surface porosity; however, micropillar
compression testing combined with nanoindentation revealed localized areas with significant
hardness. A substantial reduction in the coefficient offriction was also observed. These findings not
only provide deeper insights into the nitriding process ofcomplex alloys, like dual-phase HEAs, but
also hold promise for further exploration in the manufacturing of super-hard surfaces with
high-entropy nitrides, enhancing mechanical properties for applications in harsh environments.