Synergistic strengthening and anti-erosion mechanism of laser melting deposited CoCrNiTix medium-entropy alloys

YJ Cheng and H Yang and J Zhang and YX Guo and FP Wang and QB Liu, JOURNAL OF ALLOYS AND COMPOUNDS, 1037, 182445 (2025).

DOI: 10.1016/j.jallcom.2025.182445

In order to develop a highly anti-erosion MEA composition suitable for strengthening and repairing 904 L steel blades in strong acid reactors, a cluster formula of Cr-Ni6Co6Cr-5 with varying Ti atoms was designed to investigate the effect of Ti atoms on the strengthening and erosion resistance mechanism. The results reveal that the moderate Ti atoms (x <= 0.15 in CoCrNiTix) remain entirely dissolved into the FCC solid solution. Excessive Ti contents facilitate the formation of L1(2) nano- precipitates and inter-dendritic coarse D0(24) intermetallic phases. Adding Ti atoms effectively improves the strength yet deteriorates the ductility. Notably, the Ti-0.30 MEA exhibits the highest sigma(0.2) similar to 806.01 MPa and sigma(b) similar to 1059.52 MPa, along with a prominent work hardening rate, primarily due to coherent L1(2) precipitation strengthening combined with grain refinement. As x = 0.15, the Ti-0.15 MEA shows the best solid-particle erosion resistance since the Ti atoms completely dissolved in the dendrites markedly improve the yield strength and strain hardening capacity by mutual interactions among high-density dislocations and twins. Moreover, the single FCC phase structure ensures excellent formation ability of uniform and stable passive films against plastic distortion damage. These findings provide a paradigm for developing LAM-ed super-corrosion-resistant MEA alloys.

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