Extremely enhanced tribocorrosion behavior of an L-DED CoCrNi multiprincipal element alloy by in situ alloying

Reducing corrosion and wear has been a challenge to metal components in marine environments for a long time. However, the problems of high cost and low efficiency hinder the discovery of new anti-tribocorrosion multiprincipal element alloys (MPEA). This study reported a significant reduction in both wear and corrosion of single-phase CoCrNi MPEA through in situ laser-directed energy deposition (L-DED), which had only half the tribocorrosion rate of prealloyed samples. Furthermore, the structural evolution mechanism of in situ samples was revealed at different scales, and the interaction mechanism of tribocorrosion was clarified in detail. The results show that in situ samples had finer cells and higher microhardness due to solid solution strengthening and nanoprecipitation strengthening. The higher Cr₂O₃/Cr(OH)₃ ratio, higher R_ct, and lower I_pass indicated a denser and more protective passive film of the in situ samples. Furthermore, the in situ sample demonstrated superior tribocorrosion resistance, which was mainly due to a lower corrosion-intensified wear loss (W_C) value. Moreover, the load intensified the material loss of interactions between wear (W) and corrosion (S). This work will provide breakthroughs in the wear–corrosion trade-off of MPEA design and promote the application of anti-tribocorrosion MPEAs in marine equipment.