Extremely enhanced the tribocorrosion behavior of L-DED CoCrNi multi-principal element alloy by in-situ alloying

Reducing corrosion and wear has been a challenge to metal components in the marine environment for a long time. However, the problem of high cost and low efficiency hinder the discovery of new anti-tribocorrosion multi-principal element alloy (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), that had only half tribocorrosion rate than pre-alloyed samples. Further, structure evolution mechanism of in-situ samples was revealed under different scales and 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 nano-precipitation strengthening. The higher Cr₂O₃/Cr(OH)₃ ratio, higher R_ct, and a lower I_pass, indicated a denser and more protective passive film of in-situ samples. Further, in-situ sample demonstrated superior tribocorrosion resistance which was mainly due to lower corrosion-intensified wear loss (W_C) value. Moreover, load intensified the material loss of interactions between wear (W) and corrosion (S). This work will provide breakthrough in the wear-corrosion trade-off of MPEA design and promote the application of anti-tribocorrosion MPEAs in marine equipment.