Toughness enhancement mechanism of Ni-doped Cr2N

Abstract

In this paper, experiments combined with density functional theory (DFT) are used to investigate the toughness enhancement mechanism of Ni-doped Cr2N coatings. The deposited Cr2-xNixN (x = 0–4.5 at%) coating exhibits a single trigonal structure identified as a Cr2N-Ni solid solution. The columnar structure of the Cr2N coating, with a width of approximately 80 nm, does not change with the doping of Ni. With 2.0 at% Ni alloyed, the hardness increases from 27 GPa for Cr2N to the maximum of 34 GPa. which is mainly due to an increase in residual compressive stress and dislocation density resulting from Ni doping. Interestingly, the elastic modulus shows a linearly decreasing trend as the Ni doping content increases, which indicates that Ni alloying improves the ductility of the Cr2N coating. The sand erosion test shows that the erosion rate of the Cr2N coating is significantly reduced when the Ni doping content is 2.0 at%, decreasing from 0.42 µm·min−1 to 0.15 µm·min−1. DFT results reveal that the metallic d-d state density increases with increased d-electron concentration contributed by Ni atoms, enhancing metallic interaction along the Ni-Cr stacking plane under shear loading, which leads to the improved ductility of the Cr2-xNixN coating.