Nb-doped FeMnSiCrNi coatings: microstructure, phase transformation, shape recovery rate, wear and corrosion resistance

The lower microhardness (only 250 HV0.2) and corrosion resistance are two primary factors that seriously restrain the wide applications of laser cladding FeMnSiCrNi shape memory alloys (SMA) coatings. Herein, SMA/Nbx (x = 1, 3, 5, 7 wt%) composite coatings were fabricated for improving the microhardness and anti-corrosion. The influence of the different Nb doping amounts on the microstructure, microhardness, friction, corrosion resistance and shape recovery rate was studied. In-depth research on the strengthening mechanism by TEM reveals that the formation of Nb3Si significantly impedes the movement of dislocations, and improves the anti-wear and microhardness of the composite coating. Benefiting from doping of Nb, the obtained coating possesses higher Cr element, thus improving the robustness of the passivation film. When the Nb doping is 5 wt%, the Rct was twice as high. Simultaneously, the fabricated coating exhibits a better shape memory effect. The recovery rate reached 4.38% at a deformation of 5% when doping with 5 wt%.