Revealing the wear mechanism of NiTi alloy coatings with biomimetic sandwich structures by laser cladding

In this study, a Cu/Ni equal weight ratio composite interlayer was designed and developed, and the crack-free 316-NiTi heterogeneous coating was prepared by direct energy deposition. The microstructure reveals that the Ni/Cu composite interlayer exhibits a dendritic morphology. The composite interlayer grows towards the NiTi layer in the form of columnar dendrites, and the elemental distribution spectra show a gradient distribution of Ni elements. The microhardness of the 316-Cu/Ni-NiTi composite sandwich was 388 HV, which was a 112% increase in microhardness compared to the 316 substrates. 316-Cu/Ni-NiTi exhibited good bond strength, with tensile specimens prepared in the building direction achieving a ultimate tensile strength of 590 MPa and a maximum strain of 6.9%. The wear resistance of 316-Cu/Ni-NiTi coating against Al2O3 with a diameter of 6 mm on a reciprocating ball-on-plate tribometer and its response to different loads were investigated. The wear resistance of the 316-Cu/Ni-NiTi specimens was higher than that of the 316 substrate and other similar coatings under the same experimental conditions. The 316-Cu/Ni-NiTi coating designed in this study shows great potential as a repair and remanufactured stainless steel in the field of engineering applications due to its good wear resistance under different loads.