Microstructure and Micromechanical Properties of Ni-Ti-Si Coating Deposited by Laser Cladding

A cladding layer 55Ni-35Ti-10Si (at%) was synthesized on copper using laser cladding, which was composed of two kinds of microstructures. The microstructures of the cladding layer were characterized by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The results show that the phases in upper layer are Ti solid solution+Ni3Si and the morphology is dendritic. The under layer is composed of Ti solid solution+Cu solid solution and the morphology is cellulate. The crystal growth in solidification process was analysed using a modification model which is combined Kurz-Giovanola-Trivedi (KGT) model with Lipton-Kurz-Trivedi (LKT) model. The mechanism of cladding layer stratification was studied by thermodynamics. The microhardness of cladding layer was tested. The average hardness (HV) of upper layer and under layer are 8000 and 2200 MPa, respectively. The synthesis of under layer is beneficial to the performance transition between the cladding layer and substrate, increasing the stability of cladding layer.