Tensile Behaviors of Laser-Discrete-Quenched Substrate/Nickel Coating of Electroplated Grinding Wheel

Electroplated grinding wheel has significant advantages, such as longer service life, higher removal rate, reduction of preparation work, reapplication of the wheel bub. Then it is an efficient, green and eco-friendly abrasive tool. In order to reveal the mechanism that the service life of the electroplated grinding wheel is increased by pre-quenched substrate, the tensile behavior and interfacial stresses of the laser-discrete-quenched substrate/nickel coating were studied through tensile experiment and simulation. The results show that random initial cracks appear in the nickel coating over the unquenched zone before the tensile experiment. There is an inter-diffusion region at the interface of steel substrate and nickel coating; in comparison with the unquenched zone, the size of the inter-diffusion region in the laser-quenched zone was decreased significantly (e.g., 1.2 μm in comparison with 2.6 μm). In tensile testing, the coating over the pre-quenched specimen remains bonded with the substrate firmly even the fracture occurs. In contrast, the damages in the forms of blistering, stripping and exfoliating occurred in the coating over the unquenched specimen. When a fracture occurs, there is a significant difference of the ultimate strains of quenched and unquenched zones; the ultimate strain of quenched zone is 0.0714, while that of the unquenched zone is 0.1667. At the bonding interface, the pre-quenched specimen ensured the overall shear stress and the maximum normal stress, which are lower than those of unquenched specimen. The initial cracks in pre-quenched specimen propagate during stretching, the effect of the absorbed strain energy reduces strain mismatch between the substrate and coating at the interface, and this improves the bonding strength at the interface of the laser-discrete-quenched specimen significantly.