A study on the formation conditions of amorphous nickel-phosphorus (Ni-P) alloy by laser-assisted electrodeposition

Highlights: • Laser irradiation improves grain size and degree of amorphous. • Laser irradiation removes the bubbles and improves the surface quality. • The laser energy offsets part of the residual tensile stress. • Laser irradiation improves the hardness, corrosion and wear resistance. The formation of electrodeposited amorphous Ni-P alloy requires numerous tiny crystal nuclei and disorderly arranged atoms. In this paper, laser irradiation is introduced into the electrodeposition process by a cyclic reciprocating scanning manner. The laser thermal effect not only enhances the formation of amorphous Ni-P alloy with smaller nucleus and better density, but also accelerates the reduction of ions and hence hydrogen evolution at the cathode. The transient high-temperature zone occurs under laser irradiation, leading to micro-area agitation formation, so that the gas deposited in the cathode can be eliminated in time, and the pore defects generated in the deposited layer can be reduced. In addition, part of the heat generated by laser irradiation is absorbed by the reducing ions and deposited on the substrate in the form of compressive stress, which may reduce the overall residual tensile stress of the coating. Amorphous Ni-P alloy heat treatment will increase the hardness but decrease the corrosion resistance. However, the results show that laser irradiation can improve the corrosion and wear resistance of the coating simultaneously.