Preparation and characterization of Ni–P–nanoTiN electroless composite coatings

Ni–P–nanoTiN composite coatings were prepared successfully by electroless plating technique on AZ31 magnesium alloys. The composition, morphology, structure and phase transformation behaviour of the composite coatings were characterized respectively by using of scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). The micro-hardness and wear resistance of the nano composite coatings, both in as-deposited and heat treated states, were investigated. The results demonstrated that the composite coatings, which contained nano TiN particles, exhibited much better properties in hardness and wear resistance than the conventional Ni–P coatings and original AZ31 magnesium alloys. These enhancements of properties are attributed to the nano TiN particles uniformly distributed in the Ni–P matrix.

Research highlights▶ The uniform Ni–P–nanoTiN coatings were successfully deposited on AZ31 magnesium alloys substrate by electroless plating after appropriate pretreatments for the substrate. ▶ The Ni–P–nanoTiN composite coatings were composed of compact fine nodules uniform in size without any pores or cracks, and the nanoTiN particles uniformly distributed in the Ni–P matrix. ▶ The introduction of nanoTiN particles in the Ni–P matrix significantly improve the wear resistance compared with the conventional Ni–P coatings and original AZ31 magnesium alloys.