Abstract: In order to investigate the damage of the nickel- phosphorous (NiP) coating the surface on computer hard disk substrate after SiO2 nanoparticle impact, a test of nanoparticle impact on a hard disk substrate with the NiP coating is carried out and the variation of the microstructure of the impacted surface is examined by using a high resolution transmission electron microscope (HRTEM), an atomic force microscope (AFM), an auger electron spectrogram (AES), and an X-ray photoelectron spectroscopy (XPS). The experimental results indicate that lots of fine craters and scratches in the nano-scale can be seen on the impacted surface, and some nanoparticles can be embedded in the surface during the impacts. HRTEM observations from the cross-section specimen under different test conditions show the existence of nano-crystalline transformation in the subsurface layer after the impact, and the sizes of these crystalline relate closely to the exposure time. Nanoparticle impacts aggravate the oxidation of the Ni-P alloy coating, and the impact with an exposure time of three minutes promotes the concentration of element phosphorus in the subsurface below about 6 nm.

Key words: Computer hard disk, Nanoparticle impact, NiP coating, Polishing