Analysis And Experimental Research On Influencing Factors Of Tribological Properties Of Head Disk Interface

In order to meet peoples demand for capacity of hard disk drives(HDDs) and increase the magnetic recording areal densities to 100Gbit/in2, this distance, known as head-media separation(HMS), should be reduced further. HDDs are widely used in various occasions that need high reliability. However, the reduction of HMS results in a decreased flying height. Consequently, the disks’ surface topography would affect the slider’s flying, and hence the contact probability between the slider and the lubricant layer or hard overcoat surface on the disks would greatly increase. Therefore, investigating the effect of disk’s surface topography on ultra-thin gas film lubrication in head/disk interface(HDI) and the stress and strain states of disk, study on the tribological performance are of vital significance to improve the reliability of the head disk interface.In this study, based on Navier-Stokes equation and the continuity equation, the Reynolds equation is modified utilizing the F-K model. The roughness of the disk interface is introduced to the modified equation. The plate and dual-track type model is built under different roughness modes. The pressure distribution and air bearing force at the head/disk interface in hard disk drive are analyzed. The paper compares and analyzes the effect of different roughness modes, flying heights and wave numbers as well as the slider monography on gas film lubrication performance.Under the quasi-static condition, a rigid hemisphere sliding over a multilayer thin film half-space is implemented to simulate the contact between the recording slider and the magnetic storage multilayer disk. The effects of different parameters such as normal load, friction coefficient and radius of slider on the von Mises, shear and principal stresses in the multilayer system are analyzed using finite element method. The failure mode of interfaces of the multilayer is investigated. Under sliding conditions, for a given normal load, the friction coefficient influences the location and magnitude of the plastic strain and it is the main reason that causes the crash of the disk.The tribological properties of a disk surface are experimentally investigated by using Nano-Indentor, Atomic Force Microscopy(AFM), Optical Contact Angle Measuring Device(OCAMD), Raman Spectroscopy(RS). The contact angle measured by OCAMD is used to characterize the wettability of the lubricant. The effect of tip radius on adhesive force is investigated by AFM, and the reason causing the variation is also studied. The tribological behaviors between the A FM tip and the disk surface is investigated.The effects of different scanning speed and normal load on friction are analyzed. Nano-Indentor is used to measure the elastic modulus and the hardness of the disk, and hence proving the validity of finite element model. The wearing behaviors of the diamond-like carbon layer(DLC) and lubricant were analyzed by friction are tester(UMT). According to the results of friction and wear experiment, the tribological behaviors of different contact pairs are discussed. The changing mechanism of friction coefficient is studied by using Raman Spectroscopy.