Effect of Vapor Lubrication on Head–Disk Clearance and Slider Wear in Inert Gas Environments

The application of dynamic flying height (DFH) control technology to hard disk drives (HDDs) reduces the clearance of the magnetic heads above the disk surface to a few nanometers. Further, such a small clearance distance sometimes causes wear of the diamond like carbon (DLC) overcoat on the slider surface at the head–disk interface (HDI) owing to contact with the disk surface. The wear mechanisms of the DLC overcoat are considered to be either mechanical wear or tribochemical wear (oxidation of carbon) [1]. Recently, a helium-filled HDD was developed to improve the storage capacity and power consumption of HDDs. In the helium-filled HDD, tribochemical wear does not occur because there is no oxygen in the HDD. In addition, there is no humidity (water vapor), which was found to affect wear at the HDI [2]. Therefore, it is important to understand the effect of humidity and an oxygen-free inert gas environment on slider wear.

Research on Cooling Action and Simulation of Temperature Distribution with Water Vapor as Coolants and Lubricants in Green Cutting

Water vapor is a good, pollution-free and economical coolants and lubricants in green machining. In order to research the cutting temperature distributions with water vapor as coolants and lubricants in machining, the experiments conducted under the conditions of water vapor as coolants and lubricants and dry cutting. The cutting temperatures are studied by metal cutting theory, and then by employing the finite element method (FEM), the temperature distribution of cutting region is simulated with application of water vapor as coolants and lubricants and dry cutting conditions. The results show that the water vapor jet flow has high force-convection heat transfer coefficient and directly cooling action to reduce cutting temperature, and the stress, the length of tool-chip interface are reduced with application of water vapor lubrication. So that the cutting thermal is decreased and water vapor has indirect cooling action. Under the conditions of indirect and direct cooling action, the cutting temperature is reduced obviously with application of water vapor as coolants and lubricants.

MEMS Lubrication by Tribochemical Reaction

A means of providing replenishable lubrication to rubbing silicon surfaces is demonstrated. Alcohol at a small fraction of saturation vapor pressure is introduced in a nitrogen environment. Pin-on-flat sliding experiments in this environment reveal a friction coefficient near 0.2, and absence of wear above a critical alcohol concentration. This lubrication approach was also demonstrated in microfabricated silicon machines, where the devices operated at least a factor of 104 longer without failure when alcohol vapor was present in the nitrogen gas environment, compared to devices in dry N2 with a chemisorbed monolayer alone. When water vapor was added to the environment, vapor lubrication by alcohol was inhibited at concentration ratios of water:alcohol = 2.5:1.