Measuring and Modeling Flash Temperatures at Magnetic Recording Head–Disk Interfaces for Well-Defined Asperity Contacts

Abstract

High-speed impacts of magnetic recording heads with small asperity defects on disk surfaces have long been a major source for reliability failures for disk drives. Consequently, determining the contacting stresses and flash temperatures that occur during these impacts is an important step toward understanding the wear and eventual failure mechanisms associated with these impacts. Here we report measurements and modeling of the flash temperatures that occur when a magnetic recording head impacts an asperity at disk-drive-like conditions (at speeds 9–15 m/s and with a few nanometers of interference). The asperities considered here have a well-defined shape with radii of curvature at their summits = 100–200 µm. One surprising result of our measurements is that the flash temperature does not increase monotonically with increasing interference, which would be expected if the flash temperature is solely from frictional heating. To explain this result, we have developed an analytical model where, in addition to frictional heating, we include the effect of contact cooling through the contact zone of the heat generated by the thermal contact sensor and the heater used for clearance control. From this modeling, we are able to estimate that fairly high coefficients of friction (µ = 0.8–3.9) occur between the magnetic recording heads and these types of asperities. These results provide not only precise understanding of the flash temperatures generated by high-speed impacts with asperities, but also insight into the contact stresses and potential wear mechanisms that occur during these contacts.