Head Material Effects on Interface Tribochemistry

Abstract

Sliding experiments between sliders made of different materials and magnetic thin-film disks were performed in a vacuum and an ambient in order to shed light on material effects in tribology. Al2O3-TiC, amorphous silicon, amorphous carbon, MnZn ferrite, and sapphire were chosen for their current or potential use as head substrate materials. In ambient, the amorphous carbon performed the best tribologically while Al2O3-TiC the worst. The wear mechanism of the slider-disk interface was studied in-situ by mass spectrometry and frictional measurements. For unlubricated interfaces, decreasing evolution of C, CO and CO2during initial sliding was accompanied by decreasing friction. For lubricated interfaces, fluorocarbon fragments with a wide range of masses were generated at a decreasing rate while friction was low and relatively constant. When the magnitude of gaseous signals increased, frictional variations rose dramatically, hydrogen evolution followed with some delay, and a wear track was formed. With amorphous silicon sliders, a significant amount of SiF4was detected which indicates a tribochemical reaction between SiO2 surface and HF that was produced by the scissioning of lubricants. Degradation mechanisms are dominated by removal of surface groups and adsorbates from solid surfaces and by scission, losses and alteration of fluorocarbon polymers. © 1994 IEEE