In order to prevent degradation of diamond surfaces in contact with ferrous metals, a TiN thin film of a few tens of nm thick was synthesized on a diamond surface with a Ti thin buffer layer of approximately 10 nm by a new atom beam method. A diamond surface was simultaneously exposed to pulsed Ti arc plasma and hyperthermal neutral N atom beam generated from an arc plasma gun (APG) and a laser breakdown-type atom beam generator, respectively. Frictional experiment of the TiN thin film was conducted by an in situ scanning electron microscopic (SEM) tribometer using a 1 mm diameter SUS304 pin with an applied force of 0.24 N. The TiN film had a relative high friction coefficient (0.4), but this film showed no notable degradation and relative steady friction. In addition, a TiN coated diamond tip by the new atom beam method showed less wear than that of non-coated diamond tips by three times in the scratching tests of iron with using an atomic force microscope (AFM). (C) 2011 Elsevier B. V. All rights reserved.