Surfaces of stainless steel SUS304 were coated with titanium oxy-nitride (TiON) films at temperatures of 400- 770degreesC using an ion-beam assisted deposition technique constructed from an electron beam evaporator for Ti evaporation and a microwave ion source for ionizing nitrogen gas. The N ions were accelerated at energies of 0.5-2.0 keV. Most of the deposited TiON films consisted of (60-80)% TiN and (40-20)% TiO2, and the fraction of TiO2 increased with increasing substrate temperature. Hardness of the TiNO films varied in the range from 160 GPa to 260 GPa with increasing substrate temperature. The titanium oxy-nitride film could be deposited on stainless steel without a significant deterioration surface layer at 600degreesC. However, when TiNO films were deposited at temperatures higher than 700degreesC, the thickness of the TiNO films were significantly thinner and a thick layer containing nitride such as Cr2N, CrFe, Fe2N and Fe4N was formed in a near surface region of stainless steel because more nitrogen diffused into stainless steel. (C) 2003 Kluwer Academic Publishers.