The structural and tribological properties of niobium nitride (NbN) films are investigated because of their potential to improve the wear-life and corrosion resistance of bearing components operating in extreme environments such as turbine engines and spacecraft. The films are deposited onto 440C stainless steel substrates by magnetron sputtering. Nitrogen partial pressure (PN,) is varied to change the crystal structure of the films. At 4 x 10(-4) torr, the films are cubic : as the partial pressure of the gas is increasing fraction of hexagonal delta’-NbN phase appears. The substrate bias potential is adjusted to affect the film microsructure. Wear properties and friction coefficients are studied using a ball-on-flat tribometer with Si(3)h(4) and stainless steel balls as the counterface materials. Film hardness and adhesion properties are measured using a nano indentation tester and a scratch tester, Chemistry and microstructure : are characterized using X-ray photoelectron spectroscopy, XRD, SEM and TEM. The films have friction coefficients of approximately 0.6 and 0.7 when slid against Si3N4 and stainless steel balls. respectively. They have hardness of about 30 GPa. and an adhesion of 2-3 kgf, ns measured by scratch testing. SEM micrographs indicate the films are smooth and dense. The films are somewhat N deficient on the basis of XPS,the film chemistry and stoichiometry do not change significantly with bias or PN2.