This paper discussed the friction coefficient evolution of a TiN coated contact during sliding wear. A hard TiN coating was prepared on a bearing steel (GCr15) substrate by applying the composite method of cathode arc and magnetron sputtering. The microstructure, microhardness, microscratch and tribological behaviour of this coating were studied to obtain the relationship between friction coefficient and other coating properties, meanwhile the full friction coefficient evolution curve with different stages during the wear process of TiN coating was shown. It was found that, coating friction and wear, as two interactive responses from a tribo-system, mutually affected each other and should be studied as a single physical phenomenon. Therefore, a novel friction-wear interactive friction model was developed to represent the evolution of friction coefficient and to predict coating breakdown. The results show that the evolution of the friction coefficient curve can reflect different stages of the wear process and the wear life can be estimated using the new friction model. (C) 2015 Elsevier B.V. All rights reserved.