This paper will present the results of indentation, one pass scratch and the repeated sliding tests to determine the critical load and the wear-life of TiN coated specimens. The sliding tests of cone(diamond)-on-disc type were performed under dry sliding conditions as well as indentation and scratch. The test specimens were 0.2% plain carbon steels. The coefficient of friction and the wear cycles to failures were measured with different coating thickness, substrate hardness and roughness. From the scratch tests it was confirmed that the critical loads increased with the hardness of the substrate, furthermore the critical loads are increased with the coating thickness and decreased with increasing surface roughness. Using the percent contact load, the ratio of sliding normal load to the critical scratch load, the cycles to failure are measured to predict the wear-life of TiN film. On the wear-life diagram, the percent contact loads and the cycles to failure show the good linear relation on log coordinate. With a decreasing load percentage, the diagram shows that the wear-limits, at which the coated steels survive more than 4000 cycles, an about 6-10% of the critical scratch loads. (C) 1998 Elsevier Science S.A. All rights reserved.