TiAlN coatings on cutting tools have good wear and oxidation behavior especially at high speed machining and, in this field, many papers have been published, but there is little research about behavior of these coatings on dies at high temperature conditions. In this research, frictional behavior of (Ti 1-X Al X )N coatings deposited on H13 hot work steel were evaluated at hot working temperatures and influence of annealing process on tribological properties were studied. The coatings were characterized using x-ray diffraction, optical and scanning electron microscopy, energy-dispersive spectroscopy and microhardness indentation. Tribological behavior of coatings was investigated using the pin-on-disc tester under the condition of 3 N load, linear velocity of 0.1 m/s and temperatures of 25 and 600 ?C. To study the oxidation behavior of coatings, weight changes of the samples were continuously monitored in oxidation furnace until 700 ?C. The results indicated that hardness increased and surface roughness and friction coefficient decreased as the aluminum concentration was increased. The results of oxidation tests indicated that TiN under thermal cycle had weight gain while TiAlN coatings showed no weight change up to 700 ?C. Presence of aluminum and formation of thin and compact Al 2 O 3 layer on TiAlN coating was found the reason for this. Among the coatings studied in this research, TiAlN coating produced with 70%Al-30%Ti target composition had the best behavior at room temperature because of high microhardness, low friction coefficient and low wear at room temperature. Based on the experimental results, TiAlN produced with 40%Al-60%Ti target composition was the best coating for dies because of low roughness, low friction coefficient and low wear at 600?C and oxidation resistance up to 700 ?C. Annealing process was studied on a number of the coated samples; heat treated under vacuum at 1000 ?C. Annealing caused oxidation of TiN coating and oxygen diffusion in TiAlN coatings and formation of TiAlON solid solution; this phase act as a solid lubricant and decreased the friction coefficient of TiAlN coatings at room temperature to values about 0.14. It was concluded that annealing cycle is a useful process to reduce improve frictional behavior of TiAlN coatings at room temperature. Key Words: Hot Work Steel, TiAlN coatings, Friction coefficient, Oxidation resistance, Annealing.
