Abstract : The gear hobbing process is the main process used for the gear manufacturing, especially in the automotive industry. The increasing productivity specifications tend to increase the cutting speed used, and to avoid the lubrication with plain oil. A new generation of hobs has been developped using new powder metal high speed steels with a high carbide content, in association with new coatings, and with new tribofinition processes of hobs. The hard and refractory (Ti,Al)N PVD coating, combined with the self-lubricating coating MoS2 has shown a great technical and economical performance in these kind of cutting operations. A review of the characterization methods of coatings has also been realized so as to evaluate the interest of each one at the various stages of a coating development. A study of the tribological and thermal functions of a cutting tool coating on the chip formation has been investigated with various experimental and analytical methods.