Improving the cutting performance of TiAlN coatings using submicron metal interlayers

TiAlN coatings as been used with success in high speed metal machining. The similar B1 TiN structure, high hardness, adhesion and high wear and oxidation resistance contributes to such ability. However, it is possible to enhance some of those properties, particularly the adhesion and cohesion of the coatings without changing significantly all the others. The introduction of submicron metal interlayers in TiAlN coatings do not affect significantly the hardness of the whole coating itself, but promote a beneficial decrease in the internal stresses and an increase in the film adhesion and cohesion which contributes to improve their performance in service. Moreover, the possibility to form morphological discontinuities in the coating due to the presence of metal interlayers can enhance diffusion barriers. So, in the present work, multilayer coatings of TiAlN with Al and Ti interlayers with approximately 3.5 mum thick were sputtered. The internal stress, hardness, Young modulus and adhesion of the coatings were evaluated as a function of number of layers.