Influence of Mo on the structure and the tribomechanical properties of arc evaporated Ti-Al-N

Today's industrial forming and machining processes of various materials, require precision and efficiency. A continuous improvement in wear resistance and mechanical properties of protective coatings is therefore a key factor for many applications. Especially, molybdenum (Mo) is a promising candidate to further improve the tribological properties of industrially high-quality coatings like Ti-Al-N. Therefore, we study the influence of Mo on the phase formation, mechanical properties, as well as wear performance of cathodic arc evaporated Ti1 − x − yAlxMoyN hard protective coatings. According to our results, we can neither confirm nor rule out a solubility limit for molybdenum up to 12 at.% Mo and bias potentials Ubias between −40 and −120 V. With increasing Mo content, the deposition rate increases―basically due to the increased evaporation rate of the powder metallurgically prepared (Ti0.5Al0.5)1 − yMoy cathodes. For bias potentials of −80 and −120 V, the hardness is 36.6 ± 1.0 and 39.0 ± 0.6 GPa, respectively, and almost independent of the Mo content. But the wear rate significantly decreases with increasing Mo content by two orders of magnitude (from 3.0 · 10−5 mm3/Nm for Ti0.56Al0.44N to ≤ 2.1 10−7 mm3/Nm for Ti0.50Al0.38Mo0.12N), accompanied by a reduction of the coefficient of friction from 1.0 to 0.5, respectively. Consequently, Ti1 − x − yAlxMoyN coatings are superior in tribomechanical properties and wear performance to conventional Ti0.56Al0.44N.