Comparative study of Ti1−xAlxN coatings alloyed with Hf, Nb, and B

Increasing requirements on hard coatings in high performance machining processes like high speed and dry cutting demand further development by alloying the already well established Ti1−xAlxN coatings. The aim of this work is to present a comparative study on quaternary Ti–Al–X–N (X = Hf, Nb, B) coatings sputtered from targets with an Al / Ti ratio of 2 and 5 at.% X in an Ar + N2 discharge. Special emphasis is laid on investigating structural, mechanical and tribological properties. X-ray diffraction showed that a more pronounced hexagonal structure appears due to the incorporation of these alloying elements thus affecting the hardness. Hf and Nb additions yield similar friction and wear properties up to 700 °C, whereas the B containing coating failed at 700 °C. Widening of the ternary metastable Ti1−xAlxN solid solution to quaternary systems is the key to further develop these coatings.