Multilayered titanium tungsten nitride coatings with a superlattice structure grown by unbalanced magnetron sputtering

This paper reports the deposition of TiN-W2N superlattice coatings using unbalance magnetron sputter deposition. Three magnetrons were used to vaporise the poisoning sensitive material titanium whereas only one magnetron was needed to deposit sufficient tungsten from a pure tungsten target. The deposition process was carried out simultaneously in one single vacuum chamber using one common reactive gas atmosphere. Titanium and tungsten were present as the individual phases of TiN and W2N and not as a TiWN solid solution. The coatings had a (200) preferred orientation with hardness values up to 3000 HV at a surprisingly low internal stress of 1.0 GPa mu m(-1) and high adhesion, L(c) 60 N, when a minimum nitrogen content was exceeded. The superlattice period evaluated by low angle XRD was between 24.5 and 172 Angstrom depending on the nitrogen partial pressure, the satellite rotation frequency in the vacuum chamber and whether it was single or three fold rotation.