Investigation of the adhesion of NbN coatings deposited by pulsed dc reactive magnetron sputtering using scratch tests

Scratch tests have been used to investigate the adhesion of niobium nitride (NbN) coatings that were deposited by pulsed dc reactive magnetron sputtering at target currents of 1.5, 2.5, and 3.5 A onto M2 tool steel and silicon wafer. The coating adhesion on each material substrate was investigated using a progressive load scratch tester (PLST) and a multi-pass scratch tester (MPST). Microhardness tests and scanning electron microscopy (SEM) were also used to examine the hardness and microstructure of the NbN coatings. These results have indicated that the structural, mechanical, and adhesion properties of the NbN coatings improve with increasing target currents. While performing PLST and MPST tests, the highest adhesion and lowest friction force were obtained for the coatings deposited at a target current of 3.5 A. In addition, the triboscobic behaviors that were observed from the MPST of the coatings indicated that the target currents affect the friction behavior of the coatings.