Influence of the nitrogen pressure on the structure and properties of (Ti,Al)N coatings deposited by cathodic vacuum arc PVD process

The aim of the research was to define the dependence of the properties of vacuum arc deposited (Ti,Al)N coatings on the nitrogen pressure and resulting composition of the generated plasma. The investigated (Ti,Al)N coatings were deposited by the cathodic arc-vacuum method using AlxTi1−x alloy cathodes with composition of 66.3 at.% Al and 33.7 at.% Ti. Experiments were carried out on the industrial multi-source arc-vacuum device MZ–383 at four values of the nitrogen pressure (3.0×10−3 mbar; 8.0×10−3 mbar; 1.3×10−2 mbar; 3.0×10−2 mbar), constant substrate bias voltage (UBIAS=−100 V) and constant arc current (I=50 A). Emission spectra of plasma were recorded in the range from 300 to 500 nm using a medium-resolution monochromator with the optical grating of 1800 lines/mm and the focal distance of 250 mm. Scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) were used to investigate the structure and chemical composition of the coatings. Hardness, Youngʹs modulus and adhesion strength of the coatings were determined using the nano-indentation method and scratch test, respectively. The relation between the nitrogen pressure, plasma composition, surface morphology and chemical composition of (Ti,Al)N coatings as well as their mechanical properties was assigned.