Investigation of nanomechanical and adhesion behavior for AlN coating and AlN/Fe2-3N composite coatings created by Active Screen Plasma Nitriding on Al 1050

Abstract

This study investigated the effect of nitriding time and temperature on the mechanical properties of the composite AlN/Fe2-3N coating deposited on the pure aluminium substrate using the novel Active Screen Plasma Nitriding (ASPN) method. ASPN treatment was performed for 2, 5, 10, 15 h at temperatures of 450,500, and 550 °C and Conventional Plasma Nitriding (CPN) treatment was carried out for 5 h at 500 °C. All treatments were performed at the 10 KHz frequency with 80% duty cycle on the Al1050 substrate under 20%H2+80%N2 atmosphere. Phase and microstructure studies were performed using, respectively, the grazing incidence x-ray diffraction (GIXRD) system and the field emission - scanning electron microscopy (FE-SEM) system equipped with energy-dispersive spectroscopy (EDS) analyzer. The mechanical strength of the coating was evaluated by the roughness, nano-hardness, nano-scratch, and adhesion strength tests performed on coated and uncoated specimens. According to the results, the uncoated Al1050 specimen, the CPN-treated specimen, and the ASPN-treated specimen had a mean nano-hardness of 0.7 ± 0.1 GPa, 10.9 ± 0.6 GPa, and 9.6 ± 0.5 GPa, respectively. It was also found that the single-phase AlN coating has a better adhesion strength and scratch strength (LC3 = 12 N) than the composite AlN/Fe2-3N coating (LC3 = 10 N). Examination of scratch mechanisms in hard AlN and AlN + Fe2-3N coatings deposited on a soft aluminium substrate showed that the failures in these coatings are due to tensile-type Hertzian cracks. However, as the load increases, the substrate undergoes increasing deformation and failures shift to chipping and interfacial spallation.