The attempt to find an alternative coating for corrosion protection of Al- alloys was made. PVD coatings are one of the possible alternatives for replacement of ecological unfriendly chromate coatings. Chromium-nitride (Cr-N) and Ni/Cr-N coatings were sputtered on aluminium substrates (AA7075 and cladded AA2024). Surface and sub-surface characterizations were performed by AFM and SEM. Special attention was given to defects incorporated into coatings, since they play important role in the corrosion protection of the coating/substrate systems. The cross-sections through the typical defects were performed by ion beam milling incorporated into the SEM. The Vickers hardness of the Cr-N with and without layer of Ni on both substrates was determined. After the coatings deposition, the values of Vickers hardness (10 mN load) increase for 10 to 100-fold compared to the substrates. The corrosion behaviour of Cr-N and Ni/Cr-N thin films was investigated in near neutral 0.1 M solution of NaCl using potentiodynamics electrochemical measurement. Cr-N and Ni/Cr-N coatings shift the corrosion potentials to more positive values. The best corrosion resistance among the tested coating/substrate systems were found for Ni/Cr-N on AA7075 substrate.
COBISS.SI-ID: 25468199
In this work we deposited a series of hydrogenated amorphous carbon (a-C:H) films and nitrogen-doped a-C:H films on silicon substrates using an ion-beam-deposition technique called anode layer source. We used different discharge voltages, which influence the sp2/sp3 carbon hybridization ratio, and we also varied the N2-to-C2H2 flow ratios. The composition was analysed by elastic recoil detection analysis (ERDA), to determine the hydrogen content, in combination with Rutherford backscattering spectroscopy (RBS), for the heavier elements. An additional set of experiments was conducted by time-of-flight (TOF) ERDA, which gives information not only about the hydrogen content but also about the content of other lighter elements (C, N and O) in the sample. The influence of the deposition parameters on the chemical composition and the structure of the films (studied by Raman spectroscopy) was thus evaluated. The discharge voltage did not have a measurable effect on the composition (but a decisive one on the structure), while the nitrogen flow variations were clearly proven in respective trends in the chemical composition and stucture variations.
COBISS.SI-ID: 25355047