جستجوی مقالات مرتبط با کلیدواژه « Multilayer coating » در نشریات گروه « مکانیک »

Nitride multilayer coatings created by Physical Vapor Deposition (PVD) method has shown a good trend in improving corrosion resistance. In this research, corrosion performance of Ti/TiN multilayer coatings with 1.5 µm in thickness which created by High Vacuum Magnetron Sputtering on 7075 Aluminum Alloy substrate was investigate.  Presence of TiN, TiOxNy and TiO2 phase in the cross-section of multilayer coatings was confirmed by XPS analysis. Creation of uniform coatings with tough surface with smooth grains by FESEM microscope and surface roughness of 142Å by AFM microscope was confirmed. Electrochemical Impedance Spectroscopy (EIS) results was proved desirable corrosion behavior of the Ti/TiN coatings. Resistance changes for coated samples was in range of 1984-808.5  witch in comparison with uncoated sample with 84.3 in resistance was shown remarkable increase in corrosion resistance between 9.6-23 times.

The existence of defects and residual stresses in the multilayer coatings could reduce their crack resistance. By using the method of molecular dynamics (MD) simulation, the crack propagation behavior in deposited Ti/TiN bilayer is compared with its perfect structure. For this purpose, TiN was deposited on Ti substrate, then crack growth was investigated in the two structures. The growth of TiN film on Ti was island growth, and the structure has defects and residual stress. The results showed that both the biaxial and normal residual stresses in the substrate and film are tensile and compression, respectively. The cohesive energy of the interface was calculated by energy difference along the atomic layers. In the following, a crack was considered perpendicular to the Ti/TiN interface in both models, with an initial length of 15 Å. Due to the brittle behavior of the ceramic layer, crack propagates rapidly until interface. The plastic deformation of the Ti layer and the structure of the interface blunt the tip of the crack and prevents to fail. Also, the critical stress for crack growth in a regular structure is found to 2.5 times of its value in the layered structure because of defects and tension in the layered structure