hossein olia - Academia.edu (original) (raw)

Papers by hossein olia

Materials research express, Jan 30, 2019

In this study, several multilayers nitride coatings were deposited on 17-4 PH stainless steel by ... more In this study, several multilayers nitride coatings were deposited on 17-4 PH stainless steel by employing a cathodic arc physical vapour deposition process to improve the resistance of this stainless steel in corrosive solution environment. Morphology and structure of the coatings were investigated by scanning electron microscopy and x-ray diffraction. Nano instrument equipped method was used to obtain the hardness of the coatings. To evaluate the corrosion resistance, the potentiodynamic polarization and electrochemical impedance spectroscopy tests, in 3.5% NaCl solution, were carried out. The potentiodynamic tests revealed the E corr shifted to more positive potential in all nitride coated that deposited on the substrate. Specimens with CrN/CrAlN multilayer coating revealed superior corrosion resistance compared with substrate and TiN/TiAlN multilayer coating. The electrochemical impedance spectroscopy measurements represent a single time constant lead to corrosion of the coatings without degradation of the substrate. The results also showed that aluminum content of the coating improved the protective role of the layer because of its ability to form the passive film.

Transactions of Nonferrous Metals Society of China, Feb 1, 2012

Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To cr... more Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between Al and Ag, mating surfaces were specially prepared and various rolling thickness reductions were applied. The minimum critical thickness reduction to begin cold weld was specified as 70% which equals 0.1630 critical rolling shape factors. The bimetallic strips were treated by diffusion annealing at 400 °C and various annealing time. The Al/Ag interface of strips was observed by scanning electron microscope to investigate the formation of hard and brittle probable phases. The effect of anneal time on diffusion distance and phase transformation was also analysed by EDS analysis and line scan. A diffusion region along the interface in the Ag side was observed and its width increased with prolonging annealing time. Some δ phases were detected close to the interface after anneal treating for 3 h and δ phase was thicker and more continuous by increasing annealing time. The microhardness measurement showed that in spite of formation of δ phase due to diffusion annealing, the interface hardness was reduced.

Materials and Corrosion, 2020

In the present study, multilayered Cr-N/Cr-Al-N coatings were prepared by cathodic arc physical v... more In the present study, multilayered Cr-N/Cr-Al-N coatings were prepared by cathodic arc physical vapor deposition (PVD) with different numbers of layers and the same total thickness on AISI 630 steel in an attempt to improve the wear and erosion-corrosion resistance. Structural analysis of the coatings was performed by field scanning electron microscopy, X-ray diffraction (XRD), and energy-dispersive spectroscopy. Depth profiles and roughness parameters of worn surfaces were calculated after erosion and wear tests. XRD indicated that nitride compounds were formed in multilayer coatings by PVD. The Cr-N/Cr-Al-N coating exhibited superior corrosion resistance compared with AISI 630 substrate. The erosioncorrosion results revealed that the smoothest wear track with the minimum erosion rate and wear depth was obtained for five-and seven-layered coatings. The failure mechanism of the bare substrate was influenced by plastic deformation via cutting and plowing, while the failure mechanism for coated samples was chipping and delamination. According to the wear results, the multilayer coatings showed a lower friction coefficient and better surface morphology that demonstrated their high ability for wear protection.

Corrosion Reviews, 2018

Physical vapor deposition (PVD) multilayered coatings with titanium nitride and chromium nitride ... more Physical vapor deposition (PVD) multilayered coatings with titanium nitride and chromium nitride top layers were deposited on UNS S17400 alloy in an attempt to improve the corrosion and corrosion-wear resistance of this stainless steel in corrosive environments. The coatings were produced in an industrial chamber by cathodic arc PVD on heat-treated and mechanically polished stainless steel specimens. The microstructures of the substrates and coatings were characterized by X-ray diffraction and scanning electron microscope equipped with an energy-dispersive X-ray spectroscopy system. To evaluate the corrosion and corrosion-wear resistance, reciprocating-sliding tribometer and electrochemical tests were conducted in 3.5% NaCl solution. The results showed that nitride coatings possess, in general, better corrosion and corrosion-wear resistance compared with bare S17400 substrates. Specimens with CrN top coating revealed a typical compact structure and superior corrosion resistance comp...