scholarly journals Electrochemical corrosion behaviour of HVOF sprayed iron-based amorphous metallic coatings on AISI 316 stainless steel in an NaCl solution

2018 ◽  
Vol 27 (3-4) ◽  
Author(s):  
S. Vignesh ◽  
K. Shanmugam ◽  
V. Balasubramanian ◽  
K. Sridhar ◽  
D. Thirumalaikumarasamy

AbstractNew thermally sprayed amorphous metallic coatings have been developed recently that may provide a viable coating option for fluid handling equipment such as propellers, impellers and pumps. They possess the inherent risk of flow-dependent erosion-corrosion problems. In this investigation, iron based (Fe) amorphous coatings were deposited on AISI 316 stainless steel substrate by the high velocity oxy-fuel (HVOF) spraying process, and the coating microstructure was characterised using an optical microscope and scanning electron microscopy. The Fe-based amorphous coating consisted of an amorphous phase, an absence of dislocations, a nanocrystalline phase, less porosity and high hardness. The corrosion behaviour of the substrate and Fe-based amorphous coatings were evaluated by means of electrochemical tests in 3.5 wt.% NaCl solution. Three kinds of electrochemical tests were employed to identify the corrosion resistance of the coating and substrate. The results showed that the Fe30Cr25Mn5Mo20W10B5C3Si2 amorphous metallic coating had a superior corrosion resistance than 316 stainless steel. It was attributed to the amorphous structure and the presence of the corrosion resistant element chromium (Cr).

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 581
Author(s):  
Ioan Milosan ◽  
Monica Florescu ◽  
Daniel Cristea ◽  
Ionelia Voiculescu ◽  
Mihai Alin Pop ◽  
...  

The appropriate selection of implant materials is very important for the long-term success of the implants. A modified composition of AISI 316 stainless steel was treated using solar energy in a vertical axis solar furnace and it was subjected to a hyper-hardening treatment at a 1050 °C austenitizing temperature with a rapid cooling in cold water followed by three variants of tempering (150, 250, and 350 °C). After the heat treatment, the samples were analyzed in terms of hardness, microstructure (performed by scanning electron microscopy), and corrosion resistance. The electrochemical measurements were performed by potentiodynamic and electrochemical impedance spectroscopy in liquids that simulate biological fluids (NaCl 0.9% and Ringer’s solution). Different corrosion behaviors according to the heat treatment type have been observed and a passivation layer has formed on some of the heat-treated samples. The samples, heat-treated by immersion quenching, exhibit a significantly improved pitting corrosion resistance. The subsequent heat treatments, like tempering at 350 °C after quenching, also promote low corrosion rates. The heat treatments performed using solar energy applied on stainless steel can lead to good corrosion behavior and can be recommended as unconventional thermal processing of biocompatible materials.


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