نوع مقاله : مقاله کامل پژوهشی
موضوعات
عنوان مقاله English
نویسندگان English
This research investigates and compares the corrosion behavior of nanocrystalline cobalt high-speed steel (HSS M35) and amorphous titanium coatings deposited on a Monel 400 alloy substrate using the Electro-Spark Deposition (ESD) method. The coatings were produced under two different input energy levels (capacitances of 100 and 300 μF). Microstructural analysis revealed that the high-speed steel coating possessed a nanocrystalline structure comprising an austenitic (Ni, 3Fe) phase and carbide nanoparticles, whereas the titanium coating, owing to ultra-rapid cooling and alloying with substrate elements (Ni, Cu), formed an amorphous structure. Potentiodynamic polarization tests in 3.5 wt.% NaCl solution indicated a significant enhancement in corrosion resistance for both coatings compared to the bare Monel 400 substrate. The corrosion current density (icorr) of the amorphous titanium coating (0.006 μA/cm²) was approximately 1.5 times lower than that of the nanocrystalline high-speed steel coating (0.009 μA/cm²) and about 70 times lower than the uncoated substrate (0.42 μA/cm²). The superior performance of the amorphous coating is attributed to the absence of grain boundaries and crystalline defects, as well as its ability to form a uniform and stable passive layer. Additionally, the nanostructured HSS coating, with a thickness of 95 µm, effectively protects the substrate from the aggressive medium, thereby improving corrosion resistance. Considering the superior performance of the amorphous titanium coating in corrosion tests, it is recommended for marine applications where corrosion resistance is a critical requirement.
کلیدواژهها English