Browsing by Keyword "Duplex"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Pitting corrosion on highly alloyed stainless steels in dilute sulphuric acid containing sodium chloride(2023-07-20) Huttunen-Saarivirta, E.; Isotahdon, E.; Que, Z.; Lindgren, M.; Mardoukhi, A.; Jorcin, J. B.; Mocnik, P.; Kosec, T.; Ouazari, Y. El; Mameng, S. Hägg; Wegrelius, L.; MATERIALES PARA CONDICIONES EXTREMASStainless steels are widely used in industrial assets and equipment. Despite their good corrosion resistance under a wide range of operating conditions, there is the possibility of pitting corrosion in the presence of chlorides. However, very few studies have identified the safe operating conditions for various high-alloyed stainless steel grades by comparing their pitting susceptibility. In this research, the susceptibility to pitting attack of five stainless steels with austenitic and duplex microstructures was examined in dilute sulphuric acid solution with varying amounts of NaCl at the temperatures of 50, 90 and 130°C. Based on potentiodynamic polarization scans, none of the test materials underwent pitting corrosion at 50°C, but differences in susceptibility to pitting attack were clear between the test materials and NaCl concentrations at the temperature of 90°C, and further temperature increase facilitated uniform corrosion. 28-day immersion tests at 90°C confirmed the pitting susceptibility of duplex grades 1.4662 (PREN 33) and 1.4462 (PREN 35) in the presence of at least 2000 mg/L NaCl, but not the susceptibility of a corresponding austenitic grade 1.4539 (PREN 34). The grades 1.4547 (PREN 43) and 1.4410 (PREN 44) were not susceptible to pitting corrosion under any of the studied conditions. The results from materials microstructural and electrochemical characterization are presented and discussed in this paper.Item Tribological and electric contact resistance properties of pulsed plasma duplex treatments on a low alloy steel(2023-02-15) Murua, Joseba; Ibañez, Iñigo; Dianova, Anastasia; Domínguez-Meister, Santiago; Larrañaga, Oihane; Larrañaga, Aitor; Braceras, Iñigo; INGENIERÍA DE SUPERFICIESLow friction low cost tribology systems involve most often use of lubricants, which must be periodically refurbished and often present environmental issues. Furthermore, use of liquid lubricants is a non-starter in many critical applications. In this work, the performance of single process duplex tribo-conditioning treatments is explored. The treatments are based on pulsed low-pressure plasma treatments, where nitriding processes are complemented with the deposition of carbonaceous solid lubricating top layers. The duplex treatments are carried out sequentially in the same chamber. The study comprised, among others, exploring the use of different residual gas mixes and pulse frequencies. Roughened blasted 42CrMo4 low alloy steel (AISI 4140 equivalent) was used as substrate. Resulting surface properties were studied with nano-indentation, profilometry and contact angle measurements. Besides, tribological studies were carried out against 100Cr6 steel at different humidities. The evolution of the coefficient of friction and the electrical contact resistance (ECR) was assessed for each test, as well as the wear rates. Results showed tribological outcomes heavily dependent of ambient conditions, and ECR of the wear track surface condition, i.e. the amount of remaining coated surfaces. The use of pulsed plasmas generated comparatively softer, smoother and more hydrophobic surfaces.