Papers by Keyword: Corrosion Properties

Abstract: Duplex stainless steels (DSSs) are being increasingly employed in the oil and gas and chemical industries, which, despite their high alloying degree and high resistance to general corrosion, are subject to pitting and crevice corrosion. According to their resistance to pitting and crevice corrosion, steels are ranked according to the PREN. However, nowadays there are many grades of DSSs, in which the content of Cr, Mo and N varies in different quantities, therefore the selection of the grade must be carried out with great care, considering not only PREN, but also the production technology, operating conditions, and the geometry of products. The crevice corrosion behaviors of three grades of duplex stainless steels quenched from 1050, 1100 and 1200 °C were studied in FeCl₃ solution at 50°C. It is shown that PREN allows to rank only different grades in terms of corrosion resistance. With a constant PREN value, but with different contents of ferrite and austenite in steel, completely different values of the corrosion rate can be obtained, therefore, PREN must be used with great care. It was found that in the studied steels, the optimal ferrite content, at which the lowest crevice corrosion rate is achieved, is at 65 vol.%.

Abstract: The paper presents the evaluation of corrosion resistance of aluminium alloy AlSi1MgMn. This alloy is used above all in any atmospheric conditions. The corrosion resistance of the alloy was evaluated by determining the open circuit potential (OCP) in solution SARS (this solution simulates the industrial atmosphere) after the 10 months of exposure time. The surface of aluminum alloys were analyzed by using energy dispersive X-ray analysis after the exposure time. The basic of corrosion characteristics (corrosion potential E_corr, corrosion rate i_corr and polarization resistance R_p) were determined by potenciodynamic measurements according to Tafel’s and Stern’s methods.

Abstract: In this study, the mechanical properties and corrosion properties of plasma nitrocarburized 304 stainless steel at various processing times was investigated. Plasma nitrocarburizing was carried out at different processing time durations which varied from 60 min to 300 min at fixed temperature of 500 °C in an atmosphere of 78 vol.% N₂, 19 vol.% H₂ and 3 vol.% CH₄. An Optical microscope and SEM coupled with EDS have been used to characterize the microstructural and the elemental depth profiles in which the thickness of the modified layers is derived. Microindentation method is used for the study of mechanical performance of the nitrocarburized material. Corrosion properties were investigated using potentiostat method in a 1 wt% NaCl solution. The result shows that the microhardness increases to a maximum value of more than two times compared to that of the untreated one. The corrosion performance was found being treatment time duration dependent.

Abstract: Institute of Materials Science at Silesian University of Technology since 6 years conducts researches to learn about the new dedicated for automotive, railway and military industries. Some of these materials belong to the group of AHS steels, characterized by the twinning induced plasticity (TWIP) effect. It is a new type of steel possessing both a high strength and a great plastic elongation, and an ideal uniform work hardening behaviour. It is therefore a good candidate for deep drawing applications in the automobile and railway industries. In the paper the of the three grades of high-manganese steels of was studied in 3.5% NaCl solution and in an “acid rain” solution with pH=3.5 environments using polarization experiments. The results of corrosion tests and analysis of show that a higher polarisation resistance and lower values of corrosion current density are observed for all studied steels in 3.5% NaCl solution. Spontaneous passivation ability has been shown only for one grade of high-manganese steel in 3.5% NaCl.

Abstract: Angular momentum pumps are very often applied on-board ships. These pumps are used in cooling circuits of medium and high power engines, power plant boilers and in bilge, ballast and fire installations. Very extensive use of angular momentum pumps on board is linked with their numerous advantages. During operation, the wear of the marine hull, the rotor and the shaft seals takes place. The research attempts to increase the service life of shafts. The article presents the research results referring to the analysis of the influence of finish treatment (turning, grinding and burnishing) on the corrosion properties of steel applied to marine pump shafts. The research was performed on a roller of 40 mm in diameter made of X5CrNi18-10 (AISI 304 L) stainless steel. The turning process was carried out by means of a WNMG WF 080408 Sandvik Coromant cutting tool with replaceable inserts. The grinding process was performed by grinding attachment for lathes. The 1 – 80×10×32 – 99C 80-N V grinding wheel was used for the process. The process of burnishing was done by SRMD burnisher from Yamato. In addition, the influence of the burnisher passes number on the corrosion properties was determined. The paper will present the results of electrochemical impedance spectroscopy and potentiodynamic research. To conduct the survey, the Atlas 0531 EU & IA potentiostat was used. Determination of the corrosion process parameters was performed by the computer programs: AtlasLab 2.0, EIS Spectrum Analyzer and Elfit2.

Abstract: Specialty stainless steels designed with higher levels of Chromium, Nickel and Molybdenum than the general austenitic grades AISI 304 and AISI 316 have distinctly superior corrosion resistance properties. The commercial production of such high alloyed stainless steels came with advent of improved steel melting, refining and casting technologies. These technological improvements made it possible to produce such steels with low carbon levels and close control of chemical composition necessary to achieve the desired phase balance and avoid formation of undesirable intermetallic phases. Further, ability to achieve low sulphur levels combined with freedom from undesirable level of tramp elements improved the hot workability characteristics. Thermodynamic aspects of steelmaking and refining in Vacuum Oxygen Decarburization ( VOD) process for manufacture of specialty grades 904L (24% Ni, 20% Cr, 4% Mo, 1.2%Cu) , 317LM ( 19% Cr, 14.5% Ni, 4% Mo,) , 2205 ( 22.5% Cr, 5% Ni, 3% Mo) at Mukand through the Triplex process route ( Ultra High Power Furnace Oxygen Top and Bottom Blown Convertor VOD) are outlined. The effects of undesirable intermetallic phases, particularly sigma phase, on mechanical and corrosion properties are discussed. Application areas for such specialty grades are reviewed. Keywords: High alloyed Stainless steels, triplex process, sigma phase, intermetallic phases, tramp elements, hot workability, corrosion properties, vacuum oxygen decarburization.

Abstract: The microstructuresandcorrosion properties of the as-cast Mg-Zn-Ca-Zralloys were investigated in this study. The results showed that the alloy was mainly composed of -Mg solid solution,Zr particle and the secondary phase of Ca₂Mg₆Zn₃. The grain size of alloy specimens decreased with the increment of Zr content. The corrosion resistances were found to increase from 0.3% to 0.5% and then decrease from 0.5% to 0.7%. The Mg-4Zn-0.5Ca-0.5Zr had the best corrosion resistance in SBF solution.This was attributed to a combination of (1) the uniform and fine microstructure of alloy, (2) continuous distributions of the secondary phases, and (3) a lower volume fraction of Zr particles.

Abstract: The microstructure and corrosion properties of the as-cast Mg-Zn-Ca-Nd alloys were investigated in this study. The results showed that the alloy was mainly composed of α-Mg solid solution and the secondary phases of MgZn, Ca₂Mg₆Zn₃ and Mg₄₁Nd₅. The portion of precipitated phases was increased with the increment of Nd content. Both electrochemical measurement and immersion test indicated that Mg-4Zn-0.5Ca-1.0Nd had the best corrosion resistance in SBF solution. This is attributed to a combination of (1) the uniform microstructure of alloy, and (2) a lower volume fraction of second phases. In the Mg-4Zn-0.5Ca-3.0Nd alloy, the corrosion rate might slow down due to finer dendrite cells were surrounded by the more continuous second phases along the grain boundary and in the α-Mg matrix.

Abstract: The manuscript considers the possibility of using of superplastic deformation at hot forging of aluminum alloys. The analysis has been conducted concerning the use of different methods for imparting ultra-fine grain structure to aluminum alloys in terms of their workability. The deformation and heat processing for thermo-strengthened aluminum alloys has been proposed in which superplastic deformation is combined with hardening. The effect of such processing on mechanical and corrosion properties of aluminum alloys is shown. The model processing of a component is demonstrated at forging under superplasticity conditions often surpass the advantages obtained.

Abstract: Mg alloys were increasingly attracting attention as a potential implant biomaterials because that there will be no need for a second surgery. However, the majority of conventional Mg alloys have been developed for automotive components and were not suitable for Mg based implants. In this paper, a new Mg-RE based materials was developed for implant biomaterials, avoiding the negative influences of previous systems. Microstructure, mechanical and corrosion properties were investigated. The result exhibited that the mechanical properties and degradable rate were sufficient to satisfy the requirement of Mg-based implants. Furthermore, the deformability of the alloy was also investigated. The fine stent pipe was prepared by cold-drawing technology. The primitive results demonstrated that this new alloy was an ideal stent materials.