34 research outputs found
Effect of calcareous deposit formation on efficiency of cathodic protection on carbon steel in simulated soil solution
Get PDFAbstract: The surface blocking properties of calcareous deposit have been shown to have a beneficial effect for cathodic protection. Though this may be true, the role of calcareous deposit has never been quantified. The purpose of this study was to investigate the effect of the formation of calcareous deposit on carbon steel induced by the application of cathodic polarisation in simulated soil solution. The solution was derived from Evian water, with [Ca2+]:[Mg2+] ratio maintained at 2:1 and chloride concentration of 0.01 mol/L. The behaviour of the metal/electrolyte interface was studied using non-invasive in-situ electrochemical techniques at OCP and at various applied potentials Eapp from –0.7 VSCE to –1.2 VSCE. A combination of voltammetry, electrochemical impedance spectroscopy with X-ray diffraction analysis of the mineral layer were utilised. One week long experiments were conducted. Results showed that at OCP, lepidocrocite, carbonated green rust, calcite and aragonite were found as the corrosion process involved anodic and cathodic zones. For cathodic protection Eapp –0.7 VSCE to –1.2 VSCE, calcite and aragonite was found. At Eapp –1.2 VSCE, brucite was found due to increased interfacial pH and as a result evolution of hydrogen bubble was observed. Normalised current curves for Eapp –1.2 VSCE showed surface coverage not exceeding 60% after 7 days. In contrast –1.1 VSCE ≤ Eapp ≤ –0.7 VSCE surface coverage was 0% at day 7. Quantification of the cathodic protection efficiency done via modelling of polarisation curves illustrated a “passivation” phenomenon which resulted from formation of hydroxyl cations. Modelling of polarisation curves allowed for acquisition of the expression for the anodic component of the current ja as a function of the applied potential Eapp. It could be predicted that the interfacial behaviour had a direct influence on the anodic Tafel coefficient. The influence of the calcareous deposit on cathodic protection efficiency can be quantified by plotting log ja vs Eapp. Eapp –0.7, –0.8 and –1.0 VSCE were shown to offer the best current inhibition with formation of calcareous layer allowing very low current density to be maintained.M.Tech. (Chemical Engineering
Erosion wear behavior of spark plasma-sintered Ti-6Al-4V reinforced with TiN nanoparticles
No full textThe extensive application of titanium alloys is delimited as their erosion wear properties deteriorate when exposed to erosive and harsh environments. The present research investigates the effects of TiN additions (2, 4, and 6 vol.%) on the Ti-6Al-4V alloy prepared by spark plasma sintering technique. Erosion wear behaviour of the composites was investigated by high-velocity solid particle erosion test and tribometer pin-on-disc friction module method. The duration of the test was 10 min, while the mass loss of the sample was recorded after 2-min interval. The surface analysis and phase identifications of the sintered composites were examined by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. Microstructural analysis revealed a transformation from lamellar with β grain boundaries in Ti-6Al-4V alloy to bimodal structures upon addition of TiN nanoparticles. XRD patterns of the alloy indicated an increase in diffraction peaks from lower intensity to high intensity with an increase in TiN nanoparticle content. Erosion is visible in Ti-6Al-4V alloy, 4 and 6 vol.% TiN, but less severe with 2 vol.% TiN addition for all the test times. However, this is due to grain detachment of the hard phase regions between the matrix and the reinforcing phase of the composites. The results showed the presence of micro-voids on the eroded surfaces. It was found that Ti-6Al-4V alloy with TiN nanoparticle addition was resistant to erosion wear, while the recorded steady-state friction coefficients for all the samples range from 0.2 to 0.4. However, an increase in microhardness values ranges from 342 to 513 HV0.1.Fil: Kganakga, Mokgoba Glodean. Universidad de Johannesburgo; NoruegaFil: Prieto, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Falodun, Oluwasegun Eso. Universidad de Johannesburgo; NoruegaFil: Tuckart, Walter Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Obadele, Babatunde Abiodun. Botswana International University of Science and Technology; BotsuanaFil: Ajibola, Olarewaju Olawale. Federal University; NigeriaFil: Olubambi, Peter Apata. Universidad de Johannesburgo; Norueg
Microstructural Evolution snd Tribocorrosion Performance sf Novel Laser Clad Ti-Ni-ZrO<sub>2</sub> Composite Coatings in 3.5% NaCl Solution
No full textPhytochemicals as green and sustainable corrosion inhibitors for mild steel and aluminium: Review
No full textTo protect metal from corrosion reactions, one of the most practical methods is to apply corrosion inhibitors. Corrosion reduction is typically achieved through cathodic protection, process control, metal impurity reduction, surface treatment techniques, and alloy incorporation. Phytochemicals, active plant ingredients, have been proven to inhibit the corrosion of mild steel and aluminum in various corrosive environments. The paper discusses how plant extracts can be used as a cheap, environmentally friendly, and renewable replacement for the harmful chemical corrosion inhibitors currently in use. The paper also provides an overview of corrosion processes, extraction of plant bioactive compounds and the research that has been conducted on the use of phytochemicals as corrosion inhibitors for mild steel and aluminum. Phytochemicals, including carbohydrates lipids, alkaloids, phenolic acids, terpenoids, and metabolites that contain nitrogen, interact with metal surfaces to act as corrosion inhibitors. In recent years, there has been growing interest in the use of natural products, such as plant extracts, as corrosion inhibitors. These inhibitors reduce corrosion rates, preventing financial losses due to metallic corrosion on industrial vessels, equipment, or surfaces
Fabrication and characterization of titanium-nickel-zirconia matrix composites prepared by spark plasma sintering
Get PDFAbstract: Ti–Ni–ZrO2 composites were prepared by spark plasma sintering (SPS). The effect of ZrO2 content on the densification, microstructure and microhardness properties of the composites were investigated. Samples were characterized by SEM, EDS and XRD analyses. Noticeably, SPS process under the sintering conditions was achieved at a sintering temperature of 950 ºC, for 10 min holding time, at 100 °C/min of heating rate and at an applied pressure of 50 MPa. This resulted in maximum densification of the powder compact and the formation of a distinguishable spherical globules rich in Ni surrounding the retained Ti. Gradient composition distribution of ZrO2 at the grain boundaries resulted into pinning effect of the grain growth. As the ZrO2 content increased from 5 to 10 vol.%, it was accompanied by a significant increase in hardness values of the sintered composites from 480 to 713 HV
Estudio tribológico de prensado en caliente de compuesto 2205 DSS reforzado por dispersión de óxido
Get PDFThis work studied the influence of ceramic oxide on the tribological behavior of hot pressed 2205 DSS composites with varying percentage composition of partially stabilized zirconia (PSZ) and alloying elements; crome (Cr) with nickel (Ni) developed by PM route. The experiment was conducted with a tribometer by ball on disc under the following parameters: WC ball of 5 mm as the counterbody, sliding load of 15 N and sliding distance of 2 mm at room temperature under dry condition. Wear tracks of the worn surface were examined with Scanning Electron Microscope (SEM); JEOL JSM-7600F with Energy Dispersive X-ray Analysis (EDX) attachment. The results revealed that small amount of PSZ could enhance wear resistance of the composite. EDX spot analyses indicated that there were transferred layers of tungsten (W) on the worn surface. Coefficient of friction (COF) and Taber Index were used to evaluate the wear property of the composites. It was found that sample with 0.5% PSZ, 0.81% Cr and 0.19% Ni has the best wear resistance.Este trabajo estudia la influencia de óxido cerámico en el comportamiento tribológico de materiales compuestos 2205 DSS de prensados calientes con una composición variable de porcentaje de partially stabilized zirconia (PSZ) y elementos de aleación; cromo (Cr) con niquel (Ni) desarrollado por ruta de pulvimetalurgia (PM). El experimento se realizó con un tribómetro de bola sobre disco, bajo los siguientes parámetros: Bola WC de 5 mm como contra cuerpo, carga deslizante de 15 N y 2 mm de distancia deslizante a temperatura ambiente en condiciones secas. Las huellas del desgaste de la superficie desgastada fueron examinados con Scanning Electron Microscope (SEM); JEOL JSM-7600F con Energy Dispersive X-ray Analysis(EDX) adjunto. Los resultados revelaron que una pequeña cantidad de PSZ puede amplificar la resistencia al desgaste del material compuesto. Los análisis EDX puntuales indicaron que había capas transferidas de tungsteno (W) en la superficie desgastada. Se utilizaron índices de coeficiente de fricción (COF) y Taber para evaluar la propiedad de desgaste de los materiales compuestos. Se encontró que la muestra con 0.5% PSZ, 0.81% de Cr y 0.19% de Ni tiene la mejor resistencia al desgaste
Microstructure and tensile properties of heat-treated Ti-Mo alloys
No full textCurrent research is focused on development of β-type titanium alloys for biomedical applications as substitutes of the undesirable Ti6Al4V alloy. Ti6Al4V alloy has a higher elastic modulus (110 GPa) than that of the human bone (10-30 GPa) and this mismatch in elastic moduli can cause stress shielding effect, which can cause bone resorption and implant failure. Moreover, the dissociation of vanadium and aluminium can cause long term diseases including Alzheimer, neuropathy. β-type titanium alloys are potential substitute materials due to their good biocompatibility and the β phase has a lower elastic modulus. The aim was to study the microstructure and tensile properties of heat-treated Ti-xMo alloys (x= 8 & 10wt%). Phase analysis was conducted using X-ray diffractometer, while the microstructure was observed using an optical microscope. The tensile properties were examined using a tensile test machine. Acicular structures of α" phase precipitated in the β matrix in Ti-8Mo alloy, while Ti-10Mo alloy showed predominant β phase. The theoretically predicted phase constituents were not consistent with the experimental findings. Ti-10Mo alloy possessed superior yield and tensile strengths, larger elongation, and lower elastic moduli than that of Ti6Al4V alloy. Based on the obtained findings, the Ti-10Mo alloy can be a potential candidate for orthopaedic application. acicular structures of α" phase
Microstructure and dry sliding wear performance of oxide dispersion strengthened austenitic stainless steel
Get PDFAbstract: The oxide dispersion strengthening (ODS) material are candidates for structural materials in nuclear reactors due to high density of small oxide particles dispersed in the matrix. In this study, the microstructure and wear performance of ZrO₂ stabilized with Y₂O₃ reinforced AISI 316L austenitic stainless steels was investigated. The ODS-316L steel powders were sintered using spark plasma sintering technique. The surface structure and composition of the sintered samples were examined by field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experimental results were compared with the untreated 316L material. Tribological tests were performed on a ball-on-disc wear tester under dry condition at different applied loads from 5 to 35 N. The sliding distance was 2 mm for 1000 s. A tungsten carbide (WC) ball was used as a counterface material. Results showed that addition of ZrO₂ significantly improved the microhardness values while the presence of ZrO2 phase in the 316L matrix reduces the friction coefficient and increased resistance to sliding wear
Effect of build direction on the microhardness and dry sliding wear behaviour of laser additive manufactured Ti-6Al-4V
Get PDFAbstract: This work presents micro structural and tribological behaviour of Ti-6Al-4V fabricated by direct metal laser sintering technique. The laser sintering was carried out at laser power of 170 W in an argon atmosphere. The microstructure, phase composition, micro hardness and wear study were determined. It has been found that specimens built vertically (VB) contained vanadium carbide (VC) and titanium oxide (TiO) phases in the present of α and β phases resulting in higher micro hardness as compared to horizontal build (HB) specimens. Wear volume loss was determined in a dry sliding wear configuration. An increase in applied load from 5 N to 25 N resulted in an increment in wear volume loss. The presence of delamination could be observed on the worn surface of HB specimen
Investigation of corrosion behaviour of carbon steel in simulated soil solution from anodic component of polarisation curve
Get PDFAbstract: Marine structures and buried pipelines are constantly exposed to extreme conditions with elements such as temperature variation, soil ion content, dissolved metals, etc posing a continuous threat on the integrity and lifespan of the structures. Quantification of these elements has been limited to studying only a few of the parameters, with the resulting corrosion behaviour not fully understood. The purpose of this study was to investigate the corrosion behaviour of carbon steel in simulated soil solution using the anodic component attained from modelled polarisation curves. The behaviour of the metal/electrolyte interface was studied using non-invasive in-situ electrochemical techniques at OCP. A combination of voltammetry, electrochemical impedance spectroscopy with X-ray diffraction analysis of the mineral layer were utilised. The expression for the anodic component of the current as a function of potential was attained from log|ja| vs. potential plots. Mathematical modelling of the experimental polarisation curves was done using OriginPro Data Analysis & Graphing Software. Results showed that at OCP, lepidocrocite, carbonated green rust, calcite and aragonite were found as the corrosion process involved anodic and cathodic zones. Voltammetry around OCP (VAOCP) and linear polarisation resistance (LPR) showed the necessity for corrosion protection as the adopted electrochemical system resulted in a progressively corrosive environment. Kinetics and mechanism of the anodic and cathodic process indicated corrosion processes similar to aerated soil conditions
