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The corrosion evaluation of buried cast iron pipe of fire hydrant system in a nuclear power station exposed to raw water for 30 years was carried out. The samples from cast iron pipe section were characterised by inductively coupled plasma atomic emission spectroscopy, optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction and laser Raman spectroscopy. Metallographic examination revealed typical flake graphite microstructure with uniform distribution, randomly oriented graphite structure, rosette grouping, for pipes of different diameters. The presence of microbes in water side of the pipes and in contact with soil was seen. SEM examination revealed loose spherical deposits, rust layers comprising of iron oxide, silica and spherical nodules covered with network structures. EDS analysis of rust layers revealed the presence of Si, Ca, S and P apart from Fe and O. XRD analysis revealed that the rust on the surfaces comprised of SiO2 and Fe2O3. The results of the study indicated that the external corrosion of cast iron pipes was due to sand and gravel type of soil in contact with pipes. EDS elemental X-ray maps revealed regions rich in Si indicating localised graphitic corrosion. Detailed corrosion characterisation studies revealed that despite signatures of graphitic corrosion, microbes and rust formation, there was no substantial reduction in the pipe thickness, and hence, the service life of buried cast iron pipes can be further extended. [ABSTRACT FROM AUTHOR]

Compounds of the general formula RE2O3·2HfO2 with RE = Sm, Eu, Gd, Dy, etc., are considered potential candidate materials for use in the control rods of future nuclear reactors. Sm2O3·2HfO2, Eu2O3·2HfO2, and Dy2O3·2HfO2 were prepared by solid-state route and characterized by XRD technique. Enthalpy increment measurements have been carried out on these compounds in the temperature range 730–1679 K by inverse drop method by using a high-temperature differential calorimeter. From the enthalpy values, other thermodynamic functions, namely heat capacity, entropy, and Gibbs energy functions, were computed. The polynomial expressions of enthalpy increments obtained for rare earth hafnate in the temperature range 298–1700 K is given as:HT0-H2980/J mol-1=259.890T+21.610×10-3T2+32.389×105T-1-90,271—Sm2O3·2HfO2HT0-H2980/Jmol-1=261.134T+22.273×10-3T2+25.988×105T-1-88,553—Eu2O3·2HfO2HT0-H2980/Jmol-1=255.016T+18.030×10-3T2+29.332×105T-1-87,474—Dy2O3·2HfO2 [ABSTRACT FROM AUTHOR]

Diluent degradation products in gamma radiolyzed Plutonium URanium Extraction (PUREX) solvent were characterized, under the conditions similar to those prevailing in the hot cell for reprocessing. Alkali wash of the degraded solvent followed by vacuum distillation resulted in primary separation. Column separation of the distillation residue followed by spectroscopic analysis using GC-MS and NMR revealed the residue predominantly to be a mixture of dodecan-3-ol, dodecan-4-ol, and dodecan-5-ol in the ratio of 2:1:6, respectively and a mixture of 2-nitrododecane, 3-nitrododecane, 4-nitrododecane, and 5-nitrododecane in the ratio of 2:2:1:1, respectively. The identified compounds were confirmed by synthesizing them individually and comparing their spectral data. [ABSTRACT FROM PUBLISHER]

A novel and facile approach like polishing as well as etching followed by dip coating using low surface energy material, perfluoro octyl tri ethoxy silane was attempted to create superhydrophobic (SHP) surface modification on Mod.9Cr-1Mo. A water contact angle (CA) of 150° ± 1° was achieved with advancing angle (θadv) as 163°, Receding Angle (θrec) as 148°, contact angle hysteresis (CAH) as 15º and tilting angle (TA) as 7º. Characterization of the surface by atomic force microscopy and surface profilometer revealed the micro–nano topography on the surface ranging between 63.5 nm and 4.3 µm. The enhanced corrosion performance and the antibacterial properties were confirmed using electrochemical impedance spectroscopy (EIS) and epifluorescence microscopy. [ABSTRACT FROM AUTHOR]

This article investigates the in-vitro biocompatibility and corrosion behaviour of strontium ion incorporated TiO2 nanotube arrays formed by anodization method for orthopaedic applications. The morphological studies were carried out using field emission scanning electron microscopy, atomic force microscopy, attenuated total reflectance fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thin film X-ray diffraction techniques. The morphological investigation indicated that the length and the average diameter of nanotube were 2.1 ± 0.3 µm and 110 ± 4 nm, respectively. The wettability measurements showed that the TiO2 nanotube arrays have super wettability, as well as, strontium ion incorporated TiO2 nanotube arrays exhibited hydrophilic behaviour. Excellent in-vitro bioactivity was observed for TiO2 nanotube arrays with strontium ions. Electrochemical studies in Hank’s solution showed that the TiO2 nanotube arrays with strontium ions have enhanced corrosion resistance. [ABSTRACT FROM PUBLISHER]

The liquid-liquid equilibrium (LLE) for the system water-dodecane-butanol was estimated using the UNIQUAC model. In the UNIQUAC model interaction parameters were estimated from the vapor-liquid equilibrium (VLE) and LLE data of their constituent binary pairs. The water-dodecane-butanol LLE was experimentally measured at 298.15 K. Phase stability constraints were taken into account while calculating the binary interaction parameters from the mutual solubility data. The COSMO-RS method was used to estimate the activity coefficient in the miscible binary pair. The ternary LLE composition was predicted using the experimental VLE data as well as using the COSMO-RS calculated activity coefficient data along with the experimental mutual solubility data. In the latter case the root mean square deviation (RMSD) for the distribution of butanol between aqueous and organic phase is 0.24%. The corresponding UNIFAC model prediction is 7.63%. [ABSTRACT FROM AUTHOR]

Ruthenium from pure nitrosyl nitrate solution, nitrate, and from simulated high level liquid waste (SHLLW) in HNO3medium has been separated by oxidizing with ammonium ceric nitrate (ACN) and trapping the RuO4vapor in n-paraffin hydrocarbon (NPH). Systematic studies for improving the separation efficiency yielded 80% Ru from nitrosyl nitrate solutions in 1M HNO3, using 0.02–0.04M Ce(IV) as the oxidizing agent at ambient temperature. The optimum process parameters for separating 80–90% Ru from ruthenium nitrate and waste solution (in the form of Ru(NO3)3) were determined to be 0.04M ACN in 4M nitric acid at ambient temperature. The black ruthenium oxide suspension at the interface between the organic and aqueous phases was characterized by EELS and XPS techniques. From the systematic parametric study conducted for the separation of Ru from waste solutions, it is understood that nitric acid concentration in the range 0.5–1M and ACN in the range 0.02–0.04M at ambient temperature are the optimized process parameters for improving the separation efficiency, since in the HLLW, Ru will be in the form of nitrosyl nitrate complexes rather than nitrate solution. [ABSTRACT FROM AUTHOR]

In cooling water systems, many concrete structures in the form of tanks, pillars and reservoirs that come in contact with aggressive seawater are being deteriorated by chemical and biological factors. The nuclear industry has decided to partially replace the Portland cement with appropriate pozzolans such as fly ash, which could densify the matrix and make the concrete impermeable. Three types of concrete mixes, viz., normal concrete (NC), concrete with fly ash and superplasticizer (FA) and concrete with only superplasticizer (SP) were fabricated for short- and long-term exposure studies and for screening out the better concrete in seawater environments. Biofilm characterization studies and microscopic studies showed excellent performance of FA concrete compared to the other two. Laboratory exposure studies in pure cultures ofThiobacillus thiooxidansandFusarium oxysporumwere demonstrated for the inhibition of microbial growth on fly ash. Epifluorescence and scanning electron microscopic studies supported the better performance of the FA specimen. Thus, the present study clearly showed that FA concrete is less prone to biofilm formation and biodeterioration. [ABSTRACT FROM PUBLISHER]

The liquid-liquid equilibrium (LLE) for the system water-dodecane-butanol was estimated using the UNIQUAC model. In the UNIQUACmodel interaction parameterswere estimated fromthe vapor-liquid equilibrium(VLE) and LLE data of their constituent binary pairs.Thewater-dodecane-butanol LLE was experimentallymeasured at 298.15K. Phase stability constraints were taken into account while calculating the binary interaction parameters from the mutual solubility data. The COSMO-RS method was used to estimate the activity coefficient in the miscible binary pair. The ternary LLE composition was predicted using the experimental VLE data as well as using the COSMO-RS calculated activity coefficient data along with the experimentalmutual solubility data. In the latter case the root mean square deviation (RMSD) for the distribution of butanol between aqueous and organic phase is 0.24%. The corresponding UNIFAC model prediction is 7.63%. [ABSTRACT FROM AUTHOR]

This study mainly focuses hydrolysis reactions of uranium(VI) under an ambient atmosphere leading to colloid formation in near neutral solution using light scattering, UV–Vis and FTIR-ATR studies. UV–Vis and IR spectrum was recorded for uranyl solution at different pH range. U(VI) hydrolyzed colloids were detected and it was confirmed by the appearance of a band at 941 cm −1 in the IR spectra. Light scattering measurements were performed on colloidal U(VI) solutions formed at pH range of 7–8. The average particle diameter was determined as 32–36 nm using dynamic light scattering. Well defined colloidal species are formed with no considerable change in particle size with increasing U(VI) concentration. The weight average molecular weight of colloidal species was predicted as 763 Da by Debye plot. The second virial coefficient (A 2) was found to be −0.1139 ml g −1 Da. The present study confirms that behaviour of U(VI) contradicts conventional Zr(IV), Th(IV) and Pu(IV) solution chemistry. U(VI) polymerization is less extensive and in neutral solutions it forms only oligomers with 2–3 uranyl units. [ABSTRACT FROM AUTHOR]

Roomtemperature ionic liquids (RTILs) are the environment-friendly alternatives for organic volatile solvents in a host of synthetic, catalytic, and electrochemical applications. These are also being used for various R&D works in nuclear fuel cycle research such as the recovery and purification of nuclides of interest from spent nuclear fuel matrices. In this work, density, refractive index (nD25) at sodium D line, and thermodynamic water activity of the aqueous solution of 1-hexyl-3-methyl imidazolium bromide were determined in dilute aqueous solutions at 298.15 K. These results were used to calculate the apparent molal volumes of each solute over various concentration ranges. The measurements were performed as per ASTM procedures. Vapour pressure was derived using water activity values. Information on excess properties and structural interaction was also reported. [ABSTRACT FROM AUTHOR]

This paper describes comparative studies on the determination of di-n-butyl phosphate (DBP) by ion chromatography (IC) and gas chromatography (GC) techniques in spent solvent of PUREX process used for the reprocessing of spent nuclear fuels. The ion chromatography method involves the separation of DBP from 30% TBP-NPH (tri-n-butylphosphate diluted in normal paraffin hydrocarbon) containing heavy metal ion like uranium and nitric acid by extraction of DBP into alkaline medium. DBP was subsequently eluted by ion-exchange separation in ion chromatography column and followed by suppressed conductivity detection. DBP is quantified to a lower limit of about 1 ppm with 3% RSD. However, in order to determine DBP by gas chromatography technique DBP is first quantitatively converted into its volatile and stable derivatives by using diazomethane prior to analysis by GC. Results obtained with ion chromatographic technique are compared with those of obtained by standard gas chromatographic technique. It was observed that IC technique involves minimum steps and is much faster than GC analysis. The effect of mobile phase flow rate on the detector response, retention time, and column pressure are also investigated. [ABSTRACT FROM AUTHOR]

In-situ reduction of plutonium and uranium for the separation of U/Pu is suitable for pl utoniumrich fuels such as FBR fuels. The mathematical basis for a computer program PUSEP (Plutonium Uranium Solvent Extraction Program) for the analysis of partitioning cycle of PUREX process involving in-situ electrochemical reduction of uranium and plutonium is described in the present investigation. Model equations have been developed on the basis of the idealized model for mixer settlers incorporating distribution coefficients and redox reactions of the species involved and solved numerically to obtain concentration profiles of components. The validity of the model equations and associated computer program is tested by carrying out experiments in a proto type 20-stage electrolytic ejector mixer-settler operating without diaphragm for the electro reduction of uranium. The stage-wise experimental concentration profiles of U(VI), U(IV) and nitric acid were obtained and compared with the theoretical predictions. A reasonably good agreement is achieved between experimental and predicted concentration profiles. [ABSTRACT FROM AUTHOR]

The main process medium in the reprocessing industry is highly oxidizing nitric acid ranging from dilute to concentrated solutions containing fission products and from room temperature to boiling conditions. Corrosion resistance of materials chosen for reprocessing plants is of prime importance for uninterrupted operation. Surface modification and coatings can significantly improve the corrosion resistance of materials. A number of surface modification and coating development works such as double oxide coating on Ti for reconditioning (DOCTOR); mixed oxide coated Ti anodes (MOCTAs); nanostructured Ti, TiO2,TiN, and ZrN; bulk metallic glasses (BMGs); and superhydrophobic (SHB) coatings for corrosion protection are being pursued in our laboratory. Nanostructured coatings developed on Ti-like DOCTOR and MOCTAs showed improved corrosion resistance and longer life. Nanostructured Ti, TiO2 , and ZrN coatings deposited on type 304L stainless steel (SS) by magnetron sputtering technique and Zr-based bulk metallic Zr59 Ti3 Cu20 Al10 Ni8 alloy deposited on type 304L SS by pulsed laser deposition (PLD) technique showed improved corrosion resistance in nitric acid. SHB coating on 9Cr-1Mo and Ti lead to improved corrosion resistance and biofouling resistance of Ti. The surface modification and coating development carried out in our laboratory for corrosion protection in reprocessing plants are briefly highlighted. [ABSTRACT FROM AUTHOR]

A manganese oxidizing bacterium was isolated from the surface of steel scraps and biochemical tests and 16S rRNA sequencing analysis confirmed the isolate as Bacillus flexus. Potentiodynamic polarization curves showed ennoblement of open circuit potential, increased passive current, a lowering of breakdown potential, active re-passivation potential and enhanced cathodic current in the presence of B. flexus. Adhesion studies with B. flexus on SS304 specimens with different surface treatments demonstrated decreased adhesion on passivated and FeCl3 treated specimens due to the removal of MnS inclusions. The present study provides evidence that surface treatment of stainless steels can reduce adhesion of this manganese oxidizing bacterium and decrease the probability of microbiologically influenced corrosion. [ABSTRACT FROM PUBLISHER]

Electrophoretic deposition (EPD) was employed to coat TiO2 and TiO2+CeO2 on AISI type 304L stainless steel (SS) to improve its corrosion resistance. Coatings were obtained by following three main steps, namely formation of a suspension of the charged TiO2 particles with addition of CeO2, deposition of the suspended particles on the electrode under the influence of a dc electric field, and sintering of the particulate deposit at 1073 K for 2 h in vacuum to form a dense and continuous film. The uniform deposits of TiO2 and TiO2+CeO2 formed on the surface shown good sintering characteristics and were characterised using X-ray diffraction (XRD) technique. The electrochemical investigation of the coatings in neutral chloride media was carried out to obtain open circuit potential (OCP) and potentiodynamic anodic polarisation behaviour in order to evaluate their corrosion resistance. The electrochemical parameters shifted towards noble direction for the TiO2 and CeO2+TiO2 coated specimens in comparison with uncoated type 304L SS. The addition of CeO2 to TiO2 coating brings about a decrease in passive current density and an increase in the passivation range. The effect was significant at 15 and 20% of CeO2 addition to TiO2 coating indicating the stable nature of the coatings. [ABSTRACT FROM AUTHOR]

Laser processed Cr–SiC coatings were produced on AISI type 316L stainless steel substrate using a continuous wave CO2 laser. The microstructure of the laser processed coatings consists of planar growth at the interface, followed by columnar dendrite and fine cellular structures at the core and top surface of the molten zone. High temperature phases such as δ-ferrite, γ-austenite and M7C3 carbides were found in the resolidified microstructure. The microchemical analysis of the laser processed zone showed the presence of high concentration of silicon. The laser processed zone also exhibited high hardness around 1300 HV. [ABSTRACT FROM AUTHOR]

The influence of laser surface alloying (LSA) with Cr and Cr + Ni on the corrosion behaviour of type 304L stainless steel (SS) was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in chloride (0·5M NaCl) and acidic (1 N H2SO4) media. Surface alloying was carried out by laser cladding type 304L SS substrate with premixed powders of AISI type 316L SS and the desired alloying elements. The results indicated that Cr surface alloyed specimen exhibited a duplex (γ + α) microstructure with Cr content of ∼24 wt-%, whereas Cr + Ni surface alloyed specimen was associated with austenitic microstructure with Cr and Ni contents of ∼22 wt-% each. The potentiodynamic polarisation results in chloride solution indicated that LSA with Cr + Ni considerably enhanced the pitting corrosion resistance compared with LSA with Cr alone. In acidic media, such beneficial effects were not observed. Electrochemical impedance spectroscopy results showed an increase in semicircle arc for both chloride and acidic media for both Cr and Cr + Ni clad samples indicating improvement in the oxide film stability compared with untreated specimen. The polarisation resistance was higher and capacitance values of the laser clad specimen were lower than those in the untreated specimen. The microstructural changes and compositional variations produced by LSA are correlated to the corrosion behaviour. [ABSTRACT FROM AUTHOR]

Fretting fatigue is a typical wear phenomena effecting from conjoint action of fretting and cyclic load under fixed contact pressure. The aim of the present work is to investigate the effect of surface modification processes such as plasma nitriding, ion implantation and laser nitriding in preventing fretting fatigue failures of Ti–6Al–4V and Ti–6Al–7Nb contact pairs. Surface modified contact pads and calibrated proof ring was used to apply contact pressure normal to the fatigue specimen. The surface modified layers and fretting fatigue damage is shown with optical and SEM micrographs. Friction coefficient between fretting contacts is continuously recorded to explain the sequence of damage during fretting process. Plasma nitrided pairs have performed better than all other processes with minimal damage and low friction (0·1). The facture of ion implanted pairs was similar to that of unmodified alloys. Laser nitrided pairs have shown premature failure owing to higher case depth. [ABSTRACT FROM AUTHOR]

Microstructural parameters such as the average domain size, effective domain size at a particular crystallographic direction, and microstrain within the domains of titanium and Ti-5 pct Ta-2 pct Nb, irradiated with 116 MeV O5+ ion, have been characterized as a function of dose by X-ray diffraction line-profile analysis (XRDLPA) using different model-based approaches. The dislocation density and stacking-fault probabilities have also been estimated from the analysis. The analysis revealed that there was a significant decrease of the average domain size with dose as compared to the unirradiated sample. The estimated values of dislocation density increased significantly for the irradiated samples and were found to be an order of magnitude more as compared to the unirradiated one. However, the dislocation density became saturated with an increase in dose. The deformation (stacking-fault) probabilities were found to be negligible even with the increase in dose of irradiation. [ABSTRACT FROM AUTHOR]

The basic calcium phosphate mineral, hydroxyapatite (HAP) (Ca10(PO4)6(OH)2), is the prototype of one of the major constituents of bone and teeth. Thin layers of HAP were coated on the surface of type 316L stainless steel by electrophoretic deposition (EPD) from a 2·5% suspension in isopropyl alcohol, and this was followed by vacuum sintering at 800°C for 1 h. The development of HAP coatings was affected by the applied potential and time. In addition, HAP coatings were synthesised on pure Ti by electrochemical deposition and fully characterised to validate their use in orthopaedic implants. Electrodeposition was carried out from a bath containing low concentrations of Ca(NO3)2 and NH4H2PO4 at pH 6·0 by cathodic polarisation. Both types of HAP coating were fully characterised, including with respect to corrosion resistance. The advantages of these techniques include: (i) control over the composition and structure of the coating; and (ii) the ability to coat irregular surfaces easily. [ABSTRACT FROM AUTHOR]

Laser processed Si coatings with thickness in the range 100–150 μm were produced on AISI type 316L stainless steel substrate using a continuous wave CO2 laser. The experiments were done at a laser power between 1·5 kW and 1 kW, process speeds in the range 33·6–8·3 mm s-1, with a beam diameter of 1·6 mm. The microstructure of the laser processed coating consists of columnar dendrites and fine cellular structures. High temperature phases such as δ-ferrite and γ-austenite were found on the resolidified microstructure. The microanalysis technique demonstrated that the laser clad zone possessed a high concentration of Si. The crack free laser clad zone exhibited high hardness in the range 850–900 HV. [ABSTRACT FROM AUTHOR]

Laser surface alloying (LSA) of AISI 316L stainless steel with various compositions of Ni and SiC for different laser parameters was investigated. The hardness of the LSA layer was found to be a strong function of silicon content. The maximum hardness achieved was 733 HV. Columnar dendrites, equaxial dendrites and cellular structure were observed in the resolidified microstructure. XRD and EPMA studies were used to find different phases and elemental concentration, respectively. [ABSTRACT FROM AUTHOR]

This article presents the preparation, characterization, and hot-salt oxidation behavior of nitrogen-containing type 316L stainless steel (SS), surface modified with intermetallic coatings. Three different types of intermetallic coating systems, containing aluminum, titanium, and titanium/aluminum multilayers, were formed by diffusion annealing of type 316L austenitic SS containing 0.015, 0.1, 0.2, and 0.56 pct nitrogen. Analysis by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and secondary ion mass spectroscopy (SIMS) confirmed the formation of various intermetallic phases such as AIN, Al13Fe4, FeAl2, FeTi, Ti2N, and Ti3Al in the coatings. Hot salt oxidation behavior of the uncoated and surface-modified stainless steels was assessed by periodic monitoring of the weight changes of NaCl salt-applied alloys kept in an air furnace at 1023 K up to 250 hours. The oxide scales formed were examined by XRD and stereomicroscopy. Among the various surface modifications investigated in the present study, the results indicate that the titanium-modified alloys show the best hot-salt oxidation resistance with the formation of an adherent, protective, thin, and continuous oxide layer. Among the four N-containing alloys investigated, the titanium and Ti/Al multilayer modified 0.56 pct N alloy showed the best hot-salt oxidation resistance as compared to uncoated alloys. The slower corrosion kinetics and adherent scale morphology ndicate that the surface-modified titanium intermetallic coatings could provide high-temperature service applications up to 1073 K, particularly in chloride containing atmospheres, for austenitic stainless steels. [ABSTRACT FROM AUTHOR]

The present work investigates the aqueous corrosion behaviour of type 316L stainless steel (SS) containing various matrix nitrogen contents (0·015, 0·1, 0·2 and 0·56%N), surface modified by diffusion annealing of a precoated film of titanium/aluminium. Type 316L SS specimens were precoated with a Ti/Al multilayer by the electron beam deposition method and surface diffusion annealed at 1173 K for 1 h in vacuum. X-ray diffraction analysis indicated the formation of Ti[sub 3] Al, Al[sub 5] Ti[sub 2] , Al[sub 2] Ti and Al[sub 13] Fe[sub 4] intermetallic phases. Nitrides such as Ti[sub 2] N were also observed, particularly in high nitrogen steels. The interaction between the titanium/aluminium coating and the matrix constituents, particularly with nitrogen, was characterised by secondary ion mass spectrometry (SIMS). The nitrogen content at the modified surface increased with increase in the nitrogen content of the substrate matrix. SEM observation of cross-sectionally mounted surface modified alloys indicated the formation of thick adherent layers. The role of such intermetallic phases in corrosion resistance in both 0·5 M H[sub 2] SO[sub 4] and 0·5 M NaCl is discussed in detail based on open circuit potential-time measurements, potentiodynamic polarisation studies and electrochemical impedance spectroscopy (EIS) investigations. The role of matrix nitrogen in the formation of intermetallic coatings and its role in corrosion resistance in acidic and chloride media are investigated. [ABSTRACT FROM AUTHOR]

The present paper reports on the microstructure, hardness, surface roughness, phases formed and corrosion behaviour of laser nitrided Ti-13Nb-13Zr biomedical alloy. Surface melting and nitriding of the alloy were carried out using a Nd:YAG laser in pulsed mode under dilute and pure nitrogen environments. Laser nitriding of the alloy resulted in a hardness of 1600 HV and 650 HV, respectively, for pure N[sub 2] and dilute N[sub 2] + Ar environments. Cracks were not observed either on the surface or in the vertical cross-section of the samples nitrided in both environments. X-ray diffraction analysis of the sample nitrided in a pure nitrogen environment confirmed the formation of TiN, TiN[sub 0.3] , alpha and beta phases along with ZrN. Quantitative analysis using electron probe microanalysis (EPMA) showed the enrichment of Zr and Ti in the dendrites. Corrosion resistance of the laser nitrided samples in a simulated body environment (Ringer's solution) was evaluated using the potentiodynamic polarisation method, and was found to be significantly better for the laser nitrided conditions compared with the untreated alloy. [ABSTRACT FROM AUTHOR]

A Ti-6Al-7Nb alloy was surface modified using pulsed plasma nitriding and nitrogen ion implantation in order to study its microstructural changes and corrosion performance. Pulsed plasma nitriding was performed for 30 h at 913 K in a gas mixture of 3:1 N[sub 2] :H[sub 2] under a total pressure of 3 mbar. Nitrogen ion was implanted at 100 keV using a 150 keV accelerator at a dose of 2·5 × 10[sup 17] ions cm[sup 2] . Gracing incidence X-ray diffraction was employed to explore the phases formed after treatments. To characterise the nature of the modified layers produced and to correlate with the corrosion behaviour, SIMS was used. The samples were subjected to electrochemical studies, namely, open circuit potential (OCP)-time measurements and potentiodynamic cyclic polarisation in a simulated body fluid (Ringer's solution). The OCP of the pulsed plasma nitrided and N[sup +] implanted samples were found to shift towards the noble direction (-189 mV[sub SCE] and -82 mV[sub SCE] , respectively) in comparison with the untreated sample (-338 mV[sub SCE] ). The passivation current density and area of the repassivation loop were found to decrease for both treatments compared with those in the untreated condition. Nitrogen ion implantation enhanced the passivability and reduced the corrosion kinetics of the alloy with increasing tendency for repassivation. It shows very low passivation current density compared with pulsed plasma nitriding (0·086 and 0·493 μAcm[sup 2] , respectively). The nature of the modified surfaces and the reason for the variation and improvement in corrosion resistance are discussed. [ABSTRACT FROM AUTHOR]

AISI type 304L stainless steel (SS) was assessed for its corrosion resistance in nitric acid solution. The effect of variation in nitric acid concentration (1 to 10N) and temperature (298 K, 313 K, 333 K, 348 K) on the corrosion resistance of 304L SS was investigated using potentiodynamic polarisation studies. The corrosion resistance of the alloy was also studied in 1N nitric acid containing different concentrations of chloride ion (1000, 5000, and 10 000 ppm) in order to understand the tendency to pitting corrosion. The results show that the corrosion resistance of the material deteriorated for acid concentrations greater than 4N. The temperature of the acid was found to have a profound effect on the corrosion resistance, with corrosion becoming more prominent at temperatures of 333 K and above. Chloride ions up to a concentration of 10 000 ppm were found to have no effect on the pitting resistance of the material studied. [ABSTRACT FROM AUTHOR]

Crevice corrosion studies were carried out on nitrogen-bearing types 304, 316 and 317 austenitic stainless steels (SS) by a potentiodynamic anodic polarisation method in an acidic chloride medium. A special all-glass crevice assembly was used for providing reproducible crevice effects on the surface of the test specimen. The results indicated that the increase in nitrogen content improved the crevice corrosion resistance of the alloys by decreasing the active dissolution, and increasing both passive film stability and the potential at which crevice attack was stable. This was very significant for 304 and 316 SS alloys in comparison with 317 SS alloys. The combined influence of nitrogen and molybdenum was found to be very significant in providing high crevice corrosion resistance for 317 SS alloys. Optical microscopic observation revealed severe crevice attack on types 304 and 316 SS alloys compared to mild crevice attack on type 317 alloys. Based on the results of the present investigation a possible mechanism by which nitrogen addition improved the crevice corrosion resistance is discussed. [ABSTRACT FROM AUTHOR]

This study used laser melting techniques to improve the intergranular corrosion resistance of cold worked and sensitised stainless steel surfaces. Type 316 stainless steel specimens, cold worked to 5 per cent, 10 per cent and 20 per cent reductions in thickness values, were sensitised at 923K for 25 hours. These specimens were laser-surface-melted by using a 300W Nd:YAG pulsed laser, and tested according to ASTM A262 practice A and practice E tests. The results of the practice A test showed that a cellular-dendritic structure was present in the laser-melted region in contrast to a typical ditch microstructure observed for sensitised unmelted specimens and a ditch structure was not present in the melt-affected zone (MAZ). The hardness measurements across the melted, MAZ, and unmelted zones showed significant variations in their values. The results of the practice E tests showed no intergranular cracks for laser-melted specimens while the unmelted specimens (5 and 10 per cent cold working) failed the test through significant cracking. The improvement in IGC resistance is attributed to the dissolution of M23C6 carbides and the homogenisation of chromium-depleted regions. [ABSTRACT FROM AUTHOR]

Nitrogen ion implantation on a Ti6Al4V alloy with 70KeV energy was carried out at different doses ranging from 5 x 1015 to 2.5 x 1017ions/cm2. The implanted samples were subjected to open circuit potential/time measurement and cyclic polarization studies to evolve the optimum dose which can give good corrosion resistance in a simulated body fluid condition. The results show that there was an increase in corrosion resistance with increased doses up to 7 x 1016ions/cm2, beyond which it started to decrease. The stability of the passive film at a higher potential was assessed by potentiotransient techniques after impressing a constant potential of 1.5V for three hours. The results of the investigation indicate that nitrogen ion implantation can be used as a viable method to improve the corrosion resistance of orthopaedic implant devices made of Ti6Al4V alloy. The nature of the stable passive film and its influence on corrosion resistance are discussed in this paper. [ABSTRACT FROM AUTHOR]

The article presents information on surface sciences and nuclear industry. Surface science and technology are active areas of research and application in the nuclear industry. Developing wear and erosion resistant coatings is a prime area of research and development pursued for high temperature nuclear reactors including the gas cooled and liquid metal cooled reactors. Surface modification and engineering are emerging as important interdisciplinary areas involving physicists, chemists and engineers. These interdisciplinary teams are required to pool their efforts to achieve maximum benefits for critical applications in the nuclear industry.