Search

The quasi-static assemblies used in industrial applications are subjected to microsliding due to vibrations of variable amplitudes related to mechanical or aerodynamic instabilities. The titanium alloys used in such structures present extensive wear and must be protected by coatings. This article is devoted to the fretting behaviour of a coated Ti–6Al–4V alloy under free (un-imposed) displacement. The coating is made of a cupronickel alloy (CuNiIn or CuNiSi) topped by a polymer bonded solid lubricant MoS 2 . A fretting map was established to highlight the boundary between wear and seizure. An energetic coefficient of wear considering the global wear volume of the contact and the tribological parameters such as sliding distance and dissipated energy was established. Various morphologies of the third body observed in the contact were analyzed in terms of cohesion, ductility and adhesion. They were correlated to the tribological behaviour of the studied materials.

In this paper, Titanium tetrachloride (TiCl4) is analyzed/assessed and proposed as a new potential working fluid in Rankine Cycles. Besides its good thermodynamic properties, TiCl4 is in fact a fairly low cost, non-carcinogenic fluid, with zero Global Warming Potential (GWP) and Ozone Depleting Potential (ODP) and it is currently employed in high temperature industrial processes. It is however very reactive with humid air and water. A preliminary thermodynamic analysis confirms its possible application in power plants with maximum temperature up to 500 °C, considerably higher than the ORC state-of-the-art technology, performing electrical efficiencies as high as 35-40%. This suggests the potential use of TiCl4 as an alternative fluid in ORCs allowing the exploitation of high temperature sources (up to 500 °C), typically used in steam cycles. To assess the possibility of operating the cycle in such high temperature conditions, we carried out an experimental thermal stress analysis, showing that the fluid is remarkably stable at temperatures up to 500 °C, even in presence of P91 and Cupronickel, two materials typically employed in the high temperature section of power cycles. © 2016 Elsevier Ltd. All rights reserved.

Cupronickel alloys (CuNi), especially 70Cu- Ni30, are frequently used in marine applications as a construction material because of their good corrosion resistance in seawater. However, corrosion protection of cupronickel is often required to ensure its longevity. Many commercial corrosion inhibitors are ecologically unsuitable for seawater application due to their toxic impact on the marine ecosystem. The application of self- assembled monolayers (SAMs) presents potential ecologically suitable solution for increasing a corrosion resistance of cupronickel alloy. SAMs are thin assemblies of dense and well defined structure that block the active spots on the metal surface and present a barrier to electron transfer and ion penetration. They are formed spontaneously by chemical adsorption and self- organization on the surface of the metal/metal oxide. Up to date, studies of SAMs on cupronickel alloy have mainly been performed with the dip-coating method, which is time consuming, requires higher amounts of working solution and is not always practical for application in industry. The aim of this work is to investigate the possibility of cupronickel alloy protection by self-assembled monolayers of stearic acid (SA) prepared by different techniques: dip-coating, electrochemical method and spraying. Each one of these techniques has some advantages: dip- coating method is simple, electrochemical method is less time consuming, but spraying is more practical than the above mentioned methods. The protective properties of such formed monolayers are examined in artificial seawater by electrochemical polarization methods and electrochemical impedance spectroscopy while the structure of the film is determined by contact angle measurements and Fourier transform infrared spectroscopy. The results of electrochemical investigations show that by using an adequate preparation method and conditions (temperature, time, concentration, applied potential etc.) it is possible to form protective layer of carboxylic acid that significantly reduces cupronickel corrosion rate in artificial seawater. Acknowledgments: The research leading to these results has received funding from Croatian Science Foundation under grant agreement 9.01/253.

Experimental studies of film condensation of HFC134a and CFC12 on single horizontal smooth tube and three enhanced tubes have been conducted. The objective is to obtain the basic data for film condensation of HFC134a on low thermal conductivity enhanced tubes. The results indicate that the predicted condensation heat transfer coefficients of HFC134a and CFC12 on smooth tube from Nusselt theory agree with the experimental data within ± 10%. The condensation heat transfer coefficients of HFC134a are about 32.6% larger than that of CFC12 for the cupronickel Thermoexcel-C tube. The cupreous integral-fin tubes provide more than twice condensation heat transfer coefficients than that of the cupronickel Thermoexcel-C tube. The heat transfer coefficients for each integral-finned tube are also compared with existing single-tube models.

Cupronickel pipes are widely used in cooling systems. Under this application, localized corrosion is observed, particularly associated with selective corrosion of nickel (denickelification). This work studied the denickelification process in solution-treated cupronickel alloys 90-10 (Cu-10wt%Ni), with aluminum and iron additions, in 0.01 M, 0.1 M, or 0.6 M sodium chloride (NaCl) aqueous solutions. Polished surfaces of the studied materials were submitted to potentiodynamic polarization, and after that, the polarized surfaces were studied using optical microscopy (OM) and scanning electron microscopy (SEM) assisted by energy-dispersive spectroscopy (EDS). A passivity break potential (Epb) was determined in all solutions, related to the initiation of selective corrosion of nickel. When submitted to cyclic potentiodynamic polarization, alloys with higher Epb showed the higher nickel losses in localized spots. However, potentiodynamic polarization tests conducted in 0.01 M NaCl until current densitie...

Cupronickel alloys are used as heat exchanger tube materials in nuclear power plant auxiliary coolant systems. In this work, the corrosion behaviour of cupronickel (70:30) alloy in permanganic acid medium was studied. Corrosion rate was found to follow logarithmic kinetics. Cyclic polarization studies showed that cupronickel did not undergo pitting in permanganic acid medium but uniform corrosion was observed. Presence of 0.43 mol/m 3 chromate in 2.5 mol/m 3 permanganic acid was found to decrease the corrosion rate of cupronickel by 50%. EIS and XPS studies revealed that the film formed on cupronickel was protective in nature and contained oxides of copper, nickel and manganese (mainly MnOOH). The composition of the film on cupronickel that had undergone chromate treatment also showed similar film except that it contained some chromium (III).

Failure analysis of cupronickel condenser tubes of a crude distillation unit of a petrochemical refinery has been conducted. Condenser tubes carrying sea water were found to undergo premature failure which was preceded by extensive overall thinning, formation of shallow channels, pits, etc., and greyish-black internal deposits in one of the units. In the other unit, the failure of tubes was noticed without any significant overall thinning and in the presence of adherent, hard and black-brown deposits. The studies indicated that the increased velocity of sea water as well as the deficiency of iron in the alloy had resulted in failure in one case whereas relatively low velocity of water associated with deposition of sludge and bio-fouling were the causes of failure in the other case. The failure of tubes could be controlled by maintaining the water velocity within a specified range, flushing the tubes with clean water, use of anti fouling paints, selecting a more appropriate composition of the cupronickel alloy, through control of sea water sulphur level, etc.

Nickel–aluminium bronze (NAB) alloys show good corrosion resistance under marine conditions. The corrosion behaviour of cast and wrought NAB alloys is illustrated in this work through a range of electrochemical techniques including open-circuit potentiometry with time, oxygen reduction voltammetry, NAB dissolution voltammetry, potential step (or flow step) current transients and linear polarisation resistance. The galvanic coupling of NAB to stainless steel or copper is examined by zero resistance ammetery. The importance of using controlled flow working electrodes is illustrated by the use of a rotating disc electrode, a rotating cylinder electrode and a bimetallic (NAB/copper–nickel) rotating cylinder electrode. In addition to controlling the hydrodynamics, such electrodes allow charge transfer data to separate from those of mass transport control under mixed kinetic control. Longer term seawater immersion trials on planar coupons coupled to titanium or cupronickel are also reported. The relative contributions of erosion and corrosion attack are considered using a wall-jet electrode and the corrosion characteristics of NAB are compared to those of copper and copper–nickel in chloride media.

The authors carried out failure analysis of bent and branched copper-nickel alloy pipelines that had failed in marine environments. These failures were almost always dominated by a brittle stress-corrosion cracking (SCC) mode and could often be attributed to the presence of ammoniacal byproducts in the operating environment. Attempts were made to reproduce the marine-type field failures in the laboratory by testing a Cu-5.37%Ni alloy, similar to the material used in failed pipelines. The tests were performed under slow strain rate test (SSRT) conditions in aqueous ammonia and ammoniacal seawater. Results revealed that the ammonia-induced brittle SCC failures were predominant and reduced the load-bearing capacity of the alloy. The real-life failures are not simple SSRT-type failures. The operating conditions, in addition to the induced residual stresses from manufacturing/processing, subject the system pipes to external forces and widely varying pressures and fluid flow rates. This combination of stresses can produce both static and cyclic stress conditions, similar to a static load coupled with a low-amplitude cyclic load. Tests conducted under superimposed cyclic stresses on prestressed specimens were found to accelerate the stress-corrosion failures in the present copper-nickel alloy in an ammoniacal environment.

On the basis of high temperature ductility tests in single-phase cupronickel CuNi25 sample has been found a relation between microstructure, grain size and effect of ductility minimum temperature (DMT). Metallographic tests confirmed literature studies that cracks nucleate at points of two or three grain joints and cross-cut of twined grain with border of the grains. The non-homogeneous character of chemical composition concentrating in areas of grain joints and cracks at high temperature has been investigated by linear and point Cu and Ni analysis (EDS). This analysis shows that local areas of non-equilibrium formation concentrate at this places. This fact can be accepted as one of the reasons of non-homogeneous deformation, cracking and its location at DMT. Experimental results were compared with two-dimensional finite element method (FEM) simulation results of proposed hypothesis of non-uniform deformation.

In this work, the feasibility condition of Powder-In-Tube (PIT) processed wires of Fe(Se,Te) superconductor has been investigated. We faced several technical issues that are extensively described and discussed. In particular, we tested different metals and alloys as external sheaths (Cu, Ag, Nb, Ta, Ni, Fe, cupronickel, brass) concluding that the only sheath that does not affect substantially the Fe(Se,Te) phase is Fe. On the other hand, Fe sheath introduces excess iron in the Fe(Se,Te) phase, which affects the superconducting properties; we investigated the effects of the thermal treatments and of the powder composition in order to avoid it. The maximum Jc value obtained in our samples is 4 × 102 A/cm2, comparable to other published values of PIT conductors of the 11 family. We conclude that the fabrication of Fe(Se,Te) wires by PIT method is quite challenging and other approaches should be developed.

In this study, the corrosion behavior of 90%Cu-10%Ni (C70600) cupronickel alloy in artificial seawater was investigated. The corrosion tests were conducted using a rotating cylindrical electrode at different speeds. In the experiments, free corrosion potential tests, electrochemical impedance spectrum (EIS) analysis, weight loss tests, and optic microscope observation were performed. The corrosion rate of 90%Cu-10%Ni alloy in artificial seawater increased with increasing rotation speed and time. Damage period was changed with rotation speed. It was also determined that the damage to the protective film began after 3 hours at the rotation speed of 1600 rpm, and after 3 hours at 2000 rpm, and increased with increasing time. It was determined that 1200 rpm rotation speed is better than both 1200 rpm and 1600 rpm for working conditions.

Cupronickel alloys are known for their excellent corrosion resistance, especially in marine atmosphere. The development of an appropriate electroless bath involves the use of a reducing agent, complexing and stabilizing compounds and metallic salts. In this work, autocatalytic deposition of Ni–Cu–P alloys (28–95 wt.% Ni, 66–0 wt.% Cu, 7.5–3 wt.% P) has been carried out on 302 b steel sheets from bath containing: NiCl 2 ·6H 2 O, CuCl 2 ·2H 2 O, NaH 2 PO 2 , Na citrate, sulphosalicilic acid and triethanolamine. The effects of pH, temperature, and bath composition on the hardness and the composition of deposits have been studied. In addition, the deposition rates of alloy, nickel, copper and phosphorus were investigated and optimum conditions were obtained. The average rate of alloy deposition was 9 mg cm −2 h −1 and the optimum pH and temperature were 8.5 and 80 °C, respectively. The chemical stability of bath was desirable, and no spontaneous decomposition occurred. The changes in the structure of deposit by heat treatment were studied by the X-ray diffraction (XRD) method. The XRD patterns indicate that the copper content affects the structure changes. With increasing copper content, the phosphorus content decreased and the crystallinity of the deposits grew. After heat treatment of alloys with lower copper content at 400 °C for 1 h, the crystallization to Ni 3 P was observed.

All the Arabian Gulf States suffer from a shortage of fresh water resources. This deficiency is remedied through the desalination of seawater, mainly by the multi- stage flash (MSF) evaporation technique. The number of MSF distillers in Abu Dhabi is 382, producing a total quantity of 5,465,784 m 3 /d of potable water. It has been reported that these units have a tendency to suffer, at varying degrees, from a variety of corrosion and scaling problems. This paper consists of two sections. The first section describes some of the corrosion problems facing the desalination plants, concentrating mainly on the vapour-side corrosion (VSC) of condenser tubes made of cupronickel alloys, 70/30 and 90/10. The research in this section is necessary because condenser tubes are the part most prone to failure in desalination plants. Almost all of the previous cases of corrosion of condenser tubes reported were focused on water-side corrosion of the tubes. The present paper will discuss two contrasting cases of attack related to both acidic and alkaline corrosion in the vapour side. This is the first such research to be cited anywhere in this field. The second section of the paper will discuss the mechanism of the scale formation reported in the literature, and will present the actual scale formed in desalination plants, which is different from scale formed in the laboratory.

Cupronickels offer enhanced corrosion protection in marine environments by the formation of passive films on the surface. Cyclic voltammetric studies were carried on cupronickels in chloride solutions at pH 6.3 to understand the role of chloride ions in passive film formation. Increase in nickel content of the alloy and of chloride ions in solution decreases film resistance. Chloride ions take part in reduction of the passive film to copper. A solid-state model for passive film formation involving chloride ions has been attempted.

Cupronickel alloys have been extensively used in marine and offshore applications. These alloys offer desirable physical and mechanical properties to be used as a versatile engineering alloy. The oxidation resistance of these alloys was due to the formation of scales consisting of a thick, inner Cu2O layer and a thin, outer CuO layer, together with nickel rich internal oxide. These alloys are superior to bronzes in their corrosion resistance but fail under oxidizing conditions. In sulphide atmospheres they undergo sulphidization. Depending upon the alloy composition, they form layers consisting of alloy/nickel sulphide/CuS of various proportions. In chloride solutions, they undergo localized attack. For lower chloride concentration, an increase in nickel content worsens the resistance to passive film breakdown, where as for higher chloride concentration an increase in the nickel content favour passivation. In seawater, the prime source is dissolved oxygen and the corrosion product is Cu2O. This is formed by the hydrolysis of CuCl2-. The use of ozone enhanced the dissolved oxygen content. Localised attack occurred at those points where the seawater is in motion. The impingement and general corrosion resistance was improved by the addition of iron in the alloy. Sulphides and ammonia as pollutants adversely influenced the performance of the alloy. Microbial adhesion alters the protective properties of the complex layers of the alloy. The bacteria enhanced the corrosion rates in seawater with intergranular corrosion and denickelification. The minor additions of an element, use of inhibitors in the medium and cathodic protection are the main methods of corrosion control in aqueous media. The various aspects of the corrosion resistance behavior of cupronickel alloys in different environments are discussed in the review

Wetting and contact interaction of (TiC−Mo2C)−(Ni−Mo) cemented carbides by molten copper, nickel, iron and their alloys and also by the cupronickel alloy, cast iron, and steel melts is investigated. The results show that good wetting and intensive interfacial interaction for the cemented carbides in question was observed in the case of iron and nickel, their alloys with copper, cast iron, and steel. These materials are recommended for metallic binders in the preparation of composite materials—based on tungsten-free hard alloy.

Voltammetric studies on copper, nickel and cupronickel alloys of various compositions in neutral chloride solutions revealed that the passivation is due to the formation of duplex film consisting of inner compact Cu 2 0 layer with outer chloro hydroxy layer. Under transient cyclic polarisation conditions, the presence of nickel hindered the passive film formation decreasing its thickness and ohmic conductivity. The reduction of these passive films to copper was markedly favoured by chloride ions. The presence of nickel in the alloy hindered the reduction of these passive films.

Galvanic corrosion between carbon steel and soldering fluxes was studied in a concentrated LiBr solution at 383 and 433K, using extreme-value statistical analysis of pit depth in soldered parts, measurement of the amount of dissolved Fe2+ and dissolved flux compornents, and corrosion potential and galvanic current measurement. The soldering fluxes used were copper, copper alloys (Cu-Si-Mn, BAg-8, Ag 30-Cu, 70/30 Cupronickle) and nickel.Nickel flux soldered with carbon steel caused considerable galvanic corrosion of carbon steel at 383K, while carbon steel soldered with copper and copper alloy fluxes showed galvanic corrosion of the fluxes at 383 and 433K. The galvanic corrosion rate of fluxes decreased in the order of copper>Cu-Si-Mn>Ag 30-Cu>BAg-8> 70/30 cupronickel at 433K, and Cu-Si-Mn>copper>Ag 30-Cu>BAg-8>70/30 cupronickel at 388K. 70/30 cupronickel flux was considered the most suitable soldering flux in a concentrated LiBr solution at high temperature.

Thin wires required for a new type of superconducting level sensors are investigated in some virtual situations. The sensors are composed of an MgB2 wire with metal sheath and a non-superconducting wire, which are located in parallel and connected in series, to determine a level of liquid hydrogen in a container with higher reliability. The operations of the level sensors during refill and discharge of liquid hydrogen are simulated numerically by solving a one-dimensional heat balance equation. The wires have a metal material with almost constant dependence of resistivity on temperature such as cupronickel or stainless steel. The wire lengths are assumed to be 1 meter. By using the obtained numerical results, the optimum compositions of the MgB2 and non-superconducting wires are discussed for several parameters such as materials and volume fractions of metal sheaths, temperatures of pressurized liquid hydrogen, and conditions of evaporated gas.

In this work the mechanical properties of a highly alloyed cupronickel have been analyzed using a neural network technique within a Bayesian framework. In this way the mechanical properties can be represented as an empirical function of the compositional variables. This method has been used to analyze the relative contributions of the various elements to the mechanical properties. Whilst the method is entirely empirical, it will be shown that the predictions made are of metallurgical significance.

The results of the 2nd VAMAS measurement intercomparison program on low-frequency (hysteretic) a.c. loss are presented and discussed. Two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diams 0.5, 1, 3, and 12 μm; Set No. 2: cupronickel matrix, fil. diams 0.4, 0.5, and 1 μm) were subjected to interlaboratory testing. In an initial series of tests, samples in various forms (e.g. wire bundles, coils) were measured mostly by vibrating-sample- and SQUID magnetometry. Considerable scatter was noted especially in the small-filament-diameter a.c.-loss data. In a study of measurement accuracy, a supplementary series of tests compared the results of VSM measurement of a given pair of copper-matrix samples. In the light of all the results, factors contributing to a.c. loss error are discussed and recommendations are made concerning the specification of future a.c.-loss measurement intercomparisons.

The article summarizes results of part of the second VAMAS a.c. loss measurement intercomparison. This program was carried out at 17 participating laboratories on two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diam. between 0.5 and 12 μm; Set No. 2: cupronickel matrix, fil. diam. between 0.4 and 1.2 μm). The results reported here were measured by means of a.c. magnetization methods and separated into hysteresis and coupling losses. One laboratory used a calorimetric method. The data scatter in measured hysteresis losses among the participating laboratories was reasonably small for different measuring methods adopted and experimental arrangements used. On the other hand, the data scatter in coupling losses was large, mainly because in most laboratories a.c. losses were measured only at low frequencies (below 1 Hz), where the separation of coupling losses from total losses tends to be inaccurate. The comparison of measured hysteresis losses with the critical state model showed a large disagreement, which is assumed to be due to proximity effect coupling between filaments. © 1997 Elsevier Science Limited

Castings of 70–30 cupronickel (NES 824) often contain an undesirable amount of porosity, which leads to a high rejection rate for components made from this type of alloy. The possibility of removing such porosity by the application of hot isostatic pressing (hipping) to the castings has been investigated. Part of this investigation involved the hipping of artificial porosity specimens of controlled geometry and a comparison of the results obtained with the predictions of certain well known models for pressure assisted sintering. The results obtained were complicated by the effect of the specimen design on the rate of compaction which is not taken into account in any of the models. However, where the pores are truly internal the degree of agreement with both models is reasonable. It is evident that for internal porosity the removal of porosity in a typical industrial hipping operation occurs during the initial application of pressure and temperature rather than during the subsequent isothermal stag...

MARINEL is the latest alloy in a series of high-strength, age-hardenable wrought cupronickels. It combines excellent resistance to corrosion and hydrogen embrittlement with high strength and is designed particularly for use in critical subsea bolting applications. Strengthening is provided by additions of Mn, Al, Fe, Nb and Cr. In this work the microstructure of MARINEL has been studied using optical and electron microscopy with the aim of understanding the strengthening mechanisms. As part of this major program the predominant micron-scale phase has been analyzed in some detail. This paper describes the composition and crystal structure of this phase, and identifies it as the {var_epsilon} phase already seen in Incoloy alloy 909.

The microstructure of a high-strength cupronickel alloy has been analysed using a variety of techniques, and the main strengthening phase is identified as an ordered phase with L1 2 structure, based on Ni 3 Al. This phase is coherent with the copper-based matrix, and has a constrained misfit of −0.68%, as measured by X-ray diffraction techniques. The implications of these findings are discussed.

Powder-coated tape electrodes (powder-coated tapes) are used for doped and composite alloys welding. Using powder-coated tape for welding of wear-resistant alloys is stipulated by a number of factors in comparison with using electrodes for manual arc welding, flux cored wires, sintered tapes etc. The main task of mechanized arc welding of composite materials is to keep the wear-resistant particles in their initial condition and to ensure the weld metal receives them in the quantity demanded.

In this work the corrosion of cupronickel in polluted seawater is studied, as well as its protection by stearic acid, a fatty acid with self-assembling properties. The polluted seawater is simulated by 3.5% NaCl solution containing 10 ppm S2-. The corrosion properties are investigated in simulated seawater by electro-chemical methods (Tafel extrapolation method and electrochemical impedance spectroscopy). The corrosion products are studied by scanning electron microscopy.

A laboratory biofilm reactor (LBR) was modified to a new loop-type closed system in order to evaluate novel stents and catheter materials using 3D optical microscopy and Raman spectroscopy. Two metallic specimens, pure nickel and cupronickel (80% Cu-20% Ni), along with two polymers, silicone and polyurethane, were chosen as examples to ratify the system. Each set of specimens was assigned to the LBR using either tap water or an NB (Nutrient broth based on peptone from animal foods and beef extract mainly)—cultured solution with E-coli formed over 48–72 h. The specimens were then analyzed using Raman Spectroscopy. 3D optical microscopy was employed to corroborate the Raman Spectroscopy results for only the metallic specimens since the inherent roughness of the polymer specimens made such measurements difficult. The findings suggest that the closed loop-type LBR together with Raman spectroscopy analysis is a useful method for evaluating biomaterials as a potential urinary system.

Nanowires of copper can be coated from liquids to create flexible, transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these nanowire films is that copper is prone to oxidation. It was hypothesized that the resistance to oxidation could be improved by coating copper nanowires with nickel. This work demonstrates a method for synthesizing copper nanowires with nickel shells as well as the properties of cupronickel nanowires in transparent conducting films. Time- and temperature-dependent sheet resistance measurements indicate that the sheet resistance of copper and silver nanowire films will double after 3 and 36 months at room temperature, respectively. In contrast, the sheet resistance of cupronickel nanowires containing 20 mol % nickel will double in about 400 years. Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make cupronickel nanowires a promising alternative for the sustainable, efficient production of transparent conductors.

Copper is used for its high electrical and thermal conductivity, good corrosion resistance, machinability, strength, and ease of fabrication. It can be welded, brazed, or soldered. Brasses are alloys of copper and zinc, and bronze refers to any copper alloy without zinc. Cupronickel alloys contain up to 30% nickel and are always single-phase alloys.

This paper describes a study of fixing light gauge titanium tubes into copper alloy tube sheets by roller expansion. The light gauge titanium tubes of 0.5 mm wall thickness were expanded into copper alloy tube sheets. The expansion procedure was conducted according to the ASME code and the TEMA standard. Fixing of light gauge titanium tubes was as easy as that of copper alloy tubes. Tightness was sufficient, and no leakage was found in the hydraulic test at the joints of the titanium tubes and the copper nickel tube sheet. The data show that the holding strength of the tubes with the tube sheet is in proportion to the t/D of tubes ( t wall thickness, D outside diameter) and to the area expanded. Consequently, it is practical and economical to apply light gauge titanium tubes instead of conventional copper alloy tubes as the evaporator of seawater desalination plants.

The corrosion behavior of 90-10 cupronickel in Arabian Gulf water containing different concentrations of NH4NO3 in ranges of 10−3 to 10−1 M (80–8000 mg/1) has been investigated. 90-10 cupronickel gives a better resistance to corrosion in deaerated water than aerated water. For corrosion-free performance of 90-10 Cu-Ni in Arabian Gulf water, the upper level of ammonia has been determined to be 10−2 M (800 mg/1) and an upper limit for Re to be 6.0 × 104.

The ultrahigh strength cupronickel alloy Marinel and the nickel alloy Monel K-500 were saturated with gaseous hydrogen at 450°C and their fatigue behaviour was measured and compared with that of hydrogen free material. The presence of hydrogen was found to reduce thefatigue properties of Monel K-500, but did not affect the performance of Marinel alloy. No evidence of obvious microstructural change induced by hydrogen was apparent, but use of hydrogen diffusivity data was made in calculations relating to the diffusivity and trapping of hydrogen in the two materials. It was demonstrated that the solubility of hydrogen, the degree of dislocation-hydrogen interaction, and the ease of hydrogen trap formation (as a precursor to crack initiation) were lower in Marinel alloy than in Monel K-500, thus contributing to an explanation of the resistance of Marinel alloy to the debilitating effects of hydrogen.

This chapter summarizes stress corrosion cracking of copper and copper-based alloys in different chemical, thermal, and electrochemical environments. The chapter begins with description of different copper-based alloys and their common application. A description of different operating SCC mechanisms for the copper-based alloys is provided. Information regarding the chemical, thermal and electrochemical conditions that could induce SCC of the copper and copper-based alloys and additional details on the SCC mechanism of particular copper-based alloys in specific chemical conditions are also detailed. The role of secondary phase particles on SCC of copper-based alloys is discussed. SCC mitigation strategies for the copper-based alloys are discussed. A summary of the chapter is provided in the end. The aim of this chapter is to develop an understanding of SCC susceptibility of different copper-based alloys in different chemical environments.

Effects of environmental factors on localized corrosion of copper (Cu)-based materials that are candidates for use in high-level nuclear waste containers were examined. Effects of bicarbonate (HCO3−), chloride (Cl−), and sulfate (SO42−), which are present in the ground water near the proposed Yucca Mountain site for a high-level waste repository, were studied. Localized corrosion was observed only at low temperatures in environments involving combinations of high HCO3− with high Cl− or high SO42−. Uniform corrosion was observed at low concentrations of HCO3− ( 80°C, irrespective of the Cl− and SO42− concentrations. Localized corrosion observed in the Cu-based alloys was much shallower than in stainless steels and nickel (Ni)-based alloys and tended to broaden with time under potentiostatic conditions. Oxygen-free Cu (CDA-102...

Biofouling and corrosion products on 70/30 cupronickel exposed to polluted seawater were studied by SEM with EDAX analysis. Layers of corrosion products containing dissimilar levels of sulphide, iron, copper and nickel were detected. An outer porous layer covered by a biofilm was present in all samples. Only a few genera of diatoms and protozoa could be found in the biofilm. Biofilm establishment on cupronickel was delayed compared with other more inert materials previously assayed. Electrochemical measurements showed that sulphide ions affect cupronickel passivity, interfering in the formation of the outer passive layers.

The present work is part of an investigation into the use of hot isostatic pressing to recover 70–30 cupronickel castings. These alloys have particularly good corrosion resistance and, when strengthened with silicon and chromium, produce a material capable of use in very severe conditions of stress and massive corrosion. However, it is not possible to recover such castings by the application of repair welding, because of the possibility of reduced corrosion resistance in the vicinity of the weld. Hot isostatic pressing represents an alternative method of casting recovery. The results reported in the present work refer to the effect of hot isostatic pressing on mechanical properties, microstructure, and the level of segregation in the alloys. Hot isostatic pressing may be used to remove casting defects in the form of fine pores up to total porosity of 5%. However, in cases where porosity takes the form of very large defects, the mechanical properties of the recovered region are inferior to those of...

The friction resistance plays an important role to determine the amount of deflection between the wedges of toroidal coil cases of a nuclear fusion magnet under electromagnetic force, and the material combination showing high friction is required to reduce the deflection. In order to obtain the material exhibiting high friction against cryogenic structural steels, JN1 and JN2, at 4K in liquid helium, five copper and its alloys including Cr coated copper were explored under fretting condition, where a peak-to-peak slip amplitude was 100μm, a normal load 20N, a frequency 8.33Hz, and the number of fretting cycles 5×104. Cupronickel showed the highest friction of all, where the coefficient of friction reached 0.8 against JN1 and 1.1 against JN2. However, it took more than 104 fretting cycles to show the high friction. Although the wear damage resulted from adhesive wear, the friction was not so high for other metals. It appeared that the friction was inversely proportional to hardness of the materials.

The cathodic behaviour of a 70Cu-30Ni alloy in a 3% NaCl solution was studied by potential-current curves. It was shown that the corrosion current of the studied alloy increased with the rotation speed of the electrode.

Ammonia corrosion in alumi-brass tubes in steam condensers can be a serious problem. It generally occurs in the high ammonia concentration area. In this case, it is planned to replace the alumi-brass tubes by higher grade material, such as cupronickel. Therefore, it is important to minimize the area to be replaced in order to keep the equipment cost down. It is known that the ammonia concentration is related to the degree of corrosion damage. We propose a hybrid analysis method to obtain ammonia concentration by combining two-phase flow Computational Fluid Dynamics (CFD) analysis and network analysis by a chemical engineering process simulator for the tube bundle. Ammonia concentration obtained by the simulation is therefore used to determine the area to be replaced by the higher grade material tubes.

Piping and other hardware in coal preparation plants are susceptible to degradation by dissolved salts and suspended coal in the process water. Because the coal mined underground in Appalachia and the Midwest is now increasing in chlorine content, there could be an adverse impact on materials performance. In-plant tests were conducted to determine the effect of chlorine concentration in process water on corrosion and erosion rates and to explore methods of corrosion control. The results showed an inverse dependence of corrosion rate on chloride ion content of the process water. Supplementary experiments conducted in the laboratory showed that the corrosion rate of 1018 steel goes through a maximum as a function of the chloride plus sulfate concentrations in water. Also in the plant tests, cupronickel alloys not considered previously for this application performed well, but metal wastage of the cupronickels was greater than for 304 stainless steel. Success was achieved in cathodically protecting t...

For lunar or planetary bases to be viable, a robust electric generating system will be required for powering the habitat. Water heat pipes offer an attractive solution for lunar base heat rejection, and would serve as a qualification for them on other long duration missions. Successful operation near the upper end of water operating range is a requirement for the application. Results are reported for life tests on water heat pipes that were operated at various temperatures between 200 °C and 300 °C. Tests were conducted on twenty three gravity‐assisted water heat pipes. Eleven titanium/water heat pipes and ten Monel/water heat pipes were tested at temperatures above 200 °C. Two cupronickel heat pipes were also assembled and tested. Titanium alloys tested included CP‐2 titanium, as well as two beta‐titanium alloys, namely 15‐3 and Nitinol alloys. Some of the titanium alloy life tests used wicks fabricated from CP‐2 titanium screen or porous felt. Monel alloys tested included 400 and K‐500 alloys. Some of t...

Samples of a cupronickel alloy IN 768, widely used in marine applications, were prepared by conventional sand-casting and by stir-casting, without consolidation, and the metallographic structures a...

The present work is concerned with the prediction of corrosion rates of copper and cupronickel in flowing seawater (up to 16 m per second) and for filmed copper and cupronickel up to 3.5 m per second). Such predictions are not available at present and would be of use for the design and maintenance of copper based components subjected to high velocity flows. Pipe systems on board ships often use such components-pumps, valves, elbows etc. The effect of flow on corrosion currents of filmed and polished samples that allows modelling of the behaviour of surfaces of old and newly fitted components is discussed. Equations describing the flow velocity dependence of these currents are developed and used to determine the mechanism controlling the copper dissolution and to identify the dissolution reactions.

Based on the stable solid solution cluster model, cupronickel is microalloylized in this paper. Alloys with different Ni-M (M=Si, Cr, Cr+Fe) ratios are designed at constant atomic ration of Cu (72.22 at.%). The high temperature oxidation resistance and mechanism of alloy are also investigated. In the Cu-Ni-Si system, the addition of Ni-Si can enhance the oxidation resistance of the alloy from two aspects: firstly, the Ni-Si is in solid solution state when being added as a cluster, it can inhibit the chemical reactivity of Cu-Ni-Si alloy; secondly, anti-oxidation precipitation can be obtained with the increase of Si/Ni ratio. Therefore, the oxidation resistance of the alloy is not because of the formation of the compact silicon oxide film. In the Cu-Ni-Cr system, the oxidation is obviously inhibited at medium temperatures (lower than 800 ℃). But at higher temperatures, the oxidation resistance is relevant to the integrality of chrome oxide layer. The high temperature oxidation resistance is closely related to Cr/Ni ratio, hence an appropriate Cr/Ni ratio is necessary for the good high temperature oxidation resistance. Compared with the third element Cr, the forth element Fe cannot be oxidized first. Therefore, combined addition of Cr and Fe can only inhibit the medium temperature oxidation, but not high temperature oxidation.