Search

Crude oil is one of the most important sources of energy in the world. To extract its multiple components, we need oil refineries. Refineries consist of multiple parts, including heat exchangers, furnaces, and others. It is known that one of the initial operations in the refineries is the process of gradually raising the temperature of crude oil to 370 degrees centigrade or higher. Hence, in this investigation the focus is on the furnaces and the corrosion in their tubes. The investigation was accomplished by reading the thickness of the tubes for the period from 2008 to 2020 with a test in every two year, had passed from their introduction into the work. Where the thickness of more than one point was measured on each tube in the same row and the corrosion rate was extracted for three furnaces, starting from the area of ​​heat transfer by radiation to the heat transfer area of ​​the convection in three different operating units. It was found that the highest percentage corrosion value between the standard tube thickness and the thickness of conduction position was 37% with the conduction zone, and 31% with radiation zone. There, the tubes specification was tested. Five percent Cr-0.5 Moly and the temperature of radiation zone was 578 °C to 613 °C and the stack temperature was 410 °C to 450 °C. So, the results show that the maximum erosion occur at the convection zone.

Aluminium as matrix in particulars have been vastlys investigateds, this is becauses of the diverses applicationss of aluminium dues to its exceptional propertiess. Material scientistss alwayss face a challenges when it comess to the tribologicals and mechanicals propertiess of aluminium, as it exudess rather poors behaviours in these aspectss. Hences this works aims to improves the mechanicals and corrosives resistances of Aluminiums by reinforcings with aluminum oxides and Nickel throughs stir casting usings vortex techniques. Al-Ni-Al2O3composites with percentages of Ni fixed at 20 % and Al2O3differed through 4-8% in incrementss of 2 wt. % . Composites material was prepareds by stir castings using vortex techniques. The hardness value of the aluminiums matrix composites improved with increaseds percentages of Al2O3, maximums increase was obtaineds for 8% Al2O3composite, viewing an increases of about 55%. A generals corrosions and erosion-corrosions for the Al-20%Ni bases alloys and the prepareds composites were carrieds out in 3.5wt% NaCl solutions as corrosives mediums for general corrosions while in erosion-corrosions with impacts angles 90° in slurry solutions ( 1wt%SiO2sand in 3.5wt% NaCl solution as the erodent). It was founds that the general corrosions rates for composite specimens is lower than thats of the bases alloy (Al-20%Ni). In case of erosion-corrosion resultss, it was founds that the erosion corrosions resistances property of the prepareds composites improveds significantlys with the increaseds percentages of Al2O3. There wass a noticeable improvements in the corrosion resistances of the aluminiums composites compareds to its purest forms, owing to the presences of nickel. Howevers, the increases in Al2O3percentages decrease the corrosions rates. The extreme decreases was obtaineds for 8% Al2O3composites, with a decreases of 26% corrosion rates in (mpy) unit for composites material is lowers than that of the bases alloys.

Slurry jet impingement test was carried out on a laser processed nickel aluminium bronze (NAB) and the results are compared with the as-cast NAB. It is observed that the invariably, erosion corrosion rate is increasing with the jet velocity. Also, as the slurry impact angle is increased, the erosion corrosion rate of laser processed and as-cast NAB decreased. The erosion corrosion rate of laser processed sample exhibited 28 % higher erosion resistance as compared to the as-cast NAB. Enhanced surface hardness and fine grain formation due to laser processed are the main reasons for the improvement in the erosion corrosion resistance.

In the present work, a self-built device called “full scale tubular goods erosion-corrosion test system” was used to test the P110SS tubing with a total length of 10 m and a full scale PFF78-70 flat valve to study their erosion-corrosion behaviors in the acceleration simulation operating condition of a well in Sichuang oil field of China. The erosion-corrosion performance of the specimen was investigated by KH-7700 digital microscope, scanning electron microscopy (SEM), X-ray power diffraction (XRD) and energy-dispersive spectroscopy (EDS). The results indicated that the P110SS tubing suffered catastrophic erosion-corrosion; the maximum pitting corrosion rate of the P110SS in the gas phase fluid was 5.29mm/a; while that in the liquid phase fluid was 11.13mm/a; A double-layer corrosion products scale, inner FeCO3 layer and outer mixture layer mainly dominated by FeO, Fe3O4, Fe2O3 and FeO(OH), formed on the P110SS tubing. Erosion-corrosion only occurred in the stress concentration area of the valve plate hole of the PFF78-70 plate valve, and the size of the corrosion pits is about 0.5mm.

A cavitation erosion is the process based on an impact of pressure pulses on a material’s surface caused by the phenomenon of cavitation. The term cavitation is defined as a phenomenon of formation, growth and disappearance (implosion) of bubbles due to cyclic pressure variations in a liquid. The cavitation initiators are embryos (cavitation nuclei with a size up to 50 μm), located in the water or on wetted surfaces that lead to decreasing of the liquid ability to transfer tensile stresses. The role of embryos is played by micro gas bubbles, fine solid particles, micro-organisms or gas-filled pores on a surface of solid body embedded in a liquid. A rapid pressure drop occurring within the liquid and a presence of cavitational kernel causes rupture the continuity of the liquid and thus lead to the formation of steam-gas mixture areas, a so called cavitation bubbles. A cavitation bubble may be filled with a gas, a vapor or a steam/gas mixture.A course of cavitation depends on a cavitation type. In thepresent work, a mechanism of cavitiational destruction of 99,7 % titaniumtested on vibrational and jet-impact valaboratory stands, is analyzed. Results of thecavitational resistance evaluation of Ti99.7 titanium carried out onvibrational and jet-impact stands have revealed different mechanisms of acavitation destruction caused by various forms of cavitation. It was found thata surface of titanium samples tested on the vibratory stand was covered by verylarge number of microcracks which in a later stage of the research leads to theerosion of the material. The cavitational destruction of Ti samples on the jet-impact stand is initiatedby a plastic straining of subsurface area, which in the further stage leads toan erosion represented by the detachment of whole grains anda formation of deep pits on the material’s surface. Additionally, results of conducted studies have confirmed the fatigue character of the cavitationaldestruction process.

The corrosion behaviors of austenitic stainless steels, 304 and 316L as a contrast material, are investigated in hydrochloric acid corrosion under different conditions including immersion corrosion, single-phase flow and two-phase flow, respectively. The corrosion mass loss test and electrochemical test were carried out to evaluate the influence of medium temperature and concentration. The specimen surface morphologies and chemical compositions were obtained using scanning electron microscope to analyze the corrosion mechanism. The results show that the static corrosion rates of 304 and 316L steels and erosion corrosion rates of 304 steel increase obviously with the medium temperature increasing, but, the effect of hydrochloric acid concentration on their corrosion rate is less than that of the temperature. The corrosion current density values of 304 stainless steel increase and its passivation region of the polarization curve becomes narrowing and disappeared as the medium temperature increase. Uniform corrosion is the main way found on the surfaces of the stainless steels at room temperature in the hydrochloric acid solution. However, the selective corrosion occurs on their surface with the medium temperature increasing, and the higher temperature and concentration of corrosion medium, the more serious selective corrosion.

The specimens subjected to cavitation erosion were quenched from different temperatures (1000°C, 1050°C and 1100°C) but maintained the same time (25 min.) at the high temperature. The cavitation tests were made in the T2 device of the Timisoara Polytechnic University Cavitation Laboratory. This device respects integrally the recommendation of the ASTM G32-2010 Standard. The specimens microstructure and the area subjected to cavitation were examined with optic and SEM microcopies and hardness measurements. The differences arising on cavitation erosion resistance are explained through modifications of the crystalline grains dimensions, the chromium carbides proportion and some intermetallic phases not dissolved in austenite and of resistance to plastic deformation.Keywords: stainless steel, heat treatment, cavitation erosion

The rotary experiment apparatus was built to study the erosion-corrosionresistance of carbon steel, 15CrMo steel, duplex stainless steel 2205, nickel based alloy 825 and stainless steel 316L which are commonly used in the sour water environment of refinery. Based on the electrochemical test, the carbon steel and alloys corrosion rates in different ammonium hydrosulfide concentration, fluid velocity and temperature were obtained. The corrosion products film morphology was analyzed by scanning electron microscope (SEM) to find the reasons for corrosion rates difference of carbon steel and alloys. The results showed that the corrosion rates of carbon steel and alloys were increasing with fluid velocity, ammonium hydrosulfide concentration and temperature increase, when the velocity exceeds 6 m/s the corrosion rates essentially unchanged. The maximum corrosion rate of carbon steel at 60 °C and 10 wt% ammonium hydrosulfide concentration was as high as 6.5 mm/year, while the nickel based alloys 825 and stainless steel 316L were less than 1.5 mm/year. The corrosion product films of carbon steel and 15CrMo steel was loose and cracking which can easy to fall off from the substrate when subjected to fluid impact and the corrosive media can easily penetrate into the bottom of corrosion product and continue to corrode substrate. However, the corrosion film of nickel based alloys 825 and stainless steel 316L was dense and tightly bonded to substrate making it has a good corrosion resistance.

Magnesium and its alloys may be applied as cathodic protection for steel constructions. As the protectors work in water environment, one of the main degradation factors is cavitation erosion. The paper presents results of research on the cavitation erosion of magnesium casting alloy – Elektron 21. The cavitation erosion tests were performed using vibratory apparatus. After the cavitation tests eroded surface and the cross-sections of the specimens were observed by means of scanning electron microscopy. Elektron 21 did not exhibit distinct incubation period of cavitation erosion. The cavitation pits are observed mainly in the α-Mg solid solution grains and on the interfaces between intermetallic phases and the α-Mg. On the other hand, the Mg3(Nd, Gd) eutectic phases are more resistant to cavitation erosion than α-Mg. They are protecting the solid solution from degradation. However, due to their high hardness they undergo cracking and detachment of from the surface. After longer times of cavitation tests, cracks begin to propagate into the material, which leads to crushing of bigger parts of the material.

Erosion-corrosion behavior in downhole tubulars and oilfield ground gathering transferring system is interesting in optimum design. This work is addressed to investigate erosion-corrosion behavior of hydraulic perforating equipment during fracturing. The typical fracturing fluid of 0.2% hydroxypropyl guar gum solution mixed with quartz grain was selected. The relationship between erosion-corrosion rate and flow displacement, the effect of the flow impact angle on erosion-corrosion rate is performed on a jet impingement experimental apparatus. In the experiment situation, the erosion-corrosion rate reaches highest at the impact angle of 45°. The erosion-corrosion rate increased exponentially with the increase of flow displacement. The surface morphology of specimen suffer from erosion-corrosion is analyzed by scanning electron microscopy (SEM) to characterize the erosion-corrosion damage mechanisms.

Cavitation erosion performance of modified macroscopic internal structure 316L stainless steel was investigated. The samples processed by means of SLM method were subjected to cavitation erosion test. The scanning electron microscope Philips 30/ESEM was used to examine morphology of eroded surface.

The use of nanocoolant is suspected to have effects on erosion-corrosion of piping systems in heat exchanger. This study was carried out to determine the erosion corrosion of AISI 316 stainless steel in solutions containing nanoparticles. The experiments used rotating cylinder electrode (RCE) at rotational speed of 0-1800 rpm under varying temperature of 30oC-70oC. Corrosion rate was measured using linear polarization resistance (LPR) method and erosion was indicated by measuring average depth of surface of the samples (surface roughness). The results showed that both corrosion rate and surface roughness of samples have increased when temperature and rotation speed increased. The erosion-corrosion effects of nanocoolant were lower in stagnant condition. Comparing with conventional coolant, the nanofluid showed significant differences. In flow conditions, the effects were remarkable. It was also found that maximum synergism erosion and corrosion were occurred at higher temperature and high rotation speed for both of types solutions.

Ultrasonic vibratory cavitation erosion tests were carried out on studying the cavitation erosion protection performance of different type of heavy-duty engine coolants for cast iron material of wet sleeve cylinder liners. The influence of coolant type, freezing point, corrosion inhibitor content and test duration on anti-cavitation performance were analysed. The experimental results showed that the anti-cavitation erosion performance of organic acid type heavy-duty engine coolants were better than the inorganic salt type heavy-duty engine coolants. For the same formulation coolant, increasing the content of ethylene glycol or corrosion inhibitor can improve the anti-cavitation erosion performance. With the extension of ultrasonic vibration test time, the anti-cavitation erosion protection performance for cast iron was reduced.

The work of this paper proposes a new technique for estimating and predicting erosion corrosion rate for laminar and turbulent flow in pipes. The technique depends on the neural networks Artificial Intelligent algorithms. Based on experimental results, which was applied to A 106 carbon-steel pipes, the networks are trained. Four velocities (Reynolds numbers) are used for laminar and four for turbulent regimes. The experiments also used seawater containment three different concentrations of sand. For each experiment the iron losses were measured six times in three hours’ time interval. The proposed estimating/predicting system managed to find values between the readings as well as predict the behavior of the erosion corrosion rate for extra three hours. The estimated/predicted results have been developed to find the transient zone between the Laminar and Turbulent flow regimes and investigating its effects on the erosion-corrosion behavior.

The corrosion behaviour of Al (6061)-B4C-Graphite was investigated. The Aluminium Metal Matrix Composites (AMMC) was fabricated through two step stir casting method. The composites were fabricated with various volume percentages of Boron Carbide (5, 10 &15%) and Graphite (5, 10& 15%). Corrosion studies of AMMC was investigated with 4%, 8%, 12% wt. % NaCl solution at room temperature. Also erosion-corrosion test were performed on the specimens in the NaCl solution with silica sand. Erosion-corrosion tests indicated that the rate of material loss mechanism is mechanical abrasion with enhanced corrosion. The material loss mechanism was significantly higher in the case of erosion-corrosion tests.

The compatibility between phase change alloys and container steels at the high temperature is limiting their potential applications in energy storage systems. In this paper, we investigated the erosion behavior of Al-12Si-2Mg-15Cu alloy against 304 stainless steel surface. The effect of temperature and immersion time on the erosion behavior was studied. The erosion rate and erosion thickness increased with the temperature increasing. With the increase of time, the erosion layer thickness increased, but the erosion rate decreased. The mechanisms which accounted for the formation and growth of diffusion layer were studied. The results show that the corrosion is mainly due to the diffusion of Al. The presence of Si element resists the growth of Fe-Al compounds and make erosion layer brittle. Ni-compounds can decrease the diffusion rate of Al atoms. Furthermore, the erosion layer adjacent to the steel substrate is brittle and its micro-hardness is higher.

According to recent researches, aluminum alloy is an ideal choice for solar energy storage technology. But the erosion nature limits its promotion and application. Therefore, it is particularly important to research the corrosion behavior and the corrosion mechanism. In this paper, the 304 stainless steel was used as the container material. By analyzing the corrosion kinetics curves, the erosion thickness increases and the erosion rate decreases with the erosion time extension. Electron probe, X-Ray Diffraction (XRD) and other instruments were used to research the corrosion behavior and mechanism of erosion products. The results show that the erosion form is uniform corrosion. The erosion phenomenon is due to the diffusion corrosion of Al element. Si, Al0.5Fe3Si0.5 compound and Al95Fe4Cr compound in the erosion layers can retard the diffusion of Al.

The sustainable development of engineering, mechanical instrument requires higher speed and higher power. It cause a physical damage is excessive damage for underwater rotating system as cavitations and erosion, but also electrochemical corrosion by chloride ion and flow of current in marine environment. In this study, we assessed electrochemical corrosion characteristics of aluminum-bronze that are the material for the underwater rotating system used in the ocean industry and studied the complex behavior of electrochemical corrosion and cavitation corrosion through the hybrid test that also included cavitation corrosion environment. After the cavitation hybrid tests, surface of specimens are observed to measurement damage degree using 3D optical microscope and compared the average of damage depth by immersion time. The observation of the surface micro-structure suggested that the corrosion took place initially in β phase that has poor corrosion resistance in spite of high hardness.

Conventional ships generated almost no cavitation erosion because they traveled at low speed. Thus, most ships have used painting, ICCP and sacrificial anode system. However, with the activation of international trading, and the increase of low-price, large-volume cargos, ships are becoming larger and faster. As a result, damages due to cavitations and corrosions have accelerated. Cavitation and erosion corrosions cause damages to materials by physical shock waves generated from the collapse of bubbles which are generated when the moving parts rotate in seawater. The stern in particular is exposed to more severe environment due to cavitation and high flow speed. When cavitation and electrochemical damages are combined with exposure to severe environment, it has serious impact on the life span of equipment. Therefore, this study investigated the electrochemical and cavitation characteristics in sea environment for Zn primer coating which is a pretreatment process of painting for rudders for ships. As a result, corrosion resistance improved, but erosion resistance did not.

The plate of the heat exchanger leaked owing to its corrosion during the running of the whole equipment. The composition of the failure plate, microstructure, corrosion appearance and the chemical composition of the corrosion products were analyzed through Optical microscope, scanning electron microscope and chemical analysis method to find out the reason of the failure. The results show that the chemical composition of the plate meet the requirement of S31254 (254SMO) according to standard A240 /A240M-2005. The main phase was austenite among which the ferrite distributed in stripe. The corrosion happened firstly at the ferrite area under the condition of running medium with chlorine ion and sulfur ion. Incomplete solution of ferrite during the solid solution treatment was the main cause of spot corrosion, which ultimately resulted in the leaking failure owing to the corrosion.

For natural gas well, effect of flow velocity on corrosion in gas well tubing is an important factor of gas well life. In this paper, we mainly introduce corrosion problem of insufficient gas-flow velocity in tubing, multiphase flow erosion and corrosion, erosion and corrosion problem of in-tubing gas flow velocity higher than erosion flow velocity, application on selection and determination method of minimum tubing size avoiding erosion due to excessive flow velocity in gas well. For application, the technology above has a good practicality.

With the development of hydraulic fracturing technology, the failure of the equipments during production test and completion well becomes more and more severe due to the behaviors of erosion-corrosion. In this paper, the erosion-corrosion behaviors of N80, P110 and VM140 materials were investigated with the jet impingement experimental device. The corrosive rate of these materials by the weight loss method was carried out under different flow velocities and jet angles. It was observed that the weight loss of the three materials is increased by the rising of the impact velocity. The relation of erosion-corrosion weight loss to impact velocity is well described as the equation E=KVn (E is the speed, V is fluid velocity, k and n are the fitting parameters). As a results, the resistance ability for corrosion-erosion under experimental conditions is P110>N80>VM140.

In harnessing clean and renewable energy sources water turbines represent a significant portion of the power generation worldwide. Because of erosion, repair and maintenance of hydraulic turbines is a difficult problem. Material removal in hydraulic turbine components may occur either by particle erosion or cavitation erosion or by their combined action. Many ASTM standard and non standard test rigs are aimed at specific tests, like solid particle erosion, cavitation erosion. To simulate the real conditions in a laboratory setup, a novel method is employed to combine the effect of cavitation erosion and slurry erosion in the slurry pot tester. Triangular prismatic cavitation inducers are used in the conventional slurry pot tester. The aluminum test specimens are investigated in the slurry pot tester. A wide variation in material loss was noted under different exposure conditions. The maximum material loss is ascribed to combined effects of solid particle erosion and cavitation erosion.

For natural gas well, erosion damage of the strings caused by high-velocity flowing gas is an important factor of gas well string life. Aiming at the gas well erosion, the different inner mechanisms of material erosion are analysed. This paper introduces calculation of in-tubing flow velocity for preventing erosion and corrosion. By taking Puguang gas field as an example, this paper optimizes the limiting anti-erosion production rate for different tubing sizes, and selects tubing sizes for Puguang gas field. Optimal modified gas well string in Puguang gas field has good performance of erosion resistance

Erosion phenomenon is quite common in petroleum industry, as one of the main mechanisms of material degradation, occurs frequently on high-pressure pipelines in hydraulic fracturing operation. With the increasing of operation times, the erosion and corrosion defects on the inner surface of the pipeline, would lead to serious material loss and equipment failure. In this paper a new type of test machine was developed to simulate the erosive wear behavior of metal materials caused by the multiphase fluid such as fracturing fluid, and study the erosion failure mechanism by various metal erosion influencing factors including the velocity of multiphase flow, solid particles of fracturing proppant and impact angles, etc. The erosion-wear experiments on 20CrNiMo steels used in high-pressure pipelines is described in detail. Finally, the microcosmic surface testing was also used to analyze the erosion failure mechanism of metal materials for high pressure pipelines.

Neyveli Lignite Corporation Ltd., Neyveli (a Navaratna Public Sector of Government of India), Tamil Nadu, India, operates three open cast lignite mines of total capacity 24 million tones per annum (mtpa) with ‘three pit head power stations’ of capacity 2490MW. The Mine operations are influenced by the aquifers and high monsoon that necessitated huge pumping of water before excavation of lignite. Hence a network of system of pumping was established for both ground water control (GWC) and storm water Control (SWC). As the volume of water to be handled is high capacity mining pumps of capacity 1.5m3/s and 180m Head are operated. These pumps in most of the occasions handle acidic water pH less than 3.5 and sand particles loaded up to 15% and experience variety of failures including erosion corrosion problems. The ‘Mean Time Between Failures’ was less than 100 hours in Mine-I and replacement and reconditioning of units are challenging jobs for maintenance crew.

The objective of this study is to improve the high-temperature erosion-corrosion resistance Incoloy 800 for the application used as thermowell at 900°C. In weld cladding procedure, silicon carbide (SiC) particles were pre-deposited on the Incoloy 800 substrate, followed by the cladding of Ni-base alloy filler (34Ni-25Cr-0.4C-Ti-W-Mo) by a gas tungsten arc welding. A theoretical amount of SiC particles mixed with filler was 2 - 30%wt. A particle size of SiC was in the range of 50-150 mm. The results showed that the addition of 15%wt SiC led to the maximum hardness of the cladding layer. Addition of particles more than 15wt% tended to provoke cracks in cladding layer. The larger particle size exhibited the higher hardness. An erosion rate of cladding surface was further tested by the perpendicular impingement of 1-mm SiC abrasion sands on the sample surface with air flow velocity of 220 m s-1 at 900°C in air. For cladding layer with the same amount of SiC mixed, the one mixed with larger particle size exhibited the higher erosion-corrosion resistance. Likewise, for cladding layer mixed by the same size of SiC, the addition of particle with a smaller amount promoted the higher erosion-corrosion resistance. The addition of 2.6 wt% SiC particles with 150 mm size in cladding layer showed the surface with the best erosion-corrosion resistance in this study. No oxide scale was, however, observed on eroded surface due to the spallation by high impact erodent particles.

In the present work, Al–TiC composites were synthesized by Flux Assisted Synthesis (FAS) route. In this in situ method the TiC particles are generated from the reaction between the mixture of K2TiF6 salt and graphite in the molten aluminium. The XRD peaks have confirmed the presence of the TiC and no other undesirable intermetallics have formed after reaction. After casting the composites were extruded and then aged. All the cast, extruded and aged composites samples have exhibited significant improvement in mechanical properties in comparison with the monolithic alloy. The erosion corrosion test have been performed and found that wear resistance of the composites have significantly improved by the presence of TiC particles. Optical and Scanning electron microscopy were used for microstructural analysis and XRD was used for phase analysis. Mechanical testes were performed as per the ASTM standards.

It is found that the tube damage is caused by two induced factors: bubbles erosion as a dispersed phase and chemical composition of water rich in Cl- ions that result in loss of stability of protective oxide layer. The tube is subject to be erosion–corrosion in a given set of conditions, using numerical simulation techniques. The results prove to be erosion–corrosion effects owing to turbulence, bubbles dynamics affect and ensuing erosion rates. In addition, the bulk of Cl- ions which are concentrated at the bend position play a role in that.

In order to increase cavitation erosion resistance of fluid machinery, an iron-based coating was prepared by high velocity arc spraying (HVAS) on the surface of 1Cr18Ni9Ti stainless steel. The microstructure and performance were investigated respectively by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), Vickers hardness and vibratory cavitation apparatus. The results indicated that the coating had the higher hardness (8.67GPa) and the finer structure than ZG230-450 (1.86GPa) used actual in water conservancy. Compared with ZG230-450, cavitation erosion resistance of the coating was better, and the coating presented flakiness stripping mode. The results indicated that the HVAS is a promising method to prepare the cavitation resistance coating.

Al-2%Mn alloy matrix composites reinforced with Al2O3 particulates was fabricated by stirring cast, and the composites was characterized and analyzed by using a variety of analytical techniques, such as XRD, SEM, EDS, Brinell hardness tester, ring-on-block tribometer, and erosion-corrosion tester. The results show that the composites in as cast condition is mainly composed of Al,  -Al2O3, MnAl6 and Al11Mn4 phase, and the Al2O3 particles are dispersed uniformly in the Al matrix. Compared with the base aluminium and the Al-2%Mn alloy, the HB hardness of the composites is increased significantly, and the wear loss is far less under the SO4•Cl- Na•Ca• Mg corrosive alkalescent aqueous solution lubricated condition. The erosive-corrosive wear rates of the composites are lower than those of the Al-2%Mn alloy irrespective of the rotational speed or the size of grinding particles. The Al2O3 particulates reinforced Al-2%Mn alloy matrix composites possesses a good wear-resistance and erosion-corrosion resistance due to its higher hardness.

The use of materials with otherwise desirable mechanical properties is often problematic in practice as a result of corrosion. Susceptibility may arise for a number of reasons, including an electrochemically heterogeneous surface or destabilisation of a passive film. These shortcomings have historically been overcome through the use of various coatings or claddings. However, a more robust surface layer with enhanced corrosion resistance could possibly be produced via local surface alloying using a fluidised bed. A fluidised bed treatment allows a surface to be alloyed, producing a distinct surface layer up to tens of microns thick. Surface alloying additions can be selected on the basis of whether they are known or suspected to enhance the corrosion resistance of a particular material, whilst at a minimum, surface alloying likely provides a more electrochemically homogeneous surface. Electrochemical evaluations using potentiodynamic polarisations in NaCl electrolytes have shown chromised plain carbon and stainless steel surfaces have decreased rates of corrosion, decreased passive current densities, and ennobled pitting potentials relative to untreated specimens.

The investigated super duplex steel belongs to the group of stainless steels which exhibits an austenitic-ferritic microstructure with a phase fraction of about 50% austenite and 50% ferrite. The alloy shows excellent general corrosion resistance as well as a good resistance against stress corrosion cracking, corrosion fatigue and erosion corrosion. Due to these outstanding properties, the super duplex alloy is used in components for sea or waste water applications and in the offshore and chemical industry. In addition, the investigated super duplex steel exhibits a good weldability and a high strength in comparison to pure austenitic steel grades In order to optimize the production process and to provide a suitable microstructure to satisfy the customer’s requirements multiaxial forging test at various temperatures were performed in the Gleeble Maxstrain system. The force and the displacement after each anvil stroke were measured and used to distinguish the mechanical behaviour in the forging process at different thermal conditions. The recorded force and displacement is also compared with a multi step compression test to show the influence of change in the deformation direction. A certain number of samples were exposed an in-situ heat treatment after the deformation while other samples were immediately quenched after the forging to preserve the deformed microstructure, which was measured by optical microscopy and electron microscopy. Furthermore, electron back scatter diffractions scans were applied to characterize the degree of dynamic recrystallization during the forging process.

A new Fe-based amorphous / nano metallic coating with a good combination of high microhardness and excellent erosion corrosion resistance was produced by high velocity oxygen fuel (HVOF). The coating microstructure, amorphous phase content and properties under different HVOF processes were evaluated. It was found that they are very sensitive to the powder feed rate, stand-off distance and oxygen flow. This high performance amorphous / nano metallic coating could be applied as a good alternative material in erosion and corrosion environments.

In the present study, a thermowell made of Incoloy 800 (33Ni-21Cr-46Fe) was used as a part to cover and therefore to protect a thermocouple inserted in a tube used in petrochemical process. It was then subjected to the atmosphere in the tube containing moving carbon particles at 900°C. One of the critical failure types observed was the combination of both solid particle erosion and oxidation. Thermowell degradation, which accounted for the corrosion-affected-erosion of materials, was significantly observed in the area where impingement at the head surface area of thermowell. The physicochemical characterization revealed that the thermowell consisted of two layers. The inner one is the incoloy 800 base metal, whereas the outer layer was clad with a cobalt base superalloy. Kinetic of oxidation of both materials in each layer, which was performed in air at 1173K presented the different parabolic rate. Metal oxide and surface morphology of thermowell, which was investigated in the simulated condition, were then examined by XRD, OM and SEM. A finite element software was furthermore applied to simulate the flow direction and the velocity of the particles. It was found that the maximum speed of particles (180 m s-1) was at the surface where the impingement angle of particle is 90°. Comparing to the failure of themowell in service, it was concluded that the failure of thermowell depends primarily on the impingement angle of particle. Design of the shape of thermowell, as well as the cladding with the higher erosion-corrosion resistance materials, were recommended to be carried out to improve the erosion-corrosion resistance of this part.

Two types of Ni-based coatings were deposited by high velocity oxy-fuel (HVOF) spraying process on ASTM 1020 low carbon steel substrate, and AISI 321 stainless steel was applied to the contrast test. The influences of erosion rate on the erosion-corrosion synergism and erosion-wear mechanism of the two coatings were investigated systematically in a liquid/solid two-phase flow (5% H2SO4 +15% silica sand). The volume loss rates stemming from the erosion-corrosion synergism of materials increased from 42~66% to 78~85% of the total volume loss rates when the erosion rate of the flow increased from 5 m/s to 10 m/s. It was indicated that the erosion-corrosion synergism was primary for the material removing during the erosion-corrosion process. Cutting, wear and plowing were the main features for Type-A coatings, while cutting, plowing and plastic deformation were the main characters for Type-B coatings and the two steels.

Erosion corrosion and environmental chamber corrosion studies conducted on plasma sprayed samples from three different spray dried and densified nanopowders showed good resistance to corrosion. A dense, uniform and even distribution of splats and small number of microvoids and pores offered a high resistance to erosion-corrosion in sodium chloride polystyrene slurry. The coatings offer a high resistance in salt spray chamber environment.

Cr3C2- NiCr and Cr3C2- NiCr-(25) WC-Co coatings were deposited on T22 boiler steel by High Velocity Oxy-Fuel (HVOF) Technology. The coated as well as the uncoated steel samples were exposed to the actual boiler environments in a thermal power plant for 1500 hrs under cyclic conditions to evaluate their erosion-corrosion performance. Weight change measurements were taken for each sample after every 100 hrs. It has been observed that the weight change trends for coated steel with Cr3C2- NiCr and Cr3C2- NiCr-(25) WC-Co coatings followed a parabolic trend. The exposed samples were physically investigated for any macroscopic changes after each cycle of 100 hours. The uncoated steel showed blisters and spallation of its oxide scale, whereas the coated samples exhibited intact oxide scales, in general. Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDAX) was done to characterize morphology of the oxide scales. The protective nature of coatings has been explained based on the results of the study.

During plant operation, high temperature and high pressure water and steam are flowing at high velocity inside these piping systems. In pipes of power plants, local wall thinning may result from erosion/corrosion(E/C). Therefore, it is important to evaluate the nondestructive characteristics for corroded pipes to maintain the integrity of the secondary piping systems. In this study, the pressure vessel piping with corrosion used during long terms were investigated from the timefrequency analysis method. The damage of piping could be evaluated by ultrasonic parameters such as center frequency and echo waveform. Based on NDE analysis by time-frequency analysis method, it should also be possible to evaluate from various damages and defects in piping members.

The locally wall thinned phenomenon of pipes is simulated as metal loss due to erosion/corrosion. Therefore, fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. In this study, monotonic bending tests without internal pressure are conducted on 1.91-inch diameter Schedule 80 STS370 full-scale carbon steel pipe specimens. We investigated fracture strengths and failure modes of locally wall thinned pipes that welded and unwelded by four point bending test. From test results, we could be divided three types of failure modes.

With the aim to obtain the high cavitation-erosion-resistance coating for the surface safeguard of fluid machinery, two kinds of hard coatings (WC-Cr-Co and Cr3C2-NiCr) were prepared on 1Cr18Ni9Ti substrate by high velocity oxy-fuel spraying (HVOF), which microstructure and performance were investigated respectively by optical microscope, X-ray diffraction, Vickers hardness, scanning electron microscope (SEM), and vibratory cavitation apparatus. The results indicated that these two coatings had the higher hardness and the finer structure than ZG06Cr13Ni5Mo, which is used actual in water conservancy. The results of cavitation erosion continued for 39 hours presented that the mass loss of WC-Cr-Co and Cr3C2 -NiCr coatings increased ceaselessly with time, and the cavitation erosion speeds varied with time. Compared with ZG06Cr13Ni5Mo, their cavitation erosion resistance performances were better due to their higher hardness and finer structure, and WC-Cr-Co coating was much better than Cr3C2-NiCr coating. Obviously, the higher hardness and finer structure could strengthen the cavitation erosion resistance of coating materials.

A rig has been built to simulate the erosion-corrosion conditions in BFBC (Bubbling Fluidised Bed Combustion) power plants. In this particular test, 304 stainless steel tubular specimens were exposed for 3 weeks in air at 550°C. The degradation was quantified, as a function of the impact angle, from measurements of the roundness of the specimens. The maximum eroded depth varied within 25-80 μm, depending on position in the bed. The compositions, thicknesses, morphologies and structures of the oxides, formed on both eroded and protected areas, were determined by AES, SEM/EDS and X-ray diffraction. The thicknesses of the residual oxides on the eroded surfaces and on the protected areas were 1-3 μm and 0.1-0.3 pm, respectively. The compositions of the eroded oxides were significantly different from the non-eroded oxides. The mechanism of erosion-oxidation differs considerably from the mechanism of oxidation only. It is concluded that defects in the oxide scale, formed by impacts of the particles, act as short-circuit diffusion paths and a mechanism based on this conclusion is proposed.

A series of elevated temperature erosion and erosion-corrosion (E-C) tests were carried out on thermally sprayed coatings, diffusion coatings and boiler steels using a burner rig-type elevated temperature E-C tester. Test conditions simulated E-C conditions in the superheater section of a circulating fluidised bed combustor. The gas temperature was 850°C and the tubular samples were internally cooled with air to 550°C. Quartz sand (50-500 μm) was used as erosive media. Potassium chloride (KCl, 0.1%) was added to quartz in E-C tests. Cr3C2-NiCr HVOF coating performed better in hot erosion tests than metallic HVOF and arc-sprayed coatings. Cr- diffusion treatment improved erosion resistance of steel significantly. In E-C test the Cr3C2-NiCr HVOF and diffusion chromium coatings were destroyed and the dense, metallic HVOF coating performed best. Arc-sprayed coating and steel exhibited higher material loss.

Industrial processes can involve motion of hard particles that impact on metallic surfaces at high temperatures, thereby leading to erosion-corrosion damage. In this paper, results from a laboratory study of the erosion-corrosion behaviour of an Fe-1Cr-Mo steel have been compared with those of several hard commercially-applied thermal-sprayed (wire arc- and D-gun) coatings, using two test rigs that generate erosion conditions pertinent to such processes. The first is a spouting-bed rig that gives particle loadings of about 10 vol%, with impact velocities between the erodent particles and the specimens of up to 10 m s -1 ; the second is a jet-impact rig that gives lower particle loadings and higher impact velocities. Emphasis has been placed on the effects of temperature (in the range: 450 to 550°C) and impact angle (in the range: 15° to 90°) on the erosion-corrosion damage caused by silica particles in an oxidizing gas (air). Following exposures, the specimens were examined and analyzed in plan and cross section by optical and analytical scanning electron microscopy. The extents of damage, determined by measurements of thickness loss in cross section, have been compared and are discussed in terms of relevant mechanisms of erosion-corrosion. In these tests, in-situ grown oxides gave some protection to the uncoated steel while the resistance of the coated specimens to damage was determined mainly by the effect of hard phase on the extent of deformation of the surface.

The case of near net shape parts made from austenitic steel X2CrNiMo 17-13-2 and austenitic-ferritic steels X2CrNiMoN22-5-3 (wrought) and G-X3CrNiMoCuN26-6-3-3 (cast) is interstitially enriched with nitrogen by the diffusion-based process solution nitriding. In order to obtain good corrosion resistance and mechanical properties, the solution nitriding parameters and the applied cooling time are selected so, that precipitates are avoided (X2CrNiMo 17-13-2, X2CrNiMoN22-5-3) However, in case of a superimposed hydroabrasive load, the presence of nitrides in the case is found to be beneficial. The solution nitrided and the solution annealed conditions of the steels are compared with respect to their susceptibility to corrosion by means of electrochemical polarisation curves. The erosion corrosion behaviour of the materials is analysed in pilot scale flow-loop tests using particle loaded corrosive and particle loaded non-corrosive media. It is shown that solution nitriding leads to improved corrosion behaviour and/or improved erosion corrosion resistance, in particular in the case of the duplex steels.