Showing papers in "Surface Engineering in 2002"
TL;DR: In this paper, the historical evolution and development of low temperature surface alloying processes (including plasma, ion beam, gaseous and salt bath methods) is discussed. But the authors focus on the application of these technologies in the food, chemical, nuclear and medical sectors.
Abstract: The inherent poor tribological behaviour of austenitic stainless steels has been a barrier to their wider application under corrosion wear conditions. Therefore, researchers have long dreamt of developing new technologies to enhance the wear resistance of stainless steel surfaces without loss of their attractive ‘stainless’ characteristics. For example, the discovery of low temperature plasma nitriding in the mid 1980s allowed a new phase with a high hardness and good corrosion resistance to be produced on austenitic stainless steel surfaces. Since then much research and development has aimed to combine improvements in wear, corrosion and fatigue properties. This has been demonstrated by various low temperature surface alloying processes (including plasma, ion beam, gaseous and salt bath methods) and increasing numbers of academic publications, reflecting rapidly expanding niche markets in the food, chemical, nuclear and medical sectors. In this paper, the historical evolution and development of l...
178 citations
TL;DR: Active screen plasma nitriding (ASPN) as discussed by the authors is an emerging surface engineering technology that offers many advantages over the conventional dc-plasminarizing (DCPN) technology.
Abstract: Active screen plasma nitriding (ASPN) is an emerging surface engineering technology that offers many advantages over the conventional dc plasma nitriding (DCPN). In this work, samples of a low alloy steel 722M 24 were AS plasma nitrided with various gas compositions and using different active screen setups. Normal dc plasma nitriding was also performed under similar conditions for comparison. The nitrided samples were characterised with a variety of analytical techniques, including optical microscopy and SEM for morphological and structural examination, XRD for phase identification, and microhardness testing for surface hardness and hardness profile measurements. It has been shown that ASPN can achieve a similar nitriding effect as the normal DCPN but without the common problems associated with dc nitriding such as the arcing surface damage, the edging effect, and the hollow cathode effect. The mechanism of nitrogen mass transfer in AS plasma nitriding has been investigated, and a modified sputter...
131 citations
TL;DR: Active screen (AS) plasma nitriding is a new surface engineering technique which provides many advantages over conventional dc plasma nano-nondiscriminative surface engineering techniques.
Abstract: Active screen (AS) plasma nitriding is a new surface engineering technique which provides many advantages over conventional dc plasma nitriding. In this study the AS technique has been used to nitride austenitic stainless steel (AISI 316). The morphology, composition and properties of the AS plasma nitrided layers have been characterised and compared with those of the normal dc plasma nitrided layers. AS nitriding can achieve similar hardening effects for austenitic stainless steel when compared to conventional dc nitriding, and does not have the common problems associated with the dc technique such as ‘edging effect’. AS nitriding at a lower temperature of 420° C can also produce a precipitation free layer, the S phase, on a 316 stainless steel surface. The AS nitrided S phase exhibits not only high hardness and wear resistance but also very good corrosion resistance.
98 citations
TL;DR: In the early 1970s, surface hardening by inducing phase transformations through the heating effect of a laser beam was one of the first laser-based fabrication methods to be commercialised as discussed by the authors.
Abstract: Surface hardening by inducing phase transformations through the heating effect of a laser beam was one of the first laser based fabrication methods to be commercialised, in the early 1970s. However...
81 citations
TL;DR: In this article, the effect of crystallization and phase transformation behavior on the microstructure and material properties of electroless Ni-P deposits is critically reviewed and a comparison is made with other commonly used engineering deposits such as electroplated nickel and hard chromium.
Abstract: The crystallisation and phase transformation behaviour of electroless Ni-P deposits during thermal processing have a vital role in determining their material properties. Conflicting results have been reported for the correlation of crystallisation and phase transformation behaviour with deposit composition and thermal processing, and hence microstructure and material properties. These variations are believed to be caused by variations in factors including plating conditions, substrate composition and surface preparation, and testing and measuring techniques. The mechanism of electroless Ni-P plating is discussed briefly and the literature on the effect of crystallisation and phase transformation behaviour on the microstructure and material properties of electroless Ni-P deposits is critically reviewed. A comparison is made with other commonly used engineering deposits such as electroplated nickel and hard chromium. The advantages, limitations, and development of electroless Ni-P are outlined and ...
79 citations
TL;DR: In this paper, S phase layers produced on AISI 316 stainless steel by low temperature plasma nitriding and plasma carburising were examined in order to investigate their mechanical and chemical properties.
Abstract: S phase layers produced on AISI 316 stainless steel by low temperature plasma nitriding and plasma carburising were examined in order to investigate their mechanical and chemical properties. Cylindrical disc specimens were used for testing hardness, pin on disc wear and electrochemical corrosion. Toroidal specimens were used for the fatigue and fretting fatigue tests. Both plasma nitriding and carburising processes created S phase layers on the surface of AISI 316 and greatly improved the steel’s tribological properties. SEM showed that more precipitation of nitrogen occurred in the plasma nitrided specimens and GDS revealed that the nitrogen in the nitriding specimens did not penetrate as far into the substrate as the carbon in the carburising specimens. This is due to the nitrogen bonding easily with chromium in the surface layer which obstructs the diffusion of nitrogen into the substrate. The hardness tests showed that the nitriding layer was harder than the carburised layer but was more britt...
69 citations
TL;DR: In this article, a low temperature plasma carburising process has been developed to engineer the surfaces of austenitic stainless steels to achieve combined improvements in wear and corrosion resistance.
Abstract: A low temperature plasma carburising process has been developed to engineer the surfaces of austenitic stainless steels to achieve combined improvements in wear and corrosion resistance. Previous studies have investigated the chemical, mechanical and structural characteristics of this carburised layer produced on AISI 316 steel at temperatures between 400° C and 600° C. The present paper focuses on the thermal stability of this carbon S phase layer. The investigation included isothermal annealing of the S phase layer as well as microstructure and property characterisation of the specimens. The results show that the S phase is metastable. When thermally annealed at certain temperatures for long enough, the carbon S phase decomposes into chromium carbides. Correspondingly, the hardness and corrosion resistance also varied. A preliminary isothermal transformation diagram has been constructed, which provides a basic guideline for the application of low temperature plasma carburised 316 austenitic stai...
47 citations
TL;DR: In this paper, the role of the aluminium surface chemistry produced by conditioning through ambient atmospheric and ethanoic methyl phosphonic acid solution immersion was investigated, where contact angle measurement revealed rapid formation of relatively disordered self assembled monolayers (SAMs) from a 5 mM ethanoisic solution.
Abstract: Self assembly of alkyl phosphonic acids (APAs) on magnetron sputtered aluminium (MS-Al) has been investigated with particular attention on the role of the aluminium surface chemistry produced by conditioning through ambient atmospheric and ethanoic methyl phosphonic acid solution immersion. For the longest molecule investigated, decyl phosphonic acid, contact angle measurement revealed rapid formation of relatively disordered self assembled monolayers (SAMs) from a 5 mM ethanoic solution. Evidence of a reaction of the phosphonic acid head group in a condensation reaction with the hydrox yls at the alumina surface to form a phosphonate was obtained using polarisation modulation infrared reflection absorption spectroscopy (PM-IRRAS). The concentration of hydrox yl groups in the ox ide at the surface of the M S-Al, determined by X-ray photoelectron spectroscopy (XPS), increased on immersion in ethanol owing to the presence of dissolved impurity water. Adsorption of hydrocarbon impurities is also evid...
41 citations
TL;DR: Laser peening has been demonstrated to be a unique and valuable method to increase the resistance of aircraft gas turbine engine compressor and fan blades to foreign object damage (FOD) and improve high cycle fatigue (HCF) life as mentioned in this paper.
Abstract: Laser peening has been demonstrated to be a unique and valuable method to increase the resistance of aircraft gas turbine engine compressor and fan blades to foreign object damage (FOD) and improve high cycle fatigue (HCF) life. Laser peening is also known as the LaserPeen process (LPP) or laser shock processing (LSP). LaserPeen processing’s high value as a surface enhancement process to mitigate high cycle fatigue failures is driving e fforts to expand its application from gas turbine engines to aircraft structures, land vehicles, weapon systems, and for general industrial use. One of the major impediments to the broad acceptance and use of the LaserPeen process has been high processing costs with relatively low throughput. Great strides are being made to significantly decrease laser peening costs and increase throughput, thanks to three important Air Force ManTech (manufacturing technology) programmes being conducted at LSP Technologies, Inc. (LSPT). Several key issues are being addressed to mee...
38 citations
TL;DR: In this paper, the mechanical and chemical properties of carbon and nitrogen S phase on austenitic stainless steel AISI 316 produced during low temperature plasma processes with different process parameters are investigated.
Abstract: Low temperature plasma nitriding and carburising are well known as methods for improving tribological properties without deterioration of corrosion properties of austenitic stainless steels. 'S phase' is a key alloyed layer, achieved from these two plasma thermochemical processes, referred as nitrogen and carbon S phase, respectively. The present work has been focused on full characterisation of the mechanical and chemical properties of carbon and nitrogen S phase on austenitic stainless steel AISI 316 produced during low temperature plasma processes with different process parameters. A series of theoretical, experimental, and analytical studies have been conducted in order to lay the necessary foundations for fully realising application potential of these processes in various stress and environmental conditions.
32 citations
TL;DR: In this article, the application of this process to the control rod clusters of pressurised water nuclear reactors (PWR) is discussed, using, as an example, the applied of this nitriding process on the control rods of PWRs.
Abstract: Ion nitriding is an extensively industrialised process enabling steel surfaces to be hardened by nitrogen diffusion, with a resulting increase in wear, seizure and fatigue resistance. Unfortunately, its direct application to stainless steels, while enhancing their mechanical properties, also causes a marked degradation in their corrosion resistance. By adapting the plasma process however, it is possible to reconcile improvement of tribological properties with maintenance of corrosion resistance. This may be obtained by working with base nitrogen and/or base carbon plasmas. The material properties obtained with a nitrogen plasma are discussed, using, as an example, the application of this process to the control rod clusters of pressurised water nuclear reactors (PWR). This nitriding process is then compared with low temperature nitriding and/or carburising thermionically enhanced low pressure plasma processes which have been recently developed. Following this type of treatment it is possible to inc...
TL;DR: In this paper, a new CrTiAlN coating has been produced using closed field magnetron sputter ion plating and individual Ti, Al and Cr metal targets M42 high speed steel coupons, 30 ×30 × 30 mm stainless steel (316) and 635 mm diameter (¼in) high speed twisted drills were used as substrates.
Abstract: A new CrTiAlN coating has been produced using closed field magnetron sputter ion plating and individual Ti, Al and Cr metal targets M42 high speed steel coupons, 30 × 30 × 30 mm stainless steel (316) and 635 mm diameter (¼in) high speed steel twist drills were used as substrates The coating was structured as follows: a Cr rich metal adhesive layer; a monolithic CrN nitride columnar layer with increasing content of Ti and Al; and finally, the nanoscale CrTiAlN multilayer The composition ratio of Cr, Ti and Al in the multilayer was optimised and the nitrogen flow was controlled using an optical emission monitor with feedback control to produce stoichiometric CrTiAlN (metal/N ~50:50) Some of the as coated samples were heat treated in air at 600°C and 900°C, and then the coating compositions and structures were studied using XRD, GDOES, and TEM with special reference to the effects of the heat treatment The hardness, adhesion and wear properties of the coating were studied and the properties o
TL;DR: In this article, the results obtained from sliding wear tests performed at both room temperature and high temperature (100 and 300°C) on silicon carbide/nickel composite coatings annealed at 400°C in argon were reported.
Abstract: The present paper reports the results obtained from sliding wear tests performed at both room temperature and high temperature (100 and 300°C) on silicon carbide/nickel composite coatings annealed at 400°C in argon. The coatings were deposited industrially on AISI 1020 steel discs by using a proprietary self catalysing chemical reduction process (Hardex). The tests were conducted without lubrication in argon, employing a ball on disc tribometer. A load of 5 N was used at a constant sliding speed of 0·1 ms-1. The mating pair was an alumina ball of 6 mm diameter. For the tests performed at 25°C, the effect of heat treatment contributed to an improvement in the coating wear resistance of nearly 135%, when compared to the as deposited conditions. It was determined that the set of the experimental conditions for the wear test performed at high temperature, i.e. the load used, the nature of the mating surface, and the low velocity of the test, added to a small coating thickness to particle size ratio, c...
TL;DR: In this paper, X-ray diffraction has been employed to study the residual stresses and lattice strains in the carbon S phase layers produced in AISI 316 stainless steel by low temperature plasma carburising.
Abstract: X-ray diffraction has been employed to study the residual stresses and lattice strains in the carbon S phase layers produced in AISI 316 stainless steel by low temperature plasma carburising. The results show that the carbon S phase layers are under a compressively stressed condition, to a level between 1.5 and 3.5 GPa. Analysis of the evolution of stresses revealed that, among various contributing factors including composition profile, lattice misfit and thermal effects, the build up of a carbon composition profile in the layer is mainly responsible for the development of a compressive residual stress during the carburising process. A simple model has been developed to predict the residual stress in the S phase layer. The model predicted that the compressive stress developed during carburising should be much higher than the values measured by XRD. This discovery suggests that stress relaxation has occurred during the carburising process. Further analysis revealed that the strain induced in the S...
TL;DR: In this paper, the effect of annealing electrodeposited nanocrystalline nickel at 250°C was studied by microhardness testing, XRD, TEM and three-dimensional atom probe (3DAP) analysis.
Abstract: The effect of annealing electrodeposited nanocrystalline nickel at 250°C was studied by microhardness testing, XRD, TEM and three-dimensional atom probe (3DAP) analysis. TEM micrographs revealed that the type of growth is abnormal, i.e. a composite structure is formed with some large (>1 μm) grains embedded in a matrix of nanometre sized grains. 3DAP studies showed no grain boundary segregation in as deposited materials and only low levels in material annealed for 1 h. Upon annealing, a 10% increase in hardness was observed within the first five minutes, after which the hardness was maintained for long times, despite the high volume fraction of large grains. Only after extensive annealing, when the majority of the material was made up of large grains, did the hardness decrease rapidly. The results demonstrate that the hardness is not determined by a law of mixtures but by percolation of the large grains.
TL;DR: Kolsterising is a diffusion process for improving the tribological properties of austenitic and duplex stainless steels without affecting their corrosion resistance as mentioned in this paper, which alters the characteristics of the base material in a thin layer by carbon enrichment in low temperature conditions.
Abstract: Kolsterising is a diffusion process for improving the tribological properties of austenitic and duplex stainless steels without affecting their corrosion resistance. The technique alters the characteristics of the base material in a thin layer by carbon enrichment in low temperature conditions in a gaseous environment. Three distinct processes have been developed; two for steels subject to different wear exposures and a third specifically for duplex stainless steels. Tribological and other properties of treated specimens are reported.
TL;DR: In this paper, a direct current magnetron sputtering combined with electron assisted growth has been used to grow a 60 μm thick TiB2 coatings with excellent practical adhesion to the substrate.
Abstract: Direct current magnetron sputtering combined with electron assisted growth has been used to grow thick TiB2 coatings. The coatings were evaluated with respect to structure, using X-ray diffraction (XRD), and morphology, using scanning electron microscopy (SEM). Fundamental mechanical properties were examined, such as hardness (52 GPa) and Young’s modulus (590 GPa), using nanoindentation testing. The fracture toughness Kc was determined to be 4·1 MPa m1/2 based on the length of radial cracks in Vickers indentation (the Anstis method). This deposition process, which yields low stressed magnetron sputtered TiB2 coatings makes it possible to obtain 60 μm thick coatings with excellent practical adhesion to the substrate. Scratch testing revealed that no critical failure (i.e. cohesive spalling) has occurred below 70 N. The improved scratch test behaviour is attributed to the increase in load carrying capacity by depositing a thick coating. However, small cohesive cracks were generated above 35 N. This ...
TL;DR: In this paper, optical emission spectroscopy (OES) is used in situ, without disturbing the treatment environment, to monitor the active species observed in three different types of nitriding plasma: direct current (dc), active screen, and plasma immersion ion implantation (PI3).
Abstract: In order to gain the maximum potential from plasma technology in surface engineering, knowledge is required about the influence of particular plasma phase species on the treatment response In this study, optical emission spectroscopy (OES) is used in situ, without disturbing the treatment environment, to monitor the active species observed in three different types of nitriding plasma: direct current (dc), active screen, and plasma immersion ion implantation (PI3) The spectral information obtained is considered in conjunction with metallurgical characterisation of nitrided steel samples, using optical microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, and microhardness testing Active screen and dc nitriding have a similar nitriding effect in low alloy steel testpieces OES evidence shows that both ions and neutrals are involved in the plasma reactions and a multistage theory is the model of best fit for nitrogen mass transfer in these dc powered plasma nitriding techni
TL;DR: In this article, the characteristics and properties of two different sets of hydroxyapatite (HA) coatings obtained by thermal spraying two different HA powders, spray dried HA (SDHA) and spheroidisided HA (SHA), at various chamber pressures were evaluated.
Abstract: This paper reports the characteristics and properties of two different sets of hydroxyapatite (HA) coatings obtained by thermal spraying two different HA powders, spray dried HA (SDHA) and spheroidisided HA (SHA), at various chamber pressures. The evaluation of the coatings following post-spray treatment at 800°C is also included. Comparisons to the results from the as sprayed coatings were made to show the effects of post-spray heat treatment. The median particle sizes for SDHA and SHA were 35 and 47 μm, respectively. The main difference between the powders is their density and morphology. The SHA powder provides higher density and spherical morphology, and a more porous and rough surface is present in the SDHA powders. These two powders were sprayed using a controlled atmosphere plasma spraying (CAPS) system in the inert plasma spray (IPS) and high pressure plasma spray (HPPS) modes. Four different pressures of 100, 150, 200, and 250 kPa were applied in an argon atmosphere. Post-spray heat trea...
TL;DR: In this article, a low temperature carburising approach for austenitic stainless steels, the NV Pionite process, is described and a single phase expanded austenite diffusion layer with surface microhardness of 810 HV0.05 and good corrosion properties is produced.
Abstract: A novel low temperature carburising approach for austenitic stainless steels, the NV Pionite process, is described. The formation of a metal fluoride layer on the surface before carburising allows carbon to be introduced into the workpiece by gas carburising at 450-500° C. Laboratory trials using 316 have been conducted. A single phase expanded austenite diffusion layer with surface microhardness of 810 HV0.05 and good corrosion properties is produced.
TL;DR: In this paper, the duplex process of nitriding plus moderate temperature chemical vapour deposition (MTCVD) TiCN coating of titanium alloys appears promising, but the wear resistance is limited by the compound layer thickness.
Abstract: Titanium alloys show a relatively high strength to density ratio and good corrosion resistance. Their main disadvantage in many applications is the low hardness and hence low resistance to abrasive wear. The wear resistance of titanium alloys can be enhanced by nitriding, but the compound layer thickness is limited. The requirement of thicker compound layers could be fulfilled by a combination process. The duplex process of nitriding plus moderate temperature chemical vapour deposition (MTCVD) TiCN coating of titanium alloys appears promising. Either pressure nitriding or gas nitriding can be applied to Ti-6Al-4V. With pressure nitriding, homogeneous compound layers can be produced on complex shaped components; however, the combined process must be carried out discontinuously in two reactors, due to the different process parameters. When using gas nitriding, the combined process can be performed continuously in the CVD equipment. With the combined nitriding +MTCVD coating route, thick compound lay...
TL;DR: In this paper, the crack resistance of three different PVD coatings, TiN, Ti(C,N), and a multilayer system of alternating TiN and TiAlN, have been investigated.
Abstract: The crack resistance of three different PVD coatings, TiN, Ti(C,N), and a multilayer system of alternating TiN and TiAlN, have been investigated. The three coating systems were deposited onto substrates with a different surface roughness to study the influence of this pretreatment on the crack resistance of the coatings. First, the microstructure and state of stress of the three PVD systems were determined using X-ray diffraction and scanning electron microscopy. Then the coatings are loaded in tension in an ESEM to carry out in situ bending experiments, to assess the crack resistance of the layers. Studying the results of the bending experiments in relation to the characteristic properties of the coatings shows that the compressive residual stresses have a large influence on the moment the first cracks arise. After the initiation of the first crack, the crack resistance of TiN, deposited on the smoothest substrate, is much better than that of TiN/TiAlN and Ti(C,N). Increasing the interface roughn...
TL;DR: In this paper, the microstructures and corrosion properties of ferritic and austenitic stainless steels have been investigated after plasma and gas nitriding at 200-450° C.
Abstract: The microstructures and corrosion properties of ferritic and austenitic stainless steels have been investigated after plasma and gas nitriding at 200-450° C. Little difference was observed between the surface layers produced by the two nitriding techniques: that on ferritic X6Cr17 consisted of ferrite plus epsilon-carbide, that on the austenitic X5CrNi18-10 was the expanded austenite S phase. Pitting resistance of X5CrNi18-10 was improved by nitriding at up to 420° C, but deteriorated for higher nitriding temperatures. The presence of epsilon-carbides in the layer on X6Cr17 slightly reduced pitting resistance for nitriding temperatures up to 440° C. Annealing the nitrided specimens degraded corrosion resistance by redistributing the nitrogen in the surface layer and promoting chromium nitride precipitation.
TL;DR: In this article, the role of plasma nitriding, PVD coating (CrN, ZrN), and duplex treatment in counteracting thermal cracking, i.e. heat checking, of hot work tool steel is considered.
Abstract: Duplex treatments are becoming increasingly interesting in several technological applications through which complex forms of stresses act during service. In pressure die casting, for example, corrosion and erosion by molten metal and oxidation contribute, together with thermal fatigue, to excessive degradation of the dies and inserts. While the benefits introduced by combining nitriding and PVD coating have been assessed in counteracting soldering and wear problems, the resistance of such duplex systems with respect to thermal fatigue has not yet been established.In this work, the role of plasma nitriding, PVD coating (CrN, ZrN), and duplex treatment in counteracting thermal cracking, i.e. heat checking, of hot work tool steel is considered. Thermal fatigue tests carried out on a laboratory scale, highlight the negative role of coatings, although this result has to be partially ascribed to an unsuitable prenitriding treatment and heavy oxidation.
TL;DR: In this paper, the authors used optical microscopy, X-ray diffraction, and Vickers microhardness testing to characterise coating thickness and morphology, phase formation, and hardness.
Abstract: Heat treatment of alloys in fluidised bed reactors has been carried out for more than twenty five years Recently this technology has been used for surface engineering applications in the deposition of hard and/or corrosion resistant layers In the present study fluidised bed technology (FBT) has been used to deposit boride coatings on ferrous and non-ferrous metals and alloys The coatings were examined by means of optical microscopy, X-ray diffraction, and Vickers microhardness testing These techniques were used to characterise coating thickness and morphology, phase formation, and hardness The as produced coatings were generally characterised by very good adherence and uniformity On 0·5 wt-%C steel it was found that only one phase, Fe2B, was formed during the treatment Fluidised bed boriding of various steel substrates produced boride layers similar to those obtained by the pack cementation boriding method On pure Ti, a TiB layer was found, while on Ti-6Al-4V alloy both TiB and TiB2 phase
TL;DR: In this article, a non-chromate conversion film is formed on the surface of an Al-Z n-Mg-Cu alloy using a two-step cerium salt treatment.
Abstract: Non-chromate conversion films are formed on the surface of an Al-Z n-Mg-Cu alloy using a two step cerium salt treatment. The corrosion resistance of the alloy in chloride solution has been studied after the non-chromate treatment. It was found that the conversion film could greatly improve the corrosion resistance of the alloy to pitting and uniform corrosion in a chloride environment. The non-chromate film can retard both the anodic and cathodic processes. The treated alloy is not sensitive to the changes in the concentration of chloride ions and the pH value of the chloride solution.
TL;DR: In this paper, the corrosion performance of polyaniline-polypyrrole composite coatings was investigated and it was shown that applied potential and molar feed ratio of monomers strongly influence the corrosion resistant properties of the coatings.
Abstract: Polyaniline-polypyrrole composite coatings were electrochemically deposited on low carbon steel using an aqueous electrochemical process. In a previous investigation by the present authors, it has been demonstrated that the electrochemical deposition parameters affect the chemical structure and morphology of the coatings. In the present paper, the corrosion performance of these coatings is reported. Direct current polarisation tests were used to measure the corrosion rate of the coatings. It was shown that applied potential and molar feed ratio of monomers strongly influence the corrosion resistant properties of the coatings. It was also shown that the corrosion performance of the coatings was better when the adhesion strength of the coatings increased.
TL;DR: In this article, the development of regular, finely spaced, arrays of metal ridges and troughs, by surface treatment of aluminium has been probed by atomic force microscopy and transmission electron microscopy (TEM), assisted by radio frequency glow discharge optical emission spectrometry (RF GDOES).
Abstract: The development of regular, finely spaced, arrays of metal ridges and troughs, i.e. nanotex tures, by surface treatment of aluminium has been probed by atomic force microscopy (AFM) and transmission electron microscopy (TEM), assisted by radio frequency glow discharge optical emission spectrometry (rf GDOES). AFM reveals the grain orientation dependence of the tex ture and its increased dimensions with increased metal purity. TEM reveals atomic number contrast effects at the centres of metal ridges comprising the boundaries of the cells, thus implicating the composition and structure of the substrate. Enrichment of copper in the alloy immediately beneath the residual alumina film is evident in rf GDOES depth profiles; conversely, iron and silicon, present at similar levels as copper, are not detected. This suggests strongly that crucial impurities, i.e. silicon, are present as fine segregates in the alloy with a grain orientation dependent distribution originating from casting. The distribution of...
Journal Article•
TL;DR: In this article, three kinds of austenitic stainless steel components are treated: control rod clusters, for protection against wear ( thin walled tubes 0.4-1.0mm, with an outer diameter 9.70 mm and overall length 3.8-4.4 m), used in their thousands; in-core instrumentation flux thimbles, for protecting against wear and for promoting good sliding behaviour (diameter ∼8 mm, length ∼40 m).
Abstract: Many products for use in nuclear power stations have to meet strict requirements in terms of in-service corrosion resistance. This is why a large quantity of components are manufactured from austenitic stainless steels. Some of these, which undergo particularly heavy mechanical loadings, also require good wear and seizure resistance. A constant level of corrosion resistance and high wear resistance are two requirements that are difficult to reconcile when using classical processes. Three kinds of austenitic stainless steel components are treated : control rod clusters, for protection against wear ( thin walled tubes 0.4- 1.0mm, with an outer diameter 9.70 mm and overall length 3.8-4.4 m), used in their thousands ;in-core instrumentation flux thimbles, for protection against wear and for promoting good sliding behaviour (diameter ∼8 mm, length ∼40 m), used in their hundreds: fuel assembly socket head screws, for avoiding seizure during assembly (diameter ∼20mm. length ∼50mm), used in there tens of thousands. The processes used on an industrial scale involve the doping of the surface of the components by nitrogen species present in cold plasmas. The latter are produced either by glow discharge or microwave technologies. For each component, the present article details the relevant technologies used an an industrial scale, the metallurgical results (structure, thickness), as well as the mechanical characteristics and corrosion behaviour and possible applications to other industrial fields.
TL;DR: In this paper, a theoretical model based on a CFD (computational fluid dynamics) methodology has been developed to simulate the motion and heating of particles in a plasma jet during plasma spraying.
Abstract: A theoretical model based on a CFD (computational fluid dynamics) methodology has been developed to simulate the motion and heating of particles in a plasma jet during plasma spraying. The particle...