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A series of reciprocating wear tests were performed on the deep cryogenically treated and conventionally heat-treated samples of 100Cr6 bearing steel to study the wear resistance. The worn surfaces as well as the wear debris were analyzed by scanning electron microscopy. The improvement in wear resistance of the deep cryogenically treated samples ranges from 49% to 52%. This significant improvement in wear resistance can be attributed to finer carbide precipitation in the tempered martensitic matrix and the transformation of retained austenite into martensite. X-ray diffraction analysis shows that the volume fraction of retained austenite in the conventionally heat-treated samples is 14% and that of the deep cryogenically treated samples is only 3%. � University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2014.

The ability to co-deposit particulate matter in a matrix of electroless nickel has led to a new generation of composite coatings. Polycrystalline diamond is one of the many varieties of particulate matter that can be co-deposited. Composite diamond coating is a regenerative layer of diamond particles dispersed in a hard electroless nickel matrix. In this work, experiments have been carried out to study the effect of heat treatment on the wear characteristics of the electroless composite coating containing diamond particles. The results indicate substantial increase in wear resistance after heat treatment. For wear analysis, in order to overcome the difficulties in the most common 'weight loss' method, X-ray diffraction method is used. Also the concept of internal standard method of quantitative X-ray diffraction analysis with suitable modifications is employed for the study of removal of diamond particles from the matrix. Superior integrity of the diamond particles with the matrix of the coating is observed for the specimens when heat treated to around 350 �C because of the formation of phosphides. But increasing the heat treatment to about 500 �C affects the wear resistance. � 2008 Elsevier B.V. All rights reserved.

Electroless nickel (EN) coating is a well established surface engineering process that involves deposition of a metal-metalloid alloy coating on various substrates. The effect of surfactants on the surface roughness, microhardness and microstructure of electroless Nickel-Phosphorus (EN) surface protective coating obtained from an alkaline bath is presented in this paper. In this study the influence of surfactants sodium dodecylsulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) on the surface roughness, microhardness and microstructure of coated samples are investigated. EN deposits with addition of surfactant SDS and CTAB at a concentration of 0.6�g/l produce a smooth surface and the average roughness value (Ra) is 1.715�?m for SDS and 1.607�?m for CTAB which is less than the Ra value of EN deposit without surfactant addition (1.885�?m). The mean average roughness value (Ra) with addition of surfactant is 1.796�?m. It was found that without surfactant the micro hardness value of as-coated condition was 450�Hv. The micro hardness value increased to 685�Hv with addition of SDS and 675�Hv with addition of CTAB. The complete experimental details, results obtained and their analysis is presented in this paper. � 2008 Elsevier B.V. All rights reserved.

Carbon nanotubes (CNTs) have been synthesized using the arc discharge method with a rotating graphite disc as the cathode. Arcing was carried out in open air and without the use of catalysts. The current density was maintained constant through out the experiment, while, the rate of rotation of the cathode and atmosphere under which arcing was carried out were changed during experimentation. Characterization of the samples produced indicates that rotation of the cathode has a significant impact on the quality and yield of the process. It is proposed that rotation of the cathode drags plasma formed between two electrodes away from high temperature region. This results in a sudden quenching of the reactive plasma. The time available for nucleation and growth phenomena is significantly reduced and thus leads to the formation of highly graphitic multi walled CNTs (yield 60%) and traces of double walled CNTs. � 2008 Elsevier B.V. All rights reserved.

A model for the nucleation of ferrite on austenite grain boundaries and the growth of these nuclei along the grain boundary and into the grain, is developed. A cellular automaton algorithm, with transformation rules based on this model, is used to simulate the decomposition of austenite into ferrite. When performed under continuous cooling conditions, the simulations give an insight into the competition between nucleation and early growth, which determines the variation of ferrite grain size with the cooling rate and with austenite grain size. The number of ferrite grains per austenite grain, ferrite grain size and the kinetics of ferrite formation are obtained as a function of the cooling rate and austenite grain size. Contour plots of the volume fraction of ferrite in the cells at different times, enables visualization of the ferrite growth process.

Electroless Nickel-Phosphorus deposits with phosphorus content of 4.35, 5.45, 6.80, 8.10 and 9.12 Wt.% P were made, on mild steel substrates. The deposits were annealed at 60, 100, 200, 300, 330, 360, 400 and 600°C for 2 hours. The crystallization process of these deposits was studied using X-ray line profile analysis, differential scanning calorimetry and microhardness. The X-ray diffraction pattern of all the deposits indicated the presence of crystalline and amorphous phases coexisting in the as deposited condition. The lattice disorder in the crystalline phase increased with increasing phosphorus content. Profile refinement techniques have been used to separate the crystalline nickel (111) reflection from the amorphous profile. The separated (111) and (222) profiles of nickel were used for crystallite size and microstrain analysis. The crystallite size of nickel was found to vary from 50A in the as deposited condition to about 600A in the fully annealed state (400°C). The crystallite size increased sharply above 300°C, indicating the onset of precipitation. The microhardness values showed typical precipitation hardening type of behavior, increasing from an initial value of about 450 VHN in the as deposited state to the peak hardness of about 825 to 950 VHN, corresponding to a temperature range of 360 to 400°C. Differential scanning calorimetry of these deposits, indicated only one major reaction between 325 to 375°C. Ni 3 P has been identified as the final stable precipitate at 600°C.

Electroless nickel-phosphorus (EN) deposits with and without addition of surfactants were made on mild steel substrates. Two surfactants namely sodium dodecylsulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB) were used in the study. The EN coated samples were characterised using X-ray diffraction analysis and transmission electron microscopy. The XRD pattern of all the deposits indicated the presence of crystalline and amorphous phases coexisting in the as deposited condition. Profile refinement techniques have been used to separate the crystalline nickel (111) reflection from the amorphous profile. The crystallite size of nickel was found to vary from 200 nm in the as deposited condition to 80 nm with addition of surfactant. TEM study reveals a nano crystalline structure of the deposit in as plated condition and an amorphous structure with addition of surfactants. With addition of surfactants adhesion was good. The coating thickness varied from 12.7 ?m to 32.2 ?m with addition surfactants. Copyright � 2012 Inderscience Enterprises Ltd.

The effect of surfactants sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB) on the surface roughness, surface morphology and surface topography of electroless nickel (EN)-phosphorus surface protective coating obtained from an alkaline bath is presented in this paper. In this study the influence of surfactant concentrations on the surface roughness of coated samples were investigated. It was observed that the surface roughness, surface morphology and surface topography of Ni-P coating were clearly influenced by the addition of surfactants SDS and CTAB. EN deposits with addition of surfactant SDS and CTAB at a concentration of 0.6 g/l produce a smooth surface and the average roughness (Ra) value is 1.715 ?m for SDS and 1.607 ?m for CTAB which is less than the Ra value of EN deposit without surfactant addition (1.885 ?m). The mean average roughness (Ra) value with addition of surfactant is 1.796 ?m. EN deposit with addition of surfactants consists of a significant fraction of particles of nickel. In the presence of SDS, fine nickel particles have dispersed uniformly on the substrate surface resulting in smoother surface finish of the deposited layers. In the presence of CTAB, at lower concentrations (upto 0.6 g/l) coalescence of nickel particles have been deposited on the substrate surface and at the higher concentration (above 0.6 g/l) uniformly improved surface finish of the deposited layer is resulted. The complete experimental details, results obtained and their analysis are presented in this paper. � 2008 Elsevier B.V. All rights reserved.

The effect of surfactants on the surface roughness, hardness and microstructure of electroless nickel-phosphorus (ENi-P) coating obtained from an alkaline bath is presented in this paper. In this study the influence of surfactants such as Sodium Dodecyl Sulfate (SDS) and Cetyl Trimethyl Ammonium Bromide (CTAB) on the electroless Ni-P coated samples has been investigated. The variation on surface morphology was examined using Scanning Electron Microscope (HRSEM), surface roughness were measured using a stylus instrument and surface hardness were measured using a hardness tester. It was observed that the surface roughness, surface hardness and surface morphology of ENi-P coating were clearly influenced by the surfactants. Copyright � 2008, Inderscience Publishers.

In this work, the effect of process parameters such as stabilizer concentrations and plating bath temperature of the electroless Ni-P on efficiency and crystallinity are investigated. Both the nickel recovery and coating efficiencies are defined, quantified and analyzed by varying the above stated basic input process parameters. The integral breadth, crystallite size, microstrain and the relative proportions of amorphous and crystalline phases present in the coating are obtained using the X-ray diffraction technique and analysed. ? 2005 Elsevier B.V. All rights reserved.

In this work Carbon nanotubes have been synthesized by arc discharge in open air. A TIG welding ac/dc inverter was used as the power source for arc discharge. During each run of the arc discharge based synthesis, the anode was a low purity (?85% C by weight) graphite rod. The effect of varying the atmosphere on the yield of soot of the carbon nanotube containing carbon soot has been studied. Various soots were produced, purified by oxidation and characterized to confirm formation of carbon nanotubes and their relative quality, using transmission electron microscopy, Raman spectroscopy, and XRD. It was found that the yield of soot formed on the cathode is higher when synthesis is carried out in open air than when carried out in a flowing argon atmosphere. When synthesized in open air, using a 7.2-mm-diameter graphite rod as anode, the yield of soot was around 50% by weight of the graphite consumed. Current and voltage for arcing were at identical starting values in all the experiments. This modified method does not require a controlled atmosphere as in the case of a conventional arc discharge method of synthesis and hence the cost of production may be reduced. Copyright ? 2005 American Scientific Publishers All rights reserved.

The ability to co-deposit particulate matter in a matrix of electroless nickel has led to a new generation of composite coatings. Polycrystalline diamond is one of the many varieties of particulate matter that can be co-deposited. Composite diamond coating is a regenerative layer of fine diamond particles dispersed in a hard electroless nickel matrix. In this work, experiments have been carried out to study the effect of heat treatment, particle size and phosphorus content on the wear characteristics of the composite electroless coating containing diamond particles. The results indicate substantial increase in wear resistance after the coated sample containing 9-10 wt.%. P content having fine diamond particle size is annealed around 350�C. (C) 2000 Elsevier Science S.A. All rights reserved.The ability to co-deposit particulate matter in a matrix of electroless nickel has led to a new generation of composite coatings. Polycrystalline diamond is one of the many varieties of particulate matter that can be co-deposited. Composite diamond coating is a regenerative layer of fine diamond particles dispersed in a hard electroless nickel matrix. In this work, experiments have been carried out to study the effect of heat treatment, particle size and phosphorus content on the wear characteristics of the composite electroless coating containing diamond particles. The results indicate substantial increase in wear resistance after the coated sample containing 9-10 wt.%. P content having fine diamond particle size is annealed around 350 �C.

[No abstract available]

Electroless nickel-phosphorus coating has been deposited onto plain carbon steel specimens by using an alkaline bath based on NiCl2 as source of nickel cations. The tribological behaviour under dry non-lubricated conditions has been evaluated by employing the pin-on-disc test method. Two surfactants namely sodium dodecyl sulphate and cetyl trimethyl ammonium bromide were added to the EN bath for the first time in the similar kind of study. The influence of the surfactants on the hardness, friction and wear behaviour of the coatings was investigated and compared against the samples produced without addition of surfactants. Copyright � 2010 Inderscience Enterprises Ltd.

In this work, an experimental study has been carried out on the comparative performance of TiCN and TiAlN coated tools in machining of AISI 4340 hardened steel under dry, wet and minimum fluid application conditions and the analysis of results are presented. Cutting force, cutting temperature, surface finish and flank wear are compared in all the cases to understand the performance. Then, the relative influences of the machining and the minimum fluid application parameters on the machining performance of tools have been analysed and presented in this paper. � 2008, Inderscience Publishers.

Examen de la transformation ferritique dans les toles d'aciers inoxydables austenitiques 308Cb et 309Cb soudees par un procede de soudage a l'arc microplasma

O elemento combustível de um reator do tipo LMFBR consiste em um feixe de barras de arranjo triangular com espaçadores helicoidais, contido em um duto hexagonal. Neste trabalho, desenvolve-se o programa ATHEL que incorpora um método determinístico para o cálculo da distribuição de temperatura, baseado em modelos para o cálculo do coeficiente de atrito e redistribuição do escoamento axial, para o escoamento transversal e a mistura térmica turbulenta. Os resultados obtidos foram comparados com dados experimentais disponíveis na literatura, apresentando precisão semelhante aos códigos de análise mais complexa, como é o caso do COBRA e THI3D. O modelo físico utilizado e o programa desenvolvido permitem a realização de análise termohidráulica de reatores de maneira rápida e econômica. The fuel elemento f na LMFBR consists of a bundle of rods wrapped with an helical wire as spacer, surrounded by an hexagonal duct. In the present work, the ATHEL code is developed a deterministic method to calculate the temperature distribution based on models for the prediction of the friction factor and flow redistribution, for the cross flow and for the turbulent eddy dyffusivity. The obtained results are compared to available experimental data in the literature, yielding equivalent accuracy to more complex analysis code, such as COBRA and THI3D. The developed physical methods and code allow thermalhydraulics analysis of reactors in a very fast and inexpensive way.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO BANCO NACIONAL DE DESENVOLVIMENTO ECONÔMICO E SOCIAL Este trabalho prossegue a investigação sobre convecção forçada com ebulição de película em tubos verticais, na qual o regime de escoamento consiste de gotículas de líquido dispersas em vapor superaquecido. Um procedimento de cálculos já existe (baseado em um tamanho único médio de gota que sofre colapso e evapora ao longo do tubo) para determinar os fenômenos cinéticos e de transferência de calor. O principal objetivo do presente trabalho é introduzir uma mais realista distribuição nos tamanhos de gota no procedimento de cálculo com o intuito de determinar a validade do uso do tamanho único de gota para representar a real distribuição. Dados experimentais já existentes para ebulição de película de nitrogênio (70.00 menor do que G menor do que 190.000 ibm/hr/ft2 e 5.000 menor do que q / A menor do que 25.000 Btu/hr/ft2 em tubos de diâmetro interno de 0.228 menor do que D menor do que 0.462 polegadas e 8 pés de comprimento) foram usados no desenvolvimento do modelo analítico tanto para o estudo com tamanho único de gota como para tamanho múltiplo de gota. Para tamanho múltiplo de gota, o critério do número de Weber foi utilizado para prever o colapso da gota que se divide em 9 gotas menores de vários tamanhos. Os resultados do estudo com tamanho múltiplo de gota forneceram resultados semelhantes aos com tamanho único de gota, indicando de gota para descrever o fenômeno da ebulição de película com escoamento disperso. Também está incluída uma compilação de propriedade do nitrogênio, necessárias para os estudos deste trabalho. This work further investigates forced convection film boiling in vertical tubes, in whitch the flow regime consist of dispersed liquid droplets in a superheated vapor. Calculation procedures already exist (based on a single average size droplet that breaks up and evaporates as it flows along tube) for determining the kinetic and heat transfer phenomenas. The principal objective of the present work is to introduce a more realistic distribution of droplet in a superheated vapor. Calculation procedure already axist (based on a single average size droplet that braks up and evaporates as it flows along tube) for determining the kinetic and heat transfer phenomenas. The principal objective of the present work is to introduce a more realistic distribution of droplet sizes into the calculation procedure in order to determine the validity of using a single droplet size to represent a real distribution. Previous experimental data for film boiling of nitrogen (70.000 less than G less than 190.00 lbm/hr/ft2 and 50.000 less than q/As25.000 btu/br/ft2 in tubes of 0.22 less than D less than 0.462 inch diameter and 8 feer long) were usad in developing analytical models for both the single droplet size and multiple droplet size studies. For the multiple droplet size distribution, a critical Weber number was utilized to predict the breakup of a droplet into approximately 9 smaller droplets of various sizes. The results of the multiple droplets of various sizes. The results of the multiple droplet study compare well with those of the single droplet studies, thus indicating the validity of using the single droplet size model for predicting phenomena in dispersed flow boiling.