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This study aims to improve the corrosion resistance of the low carbon steel by cladding it with super duplex stainless steel using laser powder bed fusion process. Critical process parameters such as laser power, laser scan speed, hatch spacing, and powder layer thickness were optimized to achieve the best possible metallurgical bonding between the clad and the substrate. The evaporative losses experienced during the laser melting process resulted in clad layers with lower chromium content (12–25 wt. %) as compared to 26 wt. % of the feedstock powder. A clad thickness of 65.8 µm was achieved after melting ten 50 µm thick powder layers. The higher cooling rates associated with laser powder bed fusion resulted in fine high aspect ratio columnar grain structures with predominantly ferrite grains; however, widmanstätten austenite needles were observed with increasing laser scan speeds. Increasing scan speed had a negative impact on the thickness, corrosion resistance, and the pitting potential of the clads exposed to 3.5 wt.% NaCl aqueous solution. Clads produced at the lowest scan speeds showed comparable corrosion resistance to rolled and annealed super duplex stainless steel. [ABSTRACT FROM AUTHOR]

Results are given for laboratory research making it possible to describe identical processes in industrial direct current arc furnaces. On the basis of studying the dependence of iron specific evaporation rate in the anode spot zone on current density and time, an expression is obtained making it possible to evaluate the evaporation rate in the anode spot zone in these furnaces of any capacity. It is based on an analytical relationship of permissible current density on electrode diameter over a broad range of change. [ABSTRACT FROM AUTHOR]

The influence of mechanical stress on the electrochemical properties of ferritic steel SAE 1008 and austenitic stainless steel 301LN was studied using Scanning Kelvin Probe and Localized Electrochemical Impedance Spectroscopy (LEIS) techniques. The probeworking electrode Volta potential difference was mapped in situ under load. It was found that the influence of elastic deformation on the potential was small. Plastic deformation decreased the potential of steel by 150-300 mV, whereas the relaxation of the load from the plastic domain increased the Volta potential. However, some locations, which can contain residual stress, remained at low potential. The pre-strained surfaces were characterized by X-ray Photo Electronic Spectroscopy and by Atomic Force Microscopy. Distribution of the capacitance across strained and strain-free surfaces was studied by LEIS in boric/borate electrolyte. The plastic stress increases the capacitance and decreases the ability of the steels to passivate the surface indicating that emerging of pile-ups of dislocations create defective oxide films. [ABSTRACT FROM AUTHOR]

Societal pressures are mounting on electricity operators to operate traditional fossil-fuel power plants in an efficient and flexible manner in conjunction with renewable power plants. This requires the uses of high frequency start up – shut down load profiles in order to better match market demands. As such, high temperature/pressure components such as steam pipe sections and headers experience fluctuating mechanical and thermal loads. There is therefore an industrial need for the accurate prediction of fatigue and creep damage in order to estimate remnant component life. In the present work, a continuum damage model has been coupled with a Chaboche unified viscoplastic constitutive model in order to predict stress–strain behaviour of a P91 martensitic steel (a material used for power plant steam pipes) due to cyclic plasticity and damage accumulation. The experimental data used here are from the previous work [1] . Cyclic fully reversed strain controlled experiments (±0.4%, ±0.25% and ±0.2% strain ranges) and cyclic test with a dwell period (±0.5% strain ranges) for a P91 martensitic steel under isothermal conditions (600 °C) are utilised. The physically relevant material parameters are determined and optimised using experimental results. Although many material parameter identification procedures can be found in the literature [1–6] , there are uncertainties in determining the limits for the parameters used in the optimisation procedure. This could result in unrealistic parameters while optimising using experimental data. The issue is addressed here by using additional dwell test to identify the limits for stress relaxation parameters before using Cottrell's stress partition method to identify the limits for strain hardening parameters. Accumulated stored energy for damage initiation criterion and damage evolution parameters are also extracted from the experimental results. The estimated failure lifetimes for ±0.4%, ±0.25% and ±0.2% cases are 1600, 4250 and 9500 cycles, respectively, as opposed to 1424, 3522 and 10512 cycles as given by experiments. [ABSTRACT FROM AUTHOR]

The object of the pulsed Electron beam designed in this work is to modify the surface layer of metals by melting through uniform adiabatic heating in the order of a few microseconds. With a maximum diameter of the beam 70 mm, current densities of as high as 30 A/cm2, and power density on the surface of the material being 100 joule/cm2 is sufficient to melt 80 micron deep of steel with an area of 50 cm2 . The energy of the pulse is stored in a capacitor bank of about 100 kV and 5 kJ. It is shown, that if the change of inductance of the circuit is equal to the inductance of the pulse source maximum energy can be delivered to the surface. A load lock is constructed so to cover more surface areas than 50 cm2. [ABSTRACT FROM AUTHOR]

There has been significant progress in the use of laser induced breakdown spectrometry (LIBS) as a method of monitoring steel production in real time. This has the benefits of both time and cost saving. There has been a drop in the number of papers reporting methods for the analysis of fuels. This may be a function of the drop in oil prices leading to reduced finance for research. However, the determination of S is one of the hot topics in this sample type. This is possibly a consequence of companies attempting to meet the increasingly strict regulations on S emissions. Analytical methodology, e.g. LA-ICP-MS, LIBS or XRF, which produces minimal damage to the samples is still increasingly popular. This is especially true for historical or archaeological sample types, e.g. paintings, pottery and old documents; but is also applicable to forensic materials. Often, with these sample types, the analytical data are then treated using chemometrics packages so that provenance may be determined or patterns detected. Similar methodology was used for the identification of different plastics types, facilitating sorting and re-cycling. The analysis of nanoparticles is an increasingly popular subject area. Simple introduction of samples containing nanoparticles through a standard nebuliser/spray chamber sample introduction system is often complicated by the particles agglomerating. This leads to under-estimations of the concentrations present. Single particle analysis has continued to be a popular research area with real samples now being extracted and analysed rather than standard solutions. Similarly, field flow fractionation coupled with ICP spectrometry (sometimes also in conjunction with single particle analysis) has also been used to characterize nano-particulates and to distinguish between particulate and ionic species. [ABSTRACT FROM AUTHOR]

In the present paper the problem of monotonically compressed concrete columns is studied numerically, accounting for transverse steel reinforcement and concrete cracking. The positive confinement effect of the ties on the core concrete is modeled explicitly and studied in the case of distributed or concentrated vertical load. The main aim is to investigate the influence of transverse reinforcement steel characteristics on the column load carrying capacity and ductility, in order to provide an evaluation about some standards requirements about the class and ductility of steel to be used for ties. The obtained results show that the influence of transverse reinforcement steel class of ductility is negligible both on the column load carrying capacity and on its ductility. Also the dissipated energy is basically unchanged. In view of these evidences, some standards requirements about the steel class of ductility to be used for ties appear to be rather questionable. [ABSTRACT FROM AUTHOR]

Abstract: Aim of this work is proposing a systematic design approach for wear resistant components produced by Powder Metallurgy (PM). Wear is a cause of failure for many industrial PM parts. Gears and cams, for example, are subjected to rolling and rolling–sliding wear, dry or lubricated depending on the applications. The design criteria are mostly empirical, thus resulting fully conservative, sometimes excessively conservative. A need for defining design criteria for wear resistant PM parts is thus revealed, to exploit at best the specific characteristics of both technology and materials. The focus is on the case of components subject to dry wear. Particularly, this work analyses the parameters affecting dry rolling–sliding wear of PM steel parts. Dry rolling–sliding tests were performed on different PM steels, wear mechanisms were investigated and materials were characterized to obtain the knowledge base for the proposed design methodology. A diagram indicating the main steps for the design of wear resistant PM parts is described and applied. This approach can also be applied to other wear mechanisms found in PM steel parts. [Copyright &y& Elsevier]

Optimisation is the process of trying to find out the best possible solution to any problem satisfying constraints. Soft computing is the class of methods which have been inspired by the biological computational methods and nature's problem-solving strategies. Currently, these methods include neural networks, evolutionary computational models such as genetic algorithms, random cost and linguistic models such as fuzzy logic. Ant colony optimisation (ACO) is one such method applied for large engineering combinatorial optimisation problems. A design procedure utilising an ACO technique is developed for discrete optimisation of reticulated steel space trusses. The ACO algorithm is motivated by the analogy with natural phenomena, in particular the ability of a colony of ants to 'optimise' their collective endeavours. In this paper, the computational implementation of ACO is presented in a structural design context. The objective function considered is the total weight/cost of the structure subjected to material and performance constraints in the form of stress and deflection limits. In the case of reticulated space trusses, the design variables are the cross-sectional areas of members belonging to various groups. The objective function and constraints are obtained by using structural analysis package FEAST (Anonymous, 1995. FEAST user manual. Trivandrum, India: SEG, SDS Group, ISRO, VSSC) in case of structures subjected to static loading and SAP90 (Anonymous, 1990. SAP90, ETABS, SAFE - computer software for structural and earthquake engineering. Berkeley, CA: Computers and Structures) for earthquake loading for reticulated steel space trusses. The numerical examples presented demonstrate the computational advantage of the ACO for large-scale optimisation problems. [ABSTRACT FROM AUTHOR]

In this study, the dynamic reactive wetting of low-carbon, interstitial-free (IF) steel by liquid zinc was investigated. In situ contact angle measurements of a liquid zinc droplet on three steel plates that contained a fixed Mn content (0.4 wt pct) and different Si concentrations (0.1, 0.3, and 0.7 wt pct) were carried out with two charge-coupled device cameras that operated at different recording rates, 3000 frames/second and 6 frames/second. The observed contact angles for the three steel plates started at almost the same value but gradually decreased at different rates with increasing time. The steel plate of medium Si content (0.3 wt pct) showed the best wetting behavior among the tested samples. The wetting characteristics were examined by analyzing the surface coverage, the morphology, and the thickness of the nanostructured oxides that formed on the steel plates during the annealing process. [ABSTRACT FROM AUTHOR]

The present paper reports the results of a blind round robin test dedicated to the measurement of the retained austenite content of different TRIP assisted multiphase steels. Various surface and volume techniques, i.e. light microscopy, X-ray diffraction, electron backscattered diffraction (EBSD), magnetic saturation, thermal diffusivity and laser ultrasonics, were used by different partners. The compiled results show a quite large variability of the estimated retained austenite content, particularly for well established techniques, such as X-ray diffraction (XRD) and magnetisation. On the other hand, emerging techniques like EBSD, thermal diffusivity and laser ultrasonics warrant further investigations. [ABSTRACT FROM AUTHOR]

The study was carried out to evaluate the effect of the tempered martensite fraction in the fatigue behaviour of type R4 structural steel as used, quenched and tempered, in the manufacture of chains for offshore mooring systems. As the manufacturing process for these uses flash welding, the study also includes welded joints of the same steel. Different fractions of martensite were achieved by means of variations in the austenitization temperature of the material and the fatigue resistance of the tempered test pieces was evaluated by means of the kinetics of crack growth of crack under cyclic loading at a constant amplitude. The results indicated that an increase in the amount of ferrite was associated with an increase in the number of cycles to material failure, and for the same microstructural condition, the fatigue life of the welded joint was always lower than that of the base material. Finally, the fatigue behaviour of the test pieces is presented and discussed on the basis of the mechanical properties and toughness of the material. [ABSTRACT FROM AUTHOR]

Due to strain-induced martensitic transformation (SIMT), the strength, ductility and toughness of TRIP steel are enhanced. The impact deformation behavior of TRIP steel is very important because it is investigated to apply it for the shock absorption member in automobile industries. However, its behavior is still unclear since it is quite difficult to capture the transformation behavior inside the materials. There are some opinions that the deformation characteristics are not mainly depending on the martensitic transformation due to heat generation by plastic work. Here, the impact compressive deformation behavior of TRIP steel is experimentally studied by Split Hopkinson Pressure Bar (SHPB) method at room temperature. In order to catch SIMT behavior during impact deformation, volume resistivity is measured and a transient temperature is captured by using a quite thin thermocouple. Then, a finite element simulation with the constitutive model for TRIP steel is performed. The finite element equation can be derived from the rate form of principle of virtual work based on the implicit time integration scheme. Finally, the results between the computation and experiment are compared to confirm the validity of computational model. [ABSTRACT FROM AUTHOR]

We study the physicochemical and mechanical properties of galvanic coatings based on tungsten carbide and zirconium diboride and obtained as a result of electrolysis of ionic melts on steels. The thickness of the coatings does not exceed 100 µm. The application of these coatings makes the wear resistance of steel specimens 6–9 and 8–9 times higher and their abrasion resistance 7–8 and 8–10 times higher, respectively. [ABSTRACT FROM AUTHOR]