High Alloy Steel Research Articles

Determining the Diffusion Coefficient in Practice of Nitrogen and Carbon for Nitro-Carburizing High Alloy Steel

Determining the Diffusion Coefficient in Practice of Nitrogen and Carbon for Nitro-Carburizing High Alloy Steel

Influence of production technology of powder high-speed steels on the complex of formed properties

The authors analyzed the state of tool production in Russia. The main manufacturing companies and the main brands of materials used in the production of domestic tools are highlighted. Powder high-speed steels are practically not used in the domestic market, but they are widely distributed in the foreign market of tool steels due to their significant advantages in terms of basic and technological properties (including the possibility of using high-carbon and high-alloy high-speed steels). There is a new group of economically alloyed tungsten-free high-speed steels with a high content of carbon and vanadium, which are practically impossible to manufacture and apply in our traditional technology due to low technological properties. The authors give recommendations on the technology of manufacturing such steels by powder metallurgy and on the modes of their heat treatment. The paper studies a set of properties of these steels, including: basic mechanical properties (hardness, bending strength, toughness, and heat resistance), basic technological properties (pressure, cutting, grinding) and operational properties (evaluated by tool durability during turning). Structural and phase compositions of the steels and their influence on the basic and technological properties were investigated. The compaction mode affects the density of the billets. The paper presents distribution of alloying elements in the microstructure of powder high-speed steel and results of their relative grindability. Also the durability of tools was tested. There are significant advantages of high-carbon high-vanadium high-speed steels, especially in terms of technological properties, compared with traditional high-speed steels. It is possible to produce high-alloy tool steels using inexpensive carbide-forming alloying elements. The steels under consideration can be used to manufacture a wide range of tools, including hot-forming die tools. The use of powder technology opens up the prospect of developing universal economically alloyed powder tool steels.

INFLUENCE OF BORON, ZIRCONIUM, AND TELLURIUM ON THE IMPACT TOUGHNESS OF X8CrNiS18-9 STEEL

Steel X8CrNiS18-9 (standard EN 10088-3: 2005) is the most commonly used from the group of austenitic stainless steel in terms of machinability. The content of sulphur present in the steel from 0,15 to 0,35% has the exclusive task to improve the machinability. However, while sulphur improves machinability it simultaneously reduces the resistance of steel to corrosion but also affects the decrease in mechanical properties particularly steel toughness. Due to its harmful effect on the steel, as well as the fact that the non-metallic inclusions are insufficiently tested for this type of high-alloy steel the aim of this study is to determine the appropriate microalloying possibility to modify the non-metallic inclusions. The aim of this work is that explore the influence of boron, zirconium, and tellurium on the impact toughness of the mentioned steel. Change of impact toughness, depending on the chemical composition of the steel is simulated with the Matlab program.

Numerical Model of the Double-Pipe System with Protective Layer

Nowadays, higher performance is being sought in newly built power plants. The efficiency of power plants is mainly achieved by maximizing the steam parameters. Consequently, ever more expensive high-alloy steels are being used. For this reason, design concepts, in which high efficiency with lower investment costs are becoming increasingly popular. Such an innovation is the double-pipe system with a protective coating, which provides thermal insulation for the primary pipe in which the supercritical steam flows. This pipe is also cooled by an external flow by the steam with lower parameters. The article presents the developed two-dimensional numerical model. The use of the Galerkin method enables the complete transient analysis of a double-pipe system to be carried out, considering temperature-dependent material properties. The numerical model was compared with the computational fluid dynamics model. The temperature gradient in the inner pipe wall with and without coating was determined. In addition, the response of the wall temperature to a change in steam temperature was investigated. As observed, the protective layer can improve boiler performance characteristics when applied to thick-walled boiler components. It can also enable the use of less demanding steel.

Disposable Wearable Sensors Based on Nanocellulose for Biomedical Applications

Monitoring of human motor and muscle activity is used in many areas, from prosthetics during rehabilitation to training monitoring of athletes. Sensors for these tasks are usually made of flexible polymers and require recycling after the expiration date. Nanocellulose (NC) can be used as a biodegradable base for this type of sensor. The development of low-cost disposable sensors that do not require disinfection and cleaning is relevant. NC is a composite nanoscale structure of cellulose fibers (fibrils) with a high aspect ratio. The paper aim is to develop disposable wearable biodegradable bend sensors based on nanocellulose using vacuum synthesis methods and the study of their characteristics. Nanocellulose was synthesized by the TEMPO method. The sensors were created by means of magnetron sputtering of Ti/Ni or Cr/Ni thin films at the surface of nanocellulose. Measuring stand was developed to determine the change in resistance due to the bending of the sensor. It’s mechanical part consists of an elastic deformation plate made of high-alloy steel, which can be bent using a micrometric screw. The change in resistance is linearly related to the elongation of the measured sample. A Wheatstone bridge and a 24-Bit ADC HX711 were used to measure the change in resistance. During testing of the sensor for analysis of muscle activity, the sensor element was attached to the human skin with the help of medical glue BF-6. The obtained sensors were tested for biodegradability. The samples were placed in the ground at a depth of 20-30 mm. The mass of nanocellulose samples was measured using a high-precision digital balance EDIS 50 (50/0.001 g) with a built-in level. The optimal ratio of the value of sensitivity and reversibility is observed in the range of the nominal resistance of the nickel film from 10 to 100 Ohms. This is due to an increase in the surface area of ​​the Ni film, which leads to an increase in sensitivity, but at the same time there is a decrease in the repeatability of the characteristics due to a greater influence of the heterogeneous structure of nanofibrillated cellulose. In addition, sensors with different buffer layer materials - Ti and Cr - were selected for testing. For titanium-based sensors, the maximum sensitivity coefficient is 0.312%, while the deviation of the sensor signal after one bending-unfolding cycle (reversibility) is less than 0.001%. Chromium-based sensors have significantly higher sensitivity (0.9753%), but worse reversibility (7.14%). Sensors based on the Cr buffer layer showed poorly reproducible results in the cyclic mode of operation, namely: there are significant fluctuations in the signal amplitude (up to 50-60%) already after the second bending-unfolding cycle. Therefore, despite the high sensitivity of such sensors, they are unsuitable for analyzing human motor and muscle activity/ The sensors based on the Ti buffer layer showed good response (2.5-3%) and good repeatability and resistance to cyclic bending (30 times). It can be seen that the obtained dependencies are approximated by a linear law. Some deviation from linearity is obviously related to the inhomogeneity of the Ni thin film. Also, the sensors showed a good loss of mass (40% in 9 weeks) during the biodegradability test, which confirms their ability to decompose under the influence of atmospheric phenomena. So, in this work, disposable wearable sensors on a nanocellulose substrate were synthesized for the evaluation of motor and muscle activity of a person. It was found that such sensors can be used to test of finger and biceps movement during at least 10-30 full flexion-extension cycles. For test of elbow movement, it is planned to synthesize a high-elastic composite material based on nanocellulose and bioelastic material (for example, polyvinyl alcohol). Thus, the proposed sensor manufacturing technology makes it possible to obtain cheap, light, flexible disposable wearable sensors that do not require further disposal after the end of operation.

Different ways for HAZ microstructure preparation and testing on high alloy steel

The heat-affected zone (HAZ) is the part of the weld that is affected by the heat generated by the welding process during welding. The microstructure of the HAZ is very heterogeneous and consists of different zones such as the coarse-grained HAZ, the fine-grained HAZ, the intercritical HAZ, and the over-tempred HAZ [1]. All these zones are very narrow and their properties are slightly different. These properties affect the integrity of the entire weld, so in many cases the HAZ may be the worst part of the weld. Another challenge is determining the properties of the individual HAZ regions, since the entire HAZ is very narrow and inhomogeneous. For this reason, many properties cannot be determined accurately, with the exception of a few, such as hardness, for which only a small region is sufficient for measurement. Therefore, it is important to know how to produce the individual microstructure of a HAZ in a wider range of the material in order to determine the actual properties of such a HAZ. One of the ways is to measure the welding parameters during welding to determine the actual influence of the thermal cycle on the formation of the invidual microstructure of HAZ in the weld. Moreover, it is crucial to repeat this weld thermal cycle in an unaffected base metal on a thermal welding simulator to obtain a suitable microstructure of the HAZ [1,2]. The second option is to prepare the microstructure in the furnace by slow heating which is followed by rapid cooling [1,3]. Both processes must be precise and accurate to obtain suitable HAZ microstructures. This article addresses the challenges of producing HAZ microstructures on the high-alloy steel CT781, which is widely used in the automotive industry for parts subjected to high dynamic loads.

Impact of Thermophysical Properties of High-Alloy Tool Steels on Their Performance in Re-Purposing Applications

Resource efficiency and circularity in the context of sustainability are rapidly gaining importance in the steel industry. One concept regarding circular economy is "repurposing". In the context of this work, worn-out machine circular knives are used to produce new chisels for woodturning. The chisels can be extracted parallel or perpendicular to the rolling direction of the primary production process, resulting in an associated carbide orientation of the repurposed tool. The rolling direction, and therefore carbide alignment, will influence the wear resistance and the thermophysical properties, whereby the thermal conductivity will determine the temperatures at the tip of the chisel. Therefore, the thermal conductivity was investigated with the dynamic measurement method, where the specific heat capacity, density and thermal diffusivity of the extracted chisels and industrial reference chisels were measured separately. Moreover, the electrical resistivity was measured in order to calculate the electronic thermal conductivity according to the Wiedemann-Franz-Lorenz law. It was shown that all of these parameters exhibited different degrees of variability with rising temperature. In a detailed analysis, the thermal diffusivity could be identified as an essential parameter of thermal conductivity. By taking two conventional chisels with different chemical compositions and heat treatments into account, it can be seen that the microstructure determines the thermophysical properties. Considering the carbide direction, the chisels that were extracted parallel to the rolling direction showed differing thermophysical properties. Therefore, the carbide orientation is shown to play a significant role regarding the heat dissipation at the cutting edge, because differences, especially in the electronic thermal conductivity in the parallel and perpendicular extracted chisels, can be measured. In addition to the wear resistance factor, the thermal conductivity factor now also supports the removal of the repurposed chisels parallel to the rolling direction.

APPLICATION OF FRACTIONAL FACTORIAL DESIGN FOR ANALYSIS OF CUTTING ENERGY IN TURNING

Energy consumption in machining processes is a very important aspect that has been given increased importance in recent times. This article, therefore, proposes an approach for identification of the most important main and interaction effects of turning parameters regarding the cutting energy in dry longitudinal single-pass turning of low-alloyed and high-alloyed steels. Fractional factorial design was applied to arrange five parameters, namely, depth of cut, feed rate, cutting speed, rake angle and cutting edge angle at two levels. Based on the cutting tool manufacturer’s machining calculator and well-known analytical relationships, cutting energy was estimated for sixteen cutting regimes for both workpiece material groups. The analysis of obtained results involved the analysis of main and interaction effects, determination of statistically significant effects and development of cutting energy prediction models.

Influence of microstructure on hydrogen trapping and diffusion in a pre-deformed TRIP steel

Austenitic steels are known to exhibit a low hydrogen diffusion coefficient and hence a good resistance to hydrogen embrittlement. Therefore, it is an experimental challenge to investigate their hydrogen diffusion properties. In this study, the electrochemical permeation technique is used to determine the hydrogen diffusion coefficients in different pre-deformed states (φ = 0, 0.32, 0.39, 0.49) of the high-alloy austenitic TRIP steel X3CrMnNiMoN17-8-4 in a temperature range of 323 K–353 K. In combination with microstructural analysis, a correlation between phase transformation from γ-austenite to α′-martensite and dislocation density is shown. As a result of the lattice transformation from fcc to bcc, the diffusion rate of hydrogen is significantly increased (Dapp,φ = 0 = 3.6 × 10−12 cm2 s−1, Dapp, φ = 0.32 = 1.6 × 10−11 cm2 s−1at 323 K). With higher degrees of deformation, the dislocation density also increased in the martensite islands, resulting in a degressive growth of the diffusion coefficient (Dapp, φ = 0.39 = 5.3 × 10−11 cm2 s−1, Dapp, φ = 0.49 = 1.1 × 10−10 cm2 s−1at 323 K). Moreover, detailed calculations are performed to describe the way of hydrogen trapping and to give a possible mechanism of diffusion.

Microstructure and mechanical properties of M2 high speed steel produced by electron beam melting

M2 high-carbon and high-alloy steel was prepared by electron beam melting (EBM) in this study. The optimal process parameters were explored by varying the beam current, scan speed, and scanning spacing. The microstructure and properties of manufactured samples, including chemical composition, grain morphology, texture, phase composition, the relative density, compressive strength and ductility were examined by means of SEM, TEM, EBSD, as well as compression testing. The results show that the line energy is closely related to the surface morphology and microstructure of the formed samples. High line energy leads to bulging of the sample surface. Decrease of the line energy results in an increase of the cooling rate that contributes to the refinement of grains and carbides of the as-built samples. However, when the line energy is too low, spheroidizing phenomenon takes place at the sample surface, and the density of sample is decreased significantly. The optimal combination of process parameters is achieved with 7.8 mA scanning current, 2.4 m/s scanning speed and 0.1 mm scanning spacing. The relative density of the sample can reach to 99.6%, with 793HV microhardness and 2860 MPa compressive strength. Due to the rapid cooling and gradient “annealing” process during EBM, the microstructure of the single-scan layer presents a “sandwich” structure composed of fine equiaxed crystals, columnar dendrites and large equiaxed crystals in the heat-affected zone.

Electroplastic effect at tension in TRIP steel

The paper presents the results of a study of electroplastic effect in metastable high-alloyed austenitic-martensitic steel in strip form with the thickness of 0.3 mm during plastic deformation with current of different modes and regimes. Choice of the research material is due to manifestation of the TRIP effect in it, caused by martensitic transformation during deformation. The ratio of volume fractions of austenite and martensite in the steel before deformation was 50:50. Deformation behavior of the steel was studied by stress-strain curves and mechanical properties at room temperature in static tension with current by short single pulses of large density, as well as multipulse current with frequency of 1000 Hz and direct current. Microstructure in the initial, before tension, state was investigated by optical and transmission microscopy. It consists of large equiaxed grains of austenite and twinned martensite up to 80 µm in size. Phase composition of the steel before and after tension with and without current was studied by X-ray diffraction. Tensile deformation without current promotes martensitic transformation and increases the volume fraction of martensite from 50 to 82 %. The introduction of single current pulses does not influence the TRIP effect, causes power surges and confirms the occurrence of electroplastic effect. Current mode has a strong influence on manifestation of the TRIP effect, suppressing it at multipulse and direct current and causing a sharp decrease in tensile strength, yield stress, and elongation to failure. Tension with current stabilizes the austenite and reduces content of the formed martensite up to 72 % in multi-pulse mode and up to 50 % when using direct current.

Dissimilar welding of high nitrogen stainless steel and low alloy high strength steel under different shielding gas composition: Process, microstructure and mechanical properties

Ar–N2-O2 ternary shielding gas is employed in dissimilar welding between high nitrogen steel and low alloy steel. The effect of O2 and N2 is investigated based on the systematical analysis of the metal transfer, nitrogen escape phenomenon, weld appearance, nondestructive detection, nitrogen content distribution, microstructure and mechanical properties. There are two nitrogen sources of the nitrogen in the weld: high nitrogen base material and shielding gas. The effect of shielding gas is mainly reflected in these two aspects. The change of the droplet transfer mode affects the fusion ratio, N2 in the shielding gas can increase nitrogen content and promote the nitrogen uniform distribution. The addition of 2% O2 to Ar matrix can change the metal transfer from globular transfer to spray transfer, high nitrogen base material is thereby dissolved more to the molten pool, making nitrogen content increase, ferrite decrease and the mechanical properties improve. When applying N2-containing shielding gas, arc stability becomes poor and short-circuiting transfer frequency increases due to the nitrogen escape from droplets and the molten pool. Performance of the joints is improved with N2 increasing, but internal gas pores are easier to appear because of the poor capacity of low alloy steel to dissolve nitrogen, The generation of pores will greatly reduce the impact resistance. 4–8% N2 content in shielding gas is recommended in this study considering the integrated properties of the dissimilar welded joint.

LABORATORY AND OPERATING TESTING OF HIGH-ALLOY STEEL PIPES MADE BY THE LATEST TECHNOLOGIES

The purpose of the research: evaluation of the quality and durability for pipes made of high-alloyed austenitic and ferritic-austenitic steels, which are manufactured at PJSC "CENTRAVIS PRODUCTION UKRAINE" using the latest technologies, by conducting complex laboratory studies and long-term operational tests at chemical industry enterprises. Materials and methods: the research materials were experimental pipes made of high-alloyed austenitic and ferritic-austenitic chromium-nickel-molybdenum steels of the new generation, manufactured using the latest technologies. The microstructure of the pipes was investigated by metallography and electron microscopy using developed and improved methods. Corrosive researches in laboratory terms included a test on firmness against the local types of corrosion inherent in high-alloy steels: intergranular corrosion (IGC), pitting corrosion (PC), corrosion cracking (CC) and sulfide stress corrosion cracking (SSCC). The mechanical properties of the pipes were determined by tensile and impact bending tests. Long-term operational tests of pipes were carried out in conditions of industrial production at chemical industry enterprises in apparatus for the urea and caustic soda production. Research results: A high content of special low-energy grain boundaries in the theory of coincident nodes’ lattices (SG CSL) was established in the structure of pipes manufactured according to the latest technologies (≥ 75 %); high resistance of pipes against various types of the most dangerous local corrosion compared to existing analogues, a high level of mechanical properties, as well as high corrosion resistance during long-term operational tests in environments at chemical industry enterprises. The implementation of the obtained results will contribute to increasing the efficiency of production and operation for highly alloyed steel pipes in demand on the world market and increasing the competitiveness of domestically produced pipes on the European and world markets.

Peculiarities of fatigue fracture of high-alloyed heat-resistant steel after its operation in steam turbine rotor blades

The article focuses on the causes of failures of steam turbine rotor blades made of high-alloyed heat-resistant steel 15Kh11MF. Premature failure of blades is caused by technological defects (intensive corrosion-erosion wear of the blade edges, uneven structure and distribution of micro damages) that occurred because of imperfections of welding and/or surface hardening. Cracks initiated from these defects change the natural oscillation frequency of the blades, leading to their resonance and thus overload. The corrosive steam-water mixture in the phase transition zone contributes to the fracture process. Long-term operation of steel in steam turbines leads to the precipitation of carbides along the grain boundaries that weaken the cohesion between adjacent grains with subsequent pore formation and their merging into defects comparable to grain size. Fatigue crack growth resistance of steel reduces as a result of its operation. The effective threshold values of the SIF range decrease more significantly than the nominal ones due to the crack closure effect. It results from the increased roughness of the fracture surface caused by intergranular fragments protruding above the flat fatigue relief. They have been formed during steel’s operation along the damaged grain boundaries, and their number progressively increased with the operation time. To assess the current state of operated steel, the structural (the part of intergranular fragments S in the unit area of the fracture surface) and mechanical (a relative loss in fatigue crack growth resistance due to operation) indicators are proposed. The basic relationship between them makes it possible to substantiate the conditions for the safe operation of 15Kh11MF steel in STR blades.

Corrosion Properties of Ni-P-B Dispersion Coating for Industrial Knives and Blades

Industrial blades, particularly the one used in food processing, requires not only a high hardness and a good wear protection but also an adequate corrosion protection. Currently, there is a wide variety of materials being used for this purpose that satisfy the above requirements. However, they come at a cost. Typically, steel with a high number of alloyed elements is chosen because the alloyed elements improved the steel quality. For example, incorporation of nickel, chromium, phosphorus and molybdenum in the steel improves amongst others the corrosion protection. However, the thermal processing of such steel, that is quenching, repeated tempering and followed by nitriding or boriding, is lengthy and complicated which drive the cost to produce knives using such steel up.Besides steel cutting tools, there is also cutting tools made from ceramic and carbide. Compared to steel knives, carbide knives have a longer lifespan and provide a higher temperature tolerance, which results in the application of the carbide cutting tools at higher speed and for longer periods without experiencing tool failure. Admittedly, due to carbides high hardness and thus the increase in difficulty to machine carbide, the production cost of carbide cutting tools is much higher compared to their steel counterparts. For ceramics, while the material is corrosion free and can maintain hardness and wear properties at a very high temperature, it is also more brittle than steel and carbide cutting tools. This results in premature chipping of the cutting edge and a shorter lifespan of the blade.To further reducing the production cost of industrial knives, the alternative of using a low alloyed steel which is coated with a hard coating and adjacently thermally treated for 1 h is investigated. This method is chosen because the tempering process of the low alloyed steel is not as lengthy as for high alloyed steel. The homogenously incorporated boron particles in the nickel phosphorus coating reduce the subsequent thermal treatment duration due to a shorter diffusion path compared to the conventional boriding. Previous study by the author [1] shows this approach to produce a high hardness at approx. 900 HV. Electroless nickel phosphorus coating is applied due to its good anti-corrosive properties. The presence of boron as particles in the coating or as boride after thermal treatment could change the corrosion behaviour of the coating. To date, no studies have yet been done to determine its corrosion properties and benchmarking this Ni-P-B dispersion coating with the other coating systems.In this study, the corrosion behaviour of the dispersion layer as coated and after thermal treatments at different temperatures is investigated. The corrosion resistance in NaCl 3.5 % is characterized though potentiodynamic polarisation and electrochemical impedance spectrometry. The results will be evaluated and compared to the other established coating systems.[1] The previous study will be presented at 241st ECS Meeting in Vancouver, Canada and has not yet been published at the time this abstract is submitted for the 242nd ECS Meeting in Atlanta.

Determined to the microstructural and mechanical properties of deposits made of high alloy steels used in the construction of environmentally friendly hydraulic turbines

Research on hydraulic turbines, regardless of type, has shown that all materials used in the manufacture of parts that are components of the flow path, working in the same conditions, are subject to hydro-abrasive wear, in different proportions. The most attacked components are the blades and the chambers of the hydraulic turbines. In this paper are studied materials used in the construction of hydraulic turbine blades that have been previously deposited by the method of the electro-spark deposition with tungsten carbide (WC) electrodes. These deposits were made in order to offer the turbine blades as high a reliability as possible but also to be able to use such hydraulic turbines in the harshest conditions and which could provide as much energy as possible. A high-alloy stainless steel containing Cr and Ni was used as the basic material for the study. The raw samples from a hydraulic turbine blade and those submitted were analyzed both structurally using the optical stereomicroscope and the SEM electron microscope and chemically using the EDX probe. High alloy steel based on Cr and Ni but also WC deposits will be subjected to mechanical tests to see how they resist wear.

Ferritic-induced high-alloyed stainless steel produced by laser powder bed fusion (L-PBF) of 2205 duplex stainless steel: Role of microstructure, corrosion, and wear resistance

Stainless steels are dominant in application where combination of corrosion and mechanical resistances are requested. They have gained scientific attention in additive manufacturing (AM) field, and stainless steel products produced by AM find use in a wide array of applications. This study aims to evaluate the microstructure, the wear and corrosion resistances of a high-alloyed ferritic-induced stainless steel (FSS) obtained by laser powder bed fusion (L-PBF), from a duplex stainless steel (DSS) precursor, SAF 2205, used to produce gas-atomized powders. No heat treatment was applied to the ferritic-induced L-PBF stainless steel to restore the duplex structure. The L-PBF FSS was dense and high alloyed with Cr, Mo, and N (pitting resistance equivalent number, PREn, ~33), presenting a negligible corrosion current density in the order of 10−7 A.cm−2, with an enlarged passivation window ~ 1.2 V with respect to the corrosion potential, restraining the current density at the passivation plateau below 10−4 A.cm−2. Also, double-loop electrochemical potentiokinetic reactivation (DL-EPR) tests indicated unsensitized L-PBF FSS, with negligible degree of sensitization caused by the cyclic heat input during building up of the specimen. Besides be corrosion-resistant, the L-PBF FSS was hard (290 HV0.5) and wear-resistant against sliding wear, with a reduced specific wear rate of 5 × 10−4 mm3·N−1·m−1. The corrosion resistance of the L-PBF specimen (almost fully ferritic microstructure) was comparable to its hot-rolled precursor that displayed a duplex microstructure, albeit slight inferior. The L-PBF FSS was harder and more wear resistant than the DSS precursor. These results point out to the formation of a new high-alloyed ferritic-induced stainless steel, which are corrosion-resistant in chloride-rich medium and wear resistant in sliding conditions.

Controlling the Thermal and Rheological Properties of Silicate Glasses for Development of Advanced Mold Flux Systems

Development of the advanced mold flux is always mandatory to enhance both the quality and productivity of continuous casting of steels. Especially, the increasing demands for high alloy steels production and high speed casting reveals serious contradiction between two principal functions of mold flux: lubrication and controlling heat transfer. In order to overcome this problematic needs, some innovative research activities are being carried out. MAE (Mixed Alkali Effect) has been examined in alumino-borosilicate-based mold system to stabilize alkali cation and aluminum association, which enables chemically stable glassy mold flux film during casting of high alloy steels. Non-Newtonian mold fluxes could be developed by addition of Si3N4 or SiC due to the increase of stiffness of polymeric structure, which would be beneficial to satisfy the contradictory requirements of viscosity at mold top surface and mold wall. Some innovative ideas for controlling mold heat transfer without deteriorating the lubrication have been examined by dispersion of nano-size metallic particles and by modification of prenucleation motif. All these trials are closely related with glass science and engineering. Therefore, it should be highly beneficial to enhance the collaborative research activities between glass and metallurgy society for further development of advanced functional mold flux systems.

Laser Cladding-Based Surface Modification of Carbon Steel and High-Alloy Steel for Extreme Condition Applications

Laser cladding (LC) is a laser-based surface modification technique widely adopted to develop a thin coating or remanufacture worn-out mechanical components that work in extreme conditions. LC helps to generate superior surface properties and surface integrity on the substrate surface, improving the service life. This review paper provides a comprehensive overview of the LC process, different powder feeding methods, and the uniqueness of LC over other coating techniques. More specifically, the current state-of-the-art of the LC process on carbon steel and high-alloy steel-based mechanical components operating in diverse industries was elucidated. Furthermore, the effect of LC processes on mechanical properties such as wear, corrosion and fatigue properties are discussed. In addition, the LC process’s influence on microstructural features and microstructural modifications is explained. Finally, this study explores some potential applications of the LC process in diverse industries.

EVALUATION OF THE INFLUENCE OF VARIOUS FACTORS ON THE CORROSION OF STEELS DURING MOISTURE CONDENSATION UNDER THE CONDITIONS OF TRANSPORTATION OF A CORROSIVE GAS

The problem of internal corrosion is an urgent problem in the transportation of produced products with the presence of corrosive-aggressive components through gas pipelines. The presence of CO2 or H2S in the produced gas in combination with the presence of condensation water, as well as a number of other factors, stimulates the intensive development of carbon dioxide or hydrogen sulfide corrosion of a local nature. To determine the limiting rates of local corrosion, corrosion tests were performed under conditions of moisture condensation, which occurs when a temperature gradient occurs and the transported gas is rapidly cooled. A study was carried out to assess the influence of the main operational factors on corrosion processes during moisture condensation on the inner surface of the gas pipeline: humidity, temperature, type of steel, the presence of a weld and the presence of alcohol, monoethylene glycol and acidic environments. It has been established that many of the above corrosion parameters accelerate local corrosion of carbon and low alloy steels, thedevelopment rate of which reaches up to several mm/year. It has been determined that the rate of development of corrosion processes during the condensation of water-glycol and water-alcohol solutions depends on the amount and composition of the liquid condensing on the metal surface. High-alloy steel 12X18H10T (with 18% Cr) showed resistance to corrosion conditions during moisture condensation.