Austenitic Chromium-nickel Steels Research Articles

Surface Nanocrystallization and Improvement of the Mechanical and Tribological Properties of AISI 304 Steel Using Multi-Pass Nanostructuring Burnishing.

Owing to their high producibility and resistance to corrosion, austenitic chromium-nickel steels are widely used in the chemical, petroleum, and food industries. However, their significant disadvantage lies in their poor structural performance, which cannot be improved by heat treatment. This significantly limits the usability of these steels in parts of machines that operate under friction loads. Hardening can be achieved by decreasing the size of grains and applying deformation-induced martensitic transformation. Nanostructuring burnishing (NSB) may be one of the technologies suited for producing parts of tribological assemblies with enhanced operating characteristics. Nanostructuring burnishing using a sliding indenter is being developed as a method of industrial surface nanocrystallization through severe plastic deformation used in the mechanical machining of various types of parts. This article investigates the possibility of enhancing the mechanical and tribological properties of nanocrystallized surfaces of austenitic steels, which are formed through nanostructuring burnishing using a tool with a natural diamond spherical indenter and a change in sliding speed from 40 to 280 m/min with one, three, and five passes. Increasing the tool sliding speed makes surface nanostructuring machining of big parts highly effective. This paper aims to establish the influence exerted by the sliding speed and number of indenter passes on the formation of a nanocrystalline structure, as well as on the modification of microhardness and residual stresses, texture, and tribological properties of the surface layer in the nanostructuring burnishing of AISI 304 steel. Transmission microscopy and microdurometry, 3D-profilometry, and tribological tests of surfaces nanocrystallized with the "ball-on-disk" scheme with dry and lubricated friction established the optimal values of speed and number of passes for a spherical indenter in nanostructuring burnishing.

Monitoring of relative magnetic permeability variation during cyclic bending testing of austenitic steel grade 10Kh18n10t samples

Cyclic bending testing of austenitic chromium-nickel steel grade 10Kh18N10T samples was carried out. Evalution of relative magnetic permeability showed its noticeable increase when the samples became fractured. This increase is related to deformation martensite appearance. Additional experiment showed, that deformation martensite formation starts before the actual destruction of the sample.

The effect of the method for producing chromium-nickel stainless steel powders on the strain state and properties of the outer cage of a spherical hinge joint

The paper substantiates the relevance of studying powder metallurgy methods and efficiency of applying them to the production of spherical bearings of highly loaded spherical hinge joints. It proves that the force and work of deformation, as well as the kinetics of forming of the outer cage of a spherical hinge joint made of sintered corrosion-resistant chromium-nickel steels, are influenced by the chemical composition of powders and lubricants, the protective environment and the method of sintering, the microstructure and mechanical properties of the workpiece material. It is shown that the plastic properties of ring specimens under testing depend on the perfection of interparticle contacts, the presence and distribution of chromium oxides, forming schemes and workpiece porosity. The influence of the method for the production of stainless chromium-nickel powders on the density and mechanical properties of the sintered blanks is studied. A method is proposed for evaluating the strain state during radial deformation of ring specimens made of these steel powders and estimating the maximum allowable values of strain intensity below which no cracks are formed during cold forming of porous blanks. It is revealed that, to calculate the stress state and, accordingly, strain resistance in the cold forming of the outer cages of spherical hinge joints, made of sintered corrosion-resistant steels, it is possible to use the known constitutive equations if strain intensity does not exceed the experimentally obtained limit values. The feasibility of implementing the proposed method and selecting the process parameters of cold forming of spherical hinge parts made of chromium-nickel austenitic steels is substantiated.

Explicit correlation between surface integrity and fatigue limit of surface cold worked chromium-nickel austenitic stainless steels

Explicit correlation between surface integrity and fatigue limit of surface cold worked chromium-nickel austenitic stainless steels

Влияние режимов лазерной наплавки на геометрические размеры стального трека

Introduction. Laser surfacing is one of the leading trends in the field of additive technologies, which consists in layer-by-layer build of material using a laser as an energy source. To obtain a high-quality product, it is necessary to select the optimal building parameters correctly. The problem is that such optimization is necessary for all equipment, since minor differences in its characteristics can make significant changes in the parameters of layer-by-layer build. In order to determine the optimal build mode, it is enough to analyze the effect of various equipment parameters on the characteristics of single tracks. Therefore, the purpose of this work is to determine the most important parameters of laser radiation that affect the surfacing process and the optimal mode for building a single track of chromium-nickel steel. The work investigated single tracks obtained by laser surfacing of powder from austenitic chromium-nickel steel AISI 316L. The optimization factors included such characteristics as laser power, beam speed, flow rate of supplied powder and laser spot size. The wavelength of laser radiation was 1.07 μm. Research methods. To determine the quality and geometric dimensions of single tracks, the macrostructure of cross sections of specimens was studied using metallography and scanning electron microscopy methods. Results and discussion. It is established that the optimal mode for growing single tracks of steel AISI 316L is characterized by a laser radiation power of 1,250 W and a scanning speed of 25 mm/s. In this case, the optimal powder consumption rate is 12 g/min, and the laser spot size is 4.1 mm. The work shows that the powder consumption and laser spot size have the greatest influence on the coefficient of effective use of powder material. By changing it, the surfacing performance can be increased by 10–15 %.

Applying the Hollomon-Jaffe parameter to predict changes in mechanical properties of irradiated austenitic chromium-nickel steels during isothermal exposure

<abstract> <p>The Hollomon-Jaffe parameter is widely used in metallurgy and materials science to characterize the behavior and predict the various metals' physical-mechanical properties under different temperature and time modes. The possibility of predicting changes in the mechanical properties of structural steels due to thermal influences has been studied. The paper presents the results of a study of the mechanical properties of the materials of the core components of the BN-350 reactor facility (RF) made of austenite chromium-nickel steel 12Cr18Ni10Ti (a spent fuel assembly's jacket) and 09Cr16Ni15M3Nb (an intro-channel displacer). The samples were studied both before and after radiation annealing. Annealing of steel samples at 550 ℃ reduced the yield strength and significantly restored the plasticity and ability of the material to strain hardening. The efficiency of post-radiation annealing of the materials increases with annealing temperature and leads to a transition to the reduction process. It was established that medium of high temperature annealing during heat treatment does not lead to significant changes in the mechanical properties of irradiated materials. The microstructure studied using a scanning electron microscope reasonably correlates with the results of mechanical tests. The possibility of using the Hollomon-Jaffe parameter to predict the properties of austenite chromium-nickel steel, which received damaging doses in the range from 12 to 59 dpa, was shown for the first time. Thus, for the first time, the unique coefficient (<italic>C</italic>) of the Holloman-Jaffe parameter for irradiated materials of chromium-nickel steel was experimentally determined, and dependencies characterizing the change in hardness of chromium-nickel steel on temperature and duration of post-radiation thermal exposure were established.</p> </abstract>

Modeling and simulation of welded joints of SS304H & P91 Steels: A Review

Most of the structures are fabricated by welded joints in various manufacturing units because of low cost and high strength. Welding process is largely used in almost all manufacturing units. Welded joints usually subject to welding deformation patterns. Welding deformation may lead to low dimensional accuracy, shape and aesthetics of the product, strength of the welded joint. Welding of two different materials having different mechanical properties is called dissimilar welding. Dissimilar welded joints are commonly used in power plants to connect martensitic steel components and austenitic stainless steel piping systems. Our approach involves conducting dissimilar welding on P91 and SS304H steels, and subsequently assessing the properties of the welded joints using simulation software. A 3-D thermal elastic plastic finite element computational process is designed to accurately forecast welding deformation by numerical method. Numerical and experimental outcomes were compared in terms of temperature distributions during welding and in terms of distortion. P91 is a chromium-molybdenum alloy known for its remarkable strength and exceptional resistance to high temperatures. Alloy SS304H represents an adaptation of the chromium-nickel austenitic stainless steel. This variant, Grade 304H stainless steel, offers enhanced heat-resistant properties, increased tensile yield strength, and improved short- and long-term creep strength.

Effect of Molybdenum Electron-Beam Cladding on the Heat and Wear Resistances of Surface Layers of Chromium-Nickel Austenitic Steel 12Kh18N9T

Effect of Molybdenum Electron-Beam Cladding on the Heat and Wear Resistances of Surface Layers of Chromium-Nickel Austenitic Steel 12Kh18N9T

Study of electrochemical properties of austenitic chromium-nickel steel 12Kh18N10T in concentrated sulfuric acid

Study of electrochemical properties of austenitic chromium-nickel steel 12Kh18N10T in concentrated sulfuric acid

Microstructure of conventional/PBF-LB/M 316L stainless steel hybrid joints brazed with nickel-based brazing alloys

Due to the additive manufacturing principle, laser-melted materials (PBF-LB/M) such as the austenitic chromium-nickel steel 316L have a different microstructure compared to materials produced by conventional continuous casting. The PBF-LB/M-produced 316L has a thermally metastable, anisotropic microstructure with epitaxially grown grains in which a cellular substructure is located. When brazing hybrid joints from the conventional and additive manufacturing routes with nickel-based brazing alloys, different diffusion mechanisms occur simultaneously in both joining partners. This occurs due to the different microstructural characteristics of the parent materials. The altered diffusion mechanisms lead to a new distinct microstructure in the joining zone, which influences the achievable quality of the brazed joint in a previously unknown way.

Substantiating the Process Parameters of Frictional Treatment with a Sliding Indenter for an Austenitic Chromium-Nickel Steel

Substantiating the Process Parameters of Frictional Treatment with a Sliding Indenter for an Austenitic Chromium-Nickel Steel

ATLAS 310/310S/310H

Abstract Atlas 310 / 310S / 310H are chromium-nickel austenitic stainless steels. They combine excellent high temperature properties with good ductility and weldability. Atlas 310S (UNS S31008) is used when the application environment involves moist corrodents in a temperature range lower than that which is normally considered "high temperature" service. The lower carbon content of 310S does reduce its high temperature strength as compared to that of 310H. Atlas 310H (UNS S31009) has a carbon content restricted to exclude the lower end of the Atlas 310 range. It is the grade of choice for high temperature applications. Grade 310L encompasses a series of proprietary grades, generally with a 0.03% maximum carbon and sometimes used for very specific corrosive environments such as urea production. Like other austenitic grades the 310 family has excellent toughness, even down to cryogenic temperatures, although other grades are normally used in sub-zero environments. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as heat treating and joining. Filing Code: SS-1363. Producer or source: Atlas Steels.

Наукоёмкие технологии в материаловедении: высокотемпературное сквозное азотирование жаростойкой стали

The topicality of the research is occasioned by exaggeration of working conditions of products used at high temperatures and made of heat-resistant sheet alloys, including in particular austenitic chromium-nickel steels. When steel parts under load are operated in an oxidizing atmosphere and aggressive environments, besides resistance to electrochemical and gas corrosion, they require increased strength, hardness, and heat resistance. The increase in the characteristics of these proper-ties is achieved by three-dimensional and surface hardening techniques, which include the nitration process. The applica-tion of traditional technologies of furnace gas nitriding for chromium-nickel steels is complicated due to the problems of the low rate of the nitrogen saturation, which significantly increases the process time, and the formation of chromium nitrides, which negatively affects corrosion and heat resistance. The development of new technologies for nitrogen hardening of high-alloyed chromium-containing steels is carried out in the direction of saturation process intensification and regulation of the phase composition of the nitrided layer to minimize the formation of chromium nitrides. The article is aimed at defin-ing rational technological options and modes of gas austenitic nitriding of austenic steel, making it possible to increase strength characteristics at RT and higher temperatures without sacrificing its heat resistance. Thermodynamic modeling of the phase composition based on the CALPHAD technique shows that primary ways for minimizing the release of chromium nitrides on the nitrided surface are to increase the concentration of titanium in steel and to reduce the activity of the saturat-ing gas atmosphere, which is achieved by inert gas dilution of nitrogen. Experimental studies were carried out on sheet samples of 1.5 mm thick austenic steel of the type X18N10T with a standard (0.5%Ti) and increased (1%Ti) titane content. The experiments were carried out on a laboratory installation for high-temperature nitriding (900.1200 °); pure nitrogen and mixtures of nitrogen with argon were used as saturating media. Two-stage processes consisting of nitrogen hardening in nitrogen followed by argon afterburning were also investigated. Metallographic analysis showed that at the same nitrid-ing temperature, the amount of chromium nitrides decreases in experimental steel with an increased titanium content, and dilution of nitrogen with argon reduces the temperature of chromium nitride release. According to the study of saturation process kinetic, the time of through-the-thickness nitriding of a sheet sample under different saturation modes was deter-mined, as well as the duration of de-nitriding annealing, calculated on the basis of the known thickness of the chromium nitride zone. It was found that the dispersion hardening of the zones of internal nitriding with titanium nitrides leads to an increase in the strength characteristics of steels both at RT and higher temperatures compared to the characteristics of base steel 08X18N10T after typical heat treatment, while the greatest hardening effect is achieved due to through-the-thickness nitriding of steel with 1%Ti. Recommended options for the processes of through-the-thickness nitriding of 1.5 mm sheet of experimental steel: tn=1050 ℃, N2, 16 h; tn= 1100 ℃, 50%N2 + 50%Ar, 22 h; tn=1100 ℃, N2, 5 h + tann=1200 ℃, Ar, 9 h. The temporary passive hardness of nitrided steel at RT increases by 45...50%, and when tested at 800 ℃ - by 40... 65%, de-pending on the process mode. Through-the-thickness nitriding makes it possible to raise the working temperature of steels by 100.150 ° with the same long-term strength. The heat resistance at 900 ℃ remains at the level of non-carbonated steel after two-stage processes that ensure maximum chromium nitrides removal from the surface at the annealing stage.

A General Analytical Solution for Two-Dimensional Columnar Crystal Growth during Laser Beam Welding of Thin Steel Sheets

A technique for calculating the main solidification parameters for a two-dimensional columnar crystal growth during complete penetration laser beam welding of thin steel sheets was developed. Given that the weld pool interface is described by Lamé curves (superellipses) within the horizontal plane of growth, general analytical solutions were derived for the geometry of the crystal axis and the corresponding growth rate and cross-sectional area of the crystal. A dimensionless analysis was performed to provide insights on the dependence of the solidification parameters on the shape and dimensions of the rear part of the weld pool boundary. The derived solutions were applied for the case of complete penetration laser beam keyhole welding of 2 mm thick 316L austenitic chromium-nickel steel sheets. It was shown that the reconstruction of the weld pool boundary with Lamé curves provides higher accuracy and flexibility compared to results obtained with elliptical functions. The validity of the proposed technique and the derived analytical solutions was backed up by a comparison of the obtained solutions to known analytical solutions and experimentally determined shapes and sizes of the crystals on the top surface of the sheet. The dimensions of the calculated crystal axis correlated well with the experimentally obtained results.

The Influence of Frictional Treatment and Low-Temperature Plasma Carburizing on the Structure and Phase Composition of Metastable Austenitic Steel

The features of the structure and phase composition of corrosion-resistant austenitic chromium–nickel steel (16.80 wt % Cr, 8.44 wt % Ni) subjected to carburizing in electron beam plasma at temperatures of 350 and 500°C, frictional treatment with a sliding indenter, and a combination of frictional treatment and plasma carburizing have been considered. It has been established that plasma carburizing results in the formation of a modified surface layer consisting of carbon-saturated austenite and carbides (Cr23C6, Fe3C); in this case, the formation of γC-phase occurs only at a temperature of 350°C. The depth of a modified layer increases with an increase in the carburizing temperature. It has been shown that it is useful to perform combined frictional treatment and plasma carburizing at a carburizing temperature of 350°C, since in this case the deformation-induced structure formed as a result of frictional treatment is preserved, and the precipitated carbides remain highly dispersed. In this case, frictional treatment should provide the formation of the deepest possible diffusion-active layer with a dispersed structure.

The Influence of Frictional Treatment and Low-Temperature Plasma Carburizing on the Structure and Phase Composition of Metastable Austenitic Steel

The features of the structure and phase composition of corrosion-resistant austenitic chromium–nickel steel (16.80 wt % Cr, 8.44 wt % Ni) subjected to carburizing in electron beam plasma at temperatures of 350 and 500°C, frictional treatment with a sliding indenter, and a combination of frictional treatment and plasma carburizing have been considered. It has been established that plasma carburizing results in the formation of a modified surface layer consisting of carbon-saturated austenite and carbides (Cr23C6, Fe3C); in this case, the formation of γC-phase occurs only at a temperature of 350°C. The depth of a modified layer increases with an increase in the carburizing temperature. It has been shown that it is useful to perform combined frictional treatment and plasma carburizing at a carburizing temperature of 350°C, since in this case the deformation-induced structure formed as a result of frictional treatment is preserved, and the precipitated carbides remain highly dispersed. In this case, frictional treatment should provide the formation of the deepestpossible diffusion-active layer with a dispersed structure.

THE FORMATION FEATURES OF PIPES STRENGTH CHARACTERISTICS MADE OF MASS GRADES OF AUSTENITIC STAINLESS STEELS AT ROOM AND ELEVATED TEMPERATURES

As part of the research on the development of a new standard for welded and seamless stainless steel pipes, the microstructure, phase composition and mechanical properties in the temperature range of 20-650 °C of pipe samples from austenitic chromium-nickel steels of the Fe-18Cr-10Ni family were evaluated. Significant spread of mechanical characteristics is shown, a quantitative assessment of the contribution of various hardening factors is carried out. It is noted that grain size and solid-solution hardening with carbon, nitrogen or titanium have the most significant effect on mechanical properties, providing up to 45% of the yield strength of steel. It is established that the temperature dependence of the tensile strength is determined by the resistance to the formation of deformation martensite and the intensity of the action of dynamic deformation aging.

Changes in Abrasion Resistance of Cast Cr-Ni Steel as a Result of the Formation of Niobium Carbides in Alloy Matrix

Cast austenitic chromium-nickel steel is commonly used for the manufacture of machine parts and components, which are exposed to the attack of corrosive media and abrasive wear during operation. The most commonly used grades include GX2CrNi18-9 and X10CrNi18-8 as well as GX2CrNiMo17-12-2 and X6CrNiMoNb17-12-2. To improve the abrasion resistance of cast chromium-nickel steel, primary niobium carbides were produced in the metallurgical process by increasing the carbon content and adding Fe-Nb. The microstructure of the obtained test castings consisted of an austenitic matrix and primary niobium carbides evenly distributed in this matrix. The measured hardness of the samples after heat treatment ranged from 215 to 240 HV and was higher by about 60 units than the hardness of the reference cast GX10CrNi18-9 steel, which had a hardness of about 180 HV. Compared to the reference cast steel, the abrasive wear resistance of the tested cast chromium-nickel steel (measured in Miller test) with contents of 4.4 and 5.4 wt% Nb increased only slightly, i.e., by 5% for the lower niobium content and 11% for the higher niobium content. Compared to ordinary cast GX10CrNi18-9 steel, the addition of 9.2 wt% Nb reduced the abrasive wear by almost 2.5 times.

Fracture mechanisms and properties for irradiated austenitic chromium-nickel steel over elevated temperature range and formulation of intergranular fracture criterion

The fracture mechanisms of austenitic 18Cr-9Ni steel have been investigated over the temperature range from 200° to 600 °C using the following states: (1) after neutron irradiation at temperature of 400 °C up to damage dose of 30 dpa; (2) after neutron irradiation and subsequent aging at 550 °C for 3000 h. The fracture properties and mechanisms have been determined under uniaxial tension of smooth round and notched round bars, i.e. for various stress triaxialities. Sharp decrease in the fracture strain and transition to intergranular fracture have been revealed for smooth round bars over high temperature range that indicates high temperature radiation embrittlement. Over the same temperature range the fracture strain is larger for notched round bars than for smooth round bars, moreover a portion of intergranular fracture is also larger. This finding is rather abnormal as the fracture strain usually decreases when stress triaxiality and intergranular fracture portion increase. On the basis of the obtained experimental results, for the first time, the fracture stress-controlled criterion and fracture model have been developed over temperature range of high temperature radiation embrittlement. The proposed model allows one to explain larger value of the fracture strain for notched round bars as compared with smooth round bars and also to predict fracture toughness over range of high temperature radiation embrittlement. The formulated criterion and model have been verified by comparison of the calculated and experimental values of fracture toughness for 18Cr-9Ni steel irradiated up to damage dose of (24–30) dpa. Experimental values of fracture toughness have been obtained from compact tension CT-0.5 specimens tested at 200 °C and 600 °C.

Effect of carbide particles on impact strength of surface-hardened chromium-nickel austenitic steel

The results of comparative studies of the effect of modified layers with carbide particles obtained from powders of niobium, titanium, silicon, and tungsten carbides on the impact strength characteristics of 12Kh18N9Т (AISI 321) stainless steel are presented in this research paper. The coatings were formed by the method of non-vacuum electron-beam surfacing.