Steel X6CrNiTi18-10 Research Articles

Surface Structure Analysis of X12CrNiMoV12-3 and X6CrNiTi18-10 Steel Samples Processed by Laser Shot Peening (LSP)

The aim of the experiment was to verify the influence of the chosen strategy of laser shot peening (LSP) on the structure and surface properties of samples made of martensitic steel X12CrNiMo12 and austenitic steel X6CrNiTi18-10. The analyses performed consisted of surface topography analysis of the samples, using a confocal microscope, Olympus LEX|T OLS 5000 and metallographic analysis using a Carl Zeiss Observer Z1m light microscope and a Tescan Mira 3 scanning electron microscope. The metallographic analysis was complemented by the measurement of microhardness HV0.01, which was performed using a Struers DuraScan semi-automatic hardness tester. The LSP process introduced plastic deformation into the surface layer of both materials analysed. The plasma and shock wave generated during the process further affected the surface roughness of both tested materials, which was reflected by an increase in the value of the roughness parameter Rz. Microhardness measurements showed that the influence of the LSP process can increase the surface hardness of the material. Metallographic analysis using light microscopy methods failed to identify differences between the structure near the shot peened surface and the non-peened surface, probably due to the coarse grain structure of both materials analysed.

Influence of the Boriding Process on the Properties and the Structure of the Steel S265 and the Steel X6CrNiTi18-10

In the performed experiment, changes in the microstructure of steels S265 and X6CrNiTi18-10 due to their chemical-thermal treatment by boriding were studied. The boriding process was performed in a Durborid boriding powder at 900 0C. During this process, surface layers of Fe-B borides were formed in both analyzed sorts of steels. The layers differed in their morphology and composition due to the different degree of alloying of the matrix of analyzed steels by additive elements. The formed Fe-B layers showed high adhesive and cohesive resistance in both materials. Due to changes in the micro-structure of S265 steel, especially due to significant coarsening of the original grain of its matrix, its resistance to tribological abrasion after the boriding process decreased. The opposite effect was ob-served for X6CrNiTi18-10 steels. As a result of boriding, both analyzed materials changed their corro-sion resistance.

Statistical Analysis of Corrosion Process Flow

This paper presents the results of testing two different materials in aggresive atmosphere rich in sodium chloride (NaCl) depending on different time intervals (48, 96, 168, 240 hours), in order to determine the corrosion process flow. One of the materials is general structural steel SA516 Gr.70 and the other is austenitic stainless steel X6CrNiTi18-10. The test results were statistically analyzed with the aim of obtaining statistical regression models, as well as to investigate the effect of alloying elements on the corrosion process flow. Models for predicting the corrosion process flow (mass loss) of both materials were obtained by statistical analysis and it was determined that the proportion of alloying elements influences the change in the flow. Accordingly, general structural steel is characterized by linear, while austenitic stainless steel is marked by slow corrosion process flow. This indicates that the proportion of alloying elements which improve the corrosion resistance of the material strongly affects the durability of the material in an aggressive environment.

Physicochemical Properties, Cytotoxicity, and Antioxidative Activity of Natural Deep Eutectic Solvents Containing Organic Acid

Natural deep eutectic solvents (NADES) may be considered ‘designer solvents’ due to their numerous structural variations and the possibility of tailoring their physicochemical properties. Prior to their industrial application, characterization of NADES is essential, including determination of their physicochemical properties, cytotoxicity, and antioxidative activity. The most important physicochemical properties of eight prepared NADES (choline chloride:malic acid, proline:malic acid, choline chloride:proline:malic acid, betaine:malic acid, malic acid:glucose, malic acid:glucose:glycerol, choline chloride:citric acid, and betaine:citric acid) were measured as functions of temperature and water content. In general, the structure of prepared NADES greatly influences their physical properties, which could be successfully modified and adjusted by addition of water. All tested NADES were absolutely benign and noncorrosive for investigated steel X6CrNiTi18-10. Furthermore, cytotoxicity of prepared solvents was assessed toward three human cell lines (HEK-293T, HeLa, and MCF-7 cells), and antioxidative activity was measured by the Oxygen Radical Absorbance Capacity (ORAC) method. With regard to cell viability, all tested NADES containing carboxylic acid could be classified as practically harmless and considered environmentally safe. The ORAC values indicated that the tested NADES displayed antioxidative activity.

Studies and Experimental Research on Correlation Thermal Field with Mechanical Properties of Cryogenic Steels Welded Joints with MIG Procedure

The paper presents the analysis and experimental research that is performed to correlate the welding procedure with hardness in HAZ (Heat Affected Zone) and toughness of welded joints of austenitic stainless steel X6CrNiTi18-10, used to build cryogenic tanks to liquid nitrogen storage. For this were welded a sample by MIG welding process.In a first step it was estimated the hardness of HAZ with a soft computer, and then it was made a testing to its experimental verification welding procedure. The results showed that the welding procedures developed and implemented resulted in obtaining the HAZ hardness almost equal to those of basic material. This shows that the HAZ properties are unaffected and a good weldabillity of austenitic stainless steel. In a second step the toughness were measured at room temperature and work temperature, -196°C.

Study on the near-surface residual stress state in butt-welded pipes of austenitic steel using X-ray diffraction

This study is dedicated to the analysis of the residual stress state of two-pass butt-welded pipes of the austenitic steel X6CrNiTi18-10. To this end, X-ray diffraction is used to determine the hoop and axial residual stresses on the outer and inner surfaces of the welded pipes. Measurements of the residual stresses and the radial distortion reveal that the thermal contraction of the weld and its vicinity are constrained by the tubular geometry, thus causing a characteristic residual stress state. Machining of the specimens influences the residual stress state on the surface through local plastic deformation and the introduction of machining residual stresses, which is shown by X-ray diffraction measurements after electrolytic polishing.

Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel.

The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

RESEARCH OF TECHNOLOGICAL PROPERTIES OF STEEL X6CRNITI18-10 WELDED JOINTS EXPLOITED IN NITRIC ACID MEDIUM / PLIENO X6CRNITI18-10, EKSPLOATUOJAMO AZOTO RŪGŠTIES TERPĖJE, VIRINTINIŲ JUNGČIŲ TECHNOLOGINIŲ SAVYBIŲ TYRIMAS

The repair of chemical industry equipments often requires to replace long time operated pipes or welded inserts with the simi-lar chemical composition. During the study the joints from corro-sion resistant steel X6CrNiTi18-10 were welded by manual metal arc welding with covered electrodes (MMA process 111) and tungsten inert gas welding (TIG process 141) at different welding parameters. The visual, radiographic, penetrant control and ferrite content analysis were carried out. The transverse tensile and bending samples were produced from welded samples; also the macroscopic and microscopic analyse were carried out. Atliekant chemijos pramonės įrenginių remontą, dažnai tenka pakeisti ilgą laiką eksploatuotus vamzdžius ar įvirinti analogiškos cheminės sudėties intarpus. Tyrimo metu suvirintų jungčių bandomieji pavyzdžiai iš korozijai atsparaus plieno X6CrNiTi18-10 buvo suvirinti rankiniu lankiniu būdu glaistytaisiais elektrodais (111 MMA procesas) ir lankiniu suvirinimu volframo elektrodu inertinėse dujose (141 TIG procesas), esant skirtingiems suvirinimo režimų parametrams. Suvirintiems bandiniams buvo atlikta vizualinė, radiografinė, spalvinė kontrolė, nustatytas išsiskyrusio ferito kiekis. Iš suvirintų ruošinių buvo pagaminti skersinio tempimo, lenkimo bandiniai, taip pat atlikti virintinių jungčių makroskopinis ir mikroskopinis tyrimai.

Optimum Tool Life and Cutting Speed for the Maximum Productivity at the Drilling of the Steel X6CrNiTi18-10

The research in the last decade regarding their cutting machinability have highlighted the insufficiency of the data for establishing of the optimum cutting processing conditions and the optimum cutting regime. The purpose of this paper is the optimization of the tool life and the cutting speed at the drilling of the stainless steels in terms of the maximum productivity. A nonlinear programming model to maximize the productivity at the drilling of a stainless steel is developed in this paper. The optimum cutting tool life and the associated cutting tool speed are obtained by solving the proposed mathematical model. The use of this productivity model allows greater accuracy in the prediction of the productivity for the drilling of a certain stainless steel and getting the optimum tool life and the optimum cutting speed for the maximum productivity. The obtained results can be used in production activity, in order to increase the productivity of the stainless steels machining. Finally the paper suggests new research directions for the specialists interested in this field.

Mathematical Model for Economic Optimization of the Tool Life and the Cutting Speed at Drilling of the Stainless Steel X6CrNiTi18-10

The problems related to the wear of the cutting tools wear and the tools life at the machining of the stainless steels are very important due to the chemical and mechanical characteristics of these steels [1]. Over time the research have studied the causes which produce the cutting tool wear and the methods to improve the cutting tools durability, either by creating new types of materials for tools, either by the choice of tools geometric parameters and cutting regime [2, 3]. The purpose of this paper is the optimization of the cutting tool life and the cutting speed at the drilling of the stainless steels, in terms of the global indicator of the minimum machining cost.

Methods of measuring activation and passivation potentials of Fe-Cr alloys

A novel experimental method of estimating the activation potentials of passive layers on metallic materials is developed taking into account the advantages and drawbacks of conventional methods (switching off the anodic polarization and reverse potentiodynamic activation-passivation). Theoretical principles of the proposed method of successive approximations are based on the thermodynamic possibility of forming a passive layer on the alloy surface. The method involves potentiostatic exposures in the potential range of presumable activation. The change in the current direction with time at a selected potential is considered to be an indicator of the surface state. The error of measurements is related solely to the accuracy of potentiostat and is independent of a particular mechanism of the passive layer formation. The method is supported by the example of Fe-Cr and Ni-Cr alloys, as well as 4541 steel X6CrNiTi18-10, AISI 321. The experimental data obtained are compared to the results of theoretical calculations of Flade potentials.

Cavitation erosion resistance of nanocrystalline TiN coating deposited on stainless steel

Nanocrystalline TiN coating was deposited on stainless steel X6CrNiTi18-10 by means of the cathodic arc method. The evaluation of nanocrystalline TiN coating resistance to cavitation erosion was based on the investigation performed in a cavitation tunnel with a slot cavitator and tap water as a medium. The investigations were performed at variable cavitation intensity. The estimated cavitation resistance parameters of coatings were the incubation period of damage and the instantaneous erosion rate after exposure of specified duration. It has been confirmed that the nanocrystalline TiN coating deposition on X6CrNiTi18-10 steel causes prolongation of the incubation period in comparison with the uncoated steel, the instantaneous erosion rates are close to each other, but after incubation period higher erosion rate was on the TiN coated specimen. The character of the TiN coating and uncovered substrate damage in multiple locations indicated that the hard coating micro-particles torn off during the cavitation bubbles implosion hit against the coating and the revealed areas of substrate. As a result, the TiN coating and especially the substrate of relatively low hardness beside cavitation erosion are subject to solid particle erosion with the hard torn off micro-particles of coating. The investigations and the analysis indicated that the main factors responsible for an elongated incubation period of the steel substrate/hard coating systems are the gained high hardness of substrate and high level of coating adhesion.

Cavitation erosion resistance of Cr–N coating deposited on stainless steel

Results of investigation on cavitation-erosion resistance of Cr–N coating deposited on stainless steel X6CrNiTi18-10 (1H18N9T) by means of the cathodic-arc method are presented. The evaluation of Cr–N coating resistance to cavitation erosion is based on the investigation performed in a cavitation tunnel with a slot cavitator and tap water as a medium. The investigation was performed at variable-cavitation intensity and the estimated cavitation resistance parameters of coatings were the incubation period of damage and the instantaneous erosion rate after exposure of specified duration. It has been confirmed that the incubation period of the Cr–N coating damage is approximately 50% longer than that of the uncoated X6CrNiTi18-10 steel, and the instantaneous erosion rate after exposure of specified duration is comparable in both cases. The scanning microscope analysis indicates that the damage of Cr–N coating is due mainly to its delamination, while the erosion of deeper parts of the coating is of minor importance. The character of the coating and substrate damage in multiple locations indicates that the hard coating microparticles torn-off during the cavitation bubbles implosion hit against the coating and the revealed areas of substrate. As a result, the coating and especially the substrate of relatively low hardness are subject to cavitation erosion and to solid particle erosion with the hard torn-off microparticles of coating. The results of the investigation and the analysis indicate that the factors mainly responsible for a long incubation period and low cavitation erosion rate of the steel substrate/ hard coating systems are the gained high hardness of substrate and high level of coating adhesion.

Application of the Seebeck effect for monitoring of neutron embrittlement and low-cycle fatigue in nuclear reactor steel

The monitoring of neutron embrittlement and low-cycle fatigue in nuclear reactor steel is an important topic in lifetime extension of nuclear power plants. Among several material parameters that may change due to material degradation are the thermoelectric properties. Therefore, we investigated the application of the Seebeck effect for determining material degradation of common reactor pressure vessel (RPV) steel. The Seebeck coefficients (SC) of several irradiated Charpy specimens made from Japanese reference steel JRQ were measured. The specimens suffered fluences from 0 up to 4.5 E 19 neutrons/cm 2, with energies higher than 1 MeV. Measured changes of the SC within this range were about 500 nV/°C, increasing continuously in the range under investigation. Some indications of saturation appeared at fluencies larger than 4.5 E 19 neutrons/cm 2. We obtained a linear dependency between the SC and the temperature shift Δ T 41 of the Charpy energy versus temperature curve, which is widely used to characterize material embrittlement. Similar measurements were performed on fatigue specimens made from the austenitic stainless steel X6CrNiTi18-10 (according to DIN 1.4541) that were fatigued by applying cyclic strain amplitudes of 0.28%. A clear correlation between the change of the SC and the accumulated plastic strain, i.e. number of cycles was obtained. Further investigations were made to quantify the size of the gauge volume in which the thermoelectric power (TEP), also called thermoelectric voltage, is generated. It appeared that the information gathered from a thermoelectric power measurement is very local. This fact can be used to develop a novel TEP-method acting as a thermoelectric scanning microscope (TSM). Finally, we conclude that the change of the SC has a potential for monitoring of material degradation due to neutron irradiation and thermal fatigue, but it has to be taken into account that several influencing parameters could contribute to the TEP in either an additional or extinguishing manner. A disadvantage of the method is the requirement of a clean surface without any oxide layer. This disadvantage can partially be avoided by using the proposed new TSM.

Neutron-diffraction study of martensitic transformation in austenitic stainless steel under low-cycling tensile-compressive loading

The fatigue behaviour of austenitic stainless steel, in which a martensitic phase is formed due to plastic deformation, is of some interest for practical reasons. Earlier, we reported the results of the first stage of the in situ stress-rig experiment on the ENGIN instrument at the ISIS facility, with samples from steel X6CrNiTi1810 subjected to different tensile–compressive loading cycles at a frequency of 5 Hz. This paper describes the results of the second stage of the experiment in which a series of samples subjected to 0.5 Hz was studied. Information about the mechanical properties of the austenitic matrix and the martensitic precipitates is obtained from the experimental mechanical and neutron-diffraction data.

Phase and microstructural study of surface layers produced by plasma immersion ion implantation of stainless steel X6CrNiTi1810

A complex study of austenitic stainless steel X6CrNiTi1810 modified by nitrogen plasma immersion ion implantation (PI3) at 300 and 400°C is presented. To obtain detailed information on the structure and phase compositions, conversion electron Mössbauer spectroscopy, XRD, TEM, and Rutherford back scattering spectroscopy are applied. Depending on the treatment temperature a mixture of several phases is observed by Mössbauer phase analysis and confirmed by TEM. The dominant component in specimens treated at 300°C is a paramagnetic oversaturated austenitic phase. A higher implantation temperature (400°C) evokes more pronounced diffusion of nitrogen into the specimen volume, causing a decrease of nitrogen concentration but an increase of stress in the surface layer. This influences the defect density and results in a change of the expanded austenitic phase. Nitride formation is also different depending on the temperature. Furthermore, a texturing of the grains is observed after the PI3 treatment at both temperatures.

Structure and composition of expanded austenite produced by nitrogen plasma immersion ion implantation of stainless steels X6CrNiTi1810 and X2CrNiMoN2253

The structure and phase composition of the modified surface of two different stainless steels (austenitic steel X6CrNiTi1810 and austenitic–ferritic steel X2CrNiMoN2253) after 3 h plasma immersion ion implantation of nitrogen at 400°C were compared using XRD, SEM, TEM and Mössbauer spectroscopy. Both steels show a surface layer with very similar composition. The major phase found is expanded austenite. Very fine precipitates in the near surface region are most likely decomposition products (ferrite/martensite and CrN) of the metastable expanded austenite. The stability of the expanded austenite in the austenitic–ferritic steel is lower and the amount of decomposition products is higher under the same treatment conditions.

Nitrogen plasma immersion ion implantation for surface treatment and wear protection of austenitic stainless steel X6CrNiTi1810

Plasma immersion ion implantation is an effective surface treatment for stainless steels. The influence of treatment parameters (temperature, plasma density and pressure) on the sliding wear resistance are studied here. At moderate temperatures, nitrogen remains in solid solution without forming nitrides. This increases the surface hardness and the wear resistance without affecting the passivation of the steel. This may allow the use of such steels in applications where their poor wear resistance would normally prohibit their use.

Plasma immersion ion implantation: innovative technology for surface treatment of stainless steels: Third Prize

Plasma immersion ion implantation technology was used to produce expanded austenite and to study the influence of treatment conditions and starting material on its formation and structure. Standard materials characterisation techniques, XRD, TEM, conversion electron Mössbauer spectroscopy, and Rutherford back scatter spectrometry analysis were used to determine the structure of the layers, thereby revealing the complex structure of expanded austenite. The properties of the expanded austenite layers (hardness, wear, and corrosion) were determined and correlated with the structure. Most work was concentrated on the austenitic stainless steel X6CrNiTi1810 after treatments at 300 and 400°C. Based on these results, the possibilities of influencing properties by varying the process conditions are discussed.