12Kh18N10T Stainless Steel Research Articles

Predicting the Effects of Cryogenic Treatment and Impact-Oscillatory Loading on Changes in the Strength Properties of Stainless Steels

Abstract New experimental results concerning the strength properties of stainless steels are analyzed. In particular, the strength properties of steels were improved at room temperature using the preliminary impact-oscillatory loading (IOL) in liquid nitrogen. Mechanical tests performed on stainless steel 12Kh18N10T have found the IOL conditions (deformation of the material during pulse loading—εimp = 9.69%), under which the ultimate strength of steel increases by 32.2% compared to the initial state under subsequent static tensioning. Metallographic analysis of the deformed steel revealed twinning in the microstructure. This accounts for a significant increase in ultimate strength under subsequent static tensioning. A method for estimating the ultimate strength of stainless steels of different chemical compositions by changing the percentage of the main chemical elements is proposed. To test this technique, stainless steel 12Kh18N9 was chosen. Similar studies using this steel at εimp = 9.5% in liquid nitrogen followed by static tensioning at room temperature have confirmed the effectiveness of the proposed approach.

The effects of cryogenic treatment and impact-oscillatory loading on changes in the mechanical properties and structural condition of stainless steel 12Kh18N10T

Research findings are presented dealing with the combined effect of cryogenic treatment + impact-oscillatory loading applied in different sequences on changes in the mechanical properties of stainless steel 12Kh18N10T. One-hour long cryogenic treatment and impact-oscillatory loading (IOL) applied at room temperature were shown to be practically unable to change the mechanical properties of the steel. At the same time, IOL pre-applied at a temperature of liquid nitrogen followed by static tensioning at room temperature proved to cause significant changes in the mechanical properties of the steel. Under further static tensioning, when IOL εimp = 2.7 … 12.5 % (assigned intensity range of introducing impulse energy into steel) or, more specifically, when εimp = 9.69 %, the ultimate strength of the steel was found to reach its maximum value, increasing by 32,2 % compared to baseline, while ductility decreased by 26 %. Specific physical investigations using the TEM microscope were conducted. The analysis of the steel structure of a specimen pre-subjected to IOL in liquid nitrogen at εimp = 9.63 % indicates that under such complex loading conditions the well-known mechanism of plastic deformation by sliding changes into plastic deformation by twinning upon further static tensioning, and the strength of the steel increases.

Fretting Wear of Metal–Metalopolymer Friction Couples

Test results on fretting wear of metalopolymer materials in a friction couple with structural materials—cast iron 20 and stainless steel 12Kh18N10T—performed over the direct and reverse test schemes are presented. As the metalopolymer material, we took the BELZONA 1111 two-component paste-like material based on a mixture of a metal–ceramic alloy with high-molecular polymers and oligomers.

Evaluation of the stressed state of cutting elements of coated end-milling hard-alloy combined cutters

This paper compares stresses arising in the tool material of combined end-milling cutters and their admissible values with the purpose of preventing cutter destruction. The limit stress values of tool materials for the developed endmilling hard-alloy combined cutters having an interfaced cutting part and tailpiece were investigated. The cutting part was made of a tool-grade hard alloy, and the tailpiece was made of structural steel. To determine stresses, simulation modelling was carried out in the ANSYS and Deform software. The cutting force components were found experimentally. It was assumed that lower cutting force components lead to lower stresses in the tool material. This results in a lower probability of tool material destruction. The process of cutting the hard-to-cut stainless steel 12Kh18N10T was considered at the following parameters: a cutting speed of 70 m/min, a cutting depth of 1 mm, and a feeding of 0.1 mm/tooth. The tool material VK8 with no coating and with various coatings promoting the reduction of cutting force components was studied. It was confirmed that a combined end-milling cutter 16 mm in diameter and 92 mm long can be used to cut parts with the same accuracy as using a solid end-milling hard-alloy cutter. An increase in the length of combined cutters decreases the cutting accuracy; however, for lengths 123 and 180 mm, these cutters can be used to manufacture parts applied in general machine building. Therefore, combined end-milling cutters can compete with solid cutters in terms of the manufacturing accuracy and resilience period, which limits the existing applicability of solid cutters. The cost of combined cutters is 10–60% lower than that of solid cutters.

Investigation of Uneven Properties of Stainless Steel 12Kh18N10T Depending on the Thickness of the Sheet

The authors conduct the research of the properties of a cold-rolled sheet made of corrosion-resistant steel 12Kh18N10T of a variable thickness. Further, they build hardening curves and defined their coefficients. The research identifies the patterns of the thickness impact on the nature of hardening of the sheet material 12Kh18N10T. The authors conduct the measurements of micro-hardness along the sheet thickness. The article confirms the suggestion that hardness in the sheet center decreases for various thicknesses. The authors further present a comparative analysis of hardness values distribution for the corrosion-resistant steel 12Kh18N10T and steel containing 0.08% of carbon. It is revealed that lower material thickness alters the strength parameters of the process and increases the mean material hardness. The authors provide the hardening curves for various sheet thicknesses and the dependence of hardness distribution on the thickness of these sheets.

Development of Technology for Vacuum Surface Conditioning by RF Plasma Discharge Combined With DC Discharge

Introduction. It is important to decrease light and heavy impurities influxes towards the plasma volume during the high temperature plasma experiments in fusion devices. This is why the conditioning of the wall inner vacuumsurfaces is a basic part of the fusion device operation.Problem Statement. The conventional inner vacuum chamber surface conditioning methods has a significant drawback: sputtering materials in a vacuum chamber. The inner vacuum surfaces can be also conditioned with radio-frequency (RF) discharge plasma, but the conditioning effectiveness is limited by low ion energy.Purpose. The purpose of this research is to develop vacuum surface conditioning technology by the radio frequency plasma combined with DC discharge. Materials and Methods. The noncontact passive method of optical plasma spectroscopy has been used to estimate ion plasma composition. The stainless steel outgassing has been determined in situ with the thermodesorption probe method. The sputtering of the samples has been measured with the weight loss method.Results. The studies of combined discharge have shown that: the anode voltage of combined discharge is lower than in case of the glow discharge; the stainless steel 12Kh18N10T erosion coefficient is about 1.5 times less in thecase of combined discharge than in the glow one; the thermal desorption diagnostic of wall conditions in the DSM-1 has shown better efficiency with the combined discharge as compared with the glow discharge. Theproposed technology is an original one and has no analogs.Conclusions. The reported research results have shown good prospects for the combined discharge usage for plasma walls conditioning and opportunities for using the combined discharge technology for big fusion machines.

Multifractal Analysis of Microstructures after Laser Treatment of Steels

The superficial microstructure, received by laser processing, is characterized by a high density of defects of a crystal structure and incompleteness of thermal phase and structural transformations. The degree of a neravnovesnost of such a structure can be estimated by means of multifractal ranges. As a measure for calculation of multifractals, it is possible to use any quantitative structural index, in particular, the area of microstructural objects, their perimeter and density of borders. The most informative is density of borders, which considers the area and perimeter of structural object. Microstructures of stainless steel 12kh18n10t in an initial state, after laser processing and a local laser alloying by hard-alloy powder from BK8 were investigated. Calculations of complex indicators of the structural organization of material, which showed, are executed on the basis of the multifratalnykh of ranges, that laser processing leads to, increase of orderliness and frequency. It indicates high degree of a neravnovesnost with which increase hardening increases.

Thermo-ultrasound method for determining the damage of structural material

The effect of plastic strain and temperature on the longitudinal and shear waves velocity of austenitic stainless steel 12Kh18N10T (analogue AISI 321) is investigated. Cryogenic corrosion-resistant austenitic steel 12Kh18N10T is interesting due to the fact, that during plastic deformation a martensitic phase is formed. The martensitic phase significantly changes the electromagnetic, elastic and strength properties of the entire material. The formation of a new phase in conjunction with the process of plastic deformation has a significant effect on the temperature dependence of the elastic wave velocity. As a result of the studies, numerical values of the temperature-velocity factor for longitudinal and shear ultrasonic waves in steel 12Kh18N10T were obtained. The relationship between changes of the magnetic phase and temperature-velocity factor is suggested; it can be used for determining the material damage by the ultrasound method.

Corrosion stability of austenitic steels 05Kh22AG15N8M2F and 12Kh18N10T in chloride-containing media

Comparative corrosion tests are performed of doped stainless steels: conventional stainless steel 12Kh18N10T and new high-tension austenitic steel 05Kh22AG15N8M2F with 0.47 wt % N with its flow limit being 2.5 times higher than that of the 12Kh18N10T steel. The resistance of steels to electrochemical corrosion in 3% NaCl solution is studied and field marine and atmospheric corrosion tests are performed. It is shown that the 05Kh22AG15N8M2F steel is characterized by higher corrosion stability than the 12Kh18N10T steel in both laboratory and field tests.

Study of wire tool-electrode behavior during electrical discharge machining by vibroacoustic monitoring

In the current study, the full research of wire electrode behavior during electrical discharge machining is presented. The analysis of the work preparation processes gave a possibility to clarify the main parameters (factors) influencing on the final characterization of the obtained object. For the experiments, the system MACHINE-TOOL-WORKPIECE was established. The system was equipped by vibro-acoustic accelerometers to register the signals during processing. Processing of two work pieces from stainless steel 12Kh18N10T (analogue AISI 321) and aluminum alloy D16 gave the characterization of the material behavior. Further, the analysis of SEM pictures gave the important data about the character of wire tool wear during processing. The two main natures of the wire tool wear were recognized. The scheme of the wire tool wear for rough and finish cuttings was developed to demonstrate the results of the research.

Effect of the electron beam and ion flux parameters on the rate of plasma nitriding of an austenitic stainless steel

The method of nitriding of metals in an electron beam plasma is used to change the current density and energy of nitrogen ions by varying the electron beam parameters (5–20 A, 60–500 eV). An electron beam is generated by an electron source based on a self-heated hollow cathode discharge. Stainless steel 12Kh18N10T is saturated by nitrogen at 500°C for 1 h. The microhardness is measured on transverse polished sections to obtain the dependences of the nitrided layer thickness on the ion current density (1.6–6.2 mA/cm2), the ion energy (100–300 eV), and the nitrogen-argon mixture pressure (1–10 Pa). The layer thickness decreases by 4–5 μm when the ion energy increases by 100 V and increases from 19 to 33 μm when the ion current density increases. The pressure dependence of the layer thickness has a maximum. These results are in conflict with the conclusions of the theory of the limitation of the layer thickness by ion sputtering, and the effective diffusion coefficient significantly exceeds the well-known reported data.

Effect of modes of ion-beam nitriding on the structure, microhardness, and magnetic properties of the diffusion layer on austenitic steel

The effect of modes of ion-beam nitriding on the structure, microhardness, wear resistance, and magnetic properties of diffusion layer on typical austenitic stainless steel 12Kh18N10T is studied. Optimum modes of ion-beam nitriding ensuring maximum microhardness and wear resistance of the irradiated surface are determined. The nitriding temperature, the microhardness of the surface, and the signals of the overlaid magnetic and electromagnetic transducers are shown to be related. The dependences obtained are explained and recommendations are given on their use for the nondestructive check of parameters of the nitrided layer.

Synthesis of carbon nanofibers on an austenitic stainless steel

The surface of the austenitic stainless steel 12Kh18N10T is found to be an effective catalyst for thermal synthesis of carbon nanofibers from acetylene. The morphology of the synthesized material is investigated as a function of the temperature and composition of the working gas mixture. The growth mechanism of carbon nanofibers is proposed. The inference is made that carbide (M5C2) regions formed in the surface layer upon annealing of the austenitic stainless steel in a hydrocarbon atmosphere are catalytically active zones.

Kinetics of scattered fracture in structural metals under elastoplastic deformation

The paper presents a procedure whereby the damage accumulation kinetics in structural materials, such as steel 45, stainless steel 12Kh18N10T, aluminum alloy D16T, and titanium alloy VT22, under elastoplastic deformation is studied based on variation parameters of elastic modulus and resistivity. For complex stress conditions, a continuum model for damage accumulation is proposed which relates the damage parameter to the intensity of accumulated plastic strains. The data calculated by the proposed continuum model are compared to the experimental findings of the investigation of the damage accumulation kinetics for some structural metals.

Tribological properties of detonation coatings based on titanium aluminides and aluminum titanate

Operation of coatings based on tialite, γ-TiAl, titanium aluminides with discrete inclusions of TiN and also alloys based on cobalt, nickel, and titanium in friction pairs with polyethylene grade “Chirulen” and stainless steel 12Kh18N10T is studied. It is established that tialite coatings formed from nanostructure powders of Ti-Al by detonation deposition are the best for operation under dry friction conditions in a pair with stainless steel 12Kh18N10T (minimum friction coefficient and minimum wear of the contact surfaces). It is shown that in the sliding rate range selected effective operation of material in friction pairs with polymer is provided due to transfer it to the contact surface and formation between rubbing surfaces of a thin film fulfilling the function of a solid lubricant. It is established that stable operation with the minimum wear in a friction pair with polyethylene grade “ Chirulen” is provided by a coating of γ-TiAl and Al2TiO5, and also coatings based on titanium aluminide with fine TiN inclusions.

Experimental investigations of the characteristic features of local yield layers

Distinct contours of traces of local yield layers (LYL) are observed on surfaces of tensioned specimens formed from heat-treated steel 09G2S (COST 19282-73). Single- and bimetallic specimens (basic layer — steel 09G2S, plating — stainless steel 12Kh18N10T) were investigated. In the bimetallic specimens, LYL are generated near the surface of the ferrous metal, intersect the broad face at an angle of 54.7°, and approach the surface of the plating layer at an angle of π/2; the trajectory of the curved sections of the traces on the narrow faces is approximated by a logarithmic spiral, for which the angle between the radiusvector and the tangent is equal to arctan 1/√2. It is proposed that an LYL in an elastically deformed metal is developed by conversion of a portion of the volume adjacent to the mouth of the layer to plastic metal.

Growth of layers of intermetallic phases on the interface between stainless steel 12Kh18N10T and liquid aluminum

Growth of layers of intermetallic phases on the interface between stainless steel 12Kh18N10T and liquid aluminum

Effect of hot deformation on the susceptibility to intercrystalline corrosion of steel 12Kh18N10T

1. Susceptibility to ICC of hot rolled tubing of stainless steel 12Kh18N10T depends on the hot deformation temperature; the higher the deformation temperature, the greater the susceptibility. 2. The hot deformation temperature at which susceptibility to ICC occurs decreases as the Ti/C ratio decreases and may vary from 1230 to 1100°.