Stainless Steel Layer Research Articles

Microstructure Study of the Stainless Steel Layer on AlSi Cast Alloy Prepared by Laser Deposition

The main aim of this study is structural changes on the layer of Al-Si cast alloy by laser austenitic stainless steel 17 246 deposition. In order to remelt the Al-Si alloy surface the laser of 1, 9 kW has been used for facing area, and 1.6 kW for the edge. The linear laser scan rate of the beam was set 450 mm.min-1 for facing area, and for the edge 550 mm.min-1. We observed that the thin surface made of austenitic stainless steel had a lot of splits. The purpose of this study is also to enhance inherent properties of the surface materials to create new product or improve on existing one.

Interfacial fracture morphologies of stainless steel clad plates after uniaxial tension

The interfacial fracture morphologies of stainless steel clad plates, dividing into stainless steel layer, diffusion layer and carbon steel layer, after uniaxial tension loading are investigated. It is found that the fractures occur randomly along the interface line between the stainless steel and diffusion layers, which could be induced by the stress concentration effect. The relatively high ductility of the carbon steel reduces the stress concentration to avoid the possible generation of the interfacial fracture in its layer. Furthermore, the bonding forces between the stainless steel and diffusion layers determine the distribution of the fractures. High bonding force could retain the interface without fracture, while the fractures would occur in the domains with low bonding force. This work deepens the failure mechanism of the stainless steel clad plates and is useful in the safety evaluation in their applications.

Residual stress in laser cladded rail

Abstract To improve the fatigue life of components subject to loads with high surface strain gradients, it is possible to coat them with an alloy of higher durability. The present study focuses on the effect of cladding high value track components, made of a standard rail steel UIC 900A/grade 260, with a layer of a premium martensitic stainless steel to reduce wear and fatigue. The laser cladding process inevitably generates residual stresses in the clad and parent metal, which could be detrimental to the integrity of the component. Therefore, measurements to determine the residual stress state of cladded rail were performed using semi-destructive centre-hole and deep hole drilling and non-destructive neutron diffraction techniques. Subsequently, the effects of cycling loading and wear, representative of typical service loads, on the redistribution of the residual stress field were investigated. It was observed that laser cladding causes a triaxial compressive residual stress field in the clad and near the interface and a tensile stress field in the parent material. The stress field is shown to change when the first cycle of load is applied but reaches a steady state after only 10 cycles: After the 10th cycle there is no evidence that the clad continues accumulating strain which could indicate that there is low risk of ratcheting. Wear effect on residual stress redistribution was found to be local on the surface of the specimen only.

Fabrication of Ni60+25%WC reinforced steel matrix surface composites by induction cladding

Failure of mechanical parts usually occur on the surface or start from the surface, such as wear, oxidation corrosion and fatigue. This work uses high frequency induction cladding technology to improve the overall performance of stainless steel surface. A layer of WC and stainless steel is coated on the surface of the stainless steel. The effects of different WC material contents and different induction heating current intensities on the cladding were analyzed. After the preparation of the sample, the morphology and properties of the cladding layer were analyzed by SEM, XRD and other test methods. The results show that when the content of WC is 2%-3%, the heating time is 90s and the heating current is 860A-890A. The surface of the cladding layer is most densely formed and there is no obvious over-burning phenomenon and pore generation.

Influence of heat treatment on the microstructure and corrosion resistance of martensitic stainless steel

Heat Treatment of martensitic stainless steels is used to increase the hardness that is caused by several microstructure changes. But such a treatment does affect both mechanical properties and corrosion resistance. Existing studies about the effect of austenitizing on the material properties and the corrosion resistance show contradictory results. Here we reveal the different effects of austenitizing on the passive layer of stainless steel and thus the corrosion resistance, thermodynamic phase calculations, microstructure investigations and various electrochemical measurements are performed. By potentiodynamic polarization scans the pitting potential, the critical pitting potential and the corrosion current are determined. Impedance spectroscopy are used to gain deeper insight into the passive layer properties. The results show a strong dependency of the corrosion behavior on the heat treatment where the governing corrosion mechanism are affected differently.

Experimental investigation on the mechanical and tribological coupled behaviour of bimetal composite under different states

Wear resistance and excellent mechanical properties are the main requirements in industrial applications of bimetal composites. The interfacial evolution of duplex stainless steel/low carbon steel (2205/AH36) bimetal composite after annealing and its tribological behaviour in a 3.5 wt% NaCl solution were investigated in this study. The bonding interface evolution between two layers plays a critical role in mechanical properties of composite, and the surface microstructure of stainless steel layer determines the wear and corrosion resistance. The hot-rolled composite samples were heat treated at temperatures ranging from 850 to 1150 °C in steps of 100 °C for 1 h. Optical microscopy (OM) and electron backscattered diffraction (EBSD) were employed to investigate the microstructural evolution of both component layers and bonding interface. The uniaxial tensile tests were used to investigate the tensile strength and elongation of composites after annealing at different temperatures. Ball-on-disc sliding tests were employed to study the tribological behaviour of bimetal composite, with sample discs being immersed in the solution. The variations of the coefficient of friction (COF) were recorded as a function of the sliding time, and the wear tracks of discs after tribological tests were observed by the laser scanning microscope and a scanning electron microscope (SEM). The results show that the annealing temperature significantly affects the width of bonding interface, and the total wear volume loss of duplex stainless steel of composite is dominated by the mechanical wear in the chloride solution.

Effects of surface layer of AISI 304 on micro EDM performance

Micro electrical discharge machining (micro EDM) provides an alternative in generating complex 3-D micro features in difficult-to-machine materials. The micro EDM performance depends not only on machining parameters but also on the microstructures and micro-characteristics of materials. The effect of free surface layer of austenitic stainless steel on the micro EDM performance is investigated in this paper. Experiments are carried out by machining multilayer stainless steel workpieces without and with surface treatment (acid pickling and oxidation treatment). Surface layer model is built to demonstrate the increasing influence of surface layer on micro EDM performance when the size of workpiece is decreased. The surface free energies of AISI 304 workpieces are estimated by measuring the contact angles. The results show that the steel workpiece with oxidation treatment has the highest surface free energy and the highest material removal rate compared with those without treatment and with acid pickling treatment. The influence of surface layer of steel workpiece on micro EDM performance is more significant when the discharge energy is lower due to size effects. Taper ratio of machined holes on steel workpiece without treatment is much higher than those of holes on steel workpieces with acid pickling and oxidation treatment. As a conclusion, surface treatment of steel workpiece before machining is an effective method to improve the machining efficiency and machining precision of micro EDM, especially when involving the sub-micro or nano-machining where machining is conducted on the workpiece surface.

Preparation of Cr2O3/Al2O3 bipolar oxides as hydrogen permeation barriers by selective oxide removal on SS and atomic layer deposition

Iron-nickel based stainless steel (SS) applied in nuclear plants as a substrate material barely suppresses the permeation of hydrogen plasmas, which are mainly composed of positive and negative hydrogen ions with trace amounts of non-ionized hydrogen atoms. In this work, a new Cr2O3/Al2O3 bipolar oxide barrier was prepared using atomic layer deposition (ALD) of Al2O3 on a Cr2O3 layer that was generated by removing partial oxides with cyclic voltammetry (CV) of SS that had been pre-oxidized at 550 °C in air. We found that a small layer of α-Al2O3 was formed by the template effect of Cr2O3 at the interface of this composite film. The hydrogen permeation behavior of this bipolar oxide barrier in a fusion reactor was simulated with hydrogen-discharging plasma treatment. The results demonstrated that the hydrogen permeation resistance of this bipolar oxide was superior to the original oxide or a Cr2O3 film. Impressively, hydrogen plasma treatment repaired the bipolar oxide via reduction of the defective CrO3, resulting in an improvement in the hydrogen permeation resistance. These findings demonstrate a novel method of hydrogen permeation barrier preparation on SS, providing insight into hydrogen barrier construction for future nuclear energy applications.

Properties and Technology of Applying Metal Coatings to Carbon Tape

The results of evaluating the adhesion strength and mechanical characteristics of elementary filaments used to make LUP carbon tape after metal plating the tape with titanium and stainless steel are presented. The thickness of these coatings is determined by atomic force microscopy and also by measuring the diameter of filaments before and after metal plating. Two types of single-layer coatings are considered – titanium grade VT1-0 and stainless steel grade 12X18H10T, as well as a two-layer coating consisting of a layer of titanium with a layer of stainless steel on top. To determine the adhesive strength using the pull-out method, a binder was used based on epoxy resin and an amine hardener.

Cavitation Erosion Resistance of Laser Beam Nitride Layers of X5CrNi18-10 Stainless Steel

The use of nitration in technical applications, as thermochemical treatment, regardless of the used method (ionic, gas or laser beam nitration) is realized to obtain a nitrogen rich layer, which increase the resistance to shock or abrasion, as a result of the high hardness obtained. All the previous cavitation researches showed that hardness is an important mechanical properties, for cavitation erosion resistance increase. The present paper show some results regarding the cavitation erosion behavior of laser beam nitrated layers. As basic material was used the austenitic stainless steel X5CrNi18-10. This material is frequently used for manufacturing details subjected to cavitation, such as valves, drawers of hydraulic distribution and regulation devices, or the retaining ring for butterfly valves. There were used three power regimes of the laser beams: 120 W, 180 W and 240 W. To obtain cavitation erosion was used the standard device with piezo-ceramic crystals of Timisoara Polytechnic University Cavitation Laboratory. The cavitation erosion comparisons, both with the basic material subjected only to the common thermochemical treatments and with the laboratory cavitation standard steel (OH12NDL), show that the nitrated surfaces presents increased cavitation erosion behavior, the principal factor being the important hardness increase of the nitrated layer. We mention also, that for higher laser beam powers the thickness of the nitrated layer increases. All the images obtained at the end of tests show that the cavitation exposure was stopped before overtaking the nitrated layer. So, all our results concern only the hardened layers.

Anisotropic Elastic Constants Calculation of Stainless Steel Cladded Layers of Pressure Vessel Steel Plate

Cladding stainless steel layer on the inner surface of ferrite pressure vessel is a common method to improve the corrosion resistance and save the economic cost. However, the movement of heat source and temperature gradient in the process of cladded welding will lead to the anisotropy of cladded layer material. When measuring the residual stress of pressure vessel steel plate with stainless steel cladded layers by contour method, it is necessary to know the elastic mechanical properties of stainless steel cladded layers accurately. The assumption of transversely isotropy was employed, and the relationship between the material compliance matrix and the elastic modulus of transversely isotropic material was utilized. Based on the elastic modulus of each cladded layer and the whole steel plate from the longitudinal direction (0°) until the transverse direction (90°) measured by the experiment, the independent constants S11, S13, S33 and S44 in the compliance matrix of each cladded layer and the whole steel plate were obtained by regression analysis method. Furthermore, by using the relationship between the independent constants of the stiffness matrix of the transversely isotropic material and the single crystal material, the independent constants S12 in the compliance matrix of each stainless steel cladded layer and the whole steel plate were obtained. And then the independent constants of the stiffness matrix of each cladded layer and the whole steel plate were acquired. Hence, a method for calculating the anisotropic elastic constants of the stainless steel cladded layer and the whole steel plate was proposed. The results will provide material data support for measuring residual stress of pressure vessel steel plate with stainless steel cladded layers by contour method.

Building Multi-Material components by Direct Laser Deposition

Most mechanical components are usually made of a single material, as a compromise between chemical, physical and functional properties. When designing an object, the choice of one material over another is driven by many reasons. Sometimes these reasons are not strictly technical, including for instance: biocompatibility, density, weldability, corrosion resistance, price, and appearance. Direct Laser Deposition (DLD) technology is an additive manufacturing process that allows the construction of objects by depositing material layer by layer. With DLD, the metal powder comes out of a nozzle conveyed by a flow of inert gas and is melted by a laser beam. One of the advantages of this technology over other AM technologies (such as SLM) is that it is possible to vary the composition of the deposited material by simply changing the metal powder. It is clear that with DLD technology, the properties of different metallic materials deposited together in a single object can be exploited. With this work the authors present two real-life case studies, in which the DLD technology is used to build multi-material components. Thefirst case concerns a gearbox component made of C40 steel that must work in a food environment and has therefore been completely covered with a layer of stainless steel. The second case is a flange that must have a weldable base, while the internal hole must be made of a high-performance tool-steel.

Process Analysis and Trial Tests for Hot-Rolled Stainless Steel/Carbon Steel Clad Plates

The trials of 304 stainless steel-clad plate made of plain Q345B carbon steel were performed on hot-rolling line of the Hesteel Group. After the two runs of pilot production, the key process parameters for the stainless steel/carbon steel clad plate were found to meet the GB/T 8165-2008 requirements. The interface shear strength of the clad plate was higher than 360 MPa, the yield strength of the final product was over 257 MPa, the clad plate tensile strength and elongation exceeded 351 MPa and 39.8%, respectively. The interpenetration of stainless steel and plain carbon steel layers was established to be complete, with the adequate composite interface. The tensile and shear properties of stainless steel-clad plates produced by the rolling process were at the same level as those obtained via the explosive method as an alternative, while their production cost were somewhat reduced.

回火温度对马氏体不锈钢激光熔覆层组织和性能的影响

回火温度对马氏体不锈钢激光熔覆层组织和性能的影响

Effect of Gas Content and Treatment Temperature on the Characteristic of Surface Layers of Low Temperature Plasma Nitrided 316L Austenitic Stainless Steel

The effect of gas content and treatment temperature on the surface characteristics of hardened layers of low temperature plasma nitrided 316L Austenitic Stainless Steel was investigated. The process was performed at fixed processing time at 15Hr and changing the N2 content from 10% to 25%, changing the treatment temperature from 370 °C to 430 °C. The surface hardness and the thickness of expanded austenite (S-Phase) layer increase with increasing both temperature and nitrogen content. At 430°C processing temperature and 25% N2 content, the S-phase layer thickness increased up to 13 μm and surface hardness increased about 3.5 times of that of untreated sample which is 880 HV0.1 (before treatment 250HV0.1 hardness). However, the XRD pattern of the this sample shows the presence of γ'-(Fe,Cr)4N precipitation on the surface which is the reason for the increased corrosion current density that results in increased corrosion rate. Thus the corrosion resistance degrades and presents even worst behavior comparing that of before treatment. Therefore, for increasing the corrosion behavior, further research was conducted by fixing the N2 content at 10% with changing the CH4 content from 0% to 5%. The best results were found when treated at 430°C with 5% CH4 content. At this condition the S-phase thickness increase to around 17μm and surface hardness (980 HV0.1) is improved about 3.9 times of the hardness of untreated one. This sample also showed superior corrosion resistance than the other treated samples and the untreated one due to much higher pitting potential.

Enhanced performances of deep nitriding austenitic stainless steel by a novel complex treatment

A novel combination of plasma nitriding and solution treatment was primarily developed for preparing deep nitriding austenitic stainless steel. Plasma nitriding was used to get high concentration of nitrogen in the surface layer of austenitic stainless steel at higher rate, and solution treatment was used to fully decompose the chromium nitrides formed during plasma nitriding and let nitrogen atoms dissolve into the matrix, and thus possible to get deep nitriding austenitic stainless steel. The performances of the treated samples were evaluated by optical microscopy, x-ray diffraction (XRD), micro-hardness test, electrochemical polarization and pin-on-disk tribotester. The results showed that a deep nitriding layer with effective hardening thickness of 1.0 mm composed of nitrogen expanded austenite (γN) was obtained for austenitic stainless steel by the novel complex treatment. Furthermore, the surface hardness of the PN+ST sample was up to 747 HV, 547 HV higher than 200 HV of untreated sample. The surface hardness of the specimen treated by the novel complex treatment was significantly improved, and the friction coefficient decreased from 0.8 to 0.7, the deep nitriding austenitic stainless steel had better corrosion resistance, the corrosion potential was increased from −0.534 V to −0.445 V, and the current density was decreased from 1.589 × 10−6 A cm−2 to 0.916 × 10−6 A cm−2.

An Impact Assessment of Metallization of a Carbon Tape Surface on the Mechanical Characteristics of the Filaments

Results of assessment of the mechanical characteristics of the filaments used for the production of LUP carbon tape with different types of coatings, as well as the thickness of the coatings determined by measuring of the filaments’ diameters before and after coating and with the help of an atomic-force microscope, are given. Two types of one-layer coatings made of BT1-0 titanium and 12Kh18N10T stainless steel, as well as a double-layer coating containing titanium layer coated with the stainless steel layer, are considered in this work.

Structure of the Surface Layers of Metastable Austenitic Stainless Steel Nitrided in Electron Beam Plasma

The effect of the nitriding temperature in electron beam plasma on the structural and phase composition of the surface layers of metastable austenitic stainless steels is studied. Conversion electron Mossbauer spectroscopy shows that nitriding at 350°C results in the transition of the austenite into the α (bcc) phase by the shear mechanism in the surface layers of a plate (tenths of a micron). A nitrogen supersaturated austenite and a mixture of nitrides with a predominant configuration of three nitrogen atoms in the environment of iron are formed in layers 1–5 μm thick. Nitriding at a temperature of 500°C and above leads to nitrogen supersaturated austenite decomposition, the escape of chromium and nitrogen from the matrix into nitrides CrN, Fe4N, and FexN, and the subsequent γ → α phase transformation.

Design of a shielding collimator device for a small-angle monoenergetic neutron source

To obtain a small-angle monoenergetic neutron source, a shielding collimator device is designed for the neutron source generated by a neutron tube. The device is divided into the collimator and the capture cave. The collimator is made of three layers of stainless steel and borated polyethylene and is used to constrain neutrons in a small angle. The capture cave is used to increase the number of times neutron inelastic scattering occurs in the opposite direction of the radiation field, thereby reducing the proportion of scattered neutrons in the radiation field. Material thickness, aperture size, and the optimum structure of the capture cave were simulated using MCNP. The design features a neutron emission angle within a range of 3° and neutron fluxes in the radiation field, which are higher by two orders of magnitude than those outside the radiation field. This research has practical value for the generation of monoenergetic small-angle neutron sources and neutron applications.

Microstructure and Mechanical Properties of Butt Joints between Stainless Steel SUS304L and Aluminum Alloy A6061-T6 by TIG Welding.

The tungsten inert gas (TIG) welding method most commonly used to weld ferrous metals, nonferrous metals, and other metals since it is simple, easily implemented, and achieves consistent high-quality welds. In this study, butt joints produced between aluminum alloy A6061-T6 and stainless steel SUS304L have been achieved by using TIG welding with ER4047 filler metal. The macrostructure and microstructure of the resulting specimens were analyzed by means of an optical microscope (OM), a scanning electron microscope (SEM), and an energy dispersive X-ray spectrometer (EDS). A uniform intermetallic layer was found at the interface between the stainless steel and the weld seam having a thickness of 2 µm, and the intermetallic compound (IMC) includes Fe4Al13, Fe2Al5, and FeAl3 phases. The micro-hardness and tensile strength of the weld joints were also investigated. Due to Si content in the compensating metal, there was a prevention of iron diffusion into the aluminum, thus hindering the development of the IMC layer and reducing its thickness in such a way that the weld joint strength increases. The analyzed results show that the average micro-hardness of the stainless steel, weld seam, aluminum alloys, and IMC layer were 218 HV, 88.3 HV, 63.3 HV, and 411 HV, respectively. The fracture occurred at the brazed interface, and the ultimate tensile strength value reached 225 MPa.