Surface Layer Resistance Research Articles

Heat Resistance of Surface Layers Obtained by Electron Beam Surfacing with Cr–B Powder Mixtures

Heat Resistance of Surface Layers Obtained by Electron Beam Surfacing with Cr–B Powder Mixtures

Analyzing the Mechanical and Durability Characteristics of Steel Slag-Infused Asphalt Concrete in Roadway Construction

Steel slag is a solid byproduct of the steelmaking process, widely generated in the metallurgical industry. Due to its alkaline nature and excellent adhesive properties with asphalt, it represents a potential road construction material with outstanding road performance, making it well-suited for utilization in highway construction. This paper conducts a systematic analysis of the physical and chemical properties of steel slag, specifically South Steel Electric Furnace slag, and compares it with natural basalt and limestone aggregates. The aim is to establish a foundation for the application of steel slag in asphalt mixtures. Building upon this foundation, we carry out proportioning design for AC-13C and SMA-13 steel slag asphalt mixtures, followed by a comprehensive study of their high-temperature stability, low-temperature stability, water stability, and fatigue performance. Our research reveals variations in the chemical composition of different steel slags, with CaO, SiO2, and Fe2O3 being the primary components. The content of harmful elements varies depending on the steelmaking raw materials and additives used. Notably, the optimum asphalt-to-aggregate ratios for AC-13C and SMA-13 significantly surpass the specified requirements. The freeze–thaw splitting strength ratio and residual stability of steel slag AC-13C and SMA-13 asphalt mixtures exceed the specified requirements, with AC-13C demonstrating the highest water stability, boasting a freeze–thaw splitting strength ratio of 94.07%, and a residual stability of 93.8%. In terms of fatigue characteristics, SMA-13 exhibits a longer fatigue life than AC-13C, indicating superior fatigue performance for steel slag SMA-13. Steel slag enhances the abrasion resistance and rutting resistance of asphalt pavement surface layers, fully meeting the performance requirements for high-grade road surface layers.

Structure and Abrasive Wear Resistance of Stainless-Steel Surface Layers Alloyed with Boron

Structure and Abrasive Wear Resistance of Stainless-Steel Surface Layers Alloyed with Boron

Development of technology to restore the working area of the stamp tool

Subject of research: technology for restoring the working area of a stamp tool, the structure and properties of the deposited layer of the restored stamp surface.
 Purpose of research: to develop a technology for restoring the working area of a hot deformation die insert for the formation of a gradient structure and properties of the metal over the cross section of the deposited zone.
 Methods and object of research: a technology for restoring the insertion of a worn hot-forming stamp on the beam of the front axle of a KAMAZ truck using two-layer electric arc surfacing with one type of electrode wire is presented. To obtain a gradient structure in the section of the working area of the die, heat treatment is proposed, which consists in tempering the die after the first surfacing at a temperature of 62010C, and after the second surfacing at a temperature of 52010C.
 Main results of research: it was found that after the restoration of the hot deformation die insert, the hardness of the deposited metal of the first (deep) layer was 3436 HRC, the structure was tempered troostite, the hardness of the second (outer) layer was 4246 НRC, structure tempered martensite and troostomare-tensite. This ensures high wear resistance of surface layers and crack resistance in the depth of the die metal.

Investigation of the surface layer of wheel steel by indentation method

The article considers methods of measurement of microhardness and modulus of elasticity of plasma hardened wheel steel by kinetic indentation method. It provides features of measurement of microhardness, modulus of hardness, elastic recovery, influencing on wear resistance of surface layers of steel. Measurement of these characteristics of material allows estimating and choosing optimum technology of surface modification by surface plasma hardening. It is confirmed that objectivity of determination of microhardness, modulus of elasticity, elastic recovery and flow stress depends on strict observance of imprint depth requirements depending on thickness of hardened layer. It is noted that in spite of the increased amount of factual information, obtained by indentation method, the physical substantiation of hardness micro-mechanisms remains poorly understood, which necessitates substantiation of physical representations of the nature of hardness of metallic materials. It is established that the measurement of microhardness, elastic modulus and elastic recovery by the kinetic indentation method is expedient to use for certification of the surface layer of plasma-hardened wheel steel according to the parameters of physical and mechanical characteristics.

Microstructural and electrochemical behavior of spark plasma sintered (Cu-10Zn) + Al2O3 nanocomposites

The present work deals with developing Al2O3 reinforced α-brass (Cu-10Zn) nanocomposites through spark plasma sintering and evaluated its electrochemical properties in a 3.5% NaCl aqueous solution. Microstructural analysis revealed the uniform dispersion of Al2O3 particles with inter-particle spacing ∼2.45 µm in 3 wt.% Al2O3 nanocomposites. The initiation of Al2O3 clustering and vast clustering of particles with wide particles-free-zone were observed in 6 and 9 wt.% Al2O3 nanocomposites. X-ray diffraction peaks confirm the crystallinity and incorporation of Al2O3 in the α-brass matrix. The corrosion behavior was studied by measuring the change in open-circuit potential values, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and potentiodynamic polarization (PDP) studies in 3.5% NaCl solution. The 3 wt.% Al2O3 nanocomposites exhibited lower icorr value than the Cu-10Zn matrix and other Al2O3 reinforced nanocomposites. The EIS results confirm the surface layer enhancement and resistance to charge transfer in 3 wt.% Al2O3 nanocomposites due to their uniform distribution in the matrix. The uniformly embedded reinforcement particles abridged the prospects of galvanic coupling, which resulted in the upliftment of corrosion resistance and passivation behavior. An increase in the icorr value beyond 3 wt.% Al2O3 nanocomposites was due to the clustering of reinforced nanoparticles and vast particle-free zones and caused intergranular corrosion.

Kinetics analysis and enhancement mechanism of aluminum-enhanced plasma nitriding for 42CrMo steel

Aluminum-enhanced plasma nitriding (Al-PN) was developed by a complex treatment of electrolyzing aluminum nitrate and plasma nitriding (PN) for 42CrMo steel; the kinetics and enhancement mechanism was analyzed. Optical microscope and X-ray diffractometer were used to determine the microstructure and phases constituents of the samples. The results show that much thicker case depth is obtained, with hard phases of AlN and FexAl formed in the surface layer by Al-PN treatment, which brings about much harder surface layer and excellent wear resistance. The kinetics analysis shows that the diffusion coefficient is enhanced by Al-PN, and the diffusion activation energy is reduced from 100.531 kJ/mol by PN to 45.177 kJ/mol by Al-PN. The relationship between case depth, temperature T (K) and holding time t (s) is obtained as: dAl-PN = 1.17 × 10−5exp(−5434T)t. (753 K ≤ T ≤ 793 K). Finally, the verification tests confirmed that the developed kinetics agrees quite well with the measured values; therefore, it can be used to predict the case depth for a designed process parameters in practical applications.

ANALYSIS OF TEMPERATURE DISTRIBUTION IN LASER ALLOYING OF PURE COPPER

In many cases, the use of copper is limited by the unsatisfactory properties of its surface layer, i.e., low hardness and wear resistance. Laser surface-layer treatment may be a better alternative to other techniques used in surface engineering intended for the elements, whose high conductivity, combined with high functional properties, is required. In the present work, laser alloying of pure copper with Ni powder is performed. Thermographic measurements during the process and measurements of the melt-pool dimensions after the alloying are performed. A 3-D model of a cylindrical specimen is developed. The enthalpy-based material model involving the phase change is applied. The nickel powder is taken into account with an appropriate value of the workpiece absorptance in the heat flux boundary condition imposed in the moving laser spot area. This study utilized the ANSYS-based Simulation software. Results of the temperature simulation show acceptable agreement with the experiment. The developed model can be used to predict the temperature distribution and identify the workpiece absorptance.

Increasing the wear resistance of surface layers of selected steels by TIG electric arc surface remelting process using a powder based on CaCN2

Increasing the wear resistance of surface layers of selected steels by TIG electric arc surface remelting process using a powder based on CaCN2

Low Concentration Electrolyte Enabling Cryogenic Lithium–Sulfur Batteries

AbstractLithium–sulfur chemistry suffers from poor conversion reaction kinetics, causing low‐capacity utilization of sulfur cathodes, particularly at cryogenic temperatures. Herein, based on low‐cost and abundant commercial sulfur particles directly, a low concentration electrolyte (LCE, 0.1 m) is employed to accelerate lithium–sulfur conversion reaction at low temperatures, demonstrating a broad applicability of this approach. Compared to conventional concentration (1.0 m) electrolytes, the proposed LCE successfully enhances conversion kinetics from Li2S4 to Li2S and restrains shuttle effects of polysulfides, resulting in higher capacity utilizations and more stable cycle performance at 0 and −20 °C. Further interfacial chemistry analyses on cycled electrodes reveal that a hybrid surface layer dominated by organic species as well as some favorable inorganics is constructed in the LCE, demonstrating smaller surface layer resistance. In situ EIS measurements at 0 °C and CV tests reveal main differences of electrode kinetics in 0.1 and 1 m electrolytes, further explaining the differences in working mechanism of two electrolytes. These findings elucidate the roles of LCEs on realizing faster kinetics for cryogenic lithium–sulfur batteries and provide a simple, low‐cost, and widely applicable pathway for achieving high‐performance lithium–sulfur batteries under extreme conditions.

Uncovering the Root Leading to Accelerated Capacity Fade of Li‐Ion Coin Cells in Fast Charging

Coin cells have been widely adopted for the evaluation of battery materials and chemistry. Herein, however, the coin cells are found unable to correctly reflect the fast‐charging capability of batteries. This is because, in the coin cells, the pressure between electrodes is provided by a wave spring while the wave spring cannot apply sufficient pressure to maintain the necessary electric contact for fast charging, leading to high polarization and resultant Li plating at the graphite anode. Testing on graphite/LiNi0.80Co0.10Mn0.10O2 coin cells shows that replacing the wave spring with a flat O‐ring washer dramatically stabilizes capacity retention in fast charging. Alternating current‐impedance analyses on the cells before and after 200 5 C‐charging cycles indicate that the cell with the O‐ring washer initially has a larger surface layer resistance, however, after fast‐charging test retained much smaller overall resistance compared with the cell using the wave spring. Visual observation of the cycled cell components reveals that the improvements are due to significantly reduced Li plating at the graphite anode, which is attributed to the appropriate pressure and the uniform distribution of the pressure applied by the flat O‐ring washer.

Microstructure and Wear Resistance of Plasma Surface Layers Based of Alloy Mixture CuSn10/CrxCy

Microstructure and Wear Resistance of Plasma Surface Layers Based of Alloy Mixture CuSn10/CrxCy

Exploratory Data Analysis for the Evaluation of Tribological Properties of Wear-Resistant Surface Layers Modified with Rare-Earth Metals

The role of rare Earth metals in the improvement of the properties of metals and alloys has been analysed and described in multiple studies. Their effects on changes in microstructure and mechanical properties are most pronounced. This paper focuses on the beneficial effect of rare Earth metal oxides on the wear resistance of surface layers applied to castings intended for structural elements of machinery and equipment in mining and recycling. The experiment involved modifying prepared surfaces by adding CeO2, Y2O3, and La2O3. Hardness measurements, a scratch test, and tribological tests were performed under dry and fluid friction. The maximum wear track depth and track area were measured from the surface profile. To determine correlations between the results, exploratory data analysis was employed. Heatmaps were used to illustrate strong positive and negative interactions. The addition of oxides at increasing carbon content resulted in increased hardness, lower coefficient of friction, and reduced track area and maximum track depth. Strong negative interactions between the track area and maximum track depth were found. The differences resulting from the test conditions (fluid and dry friction) were discussed. This study demonstrated the suitability of exploratory data analysis for analysing research results and confirmed the improvement of modified surface wear resistance.

Boronizing in Arms Industry

Comparison is made between several thermochemical treatment methods, with focus on boronizing. Boronizing has the potential to become a substitute for chromium plating or nitriding (gas nitriding) in the arms industry. This experimental study explored the chemical composition, hardness, corrosion resistance, tribological properties and toughness of several surface layers and coatings. The experimental substrates were EN 32CrMoV12-10 and EN 31CrMoV9 steels. Boronizing is intended for the gas tube and piston of a specific firearm. In the boride layer, the hardness of 1900 HV0.1 was reached. In the chromium and nitrided layers, hardness was 1100 HV0.1. In these experiments, original rifle tubes and disc samples were used. The thicknesses were as follows: the chromium layer: up to 70 μam, boride layer: 100 μam and nitride layer: 290 μam. Wear properties were compared using the Pin-on-Disc wear test. Fracture toughness according to Palmquist was the highest in the nitride case and the lowest in the chromium layer. Across all the layers, the range was from 2.5 to 9.5 MN/m3/2. Some differences were found between the boride layer with post-process heat treatment and layers without heat treatment. As a result of the research, it was found that Boronizing of the gas tube proved a suitable substitute for hard chrome plating or nitriding.

Mechanism and patterns of wear of chrome steels with a surface-modified layer

The paper presents the results of contact wear studies of surface layers of 6Cr4Mo2VSi steel under the action of pulsating contact stresses. Differences in wear resistance of surface layers of materials are shown, in interrelation with modes of synthesis of their structure and properties. The features of the evolution of the structure of modified layers strengthened by nitrocarburizing are revealed. The modes of thermo-chemical treatment for achieving maximum resistance to the action of pulsating contact stresses are determined.

Effect of friction stir process on the microstructure and corrosion behavior of AZ91 Mg alloy

Friction stir process (FSP) has been utilized to modify the surface microstructure of AZ91 alloy in three levels of rotation speeds and pass numbers. Microstructural and electrochemical analyses were performed on as-received and FSPed alloys, and their correlation was investigated. Optical and electron microscopy showed a significant grain refinement, accompanied by aluminum's dissolution into the matrix phase. The highest aluminum over-saturation occurred at 1200 rpm, which led to eutectic phase discontinuity at the grain boundaries. Additionally, the basal plane texture was studied using pole figures of the surface, which revealed extreme basal texture after the FSP. Utilization of X-ray diffraction (XRD) to calculate the residual stress before and after the FSP indicated substantial residual stress build-up. Accumulation of the eutectic phase at the grain boundaries led to the shift of the open circuit potential (OCP) toward more positive values in a 3.5% NaCl solution. Moreover, according to the electrochemical analyses, the corrosion rate increased after the FSP. At 1200 rpm of the rotation speed, more severe aluminum dissolution into the matrix phase increased surface layer resistance to breakdown. It was also observed that the accumulation of higher eutectic phases at the grain boundaries induces more galvanic microcells, which caused a drop of charge transfer resistance.

Interfacial barrier free organic-inorganic hybrid electrolytes for solid state batteries

Organic-inorganic hybrid solid electrolytes (HSEs) are expected to overcome the inherent limitations of rigid fragile inorganic electrolytes for solid state batteries. Li-ion conductive filler such as garnet Li7La3Zr2O12 (LLZO) is proposed for the high performance of HSEs, unfortunately, which suffers from native surface layer resistance to Li-ion transport. Here we present highly conductive polyvinylidene fluoride (PVDF)-based HSEs incorporating LLZO fillers, whose resistive barriers are eliminated by dry etching. Our optimal composition of etched LLZO fillers (30 wt%) leads to ionic conductivity of 4.05 × 10-4 S cm-1, about two-fold improvement from non-etched counterpart. Li symmetric cells with etched fillers exhibit low interfacial resistance of 110 Ω cm2 and minimal overpotential of 90 mV. Moreover, high capacity of 79 mA h g-1 is highlighted at 4C, comparable or superior to liquid electrolyte or sulfide-based electrolyte devices. Interfacial environment in HSEs ideally modified for Li-ion transport is identified by 7Li NMR measurements.

Electrochemical study and XPS analysis of chalcopyrite dissolution in sulfuric acid in the presence of ethylene glycol

The effect of ethylene glycol (EG) on chalcopyrite dissolution was studied in 1 M sulfuric acid at an open circuit potential and 25 °C. Electrochemical studies were performed having employed potentiodynamic and electrochemical impedance spectroscopy (EIS) techniques. Based on the results, the addition of 11% v/v of EG has decreased the current density from 10−4.7 to 10−5.1 A/cm2 and more addition of EG (22% v/v) has increased the current density. In the ferric-containing solution, while 5.5% v/v of EG was present, the addition of Fe3+ ions to the solution has decreased the polarization resistance value and resulted in a higher dissolution current. EIS results showed that increasing the EG concentration to 11% v/v caused an increase in both charge transfer and surface layer resistances. Besides, the composition of the inhibiting layer was studied having employed the XPS analysis. The result shows that the formation of the metal-deficient sulfide (Cu1-xFe1-yS2) is responsible for the inhibition of the chalcopyrite dissolution in 1 M sulfuric acid. However, the addition of EG to sulfuric acid media results in the appearance of the polysulfide (Cu1-x-zS2), elemental sulfur, and sulfate species on the chalcopyrite surface, which is dedicated to the facilitation of the mineral dissolution in the presence of ethylene glycol.

Research and application of anticorrosive concrete for shafts in thick and deep surface soil

Most frozen shafts of deep surface layer are located at a harsh environment, surrounding soil or groundwater with lots of corrosive ions such as SO4− and Cl−. This is deadly to the durability of concrete. Thus, concrete for shafts in deep surface soil requires excellent durability. This paper focuses on the development and preparation of anticorrosive concrete in deep surface layer shafts, and presents engineering application. The experimental results show that NC-H admixture is successfully made to prepare the concrete. The durability and impermeability of concrete are good. The Cl− diffusion coefficient of C60 is 38.1×10−14m2/s, while C90 is only 4.5×10−14m2/s. Besides, high freezing and thawing resistance is discovered. The loss of dynamic elastic modulus of C75 is less than 6.38% when the freeze-thaw cycle is 1000 times, It has high anti-sulfate ability and no corrosion to steel bar. This anticorrosive concrete has applied in many large coal mining projects. It is proved that this anticorrosive concrete has been applied to practical engineering application, and it can completely meet the requirements of cast-in-situ reinforced concrete shaft construction with deep surface layer and corrosion resistance.

Influence of Chromium Concentration on Corrosion Resistance of Surface Layers of Stainless Steel

Phase transformations occurring during the non-vacuum electron-beam surfacing using a mixture of amorphous boron and chromium powder (from 5 to 30 wt%) as well as the effect of the resulting structure on the corrosion resistance of the surface layers of chromium-nickel austenitic steel have been investigated. It has been found that when processing a powder mixture with a minimum chromium content (5 and 10 wt%), layers with a dense arrangement of borides are formed. Further increase in chromium concentration (20 and 30 wt%) leads to the formation of solid solutions in the modified layer. It has been shown that an increase in the concentration of chromium in the surface layer leads to a twofold increase in the corrosion resistance of the 12Х18Н9T (AISI 302) steel surface.