Nitrocarburizing Research Articles

Study on the microstructure and properties of 35Mn2V steel used in oil pipe by salt bath nitriding

Oil pipe is easy to fail due to wear and corrosion during its service, which seriously affects the normal oil production and causes some unnecessary losses，while salt bath nitriding can form a composite infiltration layer through the composite technology on the surface of the workpiece, which can realize the combination of nitriding and oxidation, to achieve the effect of surface strengthening and modification. In this paper, salt bath nitriding is carried out on oil pipe (35Mn2V steel) with different temperature and time, and metallographic test, loose layer grade evaluation, XRD analysis, SEM observation, corrosion wear test, etc. are conducted to study the effect of salt bath nitriding process on the structure and properties of the permeating layer, comprehensively evaluate the quality of the permeating layer, and explore the wear resistance mechanism. The results show that when 35Mn2V is nitrided at 580℃, the infiltration layer mainly consists of oxide film, porous layer, compound layer and diffusion layer, while when it is nitrided at 630℃, the infiltration layer consists of an additional nitrogenous austenite layer. The thickness of 35Mn2V compound layer increases with the increase of nitriding temperature and the extension of nitriding time, and the influence of changing nitriding temperature on the thickness is greater than that of changing nitriding time. After a short time and low temperature nitriding, the phase composition of the infiltration layer is mainly ε-Fe3N and ε-Fe3O4, after a long time and high temperature nitriding, the phase composition is mainly ε-Fe2N and Fe3O4, in which Fe3O4 is formed in the subsequent oxidation process. The degree of loose layer of the infiltration layer increases with the increase of nitriding temperature and the extension of nitriding time. Most of the loose layer grades of the infiltration layer are level 3, and a few are level 2. The degree of loose layer of the infiltration layer is determined by the process of salt bath nitriding, and the subsequent oxidation, ion stabilization and other processes have little influence on it. When 35Mn2V is subjected to corrosion wear test under small load, the friction coefficient of oxide film is small. When the loose layer is worn, the friction coefficient increases obviously. The compound layer is mainly composed of iron-nitrogen compounds, and its friction coefficient is minimal and relatively stable. When the compound layer is worn through, the friction coefficient of the diffusion layer increases.

Effect of post-oxidation times in the nitrocarburizing process on the wear behavior of an AISI 4140 steel

Abstract This study investigates the influence of post-oxidation duration on the wear performance and microstructural features of AISI 4140 steel subjected to nitrocarburizing followed by post-oxidation. For this aim, the quenched and tempered AISI 4140 samples were nitrocarburized (NC) and post-oxidized (PO) at various times (45–180 min) under low vacuum. Microstructural features were investigated using optical microscopy, scanning electron microscope (SEM), energy-dispersive X-ray spectrum analysis (EDS), X-ray diffraction (XRD) analysis, and microhardness test. Wear behavior was evaluated using a ball-on-disk tribometer. Experimental results showed that the structures consisting of nitride layer (ε-Fe2–3N) and γ′-Fe4N + iron oxide (Fe3O4) were obtained at the top surfaces of the samples. Increasing post-oxidation times resulted in a notable enhancement in the thickness of the Fe3O4 layer. The growing Fe3O4 layer has induced the closing of micro porosities for further post-oxidizing times, leading to decreased surface roughness of the samples. It was determined that the post-oxidation times have no significant effect on the hardness profiles of NC + PO samples. The highest (0.375) and lowest (0.276) mean coefficient of friction was obtained in the post-oxidation times of 150 and 180 min, respectively. The best wear rate was obtained in the post-oxidized sample for 150 min.

Bimetallic Ni‐Co Supported on Nitrogen‐Doped Carbon Nanotubes For Prox Reaction

AbstractHydrogen is a key component for a successful energy transition on a large scale since it boasts remarkable energy efficiency. Currently, H2 is mainly obtained through steam reforming of natural gas or hydrocarbons and low‐carbon alcohols but contains approximately 2 % CO, a contaminant detrimental to H2 fuel cells. Herein, an N‐doped carbon nanotube was prepared via the soft nitriding method to support nickel and cobalt for the PROX‐CO as the main reaction for hydrogen purification. The most efficient condition was achieved when the reaction temperature reached 250 °C and the Ni and Co loading rate was 7.5 %. In this situation, the CO2 selectivity reached almost 33 %, and CO conversion was 61 %. Regarding CO conversion among bimetallic catalysts at 250 °C a minimal variation occurred and the catalyst 10Ni/N‐CNTs slightly outperformed (64.4 %). The effect of N‐doping on the carbon nanotube's structure was also revealed. Nitrogen atoms incorporated into the lattice of carbon nanotubes impart an electron‐donor character. Consequently, Co oxide reduction to the metallic phase occurred at significantly lower temperatures compared to other supports such as SiO2, Al2O3, and graphene. For the bimetallic catalysts, the strong metal‐support interaction facilitated obtaining different oxide and metallic phases at milder temperatures.

Effects of stress-relief and natural aging on the geometric tolerances and functional requirements of ferritic nitrocarburized gray cast iron brake rotors

Gray cast iron (GCI) brake rotors are prone to corrosion, particularly in electric vehicles (EVs), owing to their regenerative braking systems. Ferritic nitrocarburizing (FNC) heat treatment has been used to improve the corrosion resistance and cleanability of GCI rotors. However, pre-existing residual stresses in the rotors can lead to distortion after FNC processing, thereby affecting the functional and tolerance requirements. This study investigated the effects of stress-relief (SR) heat treatment and natural aging (NA) on the natural frequency, damping properties, surface roughness, and geometric tolerances of GCI brake rotors before and after FNC treatment. The GCI brake rotors were subjected to SR and NA processes, followed by FNC treatment. The natural frequency, damping Q-factor, surface roughness, and geometric tolerances were measured and analyzed using two-way ANOVA at a 95% confidence level (α = 0.05). The results showed that SR heat treatment significantly reduced the effect of residual stresses and improved geometric tolerances compared to NA. The FNC treatment increased the surface roughness and slightly improved the damping properties but had an insignificant effect on the natural frequency. The combination of SR and FNC treatments provided the best overall performance in terms of quality, geometric tolerance, and surface finish. This study highlights the importance of SR heat treatment for optimizing the manufacturing process of FNC-treated GCI brake rotors for EVs.

Electrochemical Sensor based on N-Doped Graphite/Aluminum Silicate Nanocomposite Modified Carbon Paste for Simultaneous Detection of Paracetamol and Pamabrom

We have developed an eco-friendly sensor through innovative modification of a carbon paste electrode with nanomaterials. This modification is based on employing a mixture of aluminum silicate and nitrogen-doped graphite nanocomposite (Al2SiO5/NG/CPE), introducing the first electrochemical approach for the voltammetric determination of a combination of paracetamol (PCM) and pamabrom (PAM), which is recognized as an over-the-counter remedy for menstrual cramp relief. N-doped graphite was prepared from graphite and urea using a metal-free soft nitriding method. The morphological characterization of the Al2SiO5/NG nanocomposite was investigated using transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The experimental conditions were optimized using square wave voltammetry and cyclic voltammetry techniques to explore the impact of scan rate, pH, and concentration. The results exhibited good linearity across a wide concentration range of 0.2 nM–100.0 μM for both drugs. The limits of detection for PCM and PAM were 25 and 24 pM, respectively, while the limits of quantification were 88.3 and 80.0 pM, showing the proposed sensor’s exceptional sensitivity. Furthermore, the proposed sensor was employed to determine the PCM/PAM mixture in bulk powder, pharmaceutical dosage forms, biological fluids, and in the presence of toxic paracetamol metabolites.

Studies on the Effect of Salt Bath Temperature and Nitriding Time on Corrosion Properties of Low Silicon Spring Steel for Automotive Suspension System

Studies on the Effect of Salt Bath Temperature and Nitriding Time on Corrosion Properties of Low Silicon Spring Steel for Automotive Suspension System

Alginate Hydrogel Integrated with a Human Fibroblast-Derived Extracellular Matrix Supports Corneal Endothelial Cell Functionality and Suppresses Endothelial-Mesenchymal Transition.

Human corneal transplantation is still the only option to restore the function of corneal endothelial cells (CECs). Therefore, there is an urgent need for hCEC delivery systems to replace the human donor cornea. Here, we propose an alginate hydrogel (AH)-based delivery system, where a human fibroblast-derived, decellularized extracellular matrix (ECM) was physically integrated with AH. This AH securely combined with the ECM (ECM-AH) was approximately 50 μm thick, transparent, and permeable. The surface roughness and surface potential provided ECM-AH with a favorable microenvironment for CEC adhesion and growth in vitro. More importantly, ECM-AH could support the structural (ZO-1) and functional (Na+/K+-ATPase) markers of hCECs, as assessed via western blotting and quantitative polymerase chain reaction, which were comparable with those of a ferritic nitrocarburizing (FNC)-coated substrate (a positive control). The cell density per unit area was also significantly better with ECM-AH than the FNC substrate at day 7. A simulation test of cell engraftment in vitro showed that hCECs were successfully transferred into the decellularized porcine corneal tissue, where they were mostly alive. Furthermore, we found out that the endothelial-mesenchymal transition (EnMT)-inductive factors (Smad2 and vimentin) were largely declined with the hCECs grown on ECM-AH, whereas the EnMT inhibitory factor (Smad7) was significantly elevated. The difference was statistically significant compared to that of the FNC substrate. Moreover, we also observed that TGF-β1-treated hCECs showed faster recovery of cell phenotype on the ECM. Taken together, our study demonstrates that ECM-AH is a very promising material for hCEC culture and delivery, which endows an excellent microenvironment for cell function and phenotype maintenance.

Influence of aisi 304 austenitic stainless steel by aqueous soluted nitriding and gas nitriding

AISI 304 austenitic stainless steel has great corrosion resistance,but it lacks in hardness,strength and wear resistance.So in order to improve these various hardening techniques are followed.In the present research salt bath nitriding and gas nitriding were carried out to improve hardness and wear resistance.Three samples are treated with salt bath nitriding and the other three samples are treated by gas nitriding and the one sample is kept aside to compare the results.The samples were wear tested on pin on disc apparatus after the heat treatment.Then the samples are subjected to Scanning electron microscope test and then the results were compared

Comparison of Effect of Ferritic Nitrocarburising on En-19,En-24 and En-37 Steels

Nitrocarburizing is one of the prominent surface treatment methods for steels. The effects of ferritic nitro carburizing on En-19, En-24 and En-37 steels are compared. Microstructural investigations of FNC treated samples are carried out. Micro hardness profiles of FNC treated steels are drawn. Further wear investigations are carried out. It is observed that FNC treated En-19 steel has more wear resistance in comparison to En-24 and En-37 steels.

Dynamometric Investigation on Airborne Particulate Matter from Automobile Brake: Impact of Disc Materials on Brake Emission Factor

In this work, we evaluated the impact of disc rotors of gray cast iron (GCI), nitrocarburized (NC), and superhard ceramic-coated (SCC) GCI on the brake wear PM emissions of passenger vehicles using dynamometric measurements. The brake emission factor (BEF) of the SCC was greatly reduced by more than a factor of 1/5 compared with those for the GCI and NC for both low-steel and non-steel friction materials. Surface topological and microstructural analyses confirmed that more severe wear was pronounced for the NC rotor compared with the SCC, as evidenced by large concave pits in the wear tracks. Analysis of the size-classified airborne PM suggests that reduced micron-sized particles, which originated from the GCI disc, were responsible for the lower BEF due to the increased hardness of the SCC.

A kind of Fe3N alloy powders prepared by high-temperature chemical nitriding treatment with excellent wave-absorbing properties in C band

Firstly, the flake Fe95Si1B2P0.5Cu1.5 alloy powders were prepared by the combined technology of “medium frequency melting + 3D printing + high energy ball milling”, and then the flake single phase ε-Fe3(SiBPCu)-N powders were prepared by the chemical high temperature nitriding reaction using the flake alloy powders prepared as the precursors. The samples were characterized by Field Emission Scanning Electron Microscope (FESEM), X-ray Diffractometer(XRD) and Vector Network Analyzer, and the electromagnetic parameters and electromagnetic loss mechanism of the alloy powders prepared by different nitriding processes in 0.3–8.5 GHz band were focused, and wave-absorbing properties were optimized according to the transmission line theory finally. FESEM showed that holes were formed on the surface of the powders after nitriding, which was easy for electromagnetic waves to be absorbed. XRD confirmed that the physical phase structure of the alloy powder prepared after salt bath nitriding was ε-Fe3N, and average crystallite size of ε-Fe3N increased with the complete nitriding reaction. The generation of ε-Fe3N phase lead to an increase in the real part of the complex permittivity of the alloy powder, and the real part of the permeability decreases slightly, however, larger average crystallite size of ε-Fe3N is beneficial for the improvement of the permeability. After the nitriding reaction at 580 °C *1h, the loss mechanism of alloy powders is changed from magnetic loss dominated to a dual loss mechanism of dielectric loss dominated and magnetic loss supplemented, and the loss angle tangent value increased from 0.6 to 0.7 to 2.3–1.0, and the thickness values of interference absorption decreased significantly, which is conducive to the realization of the effect of strong absorption of thin material. Taking a multilayer laminate thickness of 5.0 mm as the design index, the optimized GF/FeSiBPCu-N powders (thickness of 1 mm)/GF composite plate has excellent wave absorption in the C-band with reflectivity R < −10 dB in the frequency band of 5.52 ∼ 8.5 GHz and a bandwidth of nearly 3 GHz, which has achieved a breakthrough.

Role of Dislocations and Deformation-Induced Martensite on Salt Bath Nitriding Response of Austenitic Stainless Steel

Role of Dislocations and Deformation-Induced Martensite on Salt Bath Nitriding Response of Austenitic Stainless Steel

Effect of Salt Bath Nitriding and Reoxidation Composite Texture on Frictional Properties of Valve Steel 4Cr10Si2Mo

In order to improve the service life of 4Cr10Si2Mo valve steel, laser processing technology was used to prepare triangular textures with different area occupancies on the surface of 4Cr10Si2Mo, and then 4Cr10Si2Mo was subjected to salt bath nitridation (salt bath temperature 580 °C) and oxidation (oxidation temperature 400 °C). The mechanism of composite surface treatment technology on friction and wear performance of valve steel was explored. The effect of triangular texture on working surface stress and hydrodynamic pressure was explored using simulation technology, and the mechanism of texture in friction was further studied. The XRD test results showed that after salt bath nitriding and reoxidation treatment, the surface of 4Cr10Si2Mo mainly contained Fe2N oxide film and Fe3O4 and other components. The XPS test showed that the nitriding layer contained Cr-N, and the surface hardness reached 710.5 HV0.5. The simulation results showed that introducing surface texture will increase the stress on the contact surface, especially near the texture. However, under lubricating conditions, the flow field in the textured lumen produces a wedge effect, which increases the oil film pressure. After salt bath nitriding composite texture treatment, the wear resistance of 4Cr10Si2Mo significantly improved under the synergistic effect of the nitrided layer dominated by the magnetite phase (Fe3O4) and the microtexture. Fe3O4 can reduce the friction coefficient and resist oxidation reactions. In addition, the texture of the area occupancy of the texture also affects the surface tribological properties. The texture with an area occupancy rate of 11.45% (low × high is 0.3 mm × 0.3 mm) had the best anti-friction effect, and the friction coefficient reduced by 65%.

Sliding wear behaviour of salt bath nitrided 316LN austenitic stainless steel

The wear behaviour of AISI 316LN austenitic stainless steel has been studied by varying the duration of nitriding. AISI 316LN steel was nitrided using salt bath nitriding which consist of a mixture of 70:30 ratio of alkaline cynates and carbonates. Nitriding was carried out for two time durations namely 60 min and 100 min. Pin-on-Disc wear test were carried out for both the untreated and treated sample at room temperature. The wear parameters were changed to understand the wear mechanism of AISI 316LN steel along with the nitrided sample by varying the sliding distance for 250 m, 500 m and 1000 m. Due to the presence of different wear mechanism the rate of wear varies as a function of sliding distance. For untreated sample the wear mechanism was dominant with adhesion, abrasion and plastic deformation. An optical micrograph, X-ray diffraction analysis, wear morphology, hardness measurement and surface roughness were carried out. Due to the presence of compound layer as a result of nitriding AISI 316LN austenitic stainless steel, the mechanism of wear was restricted to abrasive wear. Untreated specimens have more significant wear loss when compared to treated specimen as work hardening and an increase in hardness of wear track resulted in material pull out. Stability of the compound layer is achieved as a result of longer duration of nitriding. Abrasive wear is resisted to a greater extend due the availability of compound layer. AISI 316LN steel which was nitrided for 100 min exhibited a more stable compound layer when compared to the same nitrided for 60 min.

Low-pressure ferritic nitrocarburizing: a review

The purpose of this article was to present in a concise and organized way the available knowledge about ferritic nitrocarburizing in low-pressure. The authors aimed to indicate the research gap, and the whole article is a starting point for further research.The research method was the analysis of available literature, patent database and industry notes from manufacturers of modern furnaces.The ferritic nitrocarburizing process has many advantages in line with the market demand and the lack of solutions. The article summarizes the knowledge in the field of the ferritic nitrocarburizing process as a systematization of knowledge and a starting point for further research.The information described in the article requires further laboratory research.The information collected by the authors was the basis for developing the technology discussed in the LIDER/3/0025/L-12/20/NCBR/2021 project.Research on this type of treatment will enable the development of technology and will meet the expectations and needs of the industry. It will also provide benefits in the form of a better understanding of the processes and the determination of the relationship between the parameters and the properties of the obtained surface layers.

(General Student Poster Award Winner - 1st Place) Nitrogen-Doped and Phosphorus-Doped Carbon Fiber Ultramicroelectrodes As Electrochemical Sensors for Detection of Hydrogen Peroxide

Ultramicroelectrodes (UMEs) are generally defined as electrodes with sizes ≤25 µm. UMEs can be prepared by several methods including by sealing a conductive filament like thin metal wire or a single carbon fiber in a glass capillary. The small size of UMEs makes them useful as probes for measuring electroactive species in confined spaces (for example, inside living cells, etc.), and also enables very effective mass transport, resulting in rapid achievement of steady-state response and facilitating measurement of fast electrochemical reactions. Application of UMEs often requires modification of the electrode surface to improve the selectivity and the sensitivity towards the target analyte. Surface modification methods are time-consuming and may require expensive equipment. Previous research in our group demonstrated that a simple soft nitriding method could be employed to introduce surface nitrogen on carbon fiber (CF). The technique improved electrochemical response of CF-UMEs towards hydrogen peroxide (a reactive oxygen species that has been related to various malignancies and disorders) and, in separate experiments, also enabled deposition of electroactive metal nanoparticles on the UME surface. Since the presence of phosphorus heteroatoms on carbon electrodes has been shown to impart similar benefits, here we investigate a simple phosphorus doping strategy to make P-doped CF-UMEs. We compare their properties towards the electrocatalytic reduction of H2O2 to both N-doped CF-UMEs and unmodified CF-UMEs.

Modification of Surface Structure by Diffusion Processes

In the paper an effect of a diffusion technology such as gaseous ferritic nitrocarburizing on the surface properties of selected alloyed case-hardening steel was tested. The steel 18CrNiMo7-6, primarily predetermined for carburizing and frequently utilized in manufacturing of highly strained components, where high core tensile strength as well as hard surface is demanded, was exposed to gaseous ferritic nitrocarburizing. Such treated surface was subjected to experimental methods. The microstructure observation and the determination of the white layer thickness was performed on the Opto-digital microscope Olympus DSX500i. The nitriding hardness depth of the surface layer from the microhardness profiles obtained by the microhardness tester LM247 AT LECO was deduced. The wear resistance was assessed by utilizing the Scratch test method performed on the tribometer Bruker UMT-3 TriboLab. Results of the measurements present an effect of gaseous ferritic nitrocarburizing on the surface properties of the steel 18CrNiMo7-6 and provide a perception of possibility to substitute the frequently utilized carburizing by the gaseous ferritic nitrocarburizing.

A novel low temperature and green salt bath nitriding of titanium alloy

ABSTRACT A novel low temperature and green salt bath nitriding of TC4 titanium alloy was developed by adding a certain amount of K2SO4 in the KNO3 and NaNO3 salt bath. The results show that compared with as-received TC4 alloy, the surface hardness and tribological properties of the nitrided titanium alloy were greatly improved. Furthermore, based on the theoretical and experimental analysis of the effects of the K2SO4 on the inhibition of the cyanide in the nitriding salt bath and tribological properties of the nitrided samples, wonderful discoveries were obtained. The tribological properties of the nitrided samples were dominated by not only the surface hardness but also the subsurface hardness. Moreover, there exists an optimum value for K2SO4 addition (about 1 wt-%): K2SO4 can not only effectively inhibit cyanide production but also cause the hardness in the nitride layer subsurface to further be improved, resulting in the further enhancement of the tribological properties.

Possibilities of the Utilization of Ferritic Nitrocarburizing on Case-Hardening Steels.

This paper is devoted to the possibilities of the utilization of chosen chemical heat treatment technologies on steels used for manufacturing highly stressed components of military vehicles and weapons systems. The technologies chosen for this research are plasma ferritic nitrocarburizing and ferritic nitrocarburizing in a gaseous atmosphere. These technologies were applied on a steel equivalent 1.5752 (i.e., CSN 41 6426), which is suitable for carburizing. Chemical composition of the steel was verified by optical emission spectrometry. An observation of a microstructure and an assessment of the parameters of obtained white layers were performed by optical microscopy. Morphology and porosity of the surface were observed by electron microscopy. The depth of diffusion layers was evaluated in accordance with ISO 18203:2016(E) from the results of microhardness measurements. A friction coefficient was obtained as a result of measurements in accordance with a linearly reciprocating ball-on-flat sliding wear method. Wear resistance was assessed by employing the scratch test method and a profilometry. The profilometry was also utilized for surface roughness assessment. It was proved that both tested chemical heat treatment technologies are suitable for surface treatment of the selected steel. Both technologies, ferritic nitrocarburizing in plasma and a gaseous atmosphere, are beneficial for the improvement of surface properties and could lead to a suppression of geometrical deformation in comparison with frequently utilized carburizing. Moreover, the paper presents a procedure that creates a white layer-less ferritic nitrocarburized surface by utilizing an appropriate modification of chemical heat treatment parameters, thus subsequent machining is no longer required.

Sequential low-temperature plasma-assisted thermochemical treatments of the AISI 420 martensitic stainless steel

The application of low-temperature plasma carburizing (C), nitriding (N) and nitrocarburizing (NC) treatments in sequential steps on AISI 420 martensitic stainless steel was investigated through nine different treatments. Experiments were performed at 400 °C, being divided in three (8 h)-single treatments, namely C, N and NC, and six distinct (4 h + 4 h)-sequential treatments, namely C + N, N + C, C + NC, N + NC, NC + N, and NC + C, using appropriate gas mixtures for each treatment step. Sequential treatments promoted the formation of treated layers constituted of iron carbides/nitrides, chromium nitrides, and nitrogen/carbon-expanded martensite phases. Interesting results were obtained for both C + N and C + NC sequential treatments, whose application results in greater hardening depths (~20% thicker) and leads to ~40% increase on the surface hardness, when compared to the obtained for the single C treatment keeping a smooth hardness profile. From the microstructural characterization, no significant sensitization was evidenced in the outer layers obtained for all treatments comprising the carburizing step, an indicative result that the interstitial carbon retards the chromium-rich particles precipitation kinetics. The combination of N + NC treatments produced thicker and harder treated cases compared to those produced by the respective single treatments. In brief, results showed that the appropriate selection of thermochemical treatments' sequence can promote increased treatments efficiency concerning the treated layers thickness or effective surface hardness. This work also contributes to the validation of the presented processing approach, proving its advantages over single thermochemical treatments.