Nitriding Process Research Articles

Tribological and corrosive degradation of differently surface engineered 17-4 PH steel

In the present work, a high-velocity oxy-fuel (HVOF) thermal spray process was used to deposit ceramic coatings containing alumina (Al2O3)− 0.8 wt% ceria (CeO2)− 0.2 wt% reduced graphene oxide (rGO) on 17–4 PH steel. The results were compared with the nitrided 17–4 PH (N17–4 PH) steel. The mechanical characteristics of the bare substrate, nitrided substrate, and coating were evaluated regarding micro (Vickers) hardness, scratch hardness, nanoindentation, and high-temperature nanoindentation (300 °C). The tribological behavior of all the specimens mentioned earlier was studied in a universal mechanical tester in a ball on flat reciprocating wear test mode for different loads. Electrochemical responses regarding corrosion properties in 3.5 wt% aqueous salt solution were recorded and analyzed. The results showed that the ceramic coating performed better than the other two specimens regarding mechanical, tribological, and electrochemical properties. For example, the coating was nearly ten and six times more wear resistant than 17–4 PH steel and N17–4 PH steel, respectively, at 50 N load. The performance enhancement in the coating was ascribed to the coating hardness, dense microstructure, and introduction of rGO in the coatings, which participate in the tribological process. Further detailed analysis of the bare steel, ceramic coating, and the nitrided steel properties reveals that the nitriding process can be replaced with the proposed ceramic coating through the HVOF technique for tribological, corrosive, and extreme environmental applications for 17–4 PH steel.

Unraveling the Nanoscale Segregation Mechanism in N-Doped Niobium for Enhanced SRF Performance.

The nitrogen doping (N-doping) treatment for niobium superconducting radio-frequency (SRF) cavities is one of the key enabling technologies that support the development of more efficient future large accelerators. However, the N-doping results have diverged due to a complex chemical profile under the nitrogen-doped surface. Particularly, under industrial-scale production conditions, it is difficult to understand the underlying mechanism thus hindering performance improvement. Herein, a combination of spatially resolved and surface-sensitive approaches is employed to establish the detailed near-surface phase composition of thermally processed niobium. The results show that intermediate phase segregations, particularly the nanometric carbon-rich phase, can impede the nitridation process and limit the interactions between nitrogen and the niobium sub-surface. In comparison, the removal of the carbon-rich layer at the Nb surface leads to enhanced nitrogen binding at the Nb surface. Combining the RF test results, it is shown that the complex uniformity and grain boundary penetrations of impurity elements have a direct correlation with the mid-field quench behavior in the N-doped Nb cavities. Therefore, proper control of the nanometric intermediate phase formation in discrete thermal steps is critical in improving the ultimate performance and production yield of the Nb cavities.

Examination of a Hot-Work Tool Steel Treated with Different Nitriding Processes after Cyclic Heating

This research examines the effect of salt bath, and nitriding processes on hot forming tool steel. The chosen steel is BÖHLER W350 ISOBLOCK hot forming tool steel, which is widely used in the industry for pressure casting. After surface treatment, some samples were exposed to cyclic heat and corrosion effects in a molten aluminium medium, thus simulating the conditions experienced during pressure casting. Microhardness measurements were performed on the samples treated with different procedures. The results were compared using a scanning electron microscope and energy-dispersive X-ray spectrometry.

Biodegradable MoNx@Mo-foil electrodes for human-friendly supercapacitors.

With the advancement in the field of biomedical research, there is a growing demand for biodegradable electronic devices. Biodegradable supercapacitors (SCs) have emerged as an ideal solution for mitigating the risks associated with secondary surgeries, reducing patient discomfort, and promoting environmental sustainability. In this study, MoNx@Mo-foil was prepared as an active material for biodegradable supercapacitors through high-temperature and nitridation processes. The composite electrode exhibited superior electrochemical performance in both aqueous and solid-state electrolytes. In the case of the solid-state electrolyte, the MoNx@Mo-foil composite electrode-based device demonstrated excellent cycling stability and electrochemical performance. Additionally, the composite electrode exhibited rapid and complete biodegradability in a 3% H2O2 solution. Through detailed experimental analysis and performance testing, we verified the potential application of the MoNx@Mo-foil composite electrode in biodegradable supercapacitors. This work provides a new choice of degradable material for developing biomedical electronic devices.

Kinetics of Stainless Steel Material by Plasma nitriding Process for sustainable applications

Implantation of ion at low temperature and nitriding through plasma process at low-temperature prevents the corrosion resistance in stainless steel material. The outcome of nitriding process is to form precipitation of CrN on the surface. For the current research work, plasma nitriding techniques are adopted to nitride AISI 304 at low-temperatures at 5hrs, 10hrs, 15 hrs. The enriched layers are formed with combine nitrogen lead to increase in surface hardness. Austenitic and duplex steels produce expanded austenite on the material surface. Behavior of wear was monitored by pin on disc tester. The case depth were monitored and compared with a sample which is not treated. The morphology of surface were monitored and compared with the electron microscopic images. Finally hardness measurements were carried out with Rockwell hardness tester.

Investigation on AISI 253 Stainless Steel by Gas Nitriding Process for Sustainable Applications

Austenitic stainless steel is highly valued in many industries due to its unique properties, which make it appropriate for various sustainable applications like wind turbine blades, solar panel components, biomass converter equipments. AISI 253 stainless steel were chosen for this research and gas nitrided were underwent at a low temperature of about 550°C. The samples were nitride for 8 hours of nitriding, the sample was found to move from austenitic to expanded austenite phase. Extending the nitriding time to 16 hours resulted in the formation of ferrites and an increasing concentration of nitrogen in succeeding layers. The specimens were carried out with nitriding for 24 hours. Cr-N phase were formed was This new phase contributes to increase in surface hardness. Wear loss and volume loss were analyzed from the wear test. In this work , there was considerable improvement in the wear resistance after 24hours of nitriding. The samples nitrides for 24 hrs also had high hardness of 1080Hv and had negligible wear, volumetric wear loss of the specimens. The microstructure and surface morphology analysis of the nitrided samples was carried out using scanning electron microscopy which helped in establishing the microstructural behaviour of the AISI 253 stainless steel.

Evaluation of plasma nitriding process in the wear resistance of 7075 aluminum alloy

Evaluation of plasma nitriding process in the wear resistance of 7075 aluminum alloy

The influence of plasma nitriding process conditions on the microstructure of coatings obtained on the substrate of selected tool steels

This study presents the results of research into the influence of the time of the plasma nitriding process on the microstructure of the coatings obtained. Cold-work tool steels (60WCrV8, 90MnCrV8, 145Cr6), hot-work tool steel (X37CrMoV5-1) and high-speed tool steel (HS6-5-2) were selected as substrate material. The processes were carried out under industrial conditions using an Ionit device from Oerlikon Metaplas with variable process times of 2, 4 and 6 hours. According to literature data, a nitriding mixture consisting of 5% nitrogen and 95% hydrogen was chosen, which allowed the expected diffusion layer to be obtained without a white layer (composed of iron nitrides). Analysis of elemental mapping indicates that the presence and content of nitride-forming elements influences the formation of alloy additive nitrides in the microstructure of the diffusion layer. It was also found that an increase in the duration of plasma nitriding, results in an increase in the depth of the nitrided layers formed on the substrate of high-alloy steels: X37CrMoV5-1 and HS6-5-2. Nitrides of alloying additives, present in the diffusion layer, are formed in the high-alloyed the hot-work steel X37CrMoV5-1, indicating that these steels are the most suitable for plasma nitriding of the entire tool steels analysed.

Energy Transfer Process and Process Gas Flow Model in Nitric Acid Production

In the Oswald process, ammonia is reacted with oxygen under the catalyst of platinum to form oxides, which are converted into acid. Acid nitriding processes are essential in industry, and many kinds of products, such as plastics, paints, and explosives, are obtained this way. Achieving energy savings and improving production reflexes by monitoring energy consumption on a process basis in such enterprises requires defining the current process flows and structure through a model and analyzing them with parameter changes. In this study, the energy transfer process of NOx gases obtained in the ammonia oxidation reactor and used as process gas in a nitric acid production facility and the parameters affecting the process were investigated. The parameters affecting the efficiency were determined. The problems were addressed by considering the energy efficiency of the facility. The ammonia oxidation reactor is the most essential part of the system. For this reason, the operating parameters of the old reactors in the facility were compared with the revised new reactors. After the revision, the efficiency and performance of the system were examined in old and new reactors. In addition, the flow and hydrodynamic structure of the existing process gas in the new reactors were reviewed with the ANSYS Fluent program, that is, CFD analysis.

GaN/rGO nanocomposite gas sensor for enhanced NH3 sensing performances at room temperature

In this work, we developed a high-performance NH3 sensor based on GaN/rGO nanocomposites via a low-cost solvothermal method and subsequent nitridation process. The morphological, structural, and chemical compositions were investigated to demonstrate that GaN and rGO were coupled together by interfacial modulation, and the GaN/rGO heterostructure chemical bonds are successfully formed. Gas-sensing performance test results show that the fabricated GaN/rGO (2.2 wt%) NH3 sensor exhibited a high response value (92%), fast response time (11 s), and low limit of detection (500 ppb) at room temperature. In addition, reproducibility, humidity, and long-term stability tests of the GaN/rGO sensor were also conducted in this work. The enhancement sensing mechanisms are attributed to the large specific surface area, the excellent conductivity of rGO, and resistance modulation effect of the heterojunction potential. Hence, the GaN/rGO gas sensor can be regarded as a promising sensing solution for atmospheric and exhaled NH3 detection at room temperature.

Investigation of influence of ion nitriding in the glow discharge with magnetic field on microstructure and microhardness of steel HSS M2 with preliminary plastic deformation

This work was devoted to the study of the influence of magnetic field on microhardness of HSS M2steel during ion nitriding in the glow discharge. The samples were preliminarily subjected to intenseplastic torsion deformation (IPTD). Standard methods of optical metallography and microhardnessmeasurements were used in the experiments. It was found that IPTD allows creating ultrafine-grained(UFG) structure in the material, and magnetic field allows intensifying the process of ion nitriding byincreasing the number of ionization acts, which leads to an increase in the thickness of the diffusionlayer and microhardness compared to ion nitriding without preliminary IPTD and without magneticfield. The results obtained indicate the importance of using a magnetic field during ion nitridingin the glow discharge. The described effects are of potential interest for improving the mechanicalproperties of high-speed steels.

Study on reaction mechanism for the synthesis of vanadium nitride by carbothermic reduction nitridation method

Vanadium nitride (VN), as a typical transition metal nitride, has widespread applications in various fields due to its high melting point, high hardness, and excellent thermal and chemical stability. In this study, VN was synthesized through the carbon thermal reduction nitridation method using V2O3 as the main material, and the reaction mechanism was thoroughly examined. Thermodynamic analysis, coupled with thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), revealed that the reaction mechanism was not simply a direct nitridation process nor a two-step coupling of reduction and carburization. Instead, it was the result of multiple reaction mechanisms working in conjunction. Direct nitridation of V2O3 occurred throughout the entire reaction process, while indirect nitridation of VO and VC also occurred with the variation of temperature. A kinetic model was constructed based on the material thermal weight loss curve and revealed that in the carbothermal reduction nitridation system of V2O3, the solid phase reaction followed a three-dimensional diffusion model, with an activation energy of 160.244 kJ/mol, while the gas phase reaction with the solid phase followed a one-dimensional interface model, with an activation energy of 169.015 kJ/mol.

Tungsten Nitride/Tungsten Oxide Nanosheets for Enhanced Oxynitride Intermediate Adsorption and Hydrogenation in Nitrate Electroreduction to Ammonia.

Electrochemical NO3- reduction reaction (NO3RR) is a promising technique for green NH3 synthesis. Tungsten oxide (WO3) has been regarded as an effective electrocatalyst for electrochemical NH3 synthesis. However, the weak adsorption and the sluggish hydrogenation of oxynitride intermediates (NOx, e.g., *NO3 and *NO2) over WO3 materials hinder the efficiency of converting NO3- to NH3. Herein, we design a heterostructure of tungsten nitride (WN) and WO3 (WN/WO3) nanosheets to optimize *NO3 and *NO2 adsorptions and facilitate *NO2 hydrogenations to achieve a highly efficient electrochemical NO3RR to produce NH3. Theoretical calculations predict that locally introducing WN into WO3 will shorten the distance between adjacent W atoms, resulting in *NO3 and *NO2 being strongly adsorbed on W active sites in the form of bidentate ligands instead of the relatively weak monodentate ligands. Furthermore, WN facilitates H2O dissociation to supply the requisite protons, which is beneficial for *NO2 hydrogenations. Inspired by theoretical prediction, WN/WO3 nanosheets are successfully fabricated through a high-temperature nitridation process. The transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption near-edge spectroscopy investigations confirm that the amorphous WN has been locally introduced in situ into WO3 nanosheets to form a composite heterostructure. The as-prepared WN/WO3 nanosheets exhibit a high Faraday efficiency of 88.9 ± 7.2% and an appreciable yield rate of 8.4 mg h-1 cm-2 toward NH3 production, which is much higher than that of individual WO3 and WN. The enhanced adsorption and hydrogenation behaviors of *NOx over WN/WO3 are characterized by in situ Fourier-transform infrared spectroscopy, consistent with the theoretical predictions. This work develops facile and effective heterostructure nanomaterials to tune the adsorption and hydrogenation of NOx for boosting the efficiency from NO3- to NH3.

A study on adsorption, dissociation, penetration, and diffusion of nitrogen on and in α-Ti via First-principles calculations

A comprehensive description of the entire process of N2 molecules on Ti surface and in Ti bulk as well as the underlying nitridation mechanism were explored via first-principles calculations. The reaction process was divided into four steps and the mechanism for the determined reaction path was analyzed. Utilizing the methodology of the climbing image nudged elastic band (CI-NEB), we investigated the diffusion energy barrier at each step of the reaction path, and determined the minimum energy path (MEP) for the complete reaction path. The calculated adsorption energies of N atoms and N2 molecules show that they are most stable at the HCP site on the α-Ti (0001) surface. Charge transfer provided theoretical support for N2 dissociation. We calculated the diffusion energy barrier of the N atom by migrating from the HCP site to the octahedral (O) site, which the N atom prefers to occupy. The diffusion coefficient is highest when the diffusion channel travels from one O site to the next layer of the O site via the next H site, it takes the most energy to complete, compared to those other steps. Lastly, we determined the rate-determining steps of the reaction pathway for the entire nitridation process. This study provides valuable insight into the fundamental mechanisms governing the nitridation process of N2 molecules in titanium alloys. This study sheds light on the nitridation mechanism for N2 molecules in titanium alloys.

Effect of Nitrocarburizing and Post-oxidation Processes on the Microstructure and Surface Properties of AISI 4140 Steel

AISI 4140 çeliği, orta karbonlu düşük alaşımlı çelikler sınıfında yer almakta olup, yüksek sertleşebilirliğe sahip olması ve nispeten ekonomik bir çelik olması nedeniyle endüstride yaygın olarak kullanılmaktadır. AISI 4140 çeliği aynı zamanda nitrürlebilen çelikler arasında yer almaktadır. Nitrürleme işlemiyle, yüzeyde elde edilen sert nitrür tabakası sayesinde sadece aşınmaya dirençli bir yüzey değil aynı zamanda yorulma dayanımında da artış sağlanmaktadır. Bu çalışmada, düşük basınçlı gaz nitrokarbürleme işlemi ve farklı sürelerde son oksidasyon işlemi uygulanmış AISI 4140 çeliğinin mikroyapısal ve yüzey özellikleri araştırılmıştır. Bu amaçla, AISI 4140 çelik numuneler, 850 °C'de 60 dk östenitlenmiş 60 °C’de yağda soğutulmuştur. Soğutma sonrası numuneler 630 °C’de 60 dk temperlenmiştir. Gaz nitrokarbürleme işlem basamakları; 350 °C’de 45 dk ön oksidasyon, 550 °C’de 90 dk nitrürleme ve 550°C’de 480 dk nitrokarbürleme uygulanmış ve ardından numuneler 45-180 dakika aralığında su buharı kullanılarak son oksidasyon işlemine tabi tutulmuştur. Mikroyapısal karakterizasyon çalışmaları optik mikroskop, tarama elektron mikroskobu (SEM), enerji dağılımlı X ışını spektrum analizi (EDX), X ışını kırınımı (XRD) analizi, mikrosertlik ve yüzey pürüzlülüğü ölçümleriyle gerçekleştirildi. X ışını analiz sonuçlarından, numunelerin yüzey katmanının demir nitrür, ɛ-Fe2-3N ve ɣ’-Fe4N fazlarını ve demir oksit (Fe3O4) içerdiği tespit edilmiştir. Son oksidasyon süresi arttıkça, demir oksit (Fe3O4) tabaka kalınlığını arttığı belirlendi. Nitrokarbürlenmiş ve son oksidasyon işlemi uygulanmış AISI 4140 çelik numuneler içerisinde, en iyi sertlik derinliği, yüzey sertliği ve yüzey pürüzlülüğü birleşimi 150 dakikada son oksidasyon uygulanmış elde edilmiştir.

PENGARUH PROSES PACK NITRIDING TERHADAP ANGKA KEKERASAN PERMUKAAN, KEULETAN DAN STRUKTUR MIKRO PADA BAJA SS 400

The pack nitriding process is a process of increasing the surface hardness of steel by using nitrogen with the help of organic compounds as a nitrogen source in the process. The processed steel is put into a vessel which is usually made of ceramic, glass or aluminum along with a compound used as a nitrogen source. During heating,The organic compounds used in the analysis process are generally stable at temperatures up to 570 oC and removal times of 2 to 16 hours. The purpose of the pack nitriding process is to increase the surface hardness while remaining ductile inside. In this study, nitrogen was added using a pack nitriding process after which it was quenched using water. The elimination times used were 4 and 6 hours with temperature variations of 560°C, 580°C and 600°C and presenting nitrogen for the 150 gram pack nitriding process. The highest hardness value was obtained at 580 °C with a surface hardness value of 234.84 kg/mm2 with 4 hours of removal time. And the highest impact value was shown by the specimen without treatment of 158.3 Joules. The results of testing the chemical composition of the specimens without treatment and after the pack nitriding process showed that there was an increase in the nitrogen element.

To elucidate the effect of alloying elements for enhanced nitriding of aluminum: A multiscale computational study

The limitations of aluminum (Al) are discussed in certain industrial applications, owing to its low hardness and wear resistance. To overcome these limitations, surface modification techniques, such as the formation of aluminum nitride (AlN) layers on the Al surface, have been explored. However, conventional surface-nitriding processes have low productivity, and it is essential to develop a cost-effective method to ensure higher nitriding rates. This paper presents the results of a multiscale computational study on the atomic-scale mechanisms involved in gas nitriding processes and the effects of alloying elements on reaction kinetics using density functional theory calculations. This study also provides insights into the thermodynamic stability and kinetics of the process, contributing to the design and optimization of the nitriding process for the formation of AlN on Al surfaces using Thermo-Calc. and microkinetic analyses. This study demonstrates the potential of multiscale computational methods for advancing the understanding of surface modification techniques and their applications for nitriding on the surface of Al and suggests the best alloying element to enhance the nitriding rate.

Dual-Confinement Effect of Nanocages@Nanotubes Suppresses Polysulfide Shuttle Effect for High-Performance Lithium-Sulfur Batteries.

The shuttle effect of lithium polysulfides (LiPSs) severely hinders the development and commercialization of lithium-sulfur batteries, and the design of high-conductive carbon fiber-host material has become a key solution to suppress the shuttle effect. In this work, a unique Co/CoN-carbon nanocages@TiO2-carbon nanotubes structure (NC@TiO2-CNTs) is constructed using an electrospinning and nitriding process. Lithium-sulfur batteries using NC@TiO2-CNTs as cathode host materials exhibit high sulfur utilization (1527 mAh g-1 at 0.2 C) and can still maintain a discharge capacity of 663 mAh g-1 at a high current density of 5 C, and the capacity loss is only 0.056% per cycle during 500 cycles at 1 C. It is worth noting that even under extreme conditions (sulfur-loading = 90%, surface-loading = 5.0mg cm-2 (S), and E/S = 6.63µL mg-1), the lithium-sulfur batteries can still provide a reversible capacity of 4 mAh cm-2. Throughdensity functional theorycalculations, it has been found that the Co/CoN heterostructures can adsorb and catalyze LiPSs conversion effectively. Simultaneously, the TiO2 can adsorb LiPSs and transfer Li+ selectively, achieving dual confinement for the shuttle effect of LiPSs (nanocages and nanotubes). The new findings provide a new performance enhancement strategy for the commercialization of lithium-sulfur batteries.

The fatigue life and fractures of austenitic steel AISI 304 after the chemical-thermal treatment

The service life of components is related to surface abrasion, corrosion effects, as well as the occurrence of fatigue cracks. These effects begin to spread from the surface of the components and therefore it is very important to properly influence the mechanical properties of the materials to increase the service life. In chemical-thermal treatment, the resistance of the surface layer is increased by saturating the surface of the components with suitably selected chemical elements. This affects the change in structure and mechanical properties.The article will be focused on the analysis of fatigue and fracture mechanisms of samples made of austenitic steel AISI 304, which will be subjected to a dynamic test, especially the three-point bending test. Samples for tests will be used in two states, after chemical-thermal treatment and in the initial state for comparison. Plasma nitriding will be chosen as the chemical-thermal treatment. Plasma nitriding technology has been commercially used in industrial production to improve the fatigue, anti-corrosion and tribological properties of steels.The aim of the paper is to compare the microstructural changes that took place during the nitriding process and fractographic analysis of fracture surfaces of samples that will be subjected to a three-point cyclic fatigue load. Fractography should determine the crack initiation site, the mechanism of crack formation and propagation, and the type of fracture.

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.