Formation Of Nitride Layer Research Articles

Substrate modification for high performance CrAl/CrAlBN multilayers coated TiCN-based cermet through plasma nitriding

The plasma nitriding process was conducted on a TiCN-based cermet that had been coated with a multilayer CrAl/CrAlBN coating deposited via cathodic arc. The intensity of the plasma nitriding was modified by adjusting the anode current of the ionization source. To investigate the interface conditions, techniques such as electron probe X-ray microanalysis, electron backscatter diffraction, and transmission electron microscopy were employed. The results indicated that increasing the anode current led to the formation of a thicker nitrided layer and an increase in the texture coefficient of the (111) plane. Specifically, at an anode current of 200 A, the lattice mismatch degree at the TiCN/CrAlN interface decreased from 16.4 % to 3.7 %, resulting in the formation of a nearly coherent interface. The hardness, adhesion strength, and H/E ratio of the coating reached their peak values, and the coated cutting tool exhibited optimal cutting performance when machining the GH4149 superalloy.

Electrolytic Plasma Nitriding of Medium-Carbon Steel 45 for Performance Enhancement

This article analyzes the effect of electrolytic plasma nitriding on the performance of medium-carbon steel 45 under increased mechanical loads and in aggressive environments. Nitrided samples in carbamide electrolytes, both with and without the addition of ammonium nitrate, were compared to the initial material. SEM with EDX and XRD analysis was used to examine the microstructure and phase composition of nitrided samples. Wear resistance was studied using the ‘ball-on-disk’ method and Vickers microhardness testing, while corrosion resistance was studied using potentiodynamic polarization curves. The study results show that the sample without ammonium nitrate demonstrated better mechanical and corrosion properties due to a more homogeneous and denser nitride layer, approximately 10 µm thick, containing phases FeN and Fe4N. Its wear resistance doubled compared to that of the initial sample. The sample treated in an electrolyte with the addition of ammonium nitrate demonstrated a higher current density (2.8672 × 10−5 A/cm2) and a lower corrosion potential (−0.565 V) compared to the initial sample (i_corr = 1.8971 × 10⁻5 A/cm2, E_corr = −0.480 V) and the sample without ammonium nitrate (i_corr = 1.7315 × 10−5 A/cm2, E_corr = −0.376 V). This is due to the formation of an uneven nitride layer and the presence of microcracks on the surface.

THE EFFECT OF THE ELECTROLYTE COMPOSITION ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF STEEL 45 AFTER CATHODIC ELECTROLYTE-PLASMA NITRIDING

This research offers an in-depth exploration of the impact of cathodic nitriding on the structural and mechanical characteristics of 45 steel treated in different aqueous electrolytes. Through a combination of Xray diffraction and electron microscopy analyses, it was determined that the nitriding process facilitates the development of a multilayered surface structure, which includes oxide, nitride, and martensitic layers. The composition of the electrolyte plays a crucial role in determining the phase composition and thickness of the modified layers, directly influencing the steel's mechanical properties, as reflected by variations in hardness and wear resistance post-treatment. Notably, an electrolyte containing sodium carbonate (Na₂CO₃) and urea (CH₄N₂O) achieved a maximum microhardness of 986 HV due to the formation of a dense nitride layer. On the other hand, introducing ammonium nitrate to the electrolyte, while slightly decreasing the microhardness to 882 HV, resulted in the formation of a more intricate and stable phase structure, including additional nitrides and oxides, which contributed to enhanced corrosion resistance. These findings underscore the critical importance of optimizing electrolyte composition to improve the performance characteristics of steel, such as hardness, wear resistance, and corrosion resistance. This study underscores the effectiveness of cathodic nitriding as a method for significantly enhancing the mechanical and surface properties of 45 steel, thereby expanding its potential for use in high-load and aggressive environments.

Enhancement of Wear and Corrosion Resistance of Ti6Al4V Alloy through Hollow Cathode Discharge-Assisted Plasma Nitriding.

In order to improve the wear and corrosion resistance of Ti6Al4V alloy, a Ti-N compound layer was formed on the alloy by plasma nitriding at a relatively low temperature (750 °C) and within an economical processing duration (4 h), in a mixture of NH3 and N2 gases with varying ratios. The influence of the gas mixture on the microstructure, phase composition, and properties of the Ti-N layer was investigated. The results indicated that the thickness of the nitrided layer achieved in a mixed atmosphere with optimal proportions of NH3 and N2 (with a ratio of 1:2) was substantially greater than that obtained in an atmosphere of pure NH3. This suggests that appropriately increasing the proportion of N2 in the nitriding atmosphere is beneficial for the growth of the nitrided layer. The experiments demonstrated that the formation of the surface nitrided layer significantly enhances the corrosion and wear resistance of the titanium alloys.

Investigation of process parameters for modeling of ceramic composite SiSiC IN dry EDM (DEDM) cutting

The manufacturing industry is currently grappling with issues related to energy dissipation and product quality, both of which significantly impact productivity. In addressing this pertinent concern, this study endeavours to identify the key indicators that contribute a crucial role in machining process. The Dry EDM (DEDM) emerges as a novel technology, wherein environmentally friendly gases serve as an alternative dielectric medium instead of liquid EDM approaches. In conventional EDM process, hydrocarbon oils release toxic emissions while the gases used in Dry EDM process don’t produce harmful emissions and hence make the DEDM process sustainable.An investigation has been carried out to observe the influence of different gases like O2, N2 and Air on Siliconized Silicon-Carbide plate (SiSiC) of ø50mm*2 mm under Dry Electrical Discharge Machining. Effect of different tools is also observed using varying shapes of electrodes like plane Cu electrode of ø6 mm diameter with 60 mm length and tubular shape with outer diameter ø6mm and inner diameter ø5.1 mm with a length of 60 mm. The three gases are one by one supplied through a nozzle in the presence of plane Cu electrode to make the holes in SiSiC plate. The same process is executed with tubular Cu electrode. Modified Taguchi Orthogonal Array is applied to analyze the effect of control factors such as gap voltage, discharge current and pulse on-time through a series of experiments. Effect of different shape of tools and different gases is observed for the material removal rate (MRR) and surface roughness (SR) of specimen.In this paper, a latest DEDM process of swirl assisted flushing is proposed which provides a new technique to solve the problems of low MRR and poor surface integrity. Swirl assisted flushing works on Decay Law and also microscopic investigation justifies its validity. It is concluded by this research that current and Pulse on time are more contributing factors about 53.3 % and 27 % respectively. Furthermore, it is noted that DEDM increases MRR 19.5 % and lowers Ra approximately 2/3 than traditional machining. The MRR of O2 is about 3.1 times more than Air and N2 comes at least position while N2 creates better quality of surface due to formation of an inert nitride layer. Empirical relations are established for SR and MRR using Minitab 18 Software to develop a robust model. Confirmation test is performed to check the validity of developed mathematical model. The Novelty of this research is also extended by introducing a new method SAF. The results are finally evaluated by ANOVA.

Formation and properties of nitrided layer on 2205 duplex stainless steel by anodic plasma-nitriding assisted with hollow cathode discharge

2205 duplex stainless steel (2205DSS) was nitrided at 420 °C by plasma nitriding in an ammonia atmosphere under anodic potential. The nitrided layer was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The impact of the nitrided layer on the corrosion and wear resistance of 2205DSS was evaluated through electrochemical polarization tests and pin-on-disc wear experiments. The results revealed that nitrogen-expanded austenite was formed on the substrate, and the nitrided layer developed on the samples nitrided for 4 and 10 h enhanced both the corrosion and wear resistance of 2205DSS.

Shot peening pre-treatment for nano-nitriding layer formation to enhance wear and corrosion resistance in medical titanium alloys

Due to its exceptional biocompatibility, Ti6Al4V finds extensive application in the medical field, particularly in joint replacement and orthopedic surgery. To augment the wear and corrosion resistance of the titanium alloy in physiological environments, SP and PN treatments were applied. This study systematically explores the synergistic impact of SP on PN of titanium alloy through microhardness testing, micromorphology observation, microstructure characterization, as well as wear and electrochemical experiments. The findings reveal that SP refines surface grains, facilitating PN and leading to the formation of a thicker nitride layer on titanium alloy surfaces. Compared to the initial titanium alloy, surface microhardness increases by 51.4 %, and the wear rate experiences a two-order-of-magnitude reduction. Moreover, the SP-PN treatment enhances the electrochemical corrosion resistance of titanium alloys, underscoring its effectiveness in improving the wear and corrosion properties of medical titanium alloys.

Preparation and tribologic properties of Ti and Zr nitride multilayer coatings

This paper focuses on synthesis and characterization of Zr/Ti and Ti/Zr nitride multilayer coatings by magnetron plasma sputtering to enhance the tribologic properties. The synthesis of nitrides was achieved by non-reactive deposition using Ti or Zr nitride targets or by reactive deposition using Ti or Zr targets in the presence of nitrogen. The formation of nitride layers was highlighted by XRD, EDX and XPS investigations, while the tribologic properties were made with HFRR equipment. The tribological study showed that the coefficient of friction and wear scar diameter decrease in multilayer films with zirconium nitride as the upper layer.

High-temperature oxidation and diffusion studies on selected Al–Cr–Fe–Ni high-entropy alloys for potential application in thermal barrier coatings

In this work, the properties of two high-entropy alloys (HEAs) Al25Cr20Fe20Ni35 and Al20Cr20Fe20Ni40 (at.%) were compared for potential application as bond coats in thermal barrier coatings (TBCs). For this reason, both their oxidation resistance under isothermal and thermal shock conditions, as well as diffusion phenomena occurring at the substrate-HEA diffusion couple interface, were investigated. It was determined that both alloys demonstrate good phase stability and oxidation resistance during prolonged exposure to air atmosphere at 1000°C. In the initial 100 h period, selective aluminum oxidation is responsible for the protective scale growth on both materials under both isothermal and thermal shock conditions. However, only the Al20Cr20Fe20Ni40 high entropy alloy maintains a single Al2O3 layer for over 1000 h of oxidation with cyclic temperature changes. On the other hand, diffusion studies indicate that mainly iron and chromium travel between the ferritic steel substrate and the HEAs. Aluminum diffusion is seemingly limited by the unexpected formation of a thin aluminum nitride layer at the interface between the materials. From all these results it can be concluded that the Al20Cr20Fe20Ni40 alloy shows more promise for application in TBCs based on high entropy materials than Al25Cr20Fe20Ni35.

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.

Study on Hot Corrosion of Low-Nickel Cladding Metals Containing Nitrogen in K2SO4-MgSO4 Binary Molten Salt

Molten salt is usually used as the energy storage medium for solar energy heat storage pipes, and 40wt% K2SO4 + 60wt% MgSO4 is very suitable for use as a heat storage material for solar thermal power generation in tower and butterfly parabolic systems. The demand for high-temperature thermal energy storage systems has prompted research on low-cost alloys for use in high-temperature and corrosion-resistant environments. The 44% Ni-24% Cr-0.18N nitrogen-containing low-nickel flux-cored welding wire designed in this article has a corrosion resistance of up to 900 °C after welding repair, which is better than the repair ability of Inconel 625 flux-cored welding wire. Using the high-temperature static immersion corrosion method, the corrosion behavior of two deposited metals immersed in molten salt for 60 h at 900 °C was assessed. The corrosion product phase composition, corrosion morphology, and elemental distribution of the two deposited metals were systematically studied using X-ray diffraction (XRD) and a Gemini SEM 300 (Zeiss thermal field scanning electron microscope). The results showed that the corrosion weight loss of the deposited metals showed the same trend at 900 °C, with corrosion occurring slowly from 0 h to 10 h and increasing after 10 h to 60 h. It was found that 10 h was the boundary point for corrosion behavior, and the corrosion resistance of the low-nickel nitrogen-containing deposited metal is better than that of the Inconel 625 deposited metal. This was because the addition of N energy elements allowed the formation of a stable composite nitride layer to suppress corrosion.

Investigation of the effect of different types of SiN layers and cap-GaN on the surface electronic states of AlGaN/GaN heterostructures with 2DEG using X-ray and UV photoelectron spectroscopy

Determining the effect of different crystalline and amorphous passivation layers on the electronic states and surface properties of III-nitride heterostructures is an important task from the point of view of improving the performance of modern microwave and power electronic devices. In the present work the effect of in situ deposited gallium nitride and silicon nitride passivation layers on the surface electronic states of AlGaN/GaN heterostructures with a two-dimensional electron gas is investigated using the X-ray, ultraviolet and angle-resolved ultraviolet photoelectron spectroscopy (XPS, UPS, ARUPS) techniques. A thorough analysis of the experimental UPS spectra was carried out, the primary photoelectrons were extracted from the experimental spectra and the contribution of the electron states on the surface in the energy range of the AlGaN bandgap was identified. It was found that the density of states on the surface decreases by about an order of magnitude in the AlGaN bandgap during the formation of a silicon nitride layer. For the first time, it was found that a significant decrease in the density of surface states (up to a factor of 6) is observed even at extremely low thickness of the SiN ordered layer formation with the (√3 × √3)R30° superstructure.

Formation of nitrided layers in iron under thermal cycling conditions

Formation of nitrided layers in iron under thermal cycling conditions

Surface Structural–Phase Modification of Structural Steels during Gas Nitriding

The formation of a composite nitride layer in an ammonia atmosphere with the addition of carbon– and oxygen–containing gases during gas nitriding is considered. The conditions for the formation of cementite during nitriding of steel and the influence of carbon in the matrix on the release of cementite are given. After oxidation of the nitride layer, modified nitride compositions with stable gradient structural–phase states were obtained.

Effect of N2–H2 Ratio during Conventional Plasma Nitriding of Intermetallic FeAl40 Alloy on Electrochemical Corrosion Parameters in Sulphuric Acid

The intermetallic alloy FeAl40 was plasma nitrided at 575 ∘C for 4 h while varying the N2–H2 gas mixture with nitrogen contents fN2 between 0.1 and 0.9. The effect of the gas mixture on the resulting structure of the nitrided FeAl40 and the associated electrochemical corrosion behaviour in a 0.25 M H2SO4 (pH = 0.3) electrolyte were investigated using different complementary analytical methods such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray spectroscopy, electron probe microanalysis (EPMA), electrochemical polarisation and electrochemical impedance spectroscopy. Nitriding significantly changed the corrosion mechanism of FeAl40 alloys in acidic environments, ranging from consistently high material loss in untreated base material to strongly inhibited material loss. This phenomenon was the result of a corrosion product layer formed on nitrided FeAl40 during the corrosion process. Therefore, plasma nitriding reduced the corrosion rate to about 5–7 mm/year compared with 22 mm/year of the untreated FeAl40 base material. A high nitrogen content in the N2–H2 plasma of more than fN2 = 0.3 ensured the formation of protective nitrided layers on FeAl40. In addition, an approach to explaining the effect of the nitrided layer on FeAl materials was presented on the basis of thermodynamic considerations.

Formation of Functional Silicon Nitride Layers by Selective Plasmochemical Etching

At present, with the development of nanotechnology, plasma-chemical etching remains practically the only tool for transferring an integrated circuit pattern in a masking layer to a substrate material due to the fact that the pattern transfer accuracy is comparable to the size of etching gas ions. Requirements for plasma technology: permissible defects, selectivity (material selectivity), line width control, etching uniformity are becoming more stringent and, as a consequence, more difficult to implement. To increase the rate and selectivity of plasma-chemical etching of silicon nitride films during plasma processing of a gas mixture consisting of both a fluorine-containing gas and oxygen, sulfur hexafluoride with a concentration of 70–91 vol.% was used as a fluorine-containing gas with an oxygen concentration of 9–30 vol.%.

Diffusion kinetics and elemental transport in selective surface nitriding of CoCrFeNiTi0.5 high entropy powder

Ceramic coated metal powders have recently found prominence owing to their prospective application in 3D microstructured metal matrix composite synthesis. To ensure a perfect matrix-reinforcement interface in these composites, the coating process needs to be in situ. To that end, we recently developed a process for in situ nitride surface coating of CoCrFeNi high entropy alloy (HEA) powder. This approach offers various advantages over other processes including ease of controlling the surface morphology and compositional control by adjusting the nitriding parameters. In this study, we aimed to elaborate the nitride layer formation mechanism, growth kinetics, and compositional control. Mechanically alloyed CoCrFeNiTi0.5 HEA powder was used as the starting powder. The nitride layer growth on the powder was observed at different temperatures of 973, 1073 and 1173 K for 1–12 h under partial nitrogen atmosphere. The nitrogen preferentially reacted with Ti to form a continuous layer of TiN on the powder surface. Further growth was found to be diffusion-controlled by the growth rate increase with increasing nitriding temperature. Morphological investigation revealed a strong efflux of Ti through the TiN grain boundaries resulting in a scale growth at the TiN/gas interface. This growth mechanism was validated by a high TiN layer growth activation of 240 kJ.mol−1. Finally it was revealed that the Cr dissolution within the TiN layer can be achieved at higher temperature. However, to retain the integrity of the surface layer, the Cr dissolution process needs better control

High-temperature behaviour of V2AlC powders under nitrogen atmosphere

The high-temperature behaviour of V2AlC powders under nitrogen atmosphere was investigated. V2AlC began to react at above 1073 K under nitrogen, and the activation energy was calculated to be 435.42 kJ·mol−1. In the initial stage, the thermal decomposition was controlled by a surface reaction and the formation of nitride layers could inhibit further nitridation, and the final products were AlN, VCx, V(C, N)x, and VN. As the reactions proceeded, the generated nitrides and carbides caused a volume change and cracked the resulting layers, which could promote the diffusion of nitrogen and accelerate the decomposition of V2AlC. As a result, the intensive reaction above 1473 K between V2AlC and nitrogen was attributed to crack propagation and the opening of gas diffusion channels generated by the increasing temperature and persistent escape of vaporised Al.

A novel plasma nitriding process utilising HIPIMS discharge for enhanced tribological and barrier properties of medical grade alloy surfaces

The demand for improvement of lifetime and biocompatibility of medical implants is ever growing. The materials used in this challenging application must display enhanced tribological properties, biocompatibility and reduced metal ion release in long-term clinical performance. Surface modification techniques such as nitriding, can significantly improve the in-service behaviour of the medical grade alloys used for implants. This communication reports on a novel approach for nitriding of CoCrMo alloy using High Power Impulse Magnetron Sputtering, (HIPIMS) discharge for the first time. The new nitriding process has been successfully carried out in an industrial size Hauzer 1000-4 system enabled with HIPIMS technology at the National HIPIMS Technology Centre at Sheffield Hallam University, UK. Due to the significantly enhanced production of molecular (N2+) and atomic Nitrogen (N+) ion species in the HIPIMS discharge, which are primarily responsible for the nitrided layer formation, a fourfold increase in the process productivity as compared to the state of the art nitriding process was achieved. The surface layers produced exhibit excellent mechanical and tribological properties such as high hardness, high fracture toughness and wear resistance. The protection properties of the nitrided layer against corrosion in the aggressive environments of simulated body fluid (Hank’s solution) are remarkably augmented. Furthermore, the data showed that the amount of metal ions released from the HIPIMS nitrided samples was reduced by a factor of 2, 4 and 10 for Co, Cr and Mo ions respectively thus demonstrating the reliable barrier properties of the nitrided layer.

Increasing of wear resistance of machine parts by nitriding while suppressing of nitride mesh formation process

The article discusses the technology of nitriding machine parts made of alloy steels, which provides suppression of the nitride mesh formation process as a result of preliminary two-stage preparation of the surface layer for nitriding, including obtaining a surface layer of a material with an ulramelkodisperse structure followed by high-energy implantation with nitrogen ions. Comparative models of the formation of nitrided layers obtained with traditional and proposed nitriding methods, as well as models of wear under conditions of friction of the surfaces of parts, are proposed. The results of comparative wear tests of alloy steels with a nitrided layer used for the manufacture of machine parts operating under conditions of wear friction are presented. It is shown that the absence of a nitride mesh in the nitrided layer increases the wear resistance of the nitrided layer by approximately 3—4 times.