Effect Of Nitriding Temperature Research Articles

Effect of nitriding temperature and its effects on the corrosion and wear resistance of 304 austenitic stainless steel

Rapid plasma nitriding of AISI 304 austenitic stainless steel (304SS) was carried out at 440, 460 °C and 480 °C for 1 h in a mixture of NH3 and N2 with a ratio of 1:2. The phase composition, thickness of nitrided layer and properties of wear, and corrosion resistance were evaluated. After nitriding at 480 °C for 1 h, a 6.3 μm the thick nitrided layer was achieved. The influence of the nitriding process on the microstructure, morphology, hardness, corrosion, and wear resistance of the nitrided layers were also studied. Compared with unnitrided 304SS, the wear and corrosion resistances were substantially improved.

Cracking behavior of AISI 316L stainless steel powder by gas nitriding and its influence on spark plasma sintering

In this study, the effect of nitriding temperature on the deformation behavior of spherical AISI 316L powders was investigated. The results showed that the nitrogen content in powders was significantly increased by increasing the nitriding temperature under ammonia atmosphere. However, the resulted residual stress led to the deformation or even cracking in powders, the cause of drastic changes in the bulk density and fluidity of powders. Furthermore, the microstructure and properties of alloys synthesized by spark plasma sintering were also analyzed. The obtained results also indicate that the powder deformation has no influence on the consistency of sintered samples, but the nitriding temperature of AISI 316L powder obviously affects the morphology and performance of sintered samples. Nitrogen initially exists as interstitial atom in the steels till the nitriding temperature rises to 500 °C where nitrides begin to precipitate in the sample. Such morphological transition of nitrogen atoms has a significant impact on the mechanical properties of the alloys. The better corrosion resistance of the alloy prepared over 500 °C in 3.5 wt.% NaCl solution shows that the nitriding temperature also matters for corrosion performance.

Effects of nitridation temperature on properties of sintered reaction‐bonded silicon nitride

AbstractWe prepared sintered reaction‐bonded silicon nitride ceramics by using yttria and magnesia as sintering additives and evaluated effects of the nitridation temperature on their microstructure, bending strength, fracture toughness, and thermal conductivity. The effects of the nitridation temperature were large, but different depending on the property. The ratio of β‐phase in the nitrided compacts significantly increased with increasing the nitridation temperature, whereas their microstructures had no clear difference. Although the bending strength varied, it maintains a high value of 800 MPa. Fracture toughness was almost constant regardless the temperature. The thermal conductivity improved as the β‐phase in the nitrided compact increases. This resulted in a decrease of the lattice oxygen content and increase of the thermal conductivity. Therefore, elevating the nitridation temperature and consequently the β‐phase ratio should be a promising strategy for achieving compatibly high strength and high thermal conductivity, which are generally known to be in a trade‐off relationship.

Properties of rapid arc discharge plasma nitriding of AISI 420 martensitic stainless: effect of nitriding temperatures

Martensitic stainless steels (MSS) with excellent mechanical properties are potential candidates used in the nuclear, marine, aeronautical, and aerospace industries. However, surface treatments are needed to improve the wear performance of MSS. Arc discharge plasma nitriding (ADPN) was applied on selected AISI 420 stainless steel to improve the wear performance without reducing its original corrosion resistance. To avoid the formation of the CrN phase, the ADPN was performed at temperatures ranging from 400 °C to 460 °C for 1 h. The effects of nitriding temperature on the structural, mechanical, and tribological properties of the nitrided layers were examined by X-ray diffraction (XRD), Scanning electron microscope (SEM), Vickers microhardness tester, and ball-on-disk tribometer, respectively. Potentiodynamic polarization in a 3.5% NaCl solution was used to assess corrosion resistance. The surface of the specimen nitrided at 400 °C is ε-Fe2-3N phase while that of specimen nitrided at higher temperature is αN phase. The thickness of the nitrided layer could reach 15 μm in 1 h at 460 °C in virtue of the high-density and high-energy nitrogen plasma, which showed an extremely high nitriding efficiency. The brittle Fe2–3N phase layer on specimen nitrided at 400 °C contributes to unsatisfactory wear resistance with severe abrasive wear behavior, however, excellent corrosion properties. The specimen nitrided at 460 °C shows superior wear resistance but degraded corrosion property due to Ti particles covered microstructure. The specimen nitrided at 420 and 440 °C possess desirable wear and corrosion performance, as well as excellent surface quality.

Effect of plasma nitriding on M50 NiL steel – A review

Chemical Diffusion Process like Nitriding has important role in modern surface hardening. Plasma nitriding is one of the best method to improve surface hardness, wear and corrosion resistance of material, and also plasma nitriding improves surface properties. M50 NiL Steel is a low carbon high alloy steel with good strength, hardness, and wear and corrosion resistance at elevated temperatures. It is frequently utilised in the aerospace sector due to its unique features. To determine the corrosion and wear resistance of double element alternate implanted M50 NiL steel, detection methods such as scanning electron microscopy (SEM), X-Ray diffraction method (XRD), transmission electron microscopy (TEM), and potentio dynamic polarisation were utilised. The purpose of this paper is to identify the effects of plasma nitriding on M50 NiL Steel and to know the progress of surface hardening properties like micro hardness and wear for M50 NiL steel after plasma nitriding. The bearing made out of this steel is operated under heavy loads and high speeds in air craft engine. Effects of nitriding temperature on microstructure, micro hardness, and wear resistance of nitride layers with only a diffusion layer and no standard compound layer. and surface hardness is improved at low nitriding temperatures, When the nitriding temperature exceeds 575 °C, the nitride layer thickness increases, while the core and surface micro hardness drops. Mechanical Properties of nitride surfaces are studied by using Vickers hardness test and polarization tests. M50 NiL Steel was Plasma nitro carburized at low temperature and rare earth (RE) atoms are diffused into the specimen surface for better surface hardness and increased corrosion resistance. Some times to achieve exceptional properties duplex hardening is preferred and this process can be useful to obtain good hardness and same can be done for both hardened and case hardened bearing steels, with relative increase in rolling contact fatigue resistant and better tribological properties.

Surface Treatment on ESD For SC200 Superconducting Proton Cyclotron

A set of gas nitriding coating device suitable for the electrostatic deflector (ESD) of cyclotron is designed. Using this device, the TiN coating on small electrode of titanium alloy coupons was carried out in the mixture of nitrogen and ammonia. The effects of nitriding temperature and time on the reaction results were studied, the results of the coating experiment were analyzed, and the surface treatment parameters suitable for gas nitriding TiN coating on the surface of the titanium alloy electrode of the ESD were obtained. X-Ray Diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize and analyze the properties of nitrided coatings. And a high voltage discharge experiment was performed on the sample to measure its dark current. The results show that under atmospheric pressure, annealing temperature of 900 °C, and holding time of 8 h, the coating conditions of titanium alloy electrode materials has the best performance.

Influence of ceramic phase content and its morphology on mechanical properties of MgO–C refractories under high temperature nitriding

To evaluate the influences of ceramic phase content and its morphology on the mechanical properties of MgO–C refractories, pre-prepared Si powder-phenolic resin loaded with Fe2O3 was introduced to prepare MgO–C refractories via catalytic nitridation. The effects of nitriding temperature and Fe2O3 content on the phase composition, microstructure evolution and properties of MgO–C refractories were studied and compared. The results show that the increase of the nitriding temperature was conducive to the in-situ formation of the ceramic phases, and a new phase of Mg2SiO4 was formed at temperatures ≥1450 °C. Both the increase in nitriding temperature and the addition of catalyst could inhibit the growth of α-Si3N4 to promote the formation of β-Si3N4 and MgSiN2. In addition, the formation of excessive ceramic phases caused samples after nitriding to expand violently and form more porous, thereby reducing the physical properties of MgO–C refractories.

Corrosion Resistant CrNX Nanolayers Obtained by Low Temperature Ion Nitriding of Hard Chromium Coated AISI 1045 Steel

Chromium nitrides CrXN have attracted research interest due to their excellent wear and corrosion properties when are deposited on steels. Nevertheless, due to the considerable difference between CrXN and steel expansion coefficients, microcracks and delamination are still persistent problems. In this regard, this research addressed the generation of CrNX nanolayers, through an ion nitriding process, carried out on hard chromium coated AISI 1045 steel. The effect of nitriding temperature (500°C-550°C) and nitrogen content in plasma (25, 50, and 75%) on corrosion performance and layer characteristics were studied. Grazing Incidence X-ray Diffraction analysis revealed that modified surfaces are composed of nanolayers, constituted by a mixture of CrN, Cr2N, Cr, and Fe4N. Rietveld quantification shows that the fraction of chromium nitrides in the region analyzed increased with increasing both temperature and nitrogen content in plasma, resulting CrN as the predominant phase for all evaluated conditions. The electrochemical behavior of the modified nanolayers was studied by potentiodynamic polarization technique, revealing an enhancement in corrosion performance of chromium coated 1045 steel by the nitriding treatment, showing a corrosion current density 10 times lower than the untreated sample and more positive corrosion potentials for the nitrided samples concerning chromium coated 1045 steel.

Low-pressure gas nitriding of AISI 304 austenitic stainless steel: reducing the precipitation of chromium nitrides

In this study, low-pressure gas nitriding (gas pressure of 0.01 MPa) was conducted to produce a thicker nitrided layer with high hardness and anti-corrosive properties on AISI 304 austenitic stainless steel. The effects of nitriding temperature and duration on the microstructure and surface property of nitrided layers were systematically evaluated by using optical microscope, X-ray diffraction, elemental analysis, microhardness test and potentiodynamic polarization tests. The samples were also treated under conventional gas pressure of 0.1 MPa for comparison. The results show that the low-pressure gas nitriding could restrain the precipitation of chromium nitrides effectively, which is beneficial for obtaining a thicker nitrided layer. Although the activation energy of nitrogen diffusion for low-pressure nitriding (220 kJ mol−1) is higher than that for the atmospheric pressure nitriding (196 kJ mol−1), the thickness of nitrided layers for low pressure nitriding could reach to a comparable value as that for the conventional atmospheric pressure nitriding. More importantly, the surface toughness and corrosion resistance of nitrided layers could be improved by low-pressure nitriding, which is mainly attributed to the optimized nitrogen content in nitrided layers and the reduced precipitation of chromium nitrides under low-pressure.

Effect of QPQ Nitriding Parameters on Properties of Pearlite Ductile Cast Iron

The effects of nitriding temperature and time on properties of pearlite ductile cast iron were studied by wear and corrosion resistance tests. The results show that the main phases of oxide layer are Fe3O4 and Li2Fe3O4, and the main phases of compound layer are Fe3N and Fe4N. With the increase of nitriding temperature, the micro-hardness and wear resistance increase first and then decrease. The micro-hardness and wear resistance increase continuously with the prolongation of nitriding time. The corrosion resistance of the sample is relatively good when nitriding at 640 °C for 120 min.

Low-Temperature Preparation of α-Si3N4 Powder via Combined High-Energy Ball Milling and Molten Salt Nitridation Method

In this work, α-Si3N4 powder was synthesized by a combined high-energy ball milling and molten salt nitridation method using silicon powder as raw materials, and NaCl-NaF binary molten salt as reaction medium and diluents. The effects of nitridation temperature, soaking time, and NaF content in the molten salt on the formation of α-Si3N4 were investigated. The results show that the nitridation of silicon powder was completed at NaF content of 10wt% in the molten salt after nitridation at 1200°C and held for 4 h. The α-Si3N4 content in the as synthesized powder is 96wt%. The α-Si3N4 whiskers with 40-280 nm in diameter and several microns to tens of microns in length appear in the final products. The crystal growth process of α-Si3N4 whiskers follows vapor-crystal (VC) mechanism.

Selective Laser Melting of Diamond-Containing or Postnitrided Materials Intended for Impact-Abrasive Conditions: Experimental and Analytical Study

Materials with higher wear resistance are required in various applications including cutting elements (drag bits) of soft ground tunnel boring machines (TBM) to increase the productivity and to reduce the risk for workers involved in exchange operations (dangerous hyperbolic conditions). In recent work, two types of materials were produced by combining 3D printing (selective laser melting, SLM) of cellular lattice structures and spark plasma sintering (SPS) methods. The lattices were printed from (1) 316L stainless steel with diamond and (2) Ti6Al4V with nitriding. The effect of diamond content (5%, 10%, and 20%; nickel-coated particles) and unit cell size on performance was studied. The titanium alloy lattice was nitrided to increase its hardness and wear resistance. The effect of nitriding temperature (750°C, 900°C, and 1050°C) and lattice volume fraction (6%, 15%, and 24%, vol.) was investigated, and the optimized conditions were applied. The lattices were filled with 316L and Ti6Al4V powders, respectively, and consolidated by SPS. Samples were tested with the help of laboratory impact-abrasive tribodevice. Laboratory results have shown that both reinforcing approaches are beneficial and allow improvement of wear resistance in impact-abrasive conditions with great potential for TBM or similar applications. Modelling with the help of finite element method has shown that lattice structure enables reduction of peak local stresses in scratching and impact conditions.

Processing, characterization and properties of novel gradient Si3N4/SiC fibers derived from polycarbosilanes

In this work, we report a novel kind of Si3N4/SiC composite fibers, which exhibit a controlled gradient Si3N4(shell)/SiC(core) structure. These composite fibers are fabricated through a controlled nitridation and pyrolysis process on electron irradiation-cured polycarbosilane fibers. Structural and chemical analysis based on Elemental Analyzer, FT-IR, Raman spectroscopy, electron probe micro-analyzer, X-ray photoelectron spectroscopy, and X-ray diffraction confirm the gradient structure of obtained fibers, which consist a shell with high Si3N4 content and a SiC core. The as-fabricated fibers exhibit dense and smooth surfaces, and no microscopic holes or defects were observed. The effects of nitridation temperature on mechanical properties and electrical resistivity were also investigated. Combined with high mechanical properties and lightweight, the present gradient Si3N4/SiC fibers open a new strategy to fabricate multifunctional and electromagnetic wave absorbing materials.

TiN nanoparticles: synthesis and application as near-infrared photothermal agents for cancer therapy

We have developed TiN nanoparticles (NPs) as a novel near-infrared-activated photothermal agent. The effect of nitridation temperature on the optical property and photothermal performance of the TiN NPs were investigated. The nanoparticles nitrided at 1000 °C presented a significant absorption along the whole biological spectral range (i.e., for wavelengths above 700 nm). After coated with polystyrene sulfonate (PSS) and poly(diallyldimethylammonium chloride) (PDDA), they exhibited well-defined spherical morphology with average size of ~ 50 nm. We also demonstrated their therapeutic efficacy against SW1990 pancreatic cancer cells. The results indicated that the PSS/PDDA-coated TiN NPs offered several advantages including high photothermal conversion efficiency (44.6%), high photothermal stability, broad spectral tunability, low cytotoxicity and facile synthesis process. These features make TiN NPs promising alternative for use as a photothermal agent in cancer photothermal treatment.

Low-temperature gas nitriding of AISI 4140 steel accelerated by LaFeO3 perovskite oxide

Rare earth nitriding was considered as an effective method to accelerate the nitriding efficiency. However the catalytic mechanism was not clear due to the uncertainty of rare earth (RE) elements’ existence during nitriding. In the present work, the LaFeO3 perovskite oxide was attempted to use as a catalyst in the gas nitriding for the first time. The effect of nitriding temperature on the microstructure and properties of the RE nitrided layer was investigated and the catalytic mechanism of the RE was discussed. The microstructure, phase composition and microhardness profiles of nitrided layers were characterized by the optical microscope, X-ray diffraction and micro-hardness tester, respectively. The corrosion resistance of nitrided layers was tested by the potentiodynamic polarization technique. Pin-on-disc tribometer were applied to evaluate the wear property. The X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy dispersive X-ray spectroscopy were used to identify the catalytic mechanism of the RE by analyzing the chemical state and elemental distribution on the nitrided surface. The results show that a perovskite-type oxide, LaFeO3, would form after the gas nitriding, which presents an obvious catalytic activity and increases the thickness of nitrided layers. In addition, the mechanical and corrosion properties could also be improved after nitriding with RE addition. The LaFeO3 perovskite oxide could accelerate the nitriding rate by adjusting the ratio of the adsorbed nitrogen (N) and dissolved N. On the other hand, the sufficient oxygen vacancies in the LaFeO3 oxide could provide more diffusion routes for N atoms.

Effects of nitriding temperature on the structure and magnetic properties of CoFe2 alloy

It has been reported that the nitridation can increase the magnetization of α-Fe by 20%. The CoFe2 alloy has the highest magnetization among all binary alloys, thus whether the nitridation can further enhance its magnetization. In the present work, the uniform and dispersed 16-nm CoFe2O4 particles were separated by the MgO matrix in order to prepare the fine CoFe2 particles, beneficial for the nitridation reaction. With increasing the nitridation temperature, the crystal structure of the Co–Fe–N alloy experiences α″-Fe16N2 below 250 °C, γ′-Fe4N at 300 °C and e-Fe3N between 350 °C and 500 °C. The single-phase e-CoFe2N was synthesized at 400 °C, a much lower temperature than that previously reported. The results of magnetic measurement at 10 K show that the nitridation at 200 °C increases the magnetization of CoFe2 from 228 to 292 emu/g by 28%; the nitridation at temperatures of 200, 250 and 300 °C enhances both the magnetization and coercivity of the CoFe2 alloy. These CoFe2 nitrides are very interesting and of importance both from physical and industrial aspects, which deserves further investigations.

Effect of nitridation temperature on formation and properties of GaN nanowall networks on sapphire (0 0 0 1) grown by laser MBE

Vertical aligned GaN nanowall networks (NWN) have been grown on sapphire (0 0 0 1) substrates using laser assisted molecular beam epitaxy (LMBE) by tuning the sapphire pre-nitridation temperature (200–600 °C). Field emission scanning electron microscopy studies showed the formation of hexagonal shaped vertical GaN NWN with wall width of 8–20 nm on high temperature (600 °C) nitridated sapphire whereas flower shape granular GaN structure with grain size of 50–240 nm was obtained on low temperature (200 °C) nitridated sapphire. The crystalline properties of the GaN NWN have been studied using high resolution X-ray diffraction (HR-XRD). The results show that the full width at half maximum of the GaN(0 0 0 2) X-ray rocking curve has a relatively low value compared to previous reports of hetero-epitaxial grown GaN NWN on sapphire and other substrates. Raman spectroscopy measurements revealed the presence of compressive stress in film whereas tensile stress in GaN NWN structures which is also complimented by HR-XRD analysis. The room temperature photoluminescence spectroscopy measurement for NWN having tip width 8–20 nm showed a 94 meV blue-shift in near band edge emission, even though NWN experienced with tensile stress, which confirm the observation of quantum size effect. The hetero-epitaxial growth of porous GaN NWN with high crystalline quality holds promise for applications in field of nitride based sensors and the enhancement of light extraction efficiency in optoelectronics devices.

Effect of temperature and gaseous medium on the evolved microstructures of carbon fiber reinforced reaction bonded silicon nitride composites

Reaction bonded silicon nitride (RBSN) composites containing 10vol% carbon fiber were prepared using the direct nitridation method at 1200, 1300 or 1400°C by purging pure nitrogen or nitrogen-hydrogen (95% N2-5% H2) mixed gas. The effect of nitridation temperature and gaseous medium on the microstructure of RBSN were studied in detail. X-ray diffraction analysis on the resultant RBSN composites revealed a dominant α-Si3N4 phase along with β-Si3N4 and Si2N2O. The growth of silicon nitride whiskers was found to increase with the addition of carbon fibers. The microstructural analysis using TEM and SEM ascertained that there was no formation of beads at the tip of the whiskers. Hence, the growth of whiskers purely depends on gas phase reactions, i.e., it is based on vapor-solid (VS) and not vapor-liquid-solid (VLS) mechanism.

SBA‐15‐Oxynitrides as a Solid‐Base Catalyst: Effect of Nitridation Temperature on Catalytic Activity

AbstractSolid bases, such as SBA‐15‐oxynitrides, have attracted considerable interest for potential applications as catalysts in important industrial processes. Reported herein is that by simply tuning the temperature of nitridation (ammonolysis), the catalytic activity of these solid bases can be enhanced. Solid‐state NMR spectroscopy and XPS studies provided the reasoning behind this change in activity.

SBA-15-Oxynitrides as a Solid-Base Catalyst: Effect of Nitridation Temperature on Catalytic Activity.

Solid bases, such as SBA-15-oxynitrides, have attracted considerable interest for potential applications as catalysts in important industrial processes. Reported herein is that by simply tuning the temperature of nitridation (ammonolysis), the catalytic activity of these solid bases can be enhanced. Solid-state NMR spectroscopy and XPS studies provided the reasoning behind this change in activity.