Formation Of Nitride Layer Research Articles

Formation of nitrided layers on duplex steel – influence of multiphase substrate

The present paper reports the results of gas nitriding of duplex stainless steel and study of the effect of substrate structure on the nitrided layers. The differences in the growth of the layers on austenitic and ferritic substrate were studied. The microstructure and phase composition of the layers were investigated using light microscopy analysis), X-ray diffraction (XRD and grazing angle XRD – GXRD) and electron microprobe spectrometry. Moreover, the microhardness of the layers was studied. A particular role of steel substrate in layer formation was observed at a low temperature (below 500°C) nitriding. The layers were mostly composed of the S phase and expanded martensite formed on austenite and ferrite grains respectively. The substrate influence was of minor importance at treatment temperature higher than 500°C.

Importance of surface activation for nitrided layer formation on austenitic stainless steel

Gas nitriding of austenitic steel is only possible if the passive oxide layer is removed. Therefore, surface activation forms an important part of the treatment. The main objective of the present study was to investigate the influence of activation on nitrided layer's growth. Various activation treatment methods have been applied – physical (ion sputtering with various current–voltage parameters and gases) and chemical ones (phosphating and chemical etching). The effectiveness of activation has been evaluated after gas nitriding in different conditions of atmosphere composition. The layers have been investigated using transmission electron microscopy, X-ray diffraction and grazing angle X-ray diffraction, magnetic and atomic force microscopy, electron probe microanalysis. Physical activation turned out to be the most effective method. At the same time, it made it possible to reduce the quantity of ammonia in nitriding atmosphere necessary to obtain layers composed of 'expanded austenite'. Moreover, depending on the sputtering parameters and the gas used, it was possible to obtain layers with various kinds of morphology.

How Boron Nitride Forms a Regular Nanomesh on Rh(111)

Boron nitride forms nearly perfectly regular films with a thickness of precisely one atom on various metal surfaces. Here, we follow the formation of boron nitride layers on Rh(111) with scanning tunneling microscopy (STM) under realistic growth conditions, up to 1200 K. Our STM movies demonstrate in detail how the structure grows and how defects are introduced. Based on these observations we arrive at the optimal recipe for a high-quality overlayer.

Influence of hydrogen addition and gas pressure on nitride layer formation on microcrystalline silicon thin films by a hot-wire chemical vapor method using nitrogen gas

Abstract Silicon nitride is employed for insulating layers, surface passivation layers and antireflection coatings. In this paper, we report on the influence of the addition of H 2 gas to N 2 gas and the total gas pressure on the nitride layer formation on a hydrogenated microcrystalline silicon (μc-Si:H) film surface region. Following deposition of the μc-Si:H thin films, a post-deposition treatment was carried out using a hot-wire chemical vapor technique, in a mixture of N 2 /H 2 or in a N 2 atmosphere, at varying H 2 gas flow rates and total gas pressures, to form a nitride layer in the film surface region. As the H 2 gas flow rate, F (H 2 ), was increased from 2 to 10 sccm, at a N 2 gas flow rate, F (N 2 ), of 20 sccm, the surface nitridation was dramatically enhanced. Conversely, the degree of surface nitridation remained virtually unchanged with a F (H 2 ) of 10 - 15 sccm and the surface nitridation scarcely took place at F (H 2 ) of 20 sccm. The surface nitridation occurred to some extent at 0.1 Torr (with F (N 2 ) = 20 and F (H 2 ) = 10 sccm) but was dramatically enhanced as the gas pressure was increased from 0.1 to 1.0 Torr. There was a reduction in the densities of both the N and Si atoms as the gas pressure was increased from 1.0 to 6.0 Torr, however, the density of the N atoms on the subsurface region of the films (at a depth of 20 nm from the surface) increased with increasing gas pressure. These findings show the breakdown of the Si network structure by high density H radicals and the diffusion of more N atoms into the deeper region of the films.

Interaction of nitrogen plasmas with tungsten

The use of nitrogen seeding to reduce the edge plasma temperature has recently been successfully applied in ASDEX Upgrade. While the plasma performance was significantly improved compared with other seeding species such as Ar or Ne, questions remained as to the interaction of nitrogen with a tungsten first wall. In particular the formation of thick tungsten nitride layers with reduced melting temperature and increased physical sputtering was a concern. Therefore dedicated laboratory experiments have been performed to investigate the interaction of W surfaces with N plasmas. Tungsten coated Si samples were exposed to N ions from plasma and ion gun sources at energies from 20 eV to 10 keV and W surface temperatures from 300 to 750 K. After exposure to the N plasma with fluences of up to several 1023 N m−2 the N content in the samples was measured by nuclear reaction analysis. The sputter erosion was determined by measuring the thickness change of the W layer by Rutherford backscattering. The formation of W-nitride phases was investigated in separate XPS experiments where the samples were implanted in situ with kiloelectronvolt N ions. It was found that only very small fractions of N are accumulated on the W surface and that N is bound in a nitride state. At temperatures above 600 K the nitrides are no longer stable which further reduces the N uptake into the W. Moreover the accumulation of N on the surface leads to a decrease in W physical sputtering due to the lower W concentration at the surface.

Effect of process variables on gas nitriding of H13 tool steel with controlled nitriding potential

AISI H13, a typical material used for hot extrusion dies, is gas nitrided using automated two-stage controlled nitriding process with the aim to evaluate the controlled nitriding process on nitride layer formation in terms of morphology, case depth and hardness variation across the nitride layer. A sequentially coupled thermal-diffusion analysis of actual nitriding cycle is performed numerically using finite element code, ABAQUS. The results show that the growth of nitride layer and the nitrogen concentration distribution in the diffusion zone can be accurately predicted numerically in close agreement with experimental results. The influence of nitriding time, temperature and potential is studied and it is found that these parameters significantly affect the nitride layer formation in terms of nitrogen concentration and hardness variation as a function of nitride case depth.

118 ガス窒化処理によるアルミニウム合金の窒化膜形成に及ぼす合金元素の影響(コーティング・溶射・薄膜プロセス(2),ものづくりにおける基礎研究と先端技術の融合)

118 ガス窒化処理によるアルミニウム合金の窒化膜形成に及ぼす合金元素の影響(コーティング・溶射・薄膜プロセス(2),ものづくりにおける基礎研究と先端技術の融合)

Formation of Silicon Nitride Layer on Microcrystalline Silicon Thin Films by Hot-wire Chemical Vapor Method using Nitrogen and Hydrogen Gases

Right after the deposition of hydrogenated microcrystalline silicon (μc-Si:H) thin films, a post-deposition treatment was carried out using the hot-wire chemical vapor technique in N2/H2 atmosphere, to form a nitride layer in the film surface region. The influence of the gas pressure during the post-deposition treatment on the nitride layer formation was investigated. Nitriding at the surface was negligible at 0.1 Torr but was enhanced dramatically with an increase in the gas pressure from 0.1 to 1.0 Torr. Consequently, the surface was almost completely covered with the nitride layer. However, the density of N atoms at the surface reduced with increasing gas pressure from 1.0 to 6.0 Torr. On the other hand, the nitriding on the inside of the films (a depth of 20 nm from the surface) was enhanced by the increase in the gas pressure.

Studies on laser surface melting of tool steel—Part I: Surface characterization and it's electrochemical behavior

In the present study, the effect of laser surface melting of a tool steel (SAE 52100 steel) on the characteristics (microstructures, phases and residual stress) and the corrosion property of the treated surface has been undertaken. Laser surface melting is carried out using a high power (2 kW) continuous wave CO 2 laser (with a beam diameter of 3 mm) with a linear scan speed of 1–2 m/min, using different proportions of argon (Ar) and nitrogen (N 2) as shrouding atmosphere. The gas flow rate was maintained constant at 6 l/min. Laser surface melting in argon (Ar) atmosphere significantly refined the microstructure (grain size) with the presence of lath martensite. Laser surface melting in 50%Ar + 50% N 2 and 100% N 2 atmosphere led to the formation of thin nitride (consisting of Fe 4N and Fe 2N and Cr 2N) layer. Laser surface melting in 100% N 2 atmosphere developed a microstructure consisting of primary ferrite and eutectic mixtures of α-Fe and Fe 4N, Fe 3N, Fe 2N and Cr 2N. There is introduction of residual tensile micro-stress in laser surface melted surface. However, residual stress in the range of (− 800 to − 400 MPa) and (− 300 to + 100 MPa) were observed when surface melted in 100% N 2 and 50%Ar–50% N 2 atmosphere. Improvement in general and pitting corrosion resistance in a 3.56 wt.% NaCl solution was noticed after laser surface melting.

Studies on laser surface melting of tool steel — Part II: Mechanical properties of the surface

In the present study, the effect of laser surface melting using different proportions of argon and nitrogen as shrouding atmosphere on microhardness and wear resistance properties of a low alloy high carbon tool steel (SAE 52100 steel) has been undertaken. Laser surface melting in argon (Ar) atmosphere significantly refined the microstructure (grain size) with the presence of carbides (both iron and chromium) and martensites and improved microhardness (350–500 VHN) as compared to as-received SAE 52100 steel (280 VHN). Laser surface melting in 100% N 2 atmosphere led to formation of thin nitride (consisting of Fe 4N and Fe 2N and Cr 2N) layer with improved microhardness to as high as 1050 VHN. Wear studies showed a significant enhancement in wear resistance against hardened steel ball, a maximum improvement was achieved when lased using 100% N 2. The mechanism of wear was studied in details.

Nitridation of organo-silicate glass: A self-limiting process for PVD Ta 1+ xN/Ta barrier formation

Interfacial reactions of sputter-deposited Ta with a low dielectric constant Si–O–C–H material (SiCOH), and with surface-nitrided SiCOH (N-SiCOH) were investigated using X-ray photoelectron spectroscopy (XPS). The studies were carried out in a system containing a processing chamber attached to an XPS analysis chamber so that sample transport between deposition and analysis environments occurred under ultrahigh vacuum (UHV) conditions. Ta sputter deposition on unmodified SiCOH yielded an interfacial phase ∼3 nm thick composed of Ta oxide/carbide (Ta–O–C), which is known to interact only weakly with Cu. Bombardment of the vicinal SiCOH surface by 500 eV Ar + in the presence of NH 3 resulted in carbon depletion and the self-limiting nitridation of the surface, with N attachment primarily at Si sites. Subsequent Ta sputter deposition yielded reduced Ta oxide and carbide formation, and formation of a Ta-rich nitride layer of 10 Å average thickness. Subsequent deposition resulted in metallic Ta formation.

초초 임계 화력 발전소용 밸브 소재의 산화 거동

Recently ultra-supercritical steam power plants operate at <TEX>$1000^{\circ}F$</TEX> (<TEX>$538^{\circ}C$</TEX>) and 3500 psi (24.1 MPa). Thermal efficiency of power plant will be increased about 2% if steam temperature increases from <TEX>$1000^{\circ}F$</TEX> to <TEX>$1150^{\circ}F$</TEX> (<TEX>$621^{\circ}C$</TEX>). In this study valve materials Incoloy901 (IC901) and Inconel718 (IN718) were nitrided to improve the surface hardness and solid lubrication function of the valve materials. The hardness of both IC901 and IN718 increased about two times by ion nitriding. IC901, IN718 and their nitrided specimens were corroded under ultra super-critical condition (USC) of <TEX>$621^{\circ}C$</TEX>. and 3600 psi (24.8 MPa) for 2000 hours. Oxidations of both IC901 and IN718 were very small due to the formation of protective oxide layer on the surface. But the corrosion resistance of both nitrided specimens decreased because of the formation of non-protective nitride layer of <TEX>$Fe_{4}N$</TEX>, <TEX>$Fe_{2}N$</TEX> and CrN on the surface layer. The hardness of both nitrided IC901 and IN718 at <TEX>$20{\mu}m$</TEX> depth from the surface decreased about 30% and 20% respectively by USC 2000 hours.

Adsorption of trisilylamine on the Si(100) surface

AbstractAdsorption of trisilylamine (TSA) on the Si(100) surface has been studied using temperature programmed desorption (TPD) and time‐of‐flight electron stimulated desorption (TOFESD). TPD spectra exhibit the presence of three desorption states denoted by β1, β2, and β3 associated with the presence of a mono‐, di‐, and tri‐hydride state respectively. This behavior is identical with previously observed desorption studies resulting from atomic hydrogen adsorption, indicating that the nitrogen species in the adsorbate has minimal impact on the surface structure of the hydride. Preliminary electron irradiation studies are reported and indicate that the formation of a thin silicon nitride layer is induced as a result of the irradiation. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Unified retention model for localized charge trapping nonvolatile memory device

Retention after cycling in an NROM nonvolatile memory cell is investigated. Electrical characterizations combined with two-dimensional simulations were employed. By combining subthreshold current characterizations with gate-induced drain leakage measurements, the retention loss mechanisms are quantified and differentiated. A unified retention model for the NROM technology is proposed, incorporating both lateral charge transport in the nitride layer and hot carrier-induced interface-states formation. The fabrication conditions in the various studies reported in the literature and the resultant impact on interface-states formation are most likely the cause of the formally nonresolved debate regarding the origin of retention loss in NROM technology.

Structural properties of GaAs surfaces nitrided in hydrazine-sulfide solutions

The surface structure of GaAs(1 0 0), (1 1 1)A, and (1 1 1)B substrates nitrided through the wet chemical treatment in hydrazine-sulfide solution have been studied by scanning tunneling microscopy (STM) under annealing in UHV. Such treatment has earlier been shown to produce a monolayer of gallium nitride on the (1 0 0)GaAs surface. The as-nitrided substrates of all surface orientations were found to be covered by an overfilm, which contains thioarsenic compounds and has a smooth relief. Thermal desorption of the overlfilm at about 530 °C opens the own relief of the nitrided surfaces. For the (1 0 0) orientation such relief is not microscopically planar and consists of nano-scale vicinal hillocks. These hillocks occur due to surface microetching which proceeds simultaneously with the formation of the surface nitride layer. We have shown that the wet nitridation procedure forms a monolayer of surface nitride on the (1 1 1)B surface. During nitridation the (1 1 1)B surface, as well as the (1 0 0) one, is affected by the microetching in the hydrazine-sulfide solution. Therefore, it exhibits a characteristic relief formed by triangular vicinal pyramids. At the same time the nitride film is not formed on the (1 1 1)A surface, which is more chemically inert, and where the surface etching is almost absent.

Protective nitride formation on stainless steel alloys for proton exchange membrane fuel cell bipolar plates

Gas nitridation has shown excellent promise to form dense, electrically conductive and corrosion-resistant Cr-nitride surface layers on Ni–Cr base alloys for use as proton exchange membrane fuel cell (PEMFC) bipolar plates. Due to the high cost of nickel, Fe-base bipolar plate alloys are needed to meet the cost targets for many PEMFC applications. Unfortunately, nitridation of Fe-base stainless steel alloys typically leads to internal Cr-nitride precipitation rather than the desired protective surface nitride layer formation, due to the high permeability of nitrogen in these alloys. This paper reports the finding that it is possible to form a continuous, protective Cr-nitride (CrN and Cr 2N) surface layer through nitridation of Fe-base stainless steel alloys. The key to form a protective Cr-nitride surface layer was found to be the initial formation of oxide during nitridation, which prevented the internal nitridation typically observed for these alloys, and resulted in external Cr-nitride layer formation. The addition of V to the alloy, which resulted in the initial formation of V 2O 3–Cr 2O 3, was found to enhance this effect, by making the initially formed oxide more amenable to subsequent nitridation. The Cr-nitride surface layer formed on model V-modified Fe–27Cr alloys exhibited excellent corrosion resistance and low interfacial contact resistance under simulated PEMFC bipolar plate conditions.

Effects of plasma nitriding on mechanical and tribological properties of CoCrMo alloy

Surface treatments of orthopedic materials are commonly used to enhance mechanical and tribological properties. One of the well-known orthopedic materials, wrought CoCrMo alloy was nitrided at various temperatures and time periods at a gas mixture of 75%N 2–25%Ar to achieve these enhancements. SEM, XRD, pin-on-disc tribotester, and microhardness tester have been used to examine the treated materials. Analyses confirm the formation of nitride layers and the significant effect of plasma nitriding on wear rate and surface hardness.

Ion nitrided AISI H13 tool steel Part 2 – High temperature performance under sliding wear conditions

In this work, a systematic variation of the processing parameters, such as gas mixture, time of nitriding and current density, has been carried out to determine how these will influence the sliding wear behaviour of plasma nitrided layers on AISI H13. Optical profilometry and scanning electron microscopy were used to characterise the worn sample and to determine the wear mechanism. The results revealed the strong influence of the current density on the formation of different diffusion and nitrided layers, which explained the wear behaviour of the studied samples, especially for those which were tested at room temperature. It was found that the wear volume of the nitrided samples without the existence of a compound layer was around 200 times smaller than that of the untreated samples and nearly 7 times smaller than that of nitrided samples when the compound layer was present. During the tests carried out at 300°C, the wear behaviour for the nitrided samples was worse than that for the untreated ones, due to the formation of higher amount of debris as a consequence of the breakdown of the compound layer and the subsequent removal of the enriched CrN from the ferritic matrix, generating a severe abrasion wear mechanism. All the samples tested at 600°C presented a similar tribological behaviour irrespective to the processing parameters values chosen for nitriding, as a consequence of the formation of a uniform and ‘lubricious’ iron oxide layer which, however, was insufficient to protect the steel against wear at this temperature to the levels which were obtained for the samples tested at room temperature.

Nanocrystalline Structure Produced by Complex Surface Treatments: Plasma Electrolytic Nitrocarburizing, Boronitriding, Borocarburizing, and Borocarbonitriding

In present study, the feasibility of improving tribological performance of low carbon chromium steel by applying complex surface treatments which combines the method of Plasma electrolytic saturation (PES) is investigated. The different regimes of diffusion treatments on the surface affect the mechanical and tribological characteristics of the steel substrates by production of nanocrystalline interlayers. The major advantage of the PES technique was shown to be the extremely high nanocrystalline coating growth rate by the aggressive ionized particles. The combination of characteristics far exceeds the capabilities of the diffusion procedure by means of PES technique. It was found that the different compositions of interlayers produced by means of complex diffusion treatments eliminate the sharp slope of the microhardness profile. The gradual decrease of microhardness with distance from the surface, provides a good tribological performance. The boride layer reveals the highest value of microhardness among the produced interlayers. In the case of tribological performance, the boronitrided sample shows the best characteristics which are related to the formation of nanocrystalline nitride layer beneath the top boride layer.

Nitrogen Ion Beam Irradiation on Amorphous Carbon

Both bulk and thin film amorphous carbon were irradiated using a nitrogen ion beam and changes in surface roughness and composition after ion beam irradiation have been studied. Amorphous carbon thin films were prepared from toluene vapor using plasma enhanced chemical vapor deposition. Ion irradiation was performed at room temperature using a nitrogen ion beam and the ion beam energy was varied from 0.2 to 1.5 keV under the constant ion current density. Surface morphology was observed with atomic force microscopy (AFM). Depth profiles of nitrogen in the irradiated specimens were analyzed by X-ray photoelectron spectroscopy (XPS). AFM observations reveal that after the ion beam irradiation the surface of the bulk amorphous carbon becomes rough, while the surface of the amorphous carbon films becomes smooth. However, the notable difference in the surface roughness is hardly observed between low- and high-energy ion irradiation. From XPS studies, it is found that the nitrogen concentration near the surface increases after the ion irradiation for both bulk and thin films and irradiated nitrogen ions are combined with carbon, resulting in formation of carbon nitride layers. Depth profiles of nitrogen show that for the bulk specimen low-energy ion irradiation is more effective for the carbon nitride formation than high-energy ion irradiation, while for the thin films high-energy ions are implanted more deeply than low-energy ions.