Nitriding Technique Research Articles

Research on Component Phases and Microstructure Shape of a Rapid Ion Nitriding Layer

The properties of nitrided parts are closely related to the component phases of their compound layers and microstructure shape of their diffusion layers. Based upon the influence of nitriding temperature and nitrogen (N) potential on formation and decomposition of ion nitriding layer, the component phases and microstructure shape of ion nitrided layer, which was processed under cyclic N potential, was studied with x-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The mechanism of rapid ion nitriding is also discussed in this paper. The results show that if the rapid ion nitriding by the thermal cycling and the N potential cycling is controlled, the nitriding speed and nitrided layer thickness of materials can not only be enhanced compared to the conventional ion nitriding technique, but also the alloy nitrides can be obviously increased. The precipitation hardness phases of diffusion layer became more trivial and spread in all directions. It is very important to improve the quality of the nitrided layer and to enhance the properties of nitrided parts.

Corrosion properties of active screen plasma nitrided 316 austenitic stainless steel

AISI 316 austenitic stainless steel has been plasma nitrided using the active screen plasma nitriding (ASPN) technique. Corrosion properties of the untreated and AS plasma nitrided 316 steel have been evaluated using various techniques, including qualitative evaluation after etching in 50%HCl + 25%HNO 3 + 25%H 2O, weight loss measurement after immersion in 10% HCl, and anodic polarisation tests in 3.5% NaCl solution. The results showed that the untreated 316 stainless steel suffered severe localised pitting and crevice corrosion under the testing conditions. AS plasma nitriding at low temperature (420 °C) produced a single phase nitrided layer of nitrogen expanded austenite (S-phase), which considerably improved the corrosion properties of the 316 austenitic stainless steel. In contrast, AS plasma nitriding at a high temperature (500 °C) resulted in chromium nitride precipitation so that the bulk of the nitrided case had very poor corrosion resistance. However, a thin deposition layer on top of the nitrided case, which seems to be unique to AS plasma nitriding, could have alleviated the corrosion attack of the higher temperature nitrided 316 steel.

Sliding wear properties of active screen plasma nitrided 316 austenitic stainless steel

AISI 316 austenitic stainless steel has been plasma nitrided using the novel active screen (AS) plasma nitriding technique. Wear properties of the AS plasma nitrided and untreated 316 stainless steel have been investigated using a pin-on-disc tribometer with cemented tungsten carbide ball as the counterface. Experimental results have shown that AS plasma nitriding can improve the wear resistance of 316 austenitic stainless steel by more than two orders of magnitude. Wear of untreated 316 stainless steel was severe and characterized by strong adhesion, abrasion and severe plastic deformation. Whilst wear of the AS plasma nitrided 316 stainless steel was mild and dominated by oxidation wear and micro-abrasion. No clear difference, in terms of wear resistance improvement, has been found between the novel AS plasma nitriding and the conventional DC plasma nitriding under the present test conditions.

Structural Properties of Ultrathin Amorphous Silicon Oxynitride Layers

7-nm-thick amorphous silicon oxynitride (a-SiOxNy) layers were prepared at 300°C using a plasma nitridation technique on different types of crystalline Si substrates and under different ammonia flow rates, [NH3]. The compositional and structural properties of the a-SiOxNy layers were examined using current–voltage (I–V), capacitance–voltage (C–V), electron spin resonance (ESR), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) measurements. A strong correlation between the changes in the I–V, C–V characteristics and in the ESR spin density (Ns) was obtained. The use of low-resistivity Si substrates enabled us to assess simultaneously the changes in the defect density and the electrical properties. Based on the FT-IR results, the changes in the 800 and 1070 cm-1 absorption bands are discussed in connection with the structural change.

Cathodoluminescence spectra of GaN powders deposited on glass substrate

The cathodoluminescence spectra of annealed GaN powders, which were fabricated using a nitridation technique, deposited on a glass substrate, were investigated. It was found that annealing is effective for increasing the emission intensity and the UV emission of GaN powder. Electroluminescent devices were fabricated using the annealed GaN powder and UV light emission was observed from them.

Structure and corrosion behaviour of stainless steels after plasma and gas nitriding

The microstructures and corrosion properties of ferritic and austenitic stainless steels have been investigated after plasma and gas nitriding at 200-450° C. Little difference was observed between the surface layers produced by the two nitriding techniques: that on ferritic X6Cr17 consisted of ferrite plus epsilon-carbide, that on the austenitic X5CrNi18-10 was the expanded austenite S phase. Pitting resistance of X5CrNi18-10 was improved by nitriding at up to 420° C, but deteriorated for higher nitriding temperatures. The presence of epsilon-carbides in the layer on X6Cr17 slightly reduced pitting resistance for nitriding temperatures up to 440° C. Annealing the nitrided specimens degraded corrosion resistance by redistributing the nitrogen in the surface layer and promoting chromium nitride precipitation.

Comparison of the mechanical properties of nitrogen ion implantation and micro-pulsed plasma nitriding techniques of Cr–Ni alloy

Cr–Ni alloys are frequently used in dentistry for economical reasons. While they gain popularity, an increase in systemic and local concerns of these dental metals is observed. With the progressions in surface technology, the surface characteristics of the metals can be changed. In this study, nitrogen ion (N ion) implantation and plasma nitriding techniques were used to change the properties of Cr–Ni alloy (Wirollay). Nitrogen implantation at dose 1×10 17 ion/cm 2 and micro-pulsed plasma nitriding techniques were applied to Cr–Ni alloy samples. After the process, the friction coefficient was decreased in ion implantation, but this ratio was increased in the plasma nitriding technique with respect to the substrate. The roughness did not change after N ion implantation but it increased after the plasma nitriding procedure. Wear volume of the implanted and plasma nitriding samples were lower than the substrate. Hardness values were increased four times for N ion implantation and eight times for the plasma nitriding technique.

PLASMA SPECIES ANALYSIS FOR INSITU ASSESSMENT OF SURFACE TREATMENTS

In order to gain the maximum potential from plasma technology in surface engineering, knowledge is required about the influence of particular plasma phase species on the treatment response. In this study, optical emission spectroscopy (OES) is used in situ, without disturbing the treatment environment, to monitor the active species observed in three different types of nitriding plasma: direct current (dc), active screen, and plasma immersion ion implantation (PI3). The spectral information obtained is considered in conjunction with metallurgical characterisation of nitrided steel samples, using optical microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, and microhardness testing. Active screen and dc nitriding have a similar nitriding effect in low alloy steel testpieces. OES evidence shows that both ions and neutrals are involved in the plasma reactions and a multistage theory is the model of best fit for nitrogen mass transfer in these dc powered plasma nitriding techniques. OES analysis can be used for in situ monitoring of treatment quality in PI3 nitriding.

Impact of gate oxide nitridation process on 1/ f noise in 0.18 μm CMOS

The aim of this paper is to study the impact of the nitridation techniques on the 1/ f noise performances of dual gate 0.18 μm CMOS transistors. Nitrogen is often introduced to prevent boron penetration in ultrathin oxides especially when BF 2 is used for the PMOS junction implantation, but as a result the MOS transistor exhibits higher 1/ f noise because of the increased fixed trap density. We show how the nitridation process can be improved in terms of 1/ f noise characteristics, in a fully integrated technology. Projections of the 1/ f noise behaviour for different technologies are also shown, to emphasise how the 1/ f noise becomes an issue when other downscaling properties are considered for analog/RF CMOS applications.

Plasma nitridation of very thin gate dielectrics

The performance of NMOSFET devices with nitrided gate oxides has been compared using two plasma-based nitridation techniques. Specifically, remote plasma nitridation (RPN) and decoupled plasma nitridation (DPN) of 1.4 nm base oxides were evaluated. It is found that both nitridation techniques give comparable leakage current performance, where 4–10× leakage current reduction can be achieved compared to un-nitrided oxides. The flatband voltages of the DPN-nitrided gate dielectric are larger (more negative) than those of RPN-nitrided gate dielectric, possibly indicating more fixed charge for the DPN process conditions used. The normalized peak transconductance of RPN and DPN-nitrided gate dielectrics depends on the detailed nitridation conditions, but can be comparable to that of un-nitrided oxides. The normalized drive currents are largest for the DPN-nitrided oxides, most likely because of the smaller threshold voltage measured after DPN nitridation. The results suggest that for NMOSFET devices, the two nitridation processes (RPN and DPN), if properly optimized, can give comparable device performance.

プラズマ窒化によるＦｅ‐Ｃｒ合金の組織及び硬さ傾斜の制御

プラズマ窒化によるＦｅ‐Ｃｒ合金の組織及び硬さ傾斜の制御

The properties of AlN prepared by plasma nitriding and plasma source ion implantation techniques

The formation of aluminum nitride (AlN) layer on 1050 aluminum substrate has been successfully performed by a low pressure plasma nitriding process and a plasma source ion implantation process. In the plasma nitriding (PN) process, a relatively thick and uniform stable h.c.p.-AlN layer of ∼20 μm has been obtained from a gas pressure of 400 Pa N 2 gas at 480°C. In PSII technique, a metastable f.c.c.-AlN layer has been consistently observed in the implantation dose levels between 7×10 17 and 1.8×10 18 ions/cm 2. In addition an apparent peak separation between metastable f.c.c.-AlN and f.c.c.-Al phase has been observed in the XRD spectrum using a long wavelength (λ=2.29 Å) of Cr Kα X-ray.

Properties of surface layers produced on the Ti–6Al–3Mo–2Cr titanium alloy under glow discharge conditions

The recent rapid progress in surface treatment techniques requires that titanium alloys should have an improved resistance to frictional wear without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface layers of specified microstructure and phase composition. The paper presents the results of examinations of the structure and properties of surface layers formed on the Ti–6Al–3Mo–2Cr titanium alloy by glow discharge assisted nitriding and modified process known as carbonitriding (characterized by an alteration of the gaseous atmosphere in which the process is conducted). The investigations included: metallographical examinations, determination the phase and chemical composition of the layers, measurements of their corrosion and frictional wear resistance and scratch tests. The carbonitriding process increases the hardness and improves the wear and corrosion resistance compared to the nitriding technique.

Recent development of TiNi-based shape memory alloys in Taiwan

TiNi-based alloys are considered to be the most important shape memory alloys (SMAs) because of their salient shape memory effect (SME), pseudoelasticity (PE) and high damping capacity (HDC). Recent investigations focus on their transformation behaviors, thermal-mechanical treatments, manufacturing processes, and industrial applications based on the characteristics of SME, PE and HDC. The two-stage martensitic transformations of B2↔R-phase↔B19′ and B2↔B19↔B19′ have been clarified for both TiNi binary and ternary alloys. The deformation behaviors have been investigated by cold-rolling, hot-rolling and wire drawing. Both SME and PE can be improved by thermal-mechanical treatments, and the damping characteristics of TiNi and TiNiX SMAs have been systematically studied. Both B19′/B19 martensite and R-phase have high damping capacities due to the easy stress-induced movement of twin boundaries. The high temperature SMAs, Ti–Ni–X with X=Au, Pd and Zr alloys, have also been intensively studied. The ion nitriding technique has been used to improve the wear and corrosion resistance of TiNi and TiNiX SMAs. TiNi thin films have been successfully fabricated using the sputter-deposition technique. These investigations on the TiNi-based SMAs have attracted much attention and their important characteristics will be applied widely in the near future.

Impact of Nitrogen Implantation into Polysilicon Followed by Drive‐in Process on Gate Oxide Integrity

A nitridation technique involving shallow implantation of nitrogen into the polysilicon gate followed by thermal drive‐in process was studied. Successful incorporation of nitrogen into the gate oxide/polysilicon interface has been achieved, and thereby the reliability of gate oxide has been improved due to the reduced boron diffusion into the gate oxide in polysilicon gate metal oxide semiconductor devices. An amount of nitrogen segregated in the oxide was found to be independent of the nitrogen implantation dose but to depend only on the drive‐in thermal budget. Therefore, a high thermal budget in the drive‐in process with a low nitrogen implantation dose is a promising direction for this process to have a high nitrogen concentration in the oxide and a low nitrogen concentration in the polysilicon to avoid a serious poly‐depletion problem. However, it also has been found that when the amount of nitrogen incorporation in the oxide exceeds a certain limit, gate oxide reliability is degraded due to enhanced electron trapping. © 1999 The Electrochemical Society. All rights reserved.

Properties of multicomponent layers produced on high speed steel by combined nitriding and PACVD methods under glow discharge conditions

A prospective line in the development of thermo-chemical treatments under glow discharge conditions is to work out new techniques of producing multicomponent layers such as e.g. combined plasma nitriding and PACVD technique with the use of organic compounds. These layers permit widening the application range of treated parts since they improve their useful properties. The paper specifies the conditions under which the composite layers of the nitrided - Ti(NCO) type can be produced on high speed steel using a gaseous atmosphere of the organic titanium compound Ti(OC 3 H 7 ) 4 nitrogen and hydrogen and discusses the influence of the carbon and oxygen contents in the Ti(N x C y O z ) layer on its properties such as hardness and wear resistance. The composite layers of the nitrided-Ti(NCO) type have a good resistance to frictional wear. The chemical composition of these layers can be controlled. This new processes can be performed during a sole technological operation in a conventional equipment designed for glow discharge assisted techniques.

Plasma-source ion implantation compared with glow-discharge plasma nitriding of stainless steel

Abstract Plasma-source ion implantation (PSII) is a promising technology to overcome the line-of-sight limitations of beam-line ion implantation. Among the possible fields of commercial use, nitriding of stainless steels by plasma-source ion implantation seems to be one of the favourites. However, the technology of glow-discharge plasma nitriding (GDPN) is already being used commercially. Therefore, it remains to be determined whether PSII is more suitable to the demands of an industrial technology than GDPN. In particular, the incorporation rate of nitrogen during treatment has to be investigated, as the incorporation rate of nitrogen determines the depth of the nitrided layer for a given treatment time. For nitriding of stainless steel, PSII and GDPN were performed for the same treatment time of 2 h, using the same treatment voltage (700 V) and duty ratio (50%) during the nitriding process. The temperature during treatment was fixed at 380 °C and controlled by an isolated thermocouple. The only difference in the experimental conditions was the pressure, during treatment, of 0.1 Pa in the case of PSII and 500 Pa in the case of GDPN. Pure nitrogen as well as a nitrogen–hydrogen mixture was used as the feed gas. The resulting concentration profiles were determined by glow-discharge optical spectroscopy depth profiling to determine the nitrogen incorporation rate of both nitriding techniques. The surface properties were investigated by wear and hardness measurements. Both technologies yield the formation of a hard nitrided layer with an increased hardness. The highest nitrogen concentration and widest hardened layer was found in the case of PSII, using a nitrogen–hydrogen plasma.

Theoretical Investigation of Effective Quantum Dots Induced by Strain in Semiconductor Wires

AbstractA new fabrication technique for quantum dots is proposed on the basis of theoretical studies. It is known that the self-limiting phenomena of silicon oxidation are governed by the large stress induced by the volume expansion. We estimated the change in the band parameter of the silicon under the stress induced by the oxidation. The results show that the band-gap of the silicon considerably decreases under two-dimensional compressive strain. Accordingly, introducing strain to a small part of a Si wire results in the formation of a “strain-induced effective quantum dot”. Moreover, we also propose theoretically a new procedure for fabricating a silicon single electron transistor by the combination of silicon oxidation and nitridation techniques.

Surface treatment of nitriding steel 34CrAlNi7: a comparison between pulsed plasma nitriding and plasma immersion ion implantation

A study of the response of the nitriding steel, 34CrAlNi7, to two different nitriding techniques revealed remarkable differences. The techniques used were pulsed plasma nitriding and plasma immersion ion implantation over a range of temperatures from 300 to 500°C. The surface produced by the pulsed plasma nitriding consisted of a nitride layer whose thickness varied with temperature, with an underlying diffusion zone. Plasma immersion ion implantation treatment, however, formed nitrides only at the lowest temperature, with most of the nitrogen in solid solution. Although quite different surface structures resulted from the two treatments, similar improvements in wear performance were obtained.

Surface nitriding of titanium and aluminium by laser-induced plasma

Abstract In this work we study a nitriding technique for titanium and aluminium by means of laser-induced plasma. The synthesised layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problems. The method is tested on the synthesis of titanium nitride, and the role of the laser wavelength and pulse time duration is inspected by comparing layers obtained with two kinds of pulsed laser: a CO2 laser (λ=10.6 μm) and an XeCl excimer laser (λ=308 nm). The laser-plasma treatment is then applied to the superficial nitriding of aluminium, which is known to be difficult to carry out. Comparison is made between the nitriding process efficiencies of these two metals.