Glow-discharge Emission Spectroscopy Research Articles

Microstructure effect on sliding wear of 316L stainless steel selectively laser melted

Due to varying thermal cycles, the resulting microstructure of metal additive manufacturing differs from the conventionally processed counterpart alloys. Since the mechanical properties depend on the microstructure, the wear resistance of components manufactured by laser powder bed fusion (LPBF) is determined by the processing parameters. This work focuses on microhardness and sliding wear of 316L stainless steel, evaluated nanoindentation and pin-on-disc, respectively, analysed through optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and glow discharge emission spectrometry (GDOES). The results show that the LPBF-processed specimens have about 40% higher microhardness and ca. 30% lower wear rate than the wrought counterpart. The enhanced sliding wear resistance is associated with the higher density of dislocations at the cellular subgrain boundaries.

Effect of pulse frequency on the surface properties and corrosion resistance of a plasma-nitrided Ti-6Al-4V alloy

In this work, Ti-6Al-4V alloy, commonly used as implant material in biomedical applications, was treated by plasma nitriding. The nitriding process was carried out using an N2-H2 plasma (1000:500 sccm) at an operating pressure of about 866 Pa. The current regulation was about 1.8 A, the negative voltage was about 480–500 V, and the power was 840–940 W. The nitriding temperature was maintained at 650 ± 5 °C, and the nitriding time was 240 min. Bipolar pulse frequencies were varied at 25, 50, 100, 150, and 200 kHz. Analysis by grazing incidence x-ray diffraction spectrometer (GI-XRD) revealed the presence of δ-TiN and ε-Ti2N phases in all nitrided samples. The hardness depth profile was measured with a penetration depth of about 5 nm using the enhanced stiffness procedure (ESP). The results showed that all the nitrided samples had a surface hardness approximately three times that of the unnitrided sample. This result is consistent with that from glow discharge emission spectroscopy (GD-OES), which confirmed the diffusion distance of nitrogen atoms from the surface of about 5 μm. After plasma nitriding, the surface roughness tended to increase, resulting in an increase in the water contact angle (WCA) and a decrease in the work of adhesion. The specific wear rate (ball-on-disk) of all nitrided samples decreased and was significantly lower at a bipolar pulse frequency of 50 kHz. This result is consistent with the stability of the coefficient of friction (COF) after 6000 sliding cycles. Moreover, the nitrided sample at 50 kHz exhibited the lowest corrosion current density in artificial saliva based on the Tafel potential polarization method.

Simulating the carbon distribution in zirconium alloy spent fuel cladding

The diffusivity values of C in pure Zr and in Zr containing dissolved O (Zr(O)) were determined in a temperature range of 623–1023 K for Zr and 923–1123 K for Zr(O) from depth profiles of C obtained by glow-discharge emission spectroscopy. The C diffusivity in Zr(O) decreased as the O concentration in Zr increased and that for Zr containing 15 at % O was two orders of magnitude smaller than that for pure Zr. One-dimensional numerical calculations of Fick’s diffusion equation with a Soret effect indicated various non-uniform distributions of C in a 5-mm-thick Zr matrix under a temperature gradient of 573 to 773 K for 3 years, assuming a heat of transport of − 1.5 to + 1.5 eV. Isothermal annealing at 773 K for 10 years could result in a uniform distribution, whereas dissolution of O in the interstitials of the Zr matrix would hinder C transport through the interstitials.Graphical As concentration of O increased in HIP Zr by 15 at%, the diffusivity of C decreased more than two orders of magnitude.For the positive {{Q}^{*}}_{c}, concentration of C slightly segregated at the surface of the cooler side but had maximum peaks at a middle to a higher temperature zone, and depleted at the surface of the hotter side.For the negative {{Q}^{*}}_{c}, concentration of C depleted at the surface of the cooler side and at the middle to the higher temperature zone, and highly segregated at the surface of the hotter side.

Microstructure simulation and experimental evaluation of the anisotropy of 316 L stainless steel manufactured by laser powder bed fusion

PurposeThe effect of processing parameters on the microstructure of steel produced by laser-based powder bed fusion (LPBF) is a recognized opportunity for property design through microstructure control. Because the LPBF generates a textured microstructure associated with high anisotropy, it is of interest to determine the fabrication plane that would generate the desired property distribution within a component.Design/methodology/approachThe microstructure of 316 L produced by LPBF was characterized experimentally (optical, scanning electron microscopy, glow discharge emission spectrometry and X-ray diffraction), and a finite element method was used to study the microstructure features of grain diameter, grain orientation and thermal parameters of cooling rate, thermal gradient and molten pool dimensions.FindingsThe computational tool of Ansys Additive was found efficient in reproducing the experimental effect of varying laser power, scanning speed and hatch spacing on the microstructure. In particular, the conditions for obtaining maximum densification and minimum fusion defects were consistent with the experiment, and the features of higher microhardness near the component’s surface and distribution of surface roughness were also reproduced.Originality/valueTo the best of the author’s knowledge, this paper is believed to be the first systematic attempt to use Ansys Additive to investigate the anisotropy of the 316 L SS produced by LPBF.

Effect of double thermal and electrochemical oxidation on titanium alloys for medical applications

The research focuses on the development and characterization of innovative thin hybrid oxide coatings obtained in subsequent processes of thermal (TO) and electrochemical (EO) oxidation. Four different surface modifications were investigated and the microstructure was determined, the mechanical, chemical and biological properties of the Ti-13Nb-13Zr alloy were assessed using scanning electron microscopy, X-ray dispersion analysis, glow discharge emission spectroscopy, Raman spectroscopy, nanoindentation and corrosion resistance measurements. The composite layers were evaluated for antimicrobial activity, cytotoxicity bioassays and wettability tests were performed. The conducted studies of two-stage oxidation (TO + EO) have shown that it is possible to obtain layers with a different structure - crystalline and nanotubular. The formation of a nanotube layer on the surface of the crystalline layer is dependent on the thickness of the crystalline layer. The produced double titanium oxide coatings show high surface roughness, high corrosion resistance, are hydrophilic, slightly antibacterial, and not cytotoxic, which has a huge impact on the process of connecting the tissue with the implant.

Influence of laser polishing on surface roughness and microstructural properties of the remelted surface boundary layer of tool steel H11

This work investigates the influence of multi-step laser polishing on microstructural properties of the remelted surface layer of tool steel H11. Four different sets of process parameters were selected for laser polishing of initially annealed samples made from tool steel H11. In a sequential, multi-step process using continuous and pulsed laser radiation (Nd:YAG) a significant reduction of surface roughness was achieved.. The remelted layers were analyzed using roughness measurements, white light interferometry, X-ray diffractometry, electron backscatter diffraction, glow discharge emission spectroscopy, and nanoindentation hardness measurements. Laser polishing leads to a grain refinement and a significant increase in hardness. A minimal surface roughness of Ra = 50 nm was achieved in an Argon process atmosphere with an additional 6 vol% CO2. In particular the carbon concentration was significantly reduced within the remelted layer. The lower carbon concentration is correlated with a decreased maximal surface hardness down to 366 HV. High residual tensile stresses of up to 926 MPa can be introduced by laser polishing. Overall, high temperature gradients and, in particular, decarburization due to carbon diffusion processes were identified to be the major driving force for significant changes in surface roughness and microstructural properties.

Microstructure of reactive magnetron sputtered S-phase coatings with a diffusion sub-layer

The main objective of the work was to investigate the microstructure of S-phase coatings obtained by reactive magnetron sputtering at different temperatures and with various nitrogen concentrations in the working atmosphere. Particular attention was paid to the formation of a diffusion sub-layer in the austenitic substrate. The coatings were deposited on austenitic stainless steel substrates in an argon–nitrogen gas mixture. Three different nitrogen concentrations in the working gas were used in the experiments (15, 33 and 50 vol.%), and five substrate temperatures (200, 250, 300, 350 and 400 °C). The phase composition was evaluated using X-ray diffraction (XRD). X-ray microanalysis (WDS) and glow discharge emission spectroscopy (GDOES) techniques were used to study the nitrogen content and distribution in the coatings. The microstructure was investigated using a scanning electron microscope (SEM). Formation of the S-phase diffusion sub-layers was observed in the atmospheres containing 50 and 33 vol.% N2 respectively at temperatures of 300 and 350 °C or higher. Nitrogen diffusion into the substrate also occurred with the 15 vol% N2 atmosphere at 350 °C or higher although no supersaturated solution was formed in these conditions.

Composition and mechanical properties of B-C-W and B-C-Ti thin films prepared by pulse magnetron sputtering

In the present work, coatings in the material systems B-C-W and B-C-Ti have been synthesized by pulse magnetron sputtering, to exploit their potential as coatings for hard, wear resistant applications. These layers offer interesting properties, because of the possible amounts of carbides and borides that can form in the non-equilibrium deposition processes. Especially the amount of tungsten in the layers promises high wear resistance and corrosion protection at elevated temperatures.The B-C-W and B-C-Ti thin films have been deposited by pulsed magnetron co-sputtering in bipolar mode, using a boron carbide (B4C) target and a metal target (W or Ti) with a maximum total power input of 12.9W/cm2. The amount of metal in the layers has been varied by adjusting the sputtering pulse length of the respective target material. The influence of bias voltage on the properties of B-C-W coatings has been investigated and it was found out that bias voltages of −60V … −100V lower the hardness of the coatings.The hardness and the Young's modulus of the layers have been determined by nanoindentation. Whereas the majority of coatings exhibits hardness around 20GPa or lower, maximum hardness of 28GPa and Young's modulus of 420GPa are observed in a certain compositional range, in which coatings also distinguish by good thermal stability. Their composition has been analysed by using optical glow discharge emission spectroscopy (GD-OES) and Rutherford backscattering spectrometry (RBS).

Detection of a small admixture of acetone in the exhaled air for noninvasive diagnosis of type I diabetes

A method for measuring the concentration of a biomarker (acetone in human’s breath), which is based on the use of glow-discharge emission spectroscopy in air is proposed for the purpose of noninvasive glucose monitoring in diabetes patients’ blood. The experimental setup and measurement techniques are described, and preliminary results of clinical trials of the developed system under ambulatory conditions are presented.

Determination of potassium and sodium ions with diaphragm glow discharge plasma in aqueous solution

In the present work, a new apparatus of diaphragm glow discharge emission spectroscopy was described for the determination of potassium and sodium ions in aqueous solution. The discharge was formed in a pin hole on a dielectric diaphragm interposed between two submerged graphite electrodes. Effects of pH and applied voltage on the determination have been examined. It was found that decreasing the solution pH and increasing the applied voltage were favorable for the determination performance. Limits of detection for Na and K were 0.002 and 0.05 mg L−1 under the optimum conditions, respectively. It demonstrates that the diaphragm glow discharge emission spectroscopy is a promising technique in measurements of metal ions in aqueous solution, because no optical interferences from the electrodes were found.

Zinc coatings for hot sheet metal forming: Comparison of phase evolution and microstructure during heat treatment

The production of high strength steel parts via hot forming of manganese boron steels is an appropriate solution satisfying the strictest lightweight demands in modern body in white engineering. Since cathodic corrosion protection is essential for automotive parts, manufacturer demands zinc based coatings suitable for hot sheet metal forming. For that reason, microstructure and phase evolution during and after typical heat treatment, prior to hot sheet metal forming, of zinc and zinc based coatings have been investigated by glow discharge emission spectroscopy, scanning electron microscopy with EDX analysis, X-ray diffraction and nanoindentation. Therefore, characteristics of the heating behavior dependent on the different surfaces have been studied. It was hereby possible to compare the alloying behavior of hot dip zinc coating to that of electro-plated intermetallic zinc–nickel coating at different temperatures. Surface analysis revealed a ZnO layer formation on the heat treated Zn–Ni coating. Moreover, the present study proves a significant stabilization of the alloying process and the resulting phases due to the presence of nickel. Hence, electro-plated uniphase, intermetallic Zn–Ni coatings are highly suitable for hot sheet metal forming applications owing to their good thermal stability when compared to hot dip zinc coatings.

Improved voltage transfer coefficients for nonconductive materials in radiofrequency glow discharge optical emission spectrometry

In radiofrequency glow discharge emission spectrometry (RF-GDOES), the excitation voltage used to create the plasma is applied to the back or front end of the sample to be analyzed. In this paper we focus on back-applied voltage systems (a configuration that represents about half of the instruments available on the market), and on applied voltage problems (the power coupling efficiency and materials analysis are beyond the scope of this study). In the RF-GDOES of nonconductive samples, a voltage drop develops inside the material. The voltage transfer coefficient is defined as the ratio between the peak voltage in front of the sample (facing the plasma) and the peak voltage applied to the back of the sample. In this work, we show that it is possible to increase the voltage transfer coefficient by increasing the capacitance of the sample. The capacitance of a given nonconductive material depends on its surface, its thickness and its permittivity. Increasing the voltage transfer coefficient permits higher power deposition in the plasma. This study is based on an electrical equivalent circuit for the discharge device, which takes into account the sample and reactor capacitances as well as the voltage probes used for the measurements. This circuit, when modeled by a commercial electrical circuit simulator, gives the voltage transfer coefficient as a function of the sample capacitance. Different approaches to increasing the sample capacitance and their influence on the voltage transfer coefficient are presented and related to the 750.4 nm argon line intensity, which is correlated to the electron density.

Analysis of new electrical signals in respect to quantification of radio frequency glow discharge emission spectrometry

Radio frequency glow discharge optical emission spectroscopy (RF-GD-OES) is routinely used for the chemical analysis of solid samples. For quantification two independent electrical signals of the discharge are required. These are provided in real time by the glow discharge source with integrated voltage and current sensors. The available time-dependent voltage and current must be reduced. For this purpose a plasma equivalent circuit is used. It is shown that the cathode voltage and active cathode current describe the sputtering and excitation well. Measuring standard reference materials at constant cathode voltage and cathode current results in linear calibration curves.

高Ｍｎステンレス鋼の真空中ガス放出特性

An outgassing rate was measured for a stainless steel material of YUS130S, having a high-mangany content (Fe-18Cr-7Ni-11Mn-0.3N), and compared with those for a stainless steel of SUS304L. A surface processing of electropolishing followed by an in-air oxidation was examined in order to investigate the outgas reduction effect. Further, a depth profile of the surface compositions was analyzed by glow-discharge emission spectroscopy (GDS). Based on the results, the outgassing rate of YUS130S was 35% lower than that of SUS304L, when electropolished. The oxidation process in air at 450°C showed only small effect on the outgassing reduction in YUS130S, while the process was effective in the case of SUS304L. The GDS observation shows that, by electropolishing, Cr-Mn-rich and Cr-rich passive films were formed on the YUS130S and SUS304L surfaces, respectively. The further process of in-air oxidation causes a change in oxide films to Fe-Mn-rich and Fe-rich characteristics for YUS130S and SUS304 respectively.

Sputter etching of steel substrates using DC and MF pulsed magnetron discharges

For many high rate PVD processes, an adequate pre-treatment is necessary immediately before the deposition. Because the high deposition rate of some PVD techniques (e.g. electron beam (EB) evaporation) enable a very high throughput, the pre-treatment must be carried out with an adequate speed. The sputter etching in a magnetron discharge where the substrate serves as a cathode (target) seems to be a very promising pre-treatment technique for this purpose. This technique is especially suitable for flat, electrically conducting substrates like metal strips and sheets. Because of arc problems in direct current (DC) magnetron discharges due to insulating layers on the cathode surface, experiments were carried out using discharges in the medium frequency (MF) range (10–100 kHz). During the magnetron sputter etching, the light emitted by the etching plasma was investigated by optical emission spectroscopy (OES). After the magnetron sputter etching, the substrate surface was investigated by optical glow discharge emission spectroscopy (GDOES). Using a MF pulsed magnetron discharge for sputter etching, the damage caused by cathode arcs on the substrate surface could be significantly diminished. However, the MF sputter etching process needs nearly twice as much energy as the DC process to remove a contamination layer from the substrate surface.

流動層中でのニッケルのホウ化処理

Bonding is useful in surface hardening nickel (Ni) in many surface treatments. Although Ni boronized by powder-pack bonding with amorphous boron and by gas bonding with BCl3 has been reported, few reports cover bonding in a fluidized bed. We analyzed the treated layer using X-ray diffraction (XRD), glancing incidence X-ray diffraction, glow discharge emission spectrometry (GDS), and electron probe microanalyzer (EPMA). High-temperature microhardness and friction and wear characteristics of boronized Ni were studied, with the following results:(1) Bonding Ni at a high temperature over a long time in a fluidized bed showed flaking of the treated layer due to Ni siliconization.(2) The Knoop hardness was 1300HK for the sample boronized 7.2ks at 1073K. The boride layer was about 25μm thick and consisted mainly of Ni2B and Ni3B.(3) The high-temperature microhardness of boronized Ni is higher than that of untreated Ni below about 800K.(4) Friction properties and wear resistance to SUJ2 and SUS304 were improved by Ni bonding.

Plasma polymerization of fluoromethanes

Methane and fluoromethanes (CHnF4−n, 1 ≤ n ≤ 3) were subjected to an rf glow discharge plasma. All the fluoromethanes (including methane) polymerized in the plasma and formed thin films. The deposition rate of the fluoromethanes depended on their monomer structure: CH2F2, of which the F/H ratio is unity, showed the greatest deposition rate. The elimination of H and F atoms as H—F was found to be a key factor for the polymerization of fluoromethanes. The chemical composition of the polymerized film, measured with X-ray photoelectron spectroscopy and glow discharge emission spectroscopy, was also found to be strongly dependent on monomer structure. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2043–2050, 1998

無電解ニッケル‐リン合金めっき皮膜の耐食性に及ぼす上層スズめっきの影響

Electroless nickel-phosphorus alloy was plated on steels, and tin plated on top of these. Double-plating films were analyzed by glow discharge emission spectrometry (GDS) before and after heat treatment. Effects of heat treatment on X-ray diffraction patterns, anodic polarization curves, and corrosion resistance were investigated compared to electroless nickel-phosphorus alloy films. Anodic polarization currents for tin/electroless nickel-phosphorus alloy double-plating films were greatly suppressed by heat treatment at 400°C. X-ray diffraction measurements confirmed the formation of intermetallic tin-nickel compounds after heat treatment. Current values were assumed suppressed due to formation of these compounds.GDS results showed that film surfaces were blue due to nickel oxides forming on them in heating electroless nickel-phosphorus alloy films at 400°C in an atmosphere. Electroless nickel-phosphorus alloy films with a tin overlayer did not show this color, however, because intermetallic tin-nickel compounds formed on the film surface. CASS tests showed that electroless nickel-phosphorus alloy films with a tin overlayer were superior in corrosion resistance to films without this overlayer.

Comparative study on emission characteristics of d.c.- and r.f.-powered Grimm glow discharge plasmas. Use of argon spectral lines

Equivalent discharge conditions, where the intensities of the analyte are almost the same between the d.c. and the r.f. power modes, have been investigated in Grimm glow discharge emission spectrometry. The two plasmas have similar emission and sputtering characteristics, enabling the conditions to be found easily. Various emission lines of argon ion are commonly observed from the argon discharges regardless of the power modes. A method to determine the equivalent discharge conditions is suggested, based on intensity analysis of the argon ionic lines.

流動層によるオーステナイト系ステンレス（ＳＵＳ３０４）鋼のほう化処理

Boronizing is well known to improve wear and corrosion resistance, because boron forms intermetallic compounds. Although the characteristics of boronized austenitic stainless steel have been reported, little information is available on boronizing in fluidized beds. We analyzed, the boronized layer using glow discharge emission spectrometry (GDS), X-ray thin diffraction, and ESCA. We studied the friction and wear characteristics and corrosion behavior of boronized SUS 304 stainless steel, and obtained the following results, (1) The Knoop hardness was 1900HK for specimen treated for 4h at 1123K. A boronized layer was formed with three lamellar layers, the first layer mainly FeB, the second Fe2B, and the third a ferritic phase. The FeB layer had a fine structure and the physical etching of GDS was useful for observing this microstructure.(2) The boron concentration was about 50 at% in the first layer, about 40 at% in the second, and about 30 at% in the third. The boronized layer contained about 10 at% Cr. Ni and Si enrichment were detected in the ferritic phase.(3) The boronized specimen had a high wear resistance to SUJ 2 and Al2O3 than an untreated one, but the friction characteristics was not greatly improved.(4) Corrosion resistance was improved against 0.1N HCl but not against 0.1N H2SO4 or 10% oxalic acid solution.