Glow Discharge Nitriding Research Articles

Impact of Glow-Discharge Nitriding Technology on the Properties of 3D-Printed Grade 2 Titanium Alloy.

This study presents a comparative analysis of the corrosion resistance of nitrided layers on conventional Grade 2 titanium alloy and those produced by direct metal laser sintering (DMLS). Low-temperature glow-discharge nitriding of the tested materials was carried out using conventional glow-discharge nitriding (so-called nitriding at the cathode potential-TiN/CP) and with the use of an "active screen" (nitriding at the plasma potential-TiN/PP). The TiN + Ti2N + Ti(N) layers were characterized by their microstructure, nanohardness profile distribution, surface topography, and corrosion resistance. The reduction in the cathodic sputtering phenomenon in the process using the active screen allowed the creation of surface layers that retained the topography of the base material. The parameters of the glow-discharge treatment led to grain growth in the printed substrates. This did not adversely affect corrosion resistance. The corrosion resistance of nitrided layers on the printed titanium alloy is only slightly lower than that of layers on the conventional Grade 2 alloy. Iron precipitates at grain boundaries facilitate increased nitrogen diffusion, resulting in reduced nitrogen concentration in the surface layer, slight changes in corrosion potential values, and increased nitrogen concentration in the Ti(N) diffusion layer.

Diffusion Nitride Surface Layers on Aluminum Substrates Produced by Hybrid Method Using Gas Nitriding

While gas nitriding of steel is currently used in industry, nitriding of aluminum alloys remains an open challenge. The main obstacle is aluminum’s high susceptibility to passivation. The oxide film provides an effective barrier to nitrogen diffusion. Attempts to overcome this problem have mainly focused on glow discharge nitriding using cathode sputtering of an oxide layer. The produced AlN layers exhibit no diffusion zone and show limited performance properties. In this work, the effect of hybrid treatment aimed at producing diffusion layers of nitrides other than AlN on aluminum alloys was investigated on the model system of iron nitride–aluminum substrate. Hybrid treatment combines an electrochemical process involving the removal of the aluminum oxide layer from the substrate, its subsequent iron plating, and a further gas nitriding in high-purity ammonia. The obtained results prove that the hybrid treatment allows the production, at 530 °C/10 h, of diffusion layers of Fe3N iron nitrides on aluminum substrates with a nitrogen diffusion zone range in aluminum of ca. 12 µm. In alloys containing magnesium, its unfavorable effect on the nitrogen diffusion and the functional properties of the layers was observed. An interesting direction for further research is hybrid treatment of precipitation-hardened alloys without magnesium.

INCREASE OF THE CORROSION-MECHANICAL WEAR RESISTANCE OF TITANIUM ALLOYS BY NITRIDATION IN THE GLOW DISCHARGE: A REVIEW OF MODERN RESEARCH

In this work, a review of modern research in the field of increasing the corrosion-mechanical wear resistance of titanium alloys using glow discharge nitriding is carried out. Titanium alloys, due to their unique properties, namely high strength, lightness, exceptional corrosion resistance and excellent biocompatibility, are widely used in aviation, medicine, engineering and many other industries. However, operational conditions in some applications require even greater improvement of the wear resistance and corrosion resistance of these alloys, which makes the search for effective methods of their improvement an urgent scientific and engineering task. Among the promising technologies that can be used to improve the corrosion-mechanical properties of titanium alloys, low-temperature anhydrous nitriding in a glow discharge should be considered. The use of low-temperature anhydrous nitriding in a glow discharge eliminates the growth of the base grain and hydrogen embrittlement of the surface. Also, low-temperature nitriding in a glow discharge makes it possible to increase the wear resistance of the surface of titanium alloys, while the saturation of the surface with nitrogen is controlled, which allows predicting the results of processing, does not lead to a change in the shape of parts. The analysis of scientific research shows that increasing the corrosion-mechanical wear resistance of titanium alloys by means of nitriding in a glow discharge is a promising direction that opens up new opportunities for industry and science. Progress in this field depends on further research, innovative development and the integration of the latest technologies, which together will contribute to the creation of more durable, efficient and environmentally friendly materials for a wide range of applications. In general, increasing the corrosion-mechanical resistance of titanium alloys by the method of nitriding in a glow discharge is a promising direction of research in Ukraine, which can lead to the improvement of the properties of titanium alloys and the expansion of their use in various industries.

Effect of surface plastic deformation of tool steel on ion-plasma nitriding in glow discharge

In this paper the influence of surface plastic deformation of P6M5 tool steel on the characteristics of the hardened layer after ion-plasma nitriding in the glow discharge is investigated. P6M5 tool steel annealed at 850 °C was used for the study. The annealed samples were preliminarily subjected to severe plastic deformation by torsion, with cold settling by 43 % and torsion by 1.5 turns, under hydrostatic compression of 4 GPa. Ion-plasma nitriding was carried out in a gas mixture of 50 % argon, 35 % nitrogen and 15 % hydrogen, at a gas pressure of 200 Pa and a temperature of 450 °C, for 2, 4 and 6 hours. The microhardness of the surface layer of the samples was investigated by the Vickers method on inclined slides. To reveal the microstructure, the studied samples were subjected to chemical etching for 10 s with a solution of acids: C2H5OH (80 ml), HNO3 (10 ml), HCl (10 ml) and C6H3N3O7 (1 g). The thickness of the nitride zone was estimated from the obtained optical images of microstructures. It was found that surface plastic deformation of steel contributes to an increase in the rate of nitrogen diffusion into the depth of the material due to an increase in the density of dislocations and the formation of microdefects due to a highly fine-grained structure. It was found that the surface plastic deformation of steel before ion-plasma nitriding leads to an increase in the thickness of the hardened layer of tool steel P6M5 in a2 times, due to an increase in surface free energy, which contributes to the increase in adsorption of the saturating element and the formation of nitrides in the near-surface layer of nitrided material.

Effect of plasma nitriding process on the fatigue and high temperature corrosion resistance of Inconel 740H nickel alloy

The paper presents a comparison of microhardness, fatigue and high temperature corrosion of Inconel 740H nickel alloy in its as-received state and the same material with nitrided surface layers. The nitrided layers were produced using traditional glow discharge nitriding (specimens nitriding on the cathode potential) and an active screen (specimens nitriding at the plasma potential). A microstructure of the layers was characterized through the scanning electron microscopy, X-ray energy dispersive spectroscopy and X-ray diffraction analysis. Mechanical properties of the nitrided Inconel 740H alloy were examined using microhardness measurements and standard fatigue tests. It was found that Inconel 740H with a nitrided surface exhibited an improved fatigue response of 50 MPa in the whole range of stress amplitudes from 350 to 650 MPa and almost 325% increase of hardness for plasma modified surface and 250% for cathode modified surface. Additionally, the application of cathode nitriding enhanced the corrosion resistance of the alloy in question and effectively protected it against a high temperature oxidation.

Hydrogen nitrogening in great discharge with AC power

The paper substantiates and experimentally shows the possibility of anhydrous nitriding in a glow discharge (BATR) with AC power supply (AC), as well as the possibility of switching the shape of pulses, changing their polarity, which is solved by introducing a glow discharge nitriding device with a power source alternating current of a given frequency. The analysis of the results of metallographic studies of the modified layer indicated the presence of a more uniform gradient of hardness in depth (gradient decreased by 1.7 - 3.5 times), which increases the wear resistance of parts and quality indicators of strengthening parts while reducing processing costs and installation costs. At BATR in CCR with supply of current of industrial frequency the installation for realization of process becomes cheaper. The latter factor will contribute, among other aspects, to the wider introduction of BATR technologies. The use of alternating current affects the course and results of nitriding, as periodic changes in the polarity of the electrodes of the chamber contributes to the cleaning of the surface from the adsorption layer, which positively affects the nature of nitrogen saturation (gradient of microhardness times), contributes to a significant change in the phase composition of the surface modified layer and allows to expand the technological capabilities of nitriding in the direction of obtaining the required performance characteristics of working surfaces, in particular tribological characteristics

(Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy.

Plasma nitriding of titanium alloys is capable of effective surface hardening at temperatures significantly lower than gas nitriding, but at a cost of much stronger surface roughening. Especially interesting are treatments performed at the lower end of the temperature window used in such cases, as they are least damaging to highly polished parts. Therefore identifying the most characteristic defects is of high importance. The present work was aimed at identifying the nature of pin-point bumps formed at the glow discharged plasma nitrided Ti-6Al-7Nb alloy using plan-view scanning and cross-section transmission electron microscopy methods. It helped to establish that these main surface defects developed at the treated surface are (Ti,Al)O2 nano-whiskers of diameter from 20 nm to 40 nm, and length up to several hundreds of nanometers. The performed investigation confirmed that the surface imperfection introduced by plasma nitriding at the specified range should be of minor consequences to the mechanical properties of the treated material.

Phase transformations in the nitrided layer during annealing under reduced pressure

The article presents studies of phase transformations taking place in surface layers of nitrided steels as a result of their annealing at 520 °C for 5 and 10 h. Two steel grades were tested, the unalloyed AISI 1085 and the low-alloy AISI 52100. As a result of glow discharge nitriding, at 570 °C/5 h and 540 °C/12 h, respectively, nitrided layers were produced on the steels, consisting of a surface layer of iron nitrides with the structure of e + γ′ and γ′ and of similar thickness 25. The study showed that during 5 h of annealing at 520 °C, the iron nitride layer already decomposed, which was documented by the analysis of chemical composition and X-ray analysis of the surface layers of steel. Comparative studies on the hardness distribution of surface layers of nitrided as well as nitrided and subsequently annealed AISI 52100 steels showed that after both 5 and 10 h of annealing, the hardness depth profiles were very similar and the effective thickness of the diffusion layer did not change. The results obtained enabled the demonstration that the emission of nitrogen into the atmosphere during annealing of nitrided steels is not accompanied by diffusion of nitrogen into the base layer. This proves that the iron nitride layer is not a source of nitrogen for the diffusion layer during annealing at reduced pressure.

Shaping the structure and properties of titanium and Ti6Al7Nb titanium alloy in low-temperature plasma nitriding processes

Plasma nitriding of titanium Grade 2 and Ti6Al7Nb titanium alloy at 730 °C was used to produce nitrided surface layers with an outer zone consisting of nanocrystalline titanium nitride - TiN, and a Ti2N zone right above the αTi(N) diffusion area. The paper presents a comparison of structure (TEM, SEM), phase composition (XRD, SAED) surface topography (AFM, optical profilometer), corrosion (potentiodynamic method), tribological properties (‘ball-on-disc’), and adhesion (scratch-test) of TiN + Ti2N + αTi(N) type nitrided surface layers produced on Grade 2 titanium and Ti6Al7Nb titanium alloy using conventional glow-discharge nitriding (so called glow discharge nitriding at the cathode potential) and with the use of an ‘active screen’ (glow discharge nitriding at plasma potential). A reduction of cathodic sputtering in the plasma potential process made it possible to produce surface layers maintaining a high smoothness of the titanium surfaces. Due to the low surface roughness and the high compressive residual stress of the sample after nitriding at plasma potential, ‘ball-on-disc’ test results showed the lowest coefficient of friction and the lowest penetration depth for this layer and very good adhesion of the layer to the substrate – i.e. Ti6Al7Nb titanium alloy. Nitriding of titanium alloy at cathode potential increased the corrosion potential value and slightly decreased corrosion current density. The corrosion current density of the sample nitrided at plasma potential was similar to initial state Ti6Al7Nb titanium alloy. The nitriding process type (cathode potential or plasma potential) used to produce TiN + Ti2N + αTi(N) surface layers on Ti6Al7Nb titanium alloy has an influence on the microstructure of the layer, its residual stress, in particular its TiN outer titanium nitride zone, its thickness, and on its properties such as wear and corrosion resistance.

Surface Hardening of Machine Parts Using Nitriding and TiN Coating Deposition in Glow Discharge

Surface hardening of machine parts substantially improves their performance. The best results are obtained when combined hardening consists of surface nitriding and subsequent deposition of hard coatings. The nitriding of machine parts immersed in the plasma of glow coatings have been studied, and the study results are presented. Titanium atoms for coating synthesis are obtained via titanium evaporation in a hollow molybdenum anode of the discharge. Stable evaporation of titanium occurs only when the power density of electrons heating the liquid titanium does not exceed ~500 W/cm2. To start evaporation, it is only necessary to reduce the gas pressure to 0.02 Pa. To stop evaporation, it is enough to increase the gas pressure to 0.1 Pa. Fast argon and nitrogen atoms used for cleaning the machine parts, heating them, and bombarding the growing coating are obtained using a grid composed of plane-parallel plates under high negative voltage and immersed in plasma.

Effect of Ion Nitriding on the Structural and Phase Composition and Mechanical Properties of High-Speed Steel R6M5 after SPD

The effect of ion nitriding in glow discharge on the structure and mechanical properties of steel R6M5 after quenching from 1200°C and tempering at 560°C with preliminary severe plastic deformation (SPD) is studied. Application of ion nitriding in glow discharge is shown to be effective for hardening the high-speed steel RM5 after SPD.

Wear of Bearing Parts from Precision Nickel Alloys After Glow Discharge Nitriding

Wear of Bearing Parts from Precision Nickel Alloys After Glow Discharge Nitriding

Physicochemical Properties of the Surface Layers of 40Kh Steel After Hydrogen-Free Nitriding in Glow Discharge

By the methods of mathematical statistics, we deduce equations specifying the relationship between the technological parameters of hydrogen-free nitriding in glow discharge (temperature, composition of gas mixture, and its pressure) and the physicochemical properties of the nitrided surface layers of 40Kh structural steel.

The Effect of Glow Discharge Nitriding on the Corrosion Resistance of Stainless Steel Orthodontic Arches in Artificial Saliva Solution

The Effect of Glow Discharge Nitriding on the Corrosion Resistance of Stainless Steel Orthodontic Arches in Artificial Saliva Solution

Influence of the magnetic field at ion nitriding in glow discharge on probe characteristics, microhardness and structure of 08H18N10T (AISI 321) steel

The study is devoted to the influence of the magnetic field on ion nitriding of stainless steel of austenite class – 08H18N10T (AISI 321). The experimental volt-ampere characteristics (VAC) of the glow dischargewere obtained under the influence of crossed electric and magnetic fields (CEMF), plasma parameters were calculated. The microhardness measurements made it possible to establish that the surface hardness increases 1.5 times when nitriding with CEMF in comparison with that without CEMF, while the hardened layer thickness increases 1.5 times.

Low temperature plasma-assisted nitriding of austenitic steel in a ferromagnetic enhanced inductive discharge

Plasma-assisted nitriding of austenitic stainless steel AISI 321 has been performed with the use of a ferromagnetic enhanced inductive discharge as the source of nitrogen ions and radicals, in the temperature range of 300–400°C, gas pressure of 50 mTorr and ion densities of about (2.5–7.7)·1010 cm−3. A significant increase in the nitriding rate was achieved, in comparison with a low temperature glow-discharge nitriding process. A possible mechanism of the nitriding rate increase is a high atomic nitrogen density achieved in the ferromagnetic enhanced inductively coupled plasma.

Fatigue Strength of Nitrided Steels in Corrosion-Active Media of the Food Enterprises

We study the effects of the modes of nitriding in glow discharge on the low- and high-cycle fatigue of structural steels in acid, alkaline, and neutral model solutions and in air.

Use of Glow Discharge Nitriding for Raising the Surface Hardness of Bearing Parts from Precision Nickel Alloys

Precision nickel alloy 40KhNYu-VI used for fabricating nonmagnetic precision bearings is studied after nitriding in glow discharge in an experimental facility at a high temperature (730 and 900°C) and in commercial equipment at 540°C. The effect of the temperature and duration of nitriding and of the mode of heat treatment on the structure and hardness of the surface layer obtained is determined.

Effect of Post Treatment in Argon Environment of Plasma Nitrided Local Disc Brake

Plasma nitriding (also known as ion nitriding, plasma ion nitriding, or glow-discharge nitriding) is a method of surface hardening using glow-discharge technology to introduce nascent (elemental) nitrogen to the surface of a metal part subsequent diffusion into the material. Because of the formation of high compressive residual stresses in the case region, increasing surface hardness and depth parameters cause remarkable improvement in the mechanical properties of steels. In this study, the properties of a nitrided local disc brake were investigated. For that purpose, the material was nitrided at 400°C of temperature, 1.6 mbar of pressure, and 4 hours of time then followed by post-treatment in Argon (Ar) environment for various of holding time such as 10, 20, 30, 40, and 50 minutes. At these conditions the hardness increased in the range 123.1 - 223.3 VHN, the wear rate decreased in the range 21.7 × 10-9 - 3.1 × 10-9 mm3/mm kg, while before being nitrided the hardness and the wear rates were 113.5 VHN and 22.8 × 10-9 mm3/mm kg, respectively. The optimum condition for holding time during post treatments was 20 minutes. Besides that, the effect of various of N2: Ar mixture such as 90%: 10%, 80%: 20%, 70%: 30%, and 60%: 40% on the properties of local disc brake was studied. For various of gas mixing, the optimum hardness in the order of 252.7 VHN and wear rate in the order of 2.8 × 10-9 mm3/mm kg were achieved at 90%N2: 10%Ar of a gas mixture.

Application of Complex Thermochemical Treatment for Reinforcing High-Strength Precipitation-Hardening Heat-Resistant Steel Microalloyed with REM

Results of a complex thermochemical treatment of test specimens from different heats of a novel high-strength heat-resistant precipitation-hardening steel microalloyed with REM are presented. The optimum chemical composition of the steel is determined with the aim to provide precipitation hardening after vacuum carburizing. In the process of finishing nitriding in glow discharge the surface hardness of the new steel increases substantially at inconsiderable decrease in the hardness of the core. The developed modes of complex thermochemical treatment exclude the appearance of such flaws as grain boundary net and excess retained austenite.