Nitrocarburizing Research Articles

Properties of Ti-6Al-7Nb titanium alloy nitrocarburized under glow discharge conditions.

The paper presents the results of physicochemical and mechanical properties of the Ti-6Al-7Nb alloy with surface modified by formation of a diffusive nitrocarburized layer deposited in a low-temperature plasma process. The main aim of the study was to evaluate the influence of steam sterilization and exposure to Ringer's solution on the utility properties of the alloy. Based on the study of the microstructure, roughness, wettability, resistance to pitting corrosion, ion infiltration and mechanical properties, the usefulness of the proposed method of surface treatment for clinical application was proven. Deposition of the nitrocarburized layer increased the surface roughness and surface hardness, but also reduced the contact angle, and corrosion resistance with respect to the polished surfaces. The nitrocarburized layer is a barrier against the infiltration of ions to the solution and sterilization and exposure to Ringer solution have greater effect on the physicochemical properties rather than on the mechanical ones. It was found that sterilization, and exposure to Ringer's solution greatly affect the change of physicochemical properties rather than mechanical properties for both nitrocarburized layers and the Ti-6Al-7Nb alloy of mechanically polished surface.

К оценке контактно-усталостной долговечности химико-термоупрочненных зубчатых колес

Introduction. The specification of the strength characteristics of the diffusion layer of carburized (C) and nitro-carburized (NC) involute gears is described. Regulated by GOST 21354-87, the dependence of the surface endurance limit of steel parts on hardness in the region of finite (up to 10-12 million cycles) life is overstated. The work objective is to determine the maximum allowable load level of the involute gearing under the conditions of alternative failure forms and the area of correct application of GOST 21354-87 recommendations. Materials and Methods. In the case-hardened parts, both deep and surface processes of contact fracture occur simultaneously. However, these processes have essentially different mechanisms of contact-fatigue durability with fundamentally different mechanisms of the contact-fatigue life. The high-end fracture mode is determined by a variety of factors, the key ones being the level of intensity and the properties of the near-surface layers of the material. The loading capacity of the diffusion layer is investigated on the basis of the experimental data by the strength assessment procedure of a structurally inhomogeneous material. Here, Pisarenko-Lebedev generalized criterion of limiting state is used. Research Results. Consideration of the effect of the plastic properties of the material and its variation within the diffusion layer has allowed significantly increase the forecasting validity of the loading capacity level of the carburized and nitro-carburized gears for contact strength. The occurrence of the threshold value of the working surface hardness of the wheels teeth is confirmed at the level of 60-61 Rockwell units. This level increase leads to the decrease in contact-fatigue life. The plasticity parameter impact on the capability level and the variation of this parameter value for different types of the thermo-chemical treatment (TCT) is assessed. In the finite life area, deep contact fractures are leading. And the limits of contact fatigue life upon surface pitting readings should be oriented to the allowed normal deep contact stress. Discussion and Conclusions . The obtained results are in qualitative agreement with the experimental data, but they exceed them a little in some cases. Studies on the plasticity parameter value and its variation depending on the chemical composition of the steel and the TCT type are needed. But already at this stage, the results obtained can be used in the design of heavy-loaded case-hardened gears to determine the surface hardness and the diffusion layer thickness. The application domain includes the tractor track gear transmissions, oil-producing beam engines, mining and handling facilities.

Improving by postoxidation of corrosion resistance of plasma nitrocarburized AISI 316 stainless steels

Austenitic stainless steels are widely used in several industries such as chemistry, food, health and space due to their perfect corrosion resistance. However, in addition to corrosion resistance, the mechanic and tribological features such as wear resistance and friction are required to be good in the production and engineering of this type of machines, equipment and mechanic parts. In this study, ferritic (FNC) and austenitic (ANC) nitrocarburizing were applied on AISI 316 stainless steel specimens with perfect corrosion resistance in the plasma environment at the definite time (4 h) and constant gas mixture atmosphere. In order to recover corrosion resistance which was deteriorated after nitrocarburizing again, plasma postoxidation process (45 min) was applied. After the duplex treatment, the specimens’ structural analyses with XRD and SEM methods, corrosion analysis with polarization method and surface hardness with microhardness method were examined. At the end of the studies, AISI 316 surface hardness of stainless steel increased with nitrocarburizing process, but the corrosion resistance was deteriorated with FNC (570 °C) and ANC (670 °C) nitrocarburizing. With the following of the postoxidation treatment, it was detected that the corrosion resistance became better and it approached its value before the process.

Tribological Examination of Different Steel Materials after Special Heat Treatment and Salt Bath Nitriding

Abstract The main aim of the presented research was examination of new tribological pairs made of different types of steel. Materials of disc probes were submitted to unusual heat treatment processes and salt bath nitriding. The research is focused on the friction coefficients and mass losses of the material probes. Based on the results it was noticed that the best wear resistant pair was bearing steel 100Cr6 coupled with high speed steel S705. The lowest friction coefficient appeared for the pair bearing steel 100Cr6 and maraging steel C350.

KINETICS ANALYSIS OF HIGHER TEMPERATURE SALT BATH NITRIDING FOR AISI 1045 STEEL

Rapid salt bath nitriding was conducted at higher temperature above 600[Formula: see text]C instead of normally used 560[Formula: see text]C for AISI 1045 steel. Optical microscopy (OM), X-ray diffraction (XRD) and micro-hardness tester were employed to characterize the microstructure, phase constituents and micro-hardness of the treated specimens. The results showed that salt bath nitriding at higher temperature could significantly increase the compound layer thickness and higher cross-sectional hardness can be obtained. Kinetics analysis illustrated that the nitrogen atoms diffusion coefficient was obviously increased with temperature, and the activation energy of nitrogen atom diffusion was decreased from 220[Formula: see text]kJ[Formula: see text]mol[Formula: see text] to 142[Formula: see text]kJ[Formula: see text]mol[Formula: see text].

Effect of surface nitridingtreatment in a steel plate on the interfacial bonding strength of the aluminum/steel clad sheets by the cold roll bonding process

Steel sheets (08Al) with nitriding treatment and with normal wire brushing surface preparation were bonded with aluminum alloy (4A60), respectively, by cold roll bonding (CRB) process. The interface of clad sheets and the surface of the component metals after peeling off were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The peel strength of the two types Al/steel clad sheets was evaluated by peeling test. The experimental results indicated that a homogeneous Fe3N hardened and brittle layer with an average thickness of 10µm formed on the surface of steel layer subject to salt bath nitriding treatment. More cracks and gapes formed at the interface of the Al/nitrided St clad sheets than those at the Al/brushed St clad sheets during the CRB process. The degree of contact and the bonded surface area in the Al/nitrided St sheets is higher than those in the Al/brushed St sheets at a given reduction, contributing to the enhancement of bonding strength in the former case. Meanwhile, the peel strength of the Al/nitrided St clad sheets is higher than that of the Al/brushed St clad sheets, reaching 15.9N/mm and 10.9N/mm, respectively, at the same reduction of 60%. In addition, the bonding mechanism of the Al/nitrided St clad sheets is discussed and it is consistent with the film theory.

AISI 1005 Steel Plasma Treated by Different Thermochemical Surface Treatments

To modify the surface structure of AISI 1005 steel and its properties without any dimensional loss, different plasma surface treatments were performed at low temperatures (500 oC) in this study. The samples were subjected to single plasma treatments including: nitriding (N5% and N3%), carburizing (CE) and ferritic nitrocarburizing (NC) and to duplex treatments of nitriding followed by carburizing (N5%+CE and N3%+CE) and ferritic nitrocarburizing followed by carburizing (NC+CE). The gas mixture used for these treatments was varied as follows: nitriding (5%N2+95%H2 and 3%N2+97%H2), carburizing (5%CH4+95%H2) and ferritic nitrocarburizing (5%N2+1.5%CH4+93.5%H2). A microstructural characterization of the samples was carried out using optical and scanning electron microscopy in addition to XRD analysis. Microhardness testing was also performed. The XRD analysis showed a stabilization of the outermost cementite layer for all of the carburizing treatments. The results show that a greater hardness increase was achieved for the nitriding treatment as well as a more regular compound layer. However, a greater depth of hardening was obtained in samples with NC+CE and N5%+CE, which extended to the hardened depth to 800 µm.

The enhancement effect and kinetics of rare earth assisted salt bath nitriding

A rapid salt bath nitriding technology was primarily developed by adding rare earth lanthanum (RE La) in the salt bath media on the basis of normal salt bath nitriding technique (NT). Characterization of the modified surface layers was made by means of optical microscopy, X-ray diffraction, energy dispersive spectroscopy (EDS) and micro-hardness tester. The results showed that the nitriding efficiency could be significantly enhanced assisted by RE La, and the enhancement effect was RE La concentration dependent. The thickness of compound layer was increased from 13.3 μm up to 18.5 μm with 5% La addition at the temperature of 833 K for 2 h. Higher surface hardness, modestly higher sub-surface hardness and superior micro-hardness profile were obtained due to the solution of RE La atoms and consequent lattice expansion in the surface layer. Meanwhile, kinetics analysis showed that the diffusion coefficient was increased and activation energy was decreased with enhancement effect of RE La, the following kinetics formulas were obtained, dNT=0.1exp−21990/Tt and dRE=4.3×10−3exp−16319/Tt for NT and RE treatment, respectively. And the confidence level of the kinetics is examined to be perfectly agreed with the data. The main enhancement mechanism is that RE La can accelerate the decomposition rate of CNO− and thus increase the concentration of active nitrogen atoms in the salt bath medium, and especially increase the number of nitrogen atoms that meet the requirements for diffusing toward the substrate by reducing the energy barrier.

Salt Bath Nitriding of Fe3Al Based Intermetallic Compound

Iron aluminide Fe3Al was produced in a vacuum arc melting furnace. The alloy was heat treated by salt bath nitriding at 580 °C for durations of 3, 6, and 9 h. The nitride layers formed on the surface were characterized with light optical microscopy (LOM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), and micro hardness measurements. The results showed that the nitride layer thickness increased with an increase in nitriding duration, while the layer hardness did not vary. The nitride layers were composed chiefly of iron nitride and aluminum nitride phases. The dry sliding friction and wear behaviors of nitrided iron aluminides were determined. The results revealed that the wear resistance decreased with increase in the length of nitriding.

Ligand-Free Noble Metal Nanocluster Catalysts on Carbon Supports via "Soft" Nitriding.

We report a robust, universal "soft" nitriding method to grow in situ ligand-free ultrasmall noble metal nanocatalysts (UNMN; e.g., Au, Pd, and Pt) onto carbon. Using low-temperature urea pretreatment at 300 °C, soft nitriding enriches nitrogen-containing species on the surface of carbon supports and enhances the affinity of noble metal precursors onto these supports. We demonstrated sub-2-nm, ligand-free UNMNs grown in situ on seven different types of nitrided carbons with no organic ligands via chemical reduction or thermolysis. Ligand-free UNMNs supported on carbon showed superior electrocatalytic activity for methanol oxidation compared to counterparts with surface capping agents or larger nanocrystals on the same carbon supports. Our method is expected to provide guidelines for the preparation of ligand-free UNMNs on a variety of supports and, additionally, to broaden their applications in energy conversion and electrochemical catalysis.

Tribological behaviour of nitrided and nitrocarburized carbon steel used to produce engine parts

Purpose– The purpose of this study is to select a proper surface treatment to enhance wear resistance of engine camshafts. The camshaft is a relevant part of a diesel engine which works under torsion, fatigue and wear efforts. They are usually manufactured by casting, forging or machining from forged bar of low alloy steels, and in most cases, the machined surfaces are quenched and tempered by induction heating. After that, in many cases, to withstand the efforts imposed on the active surfaces and improve tribology and fatigue properties, the industry used for decades, thermochemical technologies such as salt bath or gaseous nitriding and nitrocarburizing processes.Design/methodology/approach– This paper studied the effects of plasma nitriding and plasma nitrocarburizing, on the tribological behaviour of the steel SAE 1045HM3 proposed to produce camshafts. After the plasma treatments, the change in surface roughness was measured; the modified layers were studied by X-ray techniques and its thickness by optical microscopy. The diffusion zone was evaluated by Vickers microhardness determinations. Tribology tests were performed by pin-on-disc configuration using WC ball as a counterpart.Findings– Results show that plasma nitrided samples present the best tribological behaviour compared with the nitrocarburized ones; also, the influence of the roughness produced by the thermochemical processes appears to be important.Practical implications– Although both the plasma treatments have been applied for many years, and also reported separately in the scientific literature, there was no information comparing these two treatments for carbon steels, and also, there is not much about tribology in lubricated conditions of nitrided and nitrocarburized carbon steels. In fact, it is not proved that the porosity of the nitrocarburized layer is beneficial for wear resistance in lubricated conditions. In this paper, it was proved that at least in the tested conditions, it is not.Originality/value– Gas or plasma nitrocarburizing is usually recommended for this kind of applications, although the modified layer is porous. This paper attempts to prove that nitriding could be better than nitrocarburizing, even with a thinner white layer.

Effect of Temperature on Microstructure, Corrosion Resistance, and Toughness of Salt Bath Nitrided Tool Steel

In this study, a type of hot work tool steel was modified through salt bath nitriding for 4 h at 540 and 560 °C, and post-oxidation was subsequently performed. Surface and cross-sectional hardness test results revealed that the surface hardness increased after the treatment because of the formation of compound layers and diffusion zones. Microstructures and phase analyses showed that more homogeneous compound layers and Fe3O4-phase could be generated after treatment at 560 than at 540 °C. As a result, the corrosion potential was elevated, and the corrosion current density was clearly reduced. The thickness and porosity of the compound layer were also increased with the elevated nitriding temperature. Because of the nitrogen atom solution, XRD diffraction peaks broadened, and the position of the peaks shifted to a lower angle in different degrees at different depths, thus showing the same tendency as the hardness curves. Salt bath nitriding significantly deteriorated the impact toughness from 32.3 to 5.2 J.

Kinetic analysis of direct current field enhanced salt bath nitriding

A novel rapid salt bath nitriding technology based on normal salt bath nitriding was primarily developed by additionally applying a direct current field (DCF) of 7·5 V between the treated samples, and the corresponding kinetics was investigated. The results showed that DCF could significantly enhance the nitriding efficiency, shorten the holding duration and decrease the treatment temperature. Meanwhile, the diffusion coefficient of nitrogen was increased about two times, and the activation energy was decreased from 184 to 159 kJ mol− 1. The main enhancement mechanism was discussed as well.

Ferritic Nitrocarburizing of SAE 1010 Plain Carbon Steel Parts

nitrocarburizing offers excellent wear, scuffing, corrosion and fatigue resistance by producing a thin compound layer and diffusion zone containing e (Fe2-3(C, N)), γ′ (Fe4N), cementite (Fe3C) and various alloy carbides and nitrides on the material surface. It is a widely accepted surface treatment process that results in smaller distortion than carburizing and carbonitriding processes. However this smaller distortion has to be further reduced to prevent the performance issues, out of tolerance distortion and post grinding work hours/cost in an automotive component. A numerical model has been developed to calculate the nitrogen and carbon composition profiles of SAE 1010 torque converter pistons during nitrocarburizing treatment. The nitrogen composition profiles are modeled against the part thickness to predict distortion. Experimental composition profiles of torque converter pistons are reported for model validation and to determine the effect of nitrogen composition on distortion. The surface residual stresses predicted by the model are also compared to the measured residual stresses. The correlations between nitrocarburizing temperature, distortion and composition profiles are discussed using the modeling results. CITATION: Manivannan, M., Stoilov, V., and Northwood, D., Ferritic Nitrocarburizing of SAE 1010 Plain Carbon Steel Parts, SAE Int. J. Mater. Manf. 8(2):2015, doi:10.4271/2015-01-0601. 2015-01-0601 Published 04/14/2015 Copyright © 2015 SAE International doi:10.4271/2015-01-0601 saematman.saejournals.org Downloaded from SAE International by Madhavan Manivannan, Tuesday, March 03, 2015

Surface Layers Produced by Modified Floe Ferritic Nitrocarburising

Ferritic nitrocarburising is a surface alloying heat treatment, which can provide to components high surface hardness, thus improved wear resistance. In structural steels the porosity of white layer has a key role in wear resistance: the porosity is undesirable. For tool steels the absence of white layer is undesirable. Floe process is one way to decrease the porosity of white layer. During our experiments we applied a modified Floe process on two different steels. The acontol of this process is simpler than conventional process. We measured the micro-hardness as a function of depth from the surface, and we made microscopic examination to analyse the structure of nitrided layer.

Ceramic Reinforced Metal Matrix Nano and Micro-Composite Layers Produced by Combined Laser Melt Injection Technology and Thermochemical Surface Treatment

In-situ synthesized Nb (C,N) reinforced metal-ceramic composite layers were fabricated on nitridable (16MnCr5) and non-nitridable (S235J) steel surface by combined laser melt injection technology and ferritic nitrocarburizing treatment. The feasibility of processing composites layer by an in situ reaction using laser beam were carried out. Beside that the hardness of the treated layers increases up to 1000-1170 HV0.5 in the diffusion zone and after it the hardness of the samples reach 300-450 HV0.5, which is related the Nb alloying depth (1200-1400 μm). The results of the composite layer are presented in this paper.

A Study of Effects of Ferritic Nitrocarburized Brake Disc on Its Corrosion Resistance and Braking Performances

A Study of Effects of Ferritic Nitrocarburized Brake Disc on Its Corrosion Resistance and Braking Performances

Use of Navy C-rings to study and predict distortion in heat treated components: experimental measurements and computer modelling

AbstractThe Navy C-ring has been one of the most common types of specimen used for observing the dimensional changes (distortion) after heat treatment. The dimensional changes in the Navy C-rings are generally assumed to be comparable to those in an actual heat treated component. In this paper, we first review the various types of C-rings that have been used, and the results obtained for size and shape distortions for steels that have been carburised or nitrocarburised. An overview is then presented of the parameters that are included in simulation models to predict internal stresses and distortion. Finally, we present our own experimental and modelling results for the distortion in 1010 steel C-ring samples (three thicknesses) and an automotive component (torque converter piston) subjected to a gas ferritic nitrocarburising treatment. The predictions, on the basis of the nitrocarburised layer, and measured distortions were in better agreement for the thinner C-rings where the thickness was comparable to ...

Effect of D.C. electric field on salt bath nitriding for 35 steel and kinetics analysis

A rapid salt bath nitriding technology was primarily developed by additionally applying direct current (D.C.) electric field on the basis of traditional technique (NM). Characterization of the modified surface layers was made by means of optical microscopy, Vickers micro-hardness test and X-ray diffraction analysis. The results showed that D.C. electric field could significantly enhance the nitriding efficiency and the enhancement effect was closely related to the intensity of D.C. electric field. By applying D.C electric field of 7.5V, even a little thicker compound layer could be obtained at only half duration of that in traditional technique, and the thickness of compound layer increased more than 60%, from 18μm up to 29μm at the same treating temperature of 848K and holding duration of 100min. Meanwhile, higher surface hardness, modestly higher sub-surface hardness and superior hardness profile were obtained assisted by D.C. electric field. It was also found that the diffusion coefficient of nitrogen was increased more than 1.9 times and activation energy was decreased from 184kJ/mol to 159kJ/mol enhanced by D.C. electric field. The possible enhancement mechanism is that D.C. electric field can promote chemical reactions and produce more active nitrogen atoms in the salt bath, positively charge the active atoms and force them diffuse directionally toward the surface of the treated specimen, and hence significantly improve the efficiency of the active atoms in the salt bath.

Microstructure and Properties of SAE 2205 Stainless Steel After Salt Bath Nitrocarburizing at 450 °C

Nitrocarburizing of the type SAE 2205 duplex stainless steel was conducted at 450 °C, using a type of salt bath chemical surface treatment, and the microstructure and properties of the nitrided surface were systematically researched. Experimental results revealed that a modified layer transformed on the surface of samples with the thickness ranging from 3 to 28 μm changed with the treatment time. After 2205 duplex stainless steel was subjected to salt bath nitriding at 450 °C for time less than 8 h, the preexisting ferrite zone in the surface transformed into austenite by active nitrogen diffusion. The main phase of the nitrided layer was the expanded austenite. When the treatment time was extended to 16 h, the preexisting ferrite zone in the expanded austenite was decomposed and transformed partially into e-nitride precipitate. When the treatment time extended to 40 h, the preexisting ferrite zone in the expanded austenite was transformed into e-nitride and CrN precipitate. Further, a large amount of nitride precipitated from preexisting austenite zone. The nitrided layer depth thickness changed intensively with the increasing nitriding time. The growth of the nitride layer takes place mainly by nitrogen diffusion according to the expected parabolic rate law. The salt bath nitriding can effectively improve the surface hardness. The maximum values measured from the treated surface are observed to be approximately 1400 HV0.1 after 8 h, which is about 3.5 times as hard as the untreated material (396 HV0.1). Low-temperature nitriding can improve the erosion/corrosion resistance. After nitriding for 4 h, the sample has the best corrosion resistance.