Nitrocarburizing Research Articles

Estudio comparativo de la nitrocarburación de los aceros AISI 4340 y AISI 347 mediante el proceso Tenifer-QPQ®

Este trabajo estudia las diferencias microestructurales y tribológicas de las capas formadas durante la nitrocarburación ferrítica del acero aleado AISI 4340 y la nitrocarburación austenítica del acero inoxidable estabilizado AISI 347. Las muestras se sometieron a distintos tiempos de inmersión en un baño de nitrocarburación (60, 75, 90, 105 y 120 min) a 580 ºC. Posteriormente se sometieron a un proceso de oxidación a 480 ºC para formar una capa de Fe3O4. Los estudios de la microestructura de la capa nitrocarburada se realizaron por microscopía electrónica de barrido (SEM), espectroscopía de dispersión de energías (EDS) y difracción de rayos X (XRD). Se estudió el desgaste y el coeficiente de fricción de las muestras nitrocarburadas y las muestras no tratadas mediante el ensayo pink-on disk. Los resultados muestran tres zonas bien diferenciadas en el acero AISI 4340: una capa de óxidos externa, una capa blanca o de combinación y zona de difusión. Sin embargo, no se detectó la presencia de la capa de combinación en el acero AISI 347. En ambos aceros, el coeficiente específico de desgaste (k) de las muestras nitrocarburadas fue aproximadamente treinta veces menor que el de las muestras de referencia.

Effect of Heat Treatment on Crack Propagation and Performance of Disk Brake with Cross Drilled Holes

A vehicle disk brake, which has cross drilled hole patterns on a frictional surface for improving cooling and braking performance, has propensity to cause crack problem under the harsh braking condition. In this study, the finite element analysis by using ABAQUS was adopted to investigate a cause of crack occurrence by the thermo-mechanical phenomenon around drilled hole patterns. As a remedy of the crack generation, the disk brake rotor with stress relieving and ferritic nitrocarburizing was prepared and tested on brake dynamometer in harsh condition. The test result was examined in terms of pad wear, the braking torque variation, the braking temperature changes, the crack initiation timing, and the crack propagation speed. As a test result, the disk after heat treatment showed 3.61 % higher average braking temperature than the disk without heat treatments, to suggest decreased heat dissipation performance, however, it also showed 14 % lower pad wear amount, and 0.1 % smaller braking torque variance than the disk without heat treatments, to stand for improved contact characteristics. Also, the heat treated brake rotor showed 51.3 % lower crack propagation rate which is considered as proper countermeasure of the fracture phenomenon at the edge of cross drilled hole.

Preparation of ε-Fe(Si)₃N Powder Using a Salt Bath Nitriding Reaction and a Study on the Soft Magnetic Properties of the Powder.

In this paper, a single phase ε-Fe(Si)3N powder was successfully synthesized through the salt bath nitriding reaction method. The flaky FeSi alloy powder was used as the iron source, and non-toxic CO(NH2)2 was used as the nitrogen source. The nitridation mechanism, the preparation technology, the soft magnetic properties, and the magnetization temperature dependence of the powder were studied. The research result showed that ε-Fe(Si)3N alloy powders were synthesized in a high temperature nitrification system after the surface of flaky FeSi alloy powders were activated by a high-energy ball mill. The optimum nitriding process was nitridation for 1 h at 550 °C. The ε-Fe(Si)3N powder had good thermal stability at less than 478.8 °C. It was shown that ε-Fe(Si)3N powder has good soft magnetic properties, and the saturation magnetization of the powder was up to 139 emu/g. The saturation magnetization of ε-Fe(Si)3N powder remains basically constant in the temperature range of 300–400 K. In the temperature range of 400–600 K, the saturation magnetization decreases slightly with the increase of temperature, indicating that the magnetic ε-Fe(Si)3N powder has good magnetization temperature dependence.

Experimental Study on Wear Resistance of AISI 347 Treated With Salt Bath Nitriding and Gas Nitriding Processes-A Review

The surface treatments are very much essential for improvement in terms of wear resistance and increase in the service lifetime of stainless steels as they have poor wear resistance and easily corroded to the oxidation.This paper reviews the two thermo chemical surface treatments (salt bath nitriding and gas nitriding followed by the post oxidation) applied to AISI 347material.Morphological characterizations were carried out with the help of scanning electron microscope, X-Ray Diffractometer and Pin-on-disc wear testing machine. The results of the both the processes were compared and discussed. From the detailed study made by authors the results shown that with gas nitriding the wear resistance of the material is improved more compared with the salt bath nitriding.

Microstructural Analysis of 316LN Austenitic Stainless Steel by Salt Bath Nitriding Process

Microstructural Analysis of 316LN Austenitic Stainless Steel by Salt Bath Nitriding Process

EFFECT OF TIME ON THE COMPOUND LAYER FORMED DURING SALT BATH NITRIDING OF AISI 4140 STEEL

This research was carried out to study the effect of time on the compound layer of AISI 4140 steel in salt bath nitriding. The nitriding process were implemented on AISI 4140 steel in salt bath component for different times (from 1 h to 10 h) at 580 °C. Samples of AISI 4140 steel were treated and characterized (at surface and core of samples) through the following technique: optical microscopy, scanning electron microscopy, X-ray diffraction (XRD) and microhardness tester. Shows that thick compound layers are formed during continuous salt bath nitriding. The thickness of the compound layer and surface hardness increases with increasing time.

Pd Nanoparticle Catalysts Supported on Nitrogen-Functionalized Activated Carbon for Oxyanion Hydrogenation and Water Purification

We provide an efficient, sustainable, low-cost, and potentially scalable method to prepare N-functionalized activated carbon (AC) for Pd-based catalysis with improved performance for water purification. N-functionalized AC supports were realized via “soft nitriding”, that is, low temperature heating of a urea–AC mixture, and Pd nanoparticles with a significantly increased number of surface Pd(0) sites were achieved on the supports. Moreover, Pd nanoparticles were preferentially loaded near the (treated) AC exterior surface. N-functionalization improved nitrite and bromate hydrogenation kinetics but not for chlorite and chlorate, suggesting that different mechanisms determine the reaction activity of these oxyanions.

Change of Surface Texture Parameters of Ground Surfaces after Application of Hard and Abrasion Resistant Layers

The paper deals with the change of selected 3D parameters of the surface texture of ground steels after application of diffusion technologies. The steel CSN 41 2050 and 34CrNiMo6 after nitriding and ferritic nitrocarburizing in gas and plasma were evaluated. Selected 3D surface texture parameters were measured by the coherence correlation interferometer Talysurf CCI Lite. The change in surface texture parameters is influenced by the preparation of the substrate, i.e. the grinding parameters and the used diffusion technology, as well as the chemical composition of the used steels (2), (3). The steels were ground with SiC abrasive papers with grain sizes of 120, 220, 600 and 1000 according to FEPA. Steel CSN 41 2050 showed the reduction of the observed surface texture parameters almost all types of surface treatments - roughness decreased. Only in the case of ferritic nitrocarburizing in gas occurred to the deterioration of surface roughness. Similar results were achieved at 34CrNiMo6 steel - ferritic nitrocarburizing in gas led to an increase of surface roughness. For other surface treatments the roughness decreased. Applied diffusion technologies increase the hardness of functional surfaces, corrosion resistance, fatigue strength, wear resistance and reduce coefficient of friction (4). The above-mentioned advantages of applied diffusion layers along with the reduction in surface roughness can contribute to wider use of these technologies in technical practice.

The Influence of Alloying Elements on Surface Hardness of Ferritic Nitrocarburizing Layers of Ball Screws

The article deals with a chemical composition of saturated layers after ferritic nitrocarburizing process. Experiments are focused on using of gas ferritic nitrocarburizing processes for surface treatment of ball screws due to increasing of surface hardness with low influence on the dimensional accuracy. Ferritic nitrocarburizing processes were applied to steels C 35 (sample A1), 37Cr4 (sample A2) and 42CrMo4 (sample A4) used for ball screw manufacturing, which were subsequently evaluated by electron microscopy, GDOES and microhardness methods. The results of measurement showed high influence of alloying elements on surface hardness of created carbide-nitride layer after chemical-heat treatment process. Main task was to compare microhardness after ferritic nitrocarburizing in accordance with chemical composition.

Rapid Salt Bath Nitriding of Steel AISI 1045

Carbon steel AISI 1045 (0.45% C) is studied as a model material for rapid nitriding in a salt bath at 660°C (instead of the conventional 560°C). The methods of optical microscopy, x-ray diffraction and measurement of microhardness and corrosion resistance are used to study the microstructure and the phase composition of the nitrided layer. It is shown that salt bath nitriding shortens the process considerably and raises its efficiency; the microhardness and the corrosion resistance grow and the nitride layer acquires a γ′-Fe4N phase.

Non-Toxic Environment for Ferritic Nitrocarburising Process

Experimental research aimed to find a solution for replacing components with high toxicity (or generating such components as a result of reactions occurring in the environment at processing temperatures) from the environments used for ferritic nitrocarburising process (FNCP) with non-hazardous components, but extremely active during the process. In the temperature range in which this type of processing is applied (lower than the eutectoid transformation temperature in the Fe-N phase diagram), the most commonly used media are liquid or gaseous; liquid ones contain toxic components (sodium or potassium cyanates/cyanides), and gaseous ones require complex equipments. Packing is extremely rarely used, but in this case pack-mix contain toxic components (15 � 20 wt.% sodium or potassium ferrocyanide). Urea also called carbamide (CO (NH2)2) is the active component in the pack-mixing proposed to be used for FNCP. Carbamide is used in low temperature cyanidation thermochemical heat treatment (liquid FNC), together with sodium or potassium carbonates, resulting in very toxic reaction products (sodium or potassium cyanates). Compared to cyanidation, in the version proposed in the paper, the carbamide does not react with carbonates because they are not found in the composition of the environment but decomposes in the presence or absence of oxygen (by a disproportionation reaction) with the formation of some gas molecules interesting for the process. It has been concluded that the use of carbamide together with two other components, activated charcoal (having a triple role - dispersing, storage, surface saturation) and respectively ammonium chloride as surface reaction activator, is an effective solution for achieving the desired goals by applying this type of thermochemical processing to a wide range of products made of quality steels up to alloy miscellaneous steels.

Progress with insulating nanocomposites based on ferrite plating of Sm2Fe17N3 micropowders

Abstract Typical exchange spring magnets are composed of two phases, a rare-earth hard magnetic material and a metallic soft magnetic material, whose magnetization value is higher than those of hard magnetic phases, such as α-Fe, Fe-B, or Fe-Co. A novel high-electrical-resistance composite magnet was fabricated by consolidating micron-sized ferromagnetic nitride Sm2Fe17N3 powder particles coated with a continuous nano-sized soft magnetic ferrite oxide layer, which suppressed intergrain conductivity but sustained the magnetic exchange interactions between grains [21] . A non-magnetic resin or ceramic insulator may suffice for the coated layer but gives rise to high electrical resistance of the magnet with large deterioration of magnetization. The soft magnetic ferrite oxide layer not only suppressed intergrain conductivity, but also only slightly reduced the magnetization of the magnet. At present, the only exchange spring magnet having a combination of a soft magnetic oxide and hard magnetic nitride is the ferrite/Sm2Fe17N3 composite magnet. Sm2Fe17N3 powder particles with a size of 2 μm were coated with an “iron ferrite” layer with a grain size of about 10 nm by ferrite plating, which is an aqueous process, following which the samples were consolidated by the explosive consolidation (EC) technique. The coercivity and rectangularity of the ferrite/Sm2Fe17N3 composite magnet decreased slightly compared to those of a Sm2Fe17N3 magnet. The fully dense ferrite/Sm2Fe17N3 magnet exhibited a resistivity of about 4000 μΩ cm, which is ten times larger than that of a fully dense Sm2Fe17N3 magnet. Thus, the soft magnetic ferrite layer in the composite magnet maintained the magnetic exchange coupling between ferromagnetic Sm2Fe17N3 grains and simultaneously suppressed intergrain electrical coupling to increase the resistivity. This decreased the eddy current loss and improved the high-frequency characteristics of the composite magnets. Therefore, ferrite/Sm2Fe17N3 composites are promising materials for magnets that are operated at high frequencies in advanced applications, such as electric vehicle magnets.

Nitrogen-doped carbon supported platinum catalyst via direct soft nitriding for high-performance polymer electrolyte membrane fuel cell

Control of doping levels of nitrogen to carbon support plays a key role to enhance the catalytic activity of the Pt/C catalyst toward oxygen reduction reaction. Mass-production of such materials is still challenging issue for the practical use. Here, we demonstrate a facile approach for fabrication of the nitrogen-doped Pt/C catalysts via direct soft nitriding of the Pt/C catalyst. The commercial 40 wt% Pt/C is first physically mixed with urea and then heat-treated at 300 °C, which allowed a massive production of the 6.6 atom% nitrogen-doped Pt/C catalysts without sacrificing the Pt catalysts. The specific activity increases by 46.9% after the thermal treatment, while the particle size and crystallinity of Pt remain similar to those before the thermal treatment. As a result, the fuel cell test showed a notable increase in the current density by 100% and 18.5% at 0.8 V and 0.5 V, respectively, for the membrane electrode assembly employing urea treated Pt/C catalyst. Hence, the soft nitriding by urea offers great promise as a simple, energy-efficient and eco-friendly way in manufacturing the nitrogen-doped Pt/C catalyst for the polymer electrolyte membrane fuel cell applications.

Effects on the Long-Term Aging of Low Temperature Salt Bath Nitrided AISI 321 Stainless Steel

AISI 321 stainless steel was salt bath nitrided at 430K for 8 hours, then being long-term aging treatment at different temperature. To study the changes of microstructures and performances of these samples by using X-ray diffraction (XRD), scanning electron microscopy (SEM), micro hardness tester, electrochemical workstation, and universal tensile testing machine. Experimental results showed that a nitrided layer was formed on the surface with the thickness ranging from 7.6 to 22.5 μ m varying with changing aging treatment time and temperature after dealing with salt bath nitriding. The thickness of the nitrided layer increased with increasing aging time and temperature. According to the fick’s second law, the growth of the nitride layer is mainly due to the diffusion of nitrogen, as expected. The active energy of nitrogen atoms in AISI 321 stainless steel is 340.2kJ/mol by calculated form Thermodynamics formula. The surface micro hardness significantly increased to nearly 1430 Hv0.098, which is about 4 times harder the non-treated material, and then gradually reduced. The corrosion resistance of the 321 stainless steel is increases with proper aging treatment, but when the aging time more than 15.552×106s, the corrosion resistance decrease. The tensile properties of AISI 321 ASS of strength decrease but the plastic increase a little after salt bathing nitriding and aging.

Studies on Enhancement of Silt Erosion Resistance of 13/4 Martensitic Stainless Steel by Low-Temperature Salt Bath Nitriding

Low-temperature salt bath nitriding of heat treated and tempered 13/4 Martensitic stainless steel (13/4HTT) was carried at 450 °C (N450) and 500 °C (N500) for 10 h each. The nitrided samples were characterized by using x-ray diffractometer, field emission scanning electron microscope and optical microscope. The nanohardness and elastic modulus of the cross section of nitrided specimen were measured by nanoindentation test using Hysitron TI950 triboindenter. The nitrided 13/4HTT (N450 and N500) and 13/4HTT specimens were subjected to slurry erosion test in a slurry pot tester. The test was conducted for 48 h, and weight loss was measured after every 6 h. The relative speed of slurry with respect to specimen was 4.55 m/s. It was found that the weight loss due to erosion of the N450 is 83% less than that of 13/4HTT and that of N500 was 92% more than that of 13/4HTT. The erosion mechanism is correlated to the phases present in the specimens. The improvement in the slurry erosion resistance of N450 is due to presence of expanded martensite ( $$\alpha_{N}$$ -Fe). Increasing the temperature of nitriding to 500 °C led to the decrease in the slurry erosion resistance of N500 due to the formation of brittle CrN phase.

Influence of Medium Used during Ferritic Nitro-Carburizing of AISI H-13 Hot Work Tool Steel

Influence of Medium Used during Ferritic Nitro-Carburizing of AISI H-13 Hot Work Tool Steel

A novel rare earth-salt bath nitriding of TC21-DT titanium alloy

ABSTRACTA novel rare earth (RE)-salt bath nitriding of TC21-DT titanium alloy was primarily developed by adding certain amount of RE cerium oxide (CeO2) in KNO3 and NaNO3 salt bath, heated to temperatures in the range 590–650°C for periods up to 5 h in an ambient furnace atmosphere. The results showed that Ti phases and titanium nitride phase were formed on the surface of RE added samples; while no titanium nitride phases formed on the surface of conventional one, without RE addition. Furthermore, the surface hardness of nitrided samples, incorporated with RE addition, was about two times higher than that of conventional one (340HV0.01). The main improvement mechanism was analysed as well.

EFFECT OF QPQ TREATMENT ON THE PERFORMANCE FOR H13 DIE STEEL

QPQ salt bath treatment of H13 steel was conducted by nitriding at the same temperature of 565℃ for various times, followed by the same post-oxidation process. Optical microscope, micro-hardness tester, X-ray diffraction and wear resistance tester were employed to characterize the microstructure, phase constituents, micro-hardness and wear resistance of the treated specimens. The results showed a compound layer mainly composed of ε-Fe2-3N and diffusion layer were formed during salt bath nitriding and a thin oxide layer composed of Fe3O4 was formed by post-oxidation, and the compound layer thickness increases with the nitriding time. The maximum surface hardness value of 1441 HV0.3was obtained after nitriding at 565℃ for 150 min, which is as three times high as that of untreated sample. Meanwhile the wear resistance of H13 steel is significantly improved by QPQ treatment, 150 min is the optimum nitriding time to improve the surface hardness and wear resistance of H13 steel.

Salt Bath Nitriding of CP Titanium Grade-2 and TI-6AL-4V Grade-5

Titanium is known for its strong affinity towards nitrogen. The metal forms a nitride form case of high hardness when the salt bath nitriding is carried out. The selection of Grade 2 Titanium and Grade 5 Ti6Al4V Titanium alloy, stands with the fact that CP Grade 2 Titanium is the most formable and corrosion resistant amongst the pure grades of Titanium and grade 5 alloy is biocompatible and also has excellent tribological properties. This research work attempts to solve the problem of galling by comparing the morphology of the nitride case produced in Commercially Pure Grade 2 Titanium and the nitride formations produced in the Titanium Ti6Al4V alloy through Salt bath nitriding for a time span of 24 hours. Salt Bath Nitriding imparts unique improvements in Roughness, Hardness and Wear resistance of the samples thereby widening the applications of the material.

EFFECT OF SALT BATH NITRIDING ON SURFACE ROUGHNESS BEHAVIOUR OF AISI 4140 STEEL

In the present research, AISI 4140 steel was nitrided in salt bath to study and analyze the behaviour of the surface roughness. The structural surface characterization behaviour of the nitrided steel was compared to the behaviour of the same steel which was untreated. The nitriding process was implemented in the salt bath component at ten different times (from 1 h to 10 h) when the temperature was constant at (580ºC). The influence of nitriding treatment on structural properties of the material was studied by scanning electron microscopy (SEM), microhardness tester and surface profilometer. It was found that salt bath nitriding was effective in improving the surface properties behaviour of this steel. Experimental results showed that the nitrides ε-Fe2-3(N,C) and γ’-Fe4(N,C) present in the compound layer increase the microhardness (406–502 HV0.3), the initial surface roughness values of nitrided samples were higher than those of unnitrided specimens, it also observed that the increasing the nitriding time increases the surface roughness parameters (Ra, Rq and Rz).