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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.

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.

Controlled nitriding and ferritic nitrocarburizing can significantly improve the corrosion and wear resistance of carbon and low-alloy steels. The framework for maintaining these processes is based on standards, such as AMS 2759/10 and 2759/12A, that specify tolerances for control parameters. This work investigates the impact of admissible deviations in control parameters on the performance of treated alloy samples. The findings of the study demonstrate that although tolerances are allowed, precise control in specific furnace classes is necessary to consistently obtain superior results.

This paper studies the microstructural and tribological differences of layers formed during the ferritic nitrocarburizing of AISI 4340 alloy steel and AISI 347 stabilized stainless steel. The samples were exposed to different times of immersion in a nitrocarburizing bath (60, 75, 90, 105 and 120 min) at 580 °C. Subsequently, they were subjected to an oxidation process at 480 °C in order to form a Fe3O4 layer. Surface microstructural studies were carried out by SEM-EDS and x-ray diffraction (XRD). Wear and friction coefficient of nitrocarburized samples and non-treated samples were studied by pin-on-disk test. The results show two well-differentiated zones in AISI 4340 steel: an outer oxides layer, a white layer or compound layer and a diffusion zone. However, the compound layer was not found in AISI 347 steel. In both steels, the specific wear coefficient (k) of nitrocarburated samples is about thirty times lower than the reference samples. 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.

The influence of ferritic nitrocarburizing on the high-temperature corrosion-fatigue properties of the Si-Mo-Al cast iron SiMo1000 is investigated in the present study. It was found that nitrocarburizing effectively increases the surface hardness, but dramatically decreases the fatigue and oxidation resistance of SiMo1000. The fatigue resistance is reduced due to two types of microcracks formed after nitrocarburizing. The oxidation resistance is dramatically diminished due to the formation of microcracks, and the depletion of aluminum in the matrix from nitride precipitation during the exposure at 800 °C. The corrosion-fatigue synergy is found to cause severe decarburization (i.e. graphite depletion) in nitrocarburized SiMo1000.

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.

Ferritic 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

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.

In this study, electrolytic plasma processing (EPP) was employed for surface nitrocarburizing of AISI 1020 steel in a urea electrolyte, where the substrate samples were connected cathodically to a high-voltage DC current power supply. The structural, mechanical, wear and corrosion properties of the samples treated for 3–5 min were investigated. The results show that the surface layers formed on the samples by this treatment at 220 V have a ferritic nitrocarburizing characteristic which consists of a compound layer and diffusion zone. The surface layers of the treated samples at 240 V consisted of a compound layer, martensitic layer and diffusion zone, respectively, which is a marker of austenitic nitrocarburizing. The compound layers formed at 220 V and 240 V consisted of �-Fe2-3 (N,C) and � ′ -Fe4 (N,C) phases. The hardness value of the compound layer on the substrate was about 930 HV which was 4.5 times higher than that of the substrate. The thickness of the surface layer formed on the samples was a function of time and applied voltage. The wear and corrosion resistances of the samples were improved due to the surface treatment. © 2013 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier

Ferritic nitrocarburizing is a widely employed industry process by which a strengthened nitrocarburized surface can be formed on mechanical tools or parts made of steels. Mainly composed of the e-Fe2–3(C, N) and γ′-Fe4(C, N) carbonitride phases as well as the α-Fe phase, the nitrocarburized surface has featured microstructures and properties that are directly related to the phase transformations occurring in the surface layers. Thus far, the following phase transformation sequence for the surface has generally been accepted: α-Fe + N/C → e → γ′. In the present work, these phase transformations were systematically revisited by microstructure and property characterizations in association with a controlled nitrocarburizing process by which the microstructures and properties of the surface are adjustable. Our study demonstrates that, to fully understand the microstructure and the property of a nitrocarburized surface, it is necessary to adopt the phase transformation sequence α-Fe + N/C → γ-N/C + N/C → γ′ + N/C → e, in which the existence of a transitional austenite phase containing N/C atoms (γ-N/C) must be assumed and the γ′ phase actually forms prior to the e phase.

Carbonitriding is a metallurgical surface modification technique that is widely used in the automotive industry to increase surface hardness and wear resistance. Given the problems associated with carbonitriding, such as dimensional distortion, oxidation and non-uniform surface hardness, nitrocarburizing has been proposed as an alternative heat treatment method to improve the surface characteristics. The major advantages of ferritic nitrocarburizing are the minimal dimensional changes and distortion due to the low process temperature at which no phase transformations occur. This increases productivity and product quality, and decreases costs. The focus of this study was to determine the effects of carbonitriding and ferritic nitrocarburizing processes on the dimensional changes and residual stresses in a steel used for automotive applications. Navy C-ring specimens and prototype stamped parts made from SAE 1010 plain carbon steel were used in the testing. Gas, vacuum and ion ferritic nitrocarburizing processes with different heat treatment parameters were investigated. X-ray diffraction techniques were used for the residual stresses evaluation and surface phase analysis of the specimens.

Nitrocarburizing is a case hardening process which improves the hardness and wear resistance of a component, but results in geometric distortions. Torque converter pistons (automotive component) and Navy C-ring specimens (measuring tool) made from SAE 1010 plain carbon steel were used for the distortion analysis. Navy C-rings are generally used for studying the dimensional changes of a material before analyzing the dimensional changes of the actual component. Navy C-rings of varying thicknesses were used to analyze the effect of distortions with the change in thickness. Finite element simulations of Navy C-rings and torque converter pistons were developed to study the effect of nitrocarburizing process on distortions. For thinner specimens, the predicted distortions compare favorably with the experimental values. However, the thicker C-ring specimens showed high prediction error. To better understand the prediction difference of the different C-rings and TC pistons, an empirical ratio (bulk volume to nitrocarburized volume (V/VN)) was introduced. The V/VN ratio will not only help to separate the nitrocarburized surface dominant and bulk dominant specimens, but also provide a better comparison of the C-ring size with the actual component. The reduction of bulk volume to nitrocarburized volume (V/VN) ratio led to a decrease in both the C-ring’s inner diameter (ID) and gap width (GW) distortion, and a small increase in outer diameter (OD) distortion. A composition-depth profile simulation model was also developed to predict the local distortion due to nitrocarburized phases. The local distortion results showed that the γ′-phase (Fe4N) in the diffusion zone dominates the overall magnitude of distortion. The residual stress distribution for 1-step nitrocarburizing treatment was successfully modeled and validated against the experimental stress. The surface stress for one-step nitrocarburizing treatment was found to be tensile in nature. This tensile (surface) residual stress was further reduced by introducing 2-step nitrocarburizing treatments. Using the nitrogen profile model for 2-step nitrocarburizing, it was found that the additional γ′-Fe4N phase at the surface resulted in a notable residual (tensile) stress reduction. Also, the simulated 2-step nitrocarburizing treatments produced a same level of distortion as 1-step nitrocarburizing treatments. Therefore, the proposed 2-step nitrocarburizing treatments could potentially improve both the surface quality and fatigue resistance.

The thermochemical treatments of tool steels improve the performance of the components with respect to surface hardness, wear and tribological performance as well as corrosion resistance. Compared to the conventional gas ferritic nitrocarburizing process, the original vacuum oxy-nitrocarburizing is a time-, cost-effective and environmentally-friendly gas process. Because of the oxidizing nature of the gas atmosphere, there is no need to perform subsequent post-oxidation.In this study, a vacuum oxynitrocarburizing process was carried out onto four tool steels (AISI H10, H11, H21 and D2) at 570 °C, after hardening and single tempering. The structural analysis of the compound and diffusion layers was performed by optical and electron microscopy, X-ray diffraction and glow discharge optical emission spectrometry (GDOES) methods. A largely monophase e- layer is formed with a carbon accumulation at the substrate adjacent area. The overlaying oxides adjacent to the e-carbonitride phase contained Fe 3 O 4 (magnetite) as a main constituent. A thermodynamic modelling approach was also performed to understand and optimize the process. The “Equilib module” of FactSage software which uses Gibbs energy minimization method, was used to estimate the possible products during vacuum oxynitrocarburising process.

This paper deals with the investigation of two-step salt bath nitrocarburizing technologies. For comparison, ferritic nitrocarburizing was also conducted. By means of metallographic examination, microhardness test, X-ray diffraction analysis, the microstructure, phase construction, surface hardness and hardness profiles of case hardened layers on steel treated by various nitrocarburizing techniques were investigated. The friction coefficient and ring-on-block apparatuses were employed to investigate the friction coefficient and wear-resistance of case hardened layers. Meanwhile, the surface roughness of various nitrocarburized specimens was also tested by a stylus profilometer. The experimental results indicate that thicker compound layers are achieved on the specimen surfaces treated by two-step nitrocarburizing than by ferritic nitrocarburizing; the phase constructions of two-step salt bath nitrocarburized specimen surfaces are different from that observed on ferritic nitrocarburized specimens and two distinct layers are clearly visible on the cross-sections of two-step nitrocarburized specimens which consists predominately of e-compound (Fe3N) with a tiny minority of Fe3O4 (outer layer) and carbon/nitrogen martensite with a high percentage of austenite (inner later), while the phase construction of specimen surfaces treated by ferritic nitrocarburizing is composed mainly of e-compound (Fe3N) and a small amount of Fe4N and Fe2–3N.

The present work shows the behaviour of low carbon alloyed steels as AISI-SAE 8615, after a ferritic nitrocarburizing process. Nitrocarburizing takes place at 570ºC for 3 h in an atmosphere by combustion of methanol and urea under different flow rates. Metallographic studies were performed by optical microscopy. Hardness profiles were measured and carbon percentages were also analized by emission spectrometry in order to determine the extension of the nitrocarburizing process. Optimal flow conditions have been found. The influence of the flow rate on the nitrocarburizing layer thickness has been also studied.El presente trabajo muestra el comportamiento del acero aleado de bajo contenido de carbono, AISISAE 8615, cuando se somete a un proceso de nitrocarburación ferrítica, a la temperatura de 570ºC y un tiempo de 3 h. La atmósfera reactiva ha sido generada mediante goteo variable de metanol y urea dentro del horno, utilizando distintas velocidades de flujo. Las capas nitrocarburadas fueron evaluadas mediante técnicas de microscopía óptica. Con el fin de conocer la extensión de las capas nitrocarburadas obtenidas, se realizaron medidas de microdureza y se determinaron los porcentajes de carbono en el proceso mediante espectroscopia de emisión. Se han encontrado las condiciones de flujo óptimo de la mezcla anteriormente comentada y se ha observado cómo su variación influye en el espesor de la capa nitrocarburada.

In contrast to the classical ferritic nitrocarburizing an increase in process temperature above 590°C causes a ferrite-austenite transformation beneath the compound layer during austenitic nitrocarburizing. Results of austenitic nitrocarburizing with post-oxidation treatment are given for an unalloyed steel. Investigations were made of surface structure and fatigue behaviour in a corrosive and by comparison in an inert environment. Specimens treated in a two-step process at first by austenitic and then by ferritic nitrocarburizing and specimens treated only by ferritic nitrocarburizing were also included in the investigation programme. Austenitic nitrocarburizing has an unfavourable influence on the surface structure - especially on the porous zone and the compound layer composition - compared to the ferritic nitrocarburizing and the two-step process, respectively. Hence a noticeable decrease in corrosion fatigue resistance in 5 pct NaCl-solution has been observed in case of austenitic nitrocarburized specimens. This can be attributed to an insufficient resistance against pitting corrosion. By nitrocarburizing according to the two-step process on the other hand a surface layer can be obtained which offers a higher resistance against corrosion fatigue with superimposed pitting corrosion in contrast to only ferritic or only austenitic nitrocarburizing.

Ferritic nitrocarburizing is being proposed as an alternative to gas carbonitriding to improve the surface characteristics of SAE 1010 plain carbon steel automotive components without producing unacceptable part distortion. Navy C-rings are specially designed specimens for the evaluation of the distortion (size and shape) that result from any heat treatment process. In this study, gas ferritic nitrocarburizing and nitrogen cooling was used to heat treat Navy C-ring specimens of varying thicknesses (2.8 mm–19.05 mm) at temperatures ranging from 510°C to 595°C. For each combination of part thickness and heat treatment temperature, the following parameters were evaluated: size and shape distortion; XRD and OM (optical microscopy) to characterize the nature of the nitride layers formed at the surface; X-ray determination of the residual stresses in the nitride surface layers. The various combinations of nitrocarburizing temperature and time resulted in an expansion of the OD (Outside Diameter) dimension and a small deterioration in flatness. The ID (Inside Diameter) changed from a small expansion (+0.02%) for the thickest specimens (19.05 mm) to a small contraction (-0.02%) for the thinnest specimens (2.8 mm). The gap tends to close up as the thickness decreases from the thickest to the thinnest specimens. Microstructural differences were found in the nitrided layers formed at the different heat treatment temperatures. The residual stresses in the outer e-nitride layers (Fe3N) were typically tensile. On the basis of these results, preliminary recommendations are made as to heat treatment parameters to lower distortion.

Revised! Steel Nomenclature A. Kumar Sinha, C. Wu, and G. Liu New! Classification and Mechanisms of Steel Transformation S.S. Babu Fundamental Concepts in Steel Heat Treatment A.V. Sverdlin and A.R. Ness Effects of Alloying Elements on the Heat Treatment of Steel A.V. Sverdlin and A.R. Ness Hardenability B. Liscic' Steel Heat Treatment B. Liscic' Revised! Heat Treatment with Gaseous Atmospheres J. Grosch Revised! Nitriding Techniques, Ferritic Nitrocarburizing, Austenitic Nitrocarburizing Techniques and Methods D. Pye Quenching and Quenching Technology H.M. Tensi, A. Stich, and G.E. Totten New! Distortion of Heat-Treated Components G.E. Totten and M. Narazaki New! Tool Steels E. Essadiqi and G.E. Totten New! Stainless Steel Heat Treatment A.F. Padilha, R.L. Plaut, and R.R. Rios New! Heat Treatment of Powder Metallurgy Steel Components J.W. Newkirk and S.N. Thakur APPENDICES Common Conversion Constants Temperature Conversion Table Volume Conversion Table Hardness Conversion Tables: Hardened Steel and Hard Alloys Recommended MIL 6875 Specification Steel Heat Treatment Conditions Colors of Hardening and Tempering Heats Weight Tables For Steel Bars Round and Square Bars, Specific Gravity 7.85 Index

The usefulness of the ferritic nitrocarburizing treatment for improving the tribological properties of ferrous components is well established. However, the thin compound layer of beneficial epsilon carbonitride that develops at the surface lacks the ability to bear high Hertzian stresses. Nitrocarburizing in the austenite phase field of the Fe-N-C system overcomes this disadvantage since the formation of a hard zone of martensite-bainite below the compound layer provides the back-up to withstand point loads. Results of the Falex scuffing test indicate that the failure load increases on account of the thicker compound layer at the surface. The results indicate further that the frictional heat generated during the test coupled with working by the jaws convert the retained austenite present in the sub-compound layer to harder microconstituents. The study suggests that the austenitic treatment could be, useful for applications involving simultaneous heat and work such as hot working dies. ? 1997 Elsevier Science S.A.

Gaseous ferritic nitrocarburizing was investigated as a replacement for the carbonitriding process currently used to improve the surface properties of thin-shelled, plain carbon steel automotive powertrain components. Nitrocarburizing can impart a hard, wear-resistant case suitable for light load applications at lower processing temperatures than carbonitriding, thereby potentially reducing size and shape distortions and the associated need for finish grinding. Carbonitriding and gaseous ferritic nitrocarburizing were compared with respect to size and shape distortion, retained austenite, and residual stress values. Testing was performed on a torque converter piston, an automotive powertrain component stamped from a sheet of 3-mm cold-worked SAE 1010 steel. A total of 53 pistons were used. While the heat treatment conditions for the carbonitrided pistons were similar to the current production schedule, conditions for the nitrocarburized pistons incorporated a range of processing times from 2–14 hours and temperatures from 510–605°C (950–1125°F). The results of this work were generally consistent with those from an earlier study involving the use of Navy C-ring specimens. For both the Navy C-rings and torque converter pistons, the nitrocarburizing process gave rise to lower part distortion, but resulted in overall lower compressive residual stress values than in the carbonitrided steel.

Three different surface compound layers, consisting of varying distributions of ϵ-Fe2–3(C, N) and γ'-Fe4N phases, have been produced on a plain low carbon steel by ferritic nitrocarburizing and evaluated using dry sliding wear, microhardness and scratch tests. The dry sliding wear behaviour does not appear to be significantly affected by the variations in compound layer microstructure, although the failure mechanism under point loading conditions is dependent on layer structure, and in particular on microporosity in the layer. Results are discussed in terms of layer deformation and microstructure.