Effect Of Carburization Research Articles

Failure analysis in pyrolysis furnaces: Impact of carburization and thermal cycles on tube properties

The dominant failure mechanism in radiation coil tubes in pyrolysis furnaces is the detrimental interaction between carburization and reduced material ductility. This combination results in localized deformations, significant ovalization, and cracking in the tubes. At the same time, a second critical failure mechanism emerges during emergency furnace shutdowns, characterized by brittle fractures that can generate extensive longitudinal cracks in multiple tubes. This work presents a case study on the occurrence of failures that resulted in brittle fracture rupture of several tubes in a pyrolysis furnace that accumulated 43,720 h of operation. This highlights the practical importance of monitoring and managing the integrity of coil tubes. The tube samples were analyzed using optical and scanning electron microscopy, evaluation of carburization through magnetic permeability and NACE Test TM498, identification of carbides by X-ray diffraction (XRD), and dilatometry. Additionally, thermal stress analyses were performed using the finite element method, along with tensile tests at different temperatures. It was found that the tubes of the coil that operated at lower temperatures in their operational cycle did not rupture during the emergency shutdown, unlike other coils whose tubes experienced significant failures. An important contribution from this study is the demonstration of optimized operational cycle management and thermal control are essential in preserving protective oxide layers, minimizing coke formation and the effects of carburization and creep. This can reduce shutdown frequency and maintenance costs, improving the cost-effectiveness of the cracking process.

Surface hardening of high modulus steels through carburizing and nitriding: First insights into microstructure property relationships

High modulus steels are promising materials for future lightweight design solutions, as their embedded boride particles in a ductile steel matrix increase the stiffness/density ratio. One key requirement for maturing them towards industrial application is their suitability for improving the surface hardness. In this study we investigated the effects of low-pressure carburizing and plasma nitriding on the microstructure and mechanical properties of selected Fe-TiB2- and Fe-Cr-M2B-based high modulus steels. Nitriding resulted with the formation of expanded ferrite in the strongest hardness increase to about 1100 HV0.05 from the alloy system's base hardness of 240 and 500 HV0.05, respectively, albeit with different hardness depth profiles. The Fe-Ti-B alloy indicated deformation phenomena in the ferritic matrix after nitriding, whereas nitriding of Fe-Cr-B-C resulted in a diffusion-controlled particle transformation of M2B borides into CrN nitrides of lower stiffness. Carburizing on the other hand led to a slightly lower maximum hardness value of about 800 HV0.05 over an increased depth for Fe-Cr-B, as martensite and additional M23C6 carbides were formed in the surface zone. The surface hardness of the Fe-TiB2-based alloy could not be increased by the deployed carburization parameters, most likely due to excessive Ti dissolved in the matrix. Consequences for the transfer to engineering applications as well as the refinement of both, thermochemical processing parameters and designated alloy concepts, of high modulus steels are outlined and discussed.

Study on the influence of heat treatment process on the microstructure and hardness of carburized layer of 20CrMoH steel

Abstract In this paper, the effects of different carburizing quenching processes and tempering processes on the depth of the hardened layer and microstructure of 20CrMoH were studied by means of hardness analysis and SEM microstructure analysis. The results show that: when the quenching temperatures in the range of 820-880 °C, it has little effect on the depth of the hardened layer. And the hardness value at the same depth is at a considerable level, which is not affected by the quenching temperature. When the tempering temperature range is 150-280 °C, the tempering temperature has a great influence on the depth of hardened layer. And with the gradual increase of tempering temperature, the depth of hardened layer decreases gradually. Also the hardness value at the same depth from the edge shows a monotonous decreasing trend with the gradual increase of tempering temperature.

Effects of carburizing and nitriding sequential treatment on rolling contact fatigue of M50NiL bearing steel

Effects of carburizing and nitriding sequential treatment on rolling contact fatigue of M50NiL bearing steel

Surface integrity and corrosion resistance of 18CrNiMo7-6 gear steel subjected to combined carburized treatment and wet shot peening

Typically, a cost-effective and versatile carburizing process is used to improve the surface integrity of high-value-added gear components. In this study, carburized treatment and wet shot peening (WSP) were applied to increase the corrosion resistance of 18CrNiMo7-6 gear steel. The surface integrity and corrosion resistance after carburizing and combined treatment (carburized treatment + WSP) were analyzed. The results indicated that the combined treatment converted the retained austenite surface layer within approximately 45 μm from the surface into the martensitic phase, with a 13.9 % reduction in equivalent grain size and a 23.6 % increase in dislocation density compared with carburizing. Furthermore, electrochemical experiments in a 3.5 wt% NaCl solution indicated that the combined treatment process increased the corrosion resistance compared with carburizing (55.4 % lower corrosion current density and a higher Fe2+/Fe3+ ratio). Despite the high surface roughness obtained with combined treatment, the improved corrosion resistance is primarily ascribed to the high compressive residual stress and dislocation density. This study provides insights into the surface strengthening design of 18CrNiMo7-6 gear steel for corrosive environments—particularly the synergistic strengthening effect of carburizing and WSP.

Controllable decomposition of CH4/CO using Fe3C catalyst and carbon structural properties: Combine experimental study with a ReaxFF simulation

This study utilizes a two-stage method to prepare high-performance Fe3C catalysts through the continuous reduction of Fe2O3 and carburization of metallic iron. Firstly, metal iron with well-developed pores and high specific surface area is obtained through reduction, and then the target product Fe3C is synthesized through the carburization effect of CH4. The performance analysis of the catalyst shows that it has a strong gas adsorption capacity and well-developed pores and its structural and surface chemical properties have been analyzed using XRD, TEM, and XPS methods. The carbon deposition reaction of CH4 and CO on Fe3C surface is characterized by combining Reactive force field (ReaxFF) and experimental methods, and the degree of ordering of the products has been measured which indicates that CH4 is more likely to generate carbon black with a lower degree of ordering on the surface, while CO tends to generate graphite with a higher degree of ordering.

Effect of Carburization on the Microstructure and Laser Weldability of 316L Stainless Steel

This study aims to investigate the influence of the carburizing layer on the microstructure of laser-welded joints in 316L stainless steel, aiming to enhance the properties of stainless steel components through the incorporation of carburization. Through a comprehensive experimental approach, including nanoindentation and Vickers hardness measurements, the microstructural analysis of the laser-welded specimens was conducted. The nanoindentation results reveal a significant increase in hardness, with the carburizing layer exhibiting a remarkable 215% improvement compared to the base material. In order to effectively harness the wear resistance for various applications, the examination of macroscopic characteristics in laser-welded joints reveals the necessity of regulating heat input and minimizing defects to attain welds of superior quality. Additionally, the phase transformation behavior of stainless steel during welding was found to be altered due to dilution in the fusion zone and the presence of high carbon content in the heat-affected zone of the carburizing layer. Overall, this research provides valuable insights into the microstructural changes induced by carburization and its implications for the welding performance and mechanical properties of stainless steel.

VDM 330

Abstract VDM 330 (Nicrofer 3718) is an austenitic iron-nickel-chromium-silicon alloy with good high-temperature strength and good resistance to carburization, thermal shock, and high temperature oxidation. It is used extensively in high-temperature environments where resistance to the combined effects of thermal cycling and carburization is required. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-1364. Producer or source: VDM Metals GmbH (a subsidiary of Acerinox, S.A.).

Microstructure evolution, mechanical and abrasive wear properties of NiCrSiB-SiC composite coatings prepared on 16Mn low-carbon steel by Ni-based alloy catalyzed SiC decomposition

In this study, NiCrSiB-SiC composite coatings were prepared on 16Mn low-carbon steel by vacuum cladding technology using SiC and NiCrSiB mixed powders as raw materials for enhancing their wear resistance. The effects of different content of SiC particles on the microstructure evolution, mechanical and abrasive wear properties of the coatings were investigated. The results showed that SiC particles in all the NiCrSiB-SiC composite coatings with different SiC contents were completely decomposed into C and Si under the catalysis of Ni-based alloy. The out-diffused Si into the coating mainly led to the formation of the Ni3Si eutectic phase, while the out-diffused C introduced M7C3, M3C2, M2(C, B) and other hard phases. Besides, C also diffused to the substrate, leading to a carburizing effect, which remarkably enhanced the mechanical properties of the substrate. In the NiCrSiB-SiC composite coatings with high SiC content, the decomposition of SiC led to the remaining graphite phase. However, once the concentration of SiC was over high, excess graphite would deteriorate the compactness and adhesion of the coating, weakening its wear performance. The nanoindentation and abrasive wear experiments revealed that the composite coating with 5 wt% SiC particles had lower elastic modulus (E), higher hardness (H), H/E, and H3/E2, and its wear volume was only 1/10 of that of the substrate, indicating the best mechanical and wear properties. The excellent wear performance can be attributed to the combination of the in-situ formed carbides and borides hard reinforcing phases and the tough coating matrix composed of Fe and Si dissolved γ-Ni and Ni3Si eutectic phase.

Identifying of chemical composition changes during the carburizing process of carbon steel under tension

Carburizing is a commonly employed technique used to improve carbon steel’s surface characteristics, specifically its hardness and ability to resist wear. The introduction of tension during the carburizing process adds complexities that affect the distribution of elements in the material. The research methodology includes subjecting carbon steel samples to carburizing temperatures and applying tensile stress. This approach allows for analyzing the effects of carburization and stress on the carbon steel samples. The focus of the investigation was to analyze the use of the pack carburizing technique at lower temperatures, specifically 700 °C and 750 °C, while also applying proportional-voltage tensile stresses. The study focuses on conducting a comprehensive analysis of changes in the chemical composition throughout the cross-section of the material. Advanced analytical techniques perform mapping and elemental spectrum analysis, such as scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). These techniques enable a thorough investigation of the distribution and composition of elements such as carbon, iron, silicon, magnesium, and phosphorus. According to the research findings, carbon elements were added within the temperature range of 700 °C to 750 °C during the carburization process. The carbon content in the material increased from 0.15 % in its unprocessed state to 0.73 % at a temperature of 700 °C, followed by a further increase to 1.26 % at a temperature of 750 °C. According to the study, it was found that applying tensile loads and reducing carburizing temperatures can enhance the carburizing process and result in higher carbon steel content. This can bring about cost savings and improve overall industrial efficiency

The Interplay Effects between Feed-Gas Composition and Bias Plasma Condition during Active-Screen Plasma Nitrocarburizing with a Solid Carbon Source

Recent technological development of utilizing an active screen made of solid carbon for plasma-assisted thermochemical diffusion treatments opens up new possibilities for control over the in situ generated treatment environment to guarantee reproducible treatment conditions and material responses. Until now, the investigations of active-screen plasma nitrocarburizing (ASPNC) using an active screen manufactured from solid carbon focused on the influence of a single treatment parameter variation on the material response. In this systematic study, experiments were conducted to vary the H2-N2 feed-gas composition while varying the bias plasma power. The experiments served to better understand a simultaneous variation in the mentioned parameters on the resulting treatment environment and material response during ASPNC of AISI 316L austenitic stainless steel. Therefore, nitriding and carburizing effects in the expanded austenite layer can be obtained. It is shown that an increased nitriding effect, i.e., nitrogen diffusion depth and content, was achieved in case of biased conditions and for H2-N2 feed-gas compositions with higher N2 amounts. On the contrary, an increased carburizing effect, i.e., carbon diffusion depth and content, was achieved in nonbiased conditions, independent from the H2-N2 feed-gas composition.

Synergistic effect of the combined surface modification technology on rotational bending fatigue of low carbon alloy steel

Synergistic effects of carburizing and ultrasonic surface rolling (USR) on rotational bending fatigue (RBF) of 20CrMoH steel were researched under different RBF test conditions. Besides, the effect of USR load on RBF property was also clarified. Results revealed that the combined treated specimen with the load of 1300 N achieved the best RBF property. This is due to the highest residual compressive stress (RCS) and maximum microhardness value. Both RCS and microhardness play a very important role in enhancing RBF performance.

Effect of carburizing and nitriding duplex treatment on the friction and wear properties of 20CrNi2Mo steel

In this study, the responses of 20CrNi2Mo steel to carburizing (C) and carburizing-nitriding (C + N) duplex treatment and the effects of these treatments on the friction and wear properties were systematically studied. The 20CrNi2Mo surface layers were characterized by optical microscopy (OM), laser scanning confocal microscopy (LSCM), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers microhardness tests and high-speed reciprocating friction and wear testing. The results showed that after the carburizing and nitriding duplex treatment, an approximately 5 μm thick compound layer (CL) consisting of the γ′-Fe4N and ε-Fe2-3N phases had formed on the surface, and the diffusion layer depth was approximately 220 μm. The carbides (MC) stored during carburizing were easily converted to nitrides (MN) during the nitriding process. Furthermore, the surface microhardness (879 HV) was increased by a factor of 2 compared with the substrate (420 HV), the surface residual compressive stress (−652 MPa) was increased significantly, and the surface roughness also increased. Wear analyses under different loads showed that specimen C exhibited the worst wear resistance, and its wear mechanism was mainly abrasive wear. The C + N with CL samples showed excellent wear resistance under a 20-N load; after removing the CL samples (C + N with CL), they showed excellent wear resistance under a 40-N load, and the wear mechanism was mainly adhesive wear. This work showed that the wear resistance was improved significantly by the carburizing and nitriding duplex treatment, but the CL had different effects on the wear performance under different loads.

The Effect of Carburization and Repeated Heat Treatment with Different Solutions on the Fatigue Resistance of Medium Carbon Steel

Many mechanical parts are exposed to failure as a result of mechanical stresses for design or metallurgical reasons, and the phenomenon of fatigue represents the largest area and reaches (90%) of the faults of engineering parts that are subject to periodic stresses. The risk of fatigue failure occurs without warning, so the phenomenon of fatigue resistance has taken up a large part of the research and studies concerned with the dissolution of metals. This article aims to study the effect of fatigue resistance of ASTM 1050 steel. Carbonation, repeated quenching at different temperatures (780 & 770℃) using seven different solutions, and tempering at repeated tempering after each quenching at temperatures (230 & 250℃). The stress resistance of all the studied samples decreases after the second cooling in distilled water, with the exception of the samples that were initially quenched with the same solution and then quenched again. This is one of the most significant findings. Another finding is that following a second chilling in distilled water-based solution, the resistance to fatigue stress rises, increasing by up to (8.5%) in comparison to samples that were first quenched in the same solution then diluted.

Carburizing effect-inspired bending fatigue forecasting model for spiral bevel gears

Collaborative optimization considering complex meshing interface physical performance evolution is always an important challenge for designer in recent field of spiral bevel gears. Where, an innovative root bending fatigue life forecasting model is established by considering the root flank carburizing effect for spiral bevel gears. First, root flank carburizing simulation is performed to output carburizing effect evaluations, namely the root flank hardness gradient at different carburizing layers and residual stress distribution. Then, carburizing effect-inspired root bending fatigue life forecasting model was established. Where, finite element method (FEM) based bending stress considering residual stress is determined, and root flank hardness gradient is used to compute S-N curve. Considering tooth flank carburizing effect, root bending fatigue life forecasting is performed by correlating with multiaxial fatigue criterion. Finally, the proposed forecasting model is exercised with an instance aerospace spiral bevel gears to verify the impact of key machine settings on the result root bending fatigue life.

Improving low temperature degradation of 3Y-TZP ceramics via high temperature carburizing

3Y-TZP ceramics are prepared by solid state method and surface carburization process, and the effect of surface carburization on its the low temperature degradation is studied. The conventional sintered samples completely lost its mechanical properties after aging for 15 h, while the failure time of the surface carburized samples are 300 h. In addition, the nuclear growth rate of the surface carburized samples (αd) and the nucleation rate (Nr) is lower than that of sintered samples, αd plays a dominant role in the degradation process at low temperature and is the key factor determining the aging rate. At the same time, it is found that carbon is dissolved in zirconia lattice in the form of electrically neutral atoms, which will not destroy the original charge balance and produce new oxygen vacancies when entering the interstitial site. More importantly, the precipitation rate of Y3+ from zirconia lattice is the key factor to determine the low-temperature phase transition of tetragonal-monoclinic(T-M). The treatment method of surface carburization has significantly improved the low-temperature degradation performance of 3Y-TZP ceramics, which provides a basis for the application of zirconia ceramics in low-temperature and humid environment.

Mechanical properties of carburized 316L stainless steel lattice

The effect of low-pressure carburizing (LPC) on the mechanical properties of open cellular structures was studied by taking the 316L stainless steel body-centred cubic (BCC) lattice fabricated by selective laser melting (SLM) as an example. The mechanical properties of the corresponding solid material and the microstructure of the carburized layer were also analyzed. The results showed that the depth of the carburized layer was about 450μm, composed of three sub-layers. After carburized, the yield strength of the 316L solid was obviously decreased accompanied by the reduced elongation at break. The embrittlement was also reflected in the carburized lattice so that the fracture occurred and the energy absorption capacity weakened. Simultaneously, the compressive proof strength of the lattice was improved after low-pressure carburizing due to the toughness inherent in the structure.

Effect of pack carburizing and viscosity of quenching media on AISI 1010 steel

Pack carburizing is a method of surface hardening of steel which is carried out by diffusing carbon into the material where the carbon is initially solid. This study aims to determine the effect of pack carburizing treatment on the microstructure and hardness of AISI 1010 steel. The material was then cooled slowly in the oven to a temperatur of 150oC which was then followed by air cooling. Single Quenching is then carried out by reheating the carburizing material to a temperature of 870oC and then holding it at that temperature for 60 minutes. Quenching is done by cooling the material quickly using a cooling medium of varying viscosity. The results of the composition test showed an increase in carbon content to 4.1159%. The results of microstructure observations showed that a massive pearlite structure was formed to a depth of ± 0.794 mm on the surface of the carburizing specimen. The results of the hardness test using the Vickers method showed that the hardness value of the raw material increased after carburizing to 217.88±5.13 HV due to the formation of a pearlite structure. With this increase in hardness, the application of AISI 1010 Steel material becomes wider.
 Keywords: Carburizing, Quenching, Viscosity, Hardness, Microstructure

A novel metallurgical technique for the preparation of soft magnetic iron carbide from low-grade siderite

Iron carbide (Fe3C) has attracted widespread attention as a functional material, catalyst, and magnetic material. In this study, soft magnetic Fe3C was prepared by carburization roasting, magnetic separation, and acid leaching using low-grade siderite as the raw material. The effects of carburization, subsequent magnetic separation, and acid leaching of the carburized samples on their magnetic properties were studied using a vibrating sample magnetometer (VSM), and the mechanisms of these methods were also studied. The final samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), VSM, and Mössbauer spectroscopy. Under optimized conditions, an iron carbide material comprising assaying 92.08% Fe and 6.94% C with a corresponding iron recovery rate of 73.50% was obtained. The saturation magnetization, the remanence, and coercivity values of the obtained iron carbide were 136.10 emu/g, 1.84 emu/g, and 39.11 Oe, respectively. Furthermore, Na2SO4 and NaOH were found to be useful additives for improving the carburization efficiency of iron carbide, enlarging iron carbide particles, improving the embedding relationship between iron carbide and gangue, and enhancing the dissolution of gangue in acid. The proposed technique is promising for the preparation of magnetic iron carbide materials with good soft magnetic performance.

Impact of cobalt catalyst carburization on Fischer‐Tropsch micro‐kinetics

AbstractRecent models of the Fischer‐Tropsch synthesis are able to predict quite accurately the catalyst's initial activity and selectivity. However, these micro‐kinetic models rarely consider the performance loss with time on stream and in particular the heavy product selectivity loss. In this study, a deactivation model at the micro‐kinetic scale is proposed to represent the effect of carburization on Fischer‐Tropsch catalysts performances. Comparison of different mechanisms revealed that termination reactions were the most affected by cobalt carbide formation, before reactants adsorption or chain growth. Both activity and selectivity decline could be accurately described using linear and second‐order power laws expressions of active sites concentration and termination kinetic rate constants. The obtained model predicts a monotonous evolution of activity and selectivities from 10% to 80% carburization, above which an important increase of olefin selectivity is observed. The model did not indicate any change of the surface coverages after carburization.