Papers by Keyword: Carburization

Abstract: The demand for environmentally sustainable methods to enhance the performance of low-carbon steel (LCS) has led to increased interest in organic waste-derived carburizing agents. This study explores the potential of using a blend of Shea Nut Shell (SNS) and Eggshell (ES) ash, mixed in a 1:3 ratio, as an eco-friendly carburizing medium for improving the mechanical and corrosion-resistant properties of LCS. Carburization was carried out at 900°C for 30 minutes, and the effects were assessed through comprehensive characterization. Mechanical properties such as hardness, tensile strength, and impact energy were evaluated alongside microstructural analysis using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and wear rate testing. Corrosion resistance was investigated in H₂SO₄ and NaCl environments over a 21-day period. Results show that carburized LCS achieved significantly higher hardness (514.55 HB) compared to the uncarburized counterpart (399.05 HB), with improved toughness as indicated by increased impact energy absorption. However, un-carburized LCS maintained higher tensile strength. Microstructural examination revealed enhanced carbon diffusion and pearlite formation, contributing to reduced wear in carburized samples. EDS confirmed increased surface carbon content, while corrosion behavior varied: carburized LCS performed better in saline (NaCl) conditions, whereas uncarburized LCS offered better resistance in acidic (H₂SO₄) environments. In conclusion, the SNS-ES ash mixture presents a promising route for sustainable carburization of LCS, particularly for components exposed to saline environments such as agricultural tools and automotive parts. Future work will focus on optimizing treatment durations, expanding corrosion testing in simulated service environments, and scaling the process for industrial applications.

Abstract: This study investigates the effectiveness of carbon nanotubes (CNTs) in enhancing the surface hardness of mild steel through carburization. CNTs were synthesized via chemical vapor deposition at 700°C using iron nitrate and cobalt nitrate as precursors on CaCO₃ support. Acetylene was used as the carbon source and nitrogen as the inert gas. The as-synthesized CNTs were purified using a one-step nitric acid treatment. Characterization by SEM, TGA, and FTIR revealed CNT diameters of 42-52 nm and improved thermal stability after purification, with TGA showing mass losses of 78% for as-synthesized CNTs and 85% for purified CNTs. Low carbon steel (AISI 1018) samples were carburized with as-synthesized and purified CNTs at austenitic temperatures of 750°C and 800°C for period ranging from 10 to 50 minutes. The carburizing process involved heating at 10°C/minute, followed by a defined number of boost and diffusion steps. Surface hardness was evaluated using a Vickers FM 700 micro-hardness tester, and microstructure was checked with an Olympus SC50 optical microscope. Results show that the use of purified CNTs in the carburization displayed the highest surface hardness of 191.64 ± 4.16 GPa at 800°C for 50 minutes, representing a 32% increase over the untreated substrate (145.188 ± 2.66 GPa). As-synthesized CNTs yielded a hardness value of 177.88 ± 2.35 GPa under the same conditions. At 750°C, the percentage increase in hardness for as-synthesized CNTs and purified CNTs were 10.04% and 15.77%, respectively, compared to the untreated substrate. Higher carburization temperature and longer treatment time consistently increased the surface hardness. The use of purified CNTs resulted in an increase of 6.37% hardness when compared to that of the as-synthesized CNTs at 750°C. Microstructural changes in the steel samples confirmed improved surface hardness with both purified and unpurified CNTs, with purified CNTs showing superior performance. This study therefore provides a platform for the use of CNTs for enhancing surface hardness of steel for various industrial applications requiring enhanced mechanical properties and wear resistance in low carbon steels.

Abstract: The effect of time-temperature parameters of heat treatment on the structure and properties of carburized case and the core of 19CrMnNiMo steel was studied. The critical points were determined by dilatometric analysis: Ac₁ = 740°C, AC₃ = 835°C. It was established, that after carburizing at 940 °C, prequench to 890 °C with oil cooling, quenching at 790 °C and tempering at 180 °C, martensite structure of carburized case with uniformly distributed carbides and the least amount of retained austenite is formed. The hardness of carburized case decreases smoothly from the surface into the depth, in proportion to the decrease in the carbon concentration and amounts to 60-50 HRC. The technological process of heat treatment of drill bit legs made of 19CrMnNiMo carburized steel providing minimal amount of retained austenite in structure, absence of carbide network and combination of optimum mechanical properties which is proved by a real on-site experiment is developed. Temperature conditions of carburizing, quenching and low tempering are recommended for the production of legs of roller bits.

Abstract: The study is aimed at surface strengthening of jewelry tools. Samples in the form of a tool with a flat and curved surface profile are considered. Macrophotographs of jewelry korneisen at different stages of wear, as well as after restoration and strengthening are given. The results of the influence of chemical-thermal and thermo-friction treatments on the structure and properties of U7 and U8A steels used for jewelry tools are presented. The methodology of experimental researches is given. The equipment used for each of the hardening methods investigated in this work is considered. Auxiliary media and features of sample preparation for the experiment are also described. Photos of samples and some equipment at different stages of the study are given. Data on the distribution of microhardness, photographs of microstructures in cross section of samples after different types of hardening are presented. A comparison of the strengthening efficiency of the samples after the use of different processing methods is performed.

Abstract: The technology of diffusion saturation of austenitic steels by chromium and nickel in the medium of low-melting liquid metal melts is shown. The saturation temperature was up to 1050°C, and the duration was up to 8 hours. It was found that it is the most effective to apply coatings according to the technological scheme: pre-carburization-diffusion metallization – final carburization. It was found that the coating consists of 4 layers. The surface layer has a thickness of up to 5 mkm and a microtuberance of up to 19500 MPa. The second layer, up to 12 mkm thick, has a microhardness of up to 7500 MPa. The third, up to 50 mkm thick, has a microhardness of 2300 MPa. In the fourth layer, up to 150 mkm thick, the microhardness gradually decreases from 2300 MPa to the microhardness of the base. At the same time, the total thickness of the coatings is up to 200 mkm.

Abstract: A study of the low-carbon steel with high hardenability was carried out. The steel contained the following alloying elements, wt. %: C – 0.20; Cr – 2.0; Mn – 2.0; Si – 1.04 Ni – 1.0; Mo – 0.3. The quenching – partitioning treatment of the studied steel was implemented. The microstructure of the steel consisted of the tempered martensite laths, bainite and martensite-austenite regions. The amount of the residual austenite and the carbon concentration in the residual austenite were estimated. The possibility of the quenching – partitioning treatment of the carburized steel was shown.

Abstract: The studies on cementation focus exclusively on the carbon’s movement. It is described by diffusion equations, often with constant coefficients and without regard to the liaising with temperature. It does not allow to have regard to the further carbon diffusion into the workpiece with the lower temperature range. The most accurate prediction of carbon concentration profiles depending on the parameters of the carburization regime and the chemical composition of steel is possible with the mathematical models using. However, most models show good results for Fe-C austenite without affecting the effect of alloying substitution elements. Taking into account the influence of alloying elements leads to complex empirical dependencies with difficult selected coefficients. It makes their use difficult. The study describes the simulation using the finite element method for the process of austenite’s diffusion saturation Fe-C-Cr system with carbon during cementation. Here is an example of a steel gear 15Cr2 with the temperature influence. The COMSOL Multiphysics program is used to solve the problem numerically. It is found that the model of carbon diffusion in unalloyed austenite for the single-stage cementation regime is in good contact with the experimental data for the Fe-C-Cr austenite of 15Cr2 steel. For a two-stage process, the calculation of the carbon concentration in the surface layer has a slightly greater deviation from the experimental data than it is at a greater depth.

Abstract: In this research, low carbon steel surface was modified using electrophoretic deposition (EPD) technique from a graphene oxide (GO) water suspension. The electrophoretic deposition (EPD) is the technique used for manipulation and deposition of nanomaterials. The GO coating was used as a layer to increase the hardness of low carbon steel. GO was successfully synthesized using the modified Hummers method. EPD technique was performed by applying voltage at 9 volts and the deposition time of 15 mins. The working distance between the cathode and anode was fixed at 15 mm. The GO film had been deposited by EPD technique where it was carburized at 900, 950, 1000 and 1050°C, for 60 mins. The microstructure of the carbide film was investigated using scanning electron microscopy (SEM). As the carburization temperature raised (1050°C), more volume carbon atoms reacted with iron atoms to form iron carbon (Fe₃C) layer on to the substrate surface. The carbide films are columnar crystal growth with a particle size of approximately 50 μm. The growth rate of the carbide films at 1050°C is about 8 µm/min. Energy dispersive X-ray spectrometer (EDS) was studied for chemical elements analysis. Fe, C and O elements were then detected. At carburization temperature of 1050°C, it showed that C element distribution is higher than others’ temperatures. Moreover, the hardness on the carbide films was investigated using a Vickers hardness tester under an applied load of 500 grams for 10 seconds. It was found that the hardness increased with the increasing carburization temperatures. The hardness of low carbon steel is 172.99 ± 2.28 HV. After the carburization processing via GO at temperature of 1050°C, the highest hardness of 821.42 ± 35.33 HV was obtained. It was observed that the mechanical properties of low carbon steel surface were found to be strongly influenced by the process of carburization temperature.

Abstract: N-Quench, which is a new surface heat treatment to infiltrate nitrogen into steel parts followed by quenching to achieve hardening, is gathering attention in the nitriding field as it affords low distortion while maintaining a higher effective case depth (ECD) compared with conventional nitriding. N-Quench is conducted mainly between 680°C and 800°C, where the two-phase region of ferrite and austenite exists in the Fe-N phase diagram. However, a few studies have reported on nitriding at temperatures higher than 800°C due to decomposition of NH₃, which is a key source of nitrogen infiltration. Our results revealed that in a conventional furnace such as resistance heating furnace, no nitrogen infiltrated the specimen at 930°C, which is the general carburizing temperature. On the other hand, in the infrared heating furnace, nitrogen infiltrated the specimen at 930°C successfully with lesser NH₃ introduction than that required by the conventional furnace. Therefore, in this study, the limit of NH₃ decomposition is assessed and possibility of extending the applicability of N-Quench, especially increasing the ECD while maintaining a low distortion, is examined.

Abstract: The effect of quenching from 900°C (20 min exposure) and different tempering in the 250-650°C (for 1 hour) interval, as well as additionally preliminary carburization for 8 hours at 930°C, followed by a similar heat treatment on abrasive and shock-abrasive wear of low-carbon manganese (10-24%Mn) steels, phase composition and mechanical properties was studied. It was confirmed that an increase in the manganese reduces the abrasive wear resistance and increases the impact-abrasive wear resistance. The expediency of carburization of low-carbon manganese steels is shown in order to obtain the residual austenite in the structure which amount and stability must be optimized in relation to specific abrasive impact characterized by the dynamic ratio with taking into account the chemical composition.