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G Sundararajan - One of the best experts on this subject based on the ideXlab platform.
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the effect of boron pack refreshment on the Boriding of mild steel by the spark plasma sintering sps process
Surface & Coatings Technology, 2008Co-Authors: X J Chen, L G Yu, K A Khor, G SundararajanAbstract:Mild steel samples were borided with and without boron pack refreshment using the spark plasma sintering (SPS) process. Results show that the borided samples with boron pack refreshment developed a thicker boride layer compared to that without boron pack refreshment for the same Boriding duration. When Boriding duration is t < 120 min, the Boriding growth in the samples borided with boron pack refreshment followed a parabolic growth pattern. In contrast, the boride growth in samples processed without boron-pack refreshment deviates from parabolic at t = 60 min. Computer simulation shows that the boron concentration change in the Boriding media during the Boriding process is an important factor affecting the composition and final thickness of the boride layer.
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boride layer growth kinetics during Boriding of molybdenum by the spark plasma sintering sps technology
Surface & Coatings Technology, 2006Co-Authors: L G Yu, K A Khor, G SundararajanAbstract:Abstract Molybdenum borides have potential industrial applications as abrasive, corrosion-resistant and electrode materials due to their high hardness values, chemical inertness, and electronic conductivity. In this work, boride layers are formed on the surface of Mo samples using a pack Boriding method with the assistant of the spark plasma sintering (SPS) technique. The process was performed in the temperature range 1000–1400 °C and with a holding time of 30 min at the preset temperature. The microstructure, microhardness, and fracture toughness of the molybdenum boride layer are investigated by optical microscopy, X-ray diffraction and microhardness indentations. Results showed that the boride layer, mainly composed of MoB, have thickness in the range ∼ 6–155 μm. The Boriding kinetics is studied by linking the boride layer thickness with the Boriding temperature. The activation energy and pre-exponential constant are estimated from the experimental results, and are found to be 218.8 J/mol and 1.41 cm2/s respectively. The MoB layers have a preferred orientation in the (002) direction, which is reflected by a distinct columnar growth observed in the optical micrographs of polished cross-sections of SPS samples.
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feb fe2b phase transformation during sps pack Boriding boride layer growth kinetics
Acta Materialia, 2005Co-Authors: X J Chen, K A Khor, G SundararajanAbstract:Abstract The iron boride layer growth kinetics in mild steel through the spark plasma sintering (SPS) pack-Boriding technique is investigated at 850 °C with different Boriding durations (maximum 240 min). Results show that both FeB and Fe 2 B layers form and grow on the mild steel surface with the FeB layer on the top of Fe 2 B sublayer in the samples with Boriding duration less than 90 min. However, at longer Boriding duration, the top FeB layer eventually ceases growing, starts to diminish, and, finally disappears completely by transforming into the Fe 2 B phase. Numerical simulation is implemented to explain this phenomenon. Subsequently, the diffusion coefficient of boron in FeB and Fe 2 B phase is obtained through fitting the experimental results into the model. The simulation results are found to be in good agreement with the experimental results, and the estimated diffusion coefficients of boron in FeB and Fe 2 B phases as 2.33 × 10 −9 and 4.67 × 10 −9 cm 2 /s, respectively. Both the simulation and experimental results reveal that the Fe 2 B mono-phase layer can be obtained through the transformation of FeB to Fe 2 B phase due to the depletion of boron concentration in the Boriding medium, and is indifferent to the formation of FeB phase at the very onset of the Boriding process. This provides a new approach to overcome the side effect of FeB formation in borided components.
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Boriding of mild steel using the spark plasma sintering sps technique
Surface & Coatings Technology, 2002Co-Authors: L G Yu, K A Khor, G SundararajanAbstract:The spark plasma sintering (SPS) technique was employed to perform Boriding of mild steel. A pack Boriding method that contained a silicon carbide-boron carbide powder pack mixture was utilized in this study. The process was performed in the temperature range 700-1000 °C for 30 min. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the microstructure and phase composition of the iron boride layers (FeB and Fe 2 B). Plotting lnD vs. 1/T expresses concisely the boride layer's growth rate constant (D) vs. temperature (T) relation. A linear relationship between lnD and 1/T is confirmed. The kinetics of SPS boronization are discussed, and the effect of SPS on boronization is studied. The results confirmed that SPS required significantly lower activation energy for accomplishing the Boriding operation.
I Campossilva - One of the best experts on this subject based on the ideXlab platform.
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micro abrasive wear resistance of cob co2b coatings formed in cocrmo alloy
Surface & Coatings Technology, 2015Co-Authors: G Rodriguezcastro, C D Resendizcalderon, L F Jimeneztinoco, A Menesesamador, E A Gallardohernandez, I CampossilvaAbstract:Abstract New data for micro-abrasion wear resistance of CoB/Co2B coating was obtained through a ball cratering test. The coating was formed on the surface of a CoCrMo alloy using the powder-pack Boriding method. The Boriding process was carried out at 1223 K over 5 h of treatment resulting in the formation of CoB/Co2B coating with a total thickness of 28 μm approximately. Both hardness and Young's modulus profile through the cobalt borides were evaluated by Berkovich depth-sensing indentation using a load of 25 mN. The wear coefficients of CoB and Co2B formed on CoCrMo alloy were evaluated by a Plint TE-66 micro-abrasion tester using SiC particles dissolved in deionized water as abrasive slurry. The results demonstrated that the cobalt borides have wear coefficients higher than CoCrMo and improve their micro-abrasion wear resistance. Furthermore, a wear-mode map was developed to identify the two and three body abrasion mechanisms and the transition between them modifying the concentration of SiC in the slurry and the magnitude of applied load.
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improved fracture toughness of boride coating developed with a diffusion annealing process
Surface & Coatings Technology, 2013Co-Authors: I Campossilva, M Floresjimenez, G Rodriguezcastro, E Hernandezsanchez, J Martineztrinidad, R TadeorosasAbstract:Abstract In this study, the fracture toughness of boride coatings formed at the surface of AISI 1045 steel was improved by means of a diffusion annealing process. First, the Boriding of AISI 1045 steel was performed by the powder-pack method at a temperature of 1223 K and a range of exposure times (8–12 h). The diffusion annealing process was conducted on the borided steels at a temperature of 1273 K with 8 h of exposure using a diluent atmosphere of SiC powder and bentonite. To establish the mechanical behavior of the boride coatings developed by both treatments, properties such as the real hardness and the Young's modulus were estimated at 50 μm from the surface using Vickers and Knoop testing, respectively. The fracture toughness of the boride coatings was estimated using a universal crack equation applicable independently of the cracking mode. The boride coating obtained by the Boriding process exhibited an intermediate cracking mode, while the coatings obtained by the diffusion annealing process showed a radial-median mode. The effect of the diffusion annealing process on the fracture toughness of the boride coatings revealed an increase of approximately 50% in comparison with the coatings developed by the powder-pack Boriding process.
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kinetics and boron diffusion in the feb fe 2 b layers formed at the surface of borided high alloy steel
Journal of Materials Engineering and Performance, 2012Co-Authors: I Campossilva, G Rodriguezcastro, M Ortizdominguez, C Tapiaquintero, M Y Jimenezreyes, E ChavezgutierrezAbstract:In the present study, boron diffusion in the surface layers of AISI M2 borided steels and the growth kinetics of the FeB/Fe2B layers were estimated. The Boriding of AISI M2 steel was performed according to the powder-pack method and was conducted at 1173-1323 K and at various exposure times. As a result of the Boriding process, the diffusion-controlled growth of the FeB/Fe2B layers was obtained at the surface of the high-alloy steel, and the kinetics of the growth process changed parabolically over time. The boron diffusion coefficients were estimated by solving two simultaneous equations based on the limits of the boron concentration in each layer, the boride incubation time, and the parabolic growth constant. With the proposed diffusion model, an expression, which describes the evolution of the FeB/Fe2B layers, was obtained. Moreover, the proposed model and diverse empirical models presented in the literature provided a good fit to the experimental data obtained for 10 h of exposure and different Boriding temperatures.
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diffusion model for growth of fe2b layer in pure iron
Surface Engineering, 2011Co-Authors: I Campossilva, M Ortizdominguez, M Keddam, Huseyin Cimenoglu, R Escobargalindo, M Eliasespinosa, N LopezperrusquiaAbstract:A simple diffusion model is proposed to estimate the growth kinetics of Fe2B layers created at the surface of pure iron. This model employs the mass balance equation at the Fe2B/substrate interface to evaluate the boron diffusion coefficient (DFe2B) in the boride layer. The Fe2B layers were formed using the paste Boriding process, at four temperatures with different exposure times. Analysing the results, the evolution of the parabolic growth constant (k) of the Fe2B layer is presented as a function of boron concentration and boride incubation time [t0(T)]. Furthermore, the instantaneous velocity of the Fe2B/substrate interface and the weight gain of borided pure iron were estimated for different Boriding temperatures. Finally, to validate the diffusion model, the boride layer thicknesses were predicted and experimentally verified for two Boriding temperatures and for different treatment times.
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formation and kinetics of feb fe2b layers and diffusion zone at the surface of aisi 316 borided steels
Surface & Coatings Technology, 2010Co-Authors: I Campossilva, M Ortizdominguez, C Tapiaquintero, O Bravobarcenas, Marco Antonio Donuruiz, D Bravobarcenas, M Y JimenezreyesAbstract:Abstract The kinetics of the FeB/Fe 2 B layers and diffusion zone at the surface of AISI 316 steels exposed to the powder-pack Boriding process were studied in this work. FeB/Fe 2 B layers and diffusion zone measurements were taken at different temperatures and exposure times to validate diffusion-controlled growth during the Boriding process. In order to obtain the boron diffusion coefficients at the FeB/Fe 2 B layers and diffusion zone, a mathematical model based on the mass balance at the growing interfaces was proposed. The activation energy values estimated for the FeB and Fe 2 B layers were 204 and 198 kJ mol − 1 respectively. In addition, the activation energy value obtained for the diffusion zone was 116 kJ mol − 1 . The diffusion model was extended to estimate the FeB/Fe 2 B layer thicknesses, and the depth of the diffusion zone at the temperature of 1243 K with 3 and 5 h of exposure, based on the experimental parameters ascribed to the Boriding process. Finally, the effects of the FeB/Fe 2 B growth and diffusion zone, on the weight gain of borided steels and on the instantaneous velocity of the interfaces were incorporated in the model.
K A Khor - One of the best experts on this subject based on the ideXlab platform.
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the effect of boron pack refreshment on the Boriding of mild steel by the spark plasma sintering sps process
Surface & Coatings Technology, 2008Co-Authors: X J Chen, L G Yu, K A Khor, G SundararajanAbstract:Mild steel samples were borided with and without boron pack refreshment using the spark plasma sintering (SPS) process. Results show that the borided samples with boron pack refreshment developed a thicker boride layer compared to that without boron pack refreshment for the same Boriding duration. When Boriding duration is t < 120 min, the Boriding growth in the samples borided with boron pack refreshment followed a parabolic growth pattern. In contrast, the boride growth in samples processed without boron-pack refreshment deviates from parabolic at t = 60 min. Computer simulation shows that the boron concentration change in the Boriding media during the Boriding process is an important factor affecting the composition and final thickness of the boride layer.
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boride layer growth kinetics during Boriding of molybdenum by the spark plasma sintering sps technology
Surface & Coatings Technology, 2006Co-Authors: L G Yu, K A Khor, G SundararajanAbstract:Abstract Molybdenum borides have potential industrial applications as abrasive, corrosion-resistant and electrode materials due to their high hardness values, chemical inertness, and electronic conductivity. In this work, boride layers are formed on the surface of Mo samples using a pack Boriding method with the assistant of the spark plasma sintering (SPS) technique. The process was performed in the temperature range 1000–1400 °C and with a holding time of 30 min at the preset temperature. The microstructure, microhardness, and fracture toughness of the molybdenum boride layer are investigated by optical microscopy, X-ray diffraction and microhardness indentations. Results showed that the boride layer, mainly composed of MoB, have thickness in the range ∼ 6–155 μm. The Boriding kinetics is studied by linking the boride layer thickness with the Boriding temperature. The activation energy and pre-exponential constant are estimated from the experimental results, and are found to be 218.8 J/mol and 1.41 cm2/s respectively. The MoB layers have a preferred orientation in the (002) direction, which is reflected by a distinct columnar growth observed in the optical micrographs of polished cross-sections of SPS samples.
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feb fe2b phase transformation during sps pack Boriding boride layer growth kinetics
Acta Materialia, 2005Co-Authors: X J Chen, K A Khor, G SundararajanAbstract:Abstract The iron boride layer growth kinetics in mild steel through the spark plasma sintering (SPS) pack-Boriding technique is investigated at 850 °C with different Boriding durations (maximum 240 min). Results show that both FeB and Fe 2 B layers form and grow on the mild steel surface with the FeB layer on the top of Fe 2 B sublayer in the samples with Boriding duration less than 90 min. However, at longer Boriding duration, the top FeB layer eventually ceases growing, starts to diminish, and, finally disappears completely by transforming into the Fe 2 B phase. Numerical simulation is implemented to explain this phenomenon. Subsequently, the diffusion coefficient of boron in FeB and Fe 2 B phase is obtained through fitting the experimental results into the model. The simulation results are found to be in good agreement with the experimental results, and the estimated diffusion coefficients of boron in FeB and Fe 2 B phases as 2.33 × 10 −9 and 4.67 × 10 −9 cm 2 /s, respectively. Both the simulation and experimental results reveal that the Fe 2 B mono-phase layer can be obtained through the transformation of FeB to Fe 2 B phase due to the depletion of boron concentration in the Boriding medium, and is indifferent to the formation of FeB phase at the very onset of the Boriding process. This provides a new approach to overcome the side effect of FeB formation in borided components.
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Boriding of mild steel using the spark plasma sintering sps technique
Surface & Coatings Technology, 2002Co-Authors: L G Yu, K A Khor, G SundararajanAbstract:The spark plasma sintering (SPS) technique was employed to perform Boriding of mild steel. A pack Boriding method that contained a silicon carbide-boron carbide powder pack mixture was utilized in this study. The process was performed in the temperature range 700-1000 °C for 30 min. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the microstructure and phase composition of the iron boride layers (FeB and Fe 2 B). Plotting lnD vs. 1/T expresses concisely the boride layer's growth rate constant (D) vs. temperature (T) relation. A linear relationship between lnD and 1/T is confirmed. The kinetics of SPS boronization are discussed, and the effect of SPS on boronization is studied. The results confirmed that SPS required significantly lower activation energy for accomplishing the Boriding operation.
L G Yu - One of the best experts on this subject based on the ideXlab platform.
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the effect of boron pack refreshment on the Boriding of mild steel by the spark plasma sintering sps process
Surface & Coatings Technology, 2008Co-Authors: X J Chen, L G Yu, K A Khor, G SundararajanAbstract:Mild steel samples were borided with and without boron pack refreshment using the spark plasma sintering (SPS) process. Results show that the borided samples with boron pack refreshment developed a thicker boride layer compared to that without boron pack refreshment for the same Boriding duration. When Boriding duration is t < 120 min, the Boriding growth in the samples borided with boron pack refreshment followed a parabolic growth pattern. In contrast, the boride growth in samples processed without boron-pack refreshment deviates from parabolic at t = 60 min. Computer simulation shows that the boron concentration change in the Boriding media during the Boriding process is an important factor affecting the composition and final thickness of the boride layer.
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boride layer growth kinetics during Boriding of molybdenum by the spark plasma sintering sps technology
Surface & Coatings Technology, 2006Co-Authors: L G Yu, K A Khor, G SundararajanAbstract:Abstract Molybdenum borides have potential industrial applications as abrasive, corrosion-resistant and electrode materials due to their high hardness values, chemical inertness, and electronic conductivity. In this work, boride layers are formed on the surface of Mo samples using a pack Boriding method with the assistant of the spark plasma sintering (SPS) technique. The process was performed in the temperature range 1000–1400 °C and with a holding time of 30 min at the preset temperature. The microstructure, microhardness, and fracture toughness of the molybdenum boride layer are investigated by optical microscopy, X-ray diffraction and microhardness indentations. Results showed that the boride layer, mainly composed of MoB, have thickness in the range ∼ 6–155 μm. The Boriding kinetics is studied by linking the boride layer thickness with the Boriding temperature. The activation energy and pre-exponential constant are estimated from the experimental results, and are found to be 218.8 J/mol and 1.41 cm2/s respectively. The MoB layers have a preferred orientation in the (002) direction, which is reflected by a distinct columnar growth observed in the optical micrographs of polished cross-sections of SPS samples.
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Boriding of mild steel using the spark plasma sintering sps technique
Surface & Coatings Technology, 2002Co-Authors: L G Yu, K A Khor, G SundararajanAbstract:The spark plasma sintering (SPS) technique was employed to perform Boriding of mild steel. A pack Boriding method that contained a silicon carbide-boron carbide powder pack mixture was utilized in this study. The process was performed in the temperature range 700-1000 °C for 30 min. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the microstructure and phase composition of the iron boride layers (FeB and Fe 2 B). Plotting lnD vs. 1/T expresses concisely the boride layer's growth rate constant (D) vs. temperature (T) relation. A linear relationship between lnD and 1/T is confirmed. The kinetics of SPS boronization are discussed, and the effect of SPS on boronization is studied. The results confirmed that SPS required significantly lower activation energy for accomplishing the Boriding operation.
Michael Kulka - One of the best experts on this subject based on the ideXlab platform.
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gas technique of simultaneous borocarburizing of armco iron using trimethyl borate
THE Coatings, 2020Co-Authors: Natalia Makuch, Piotr Dziarski, Michael KulkaAbstract:The gas Boriding process is an appropriate technique used for increasing the hardness and wear resistance of iron and steels. However, the boron halides (e.g., BCl3, BF3) are rarely used as a boron source during gas Boriding in industry due to the toxic character of these reagents. The possibility of the use of organic compounds as a boron source in plasma assisted processes was the instigation to determine the possibility of applying these agents for gas Boriding. In the present work trimethyl borate was used as an organic boron source. The use of a N2–H2–B(CH3O)3 atmosphere ensured the appropriate conditions for the simultaneous gas borocarburizing of Armco iron. The process was carried out at 1223 K (950 °C) for 2 h. The produced layer consisted of two zones: an outer zone containing a diffusion of boron atoms and an inner zone containing a diffusion of carbon atoms, under the outer zone. Due to the reduction of trimethyl borate with hydrogen, free atoms of carbon were released for the gas atmosphere. Therefore, there existed favorable conditions for carburizing. Unfortunately, the formation of a carburized layer was the reason for the difficult diffusion of boron atoms. As a consequence, the boron diffusion front was hindered, and the outer boride layer was relatively thin (ca. 7.8 µm). The boride layer contained only Fe2B phase, which was characterized by high hardness in the range from 1103 HV0.01 to 1546 HV0.01. The presence of iron borides in the outer layer was also the reason for increased wear resistance in comparison with untreated Armco iron.
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a kinetic model for the Boriding kinetics of aisi d2 steel during the diffusion annealing process
Protection of Metals and Physical Chemistry of Surfaces, 2018Co-Authors: Mourad Keddam, Michael KulkaAbstract:In this work, a diffusion model was proposed to estimate the boron activation energies for FeB and Fe2B layers during the pack-Boriding of AISI D2 steel at temperatures of 1223, 1253 and 1273 K for a treatment time varying between 2 and 10 h. This model considers the effect of boride incubation times during the formation of the FeB and Fe2B phases. To study the influence of diffusion annealing process on the Boriding kinetics of AISI D2 steel, the mass balance equations were modified in order to follow the evolution of boride layers as a function of annealing time for the specified Boriding parameters. Finally, the kinetic model was validated by a comparison of the experimental thicknesses of boride layers with the predicted ones at a temperature of 1243 K for 2, 4 and 6 h. A simple equation was then obtained for estimating the total time necessary to get a single boride layer (Fe2B) that depends on the Boriding parameters and on the thickness of each boride layer prior to the diffusion annealing process.
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Corrosion Behavior of Hard Boride Layer Produced on Nimonic 80A-Alloy by Gas Boriding
Transactions of the Indian Institute of Metals, 2017Co-Authors: Natalia Makuch, Michael Kulka, D. MikołajczakAbstract:The gas Boriding in N_2–H_2–BCl_3 atmosphere was applied in order to produce a wear resistant surface layer on Nimonic 80A-alloy samples. The microstructure, microhardness and corrosion resistance of the boride layer were investigated. The produced layer consisted mainly of the compact boride zone (with average thickness 71 μm), including the mixture of nickel and chromium borides of high hardness (up to 1861 HV). In order to evaluate the corrosion behavior, the two methods of corrosion tests were used: potentiodynamic corrosion test in 5% NaCl solution and immersion corrosion test in a boiling solution of H_2O, H_2SO_4 and Fe_2(SO_4)_3. The results showed that gas Boriding could provide the excellent corrosion resistance if the whole surface of a Nimonic 80A-alloy sample was covered by the continuous boride layer. Otherwise, as a consequence of selective Boriding, the significant difference in electrochemical potentials caused an accelerated uniform corrosion of the base material. Graphical Abstract
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fracture toughness of hard ceramic phases produced on nimonic 80a alloy by gas Boriding
Ceramics International, 2016Co-Authors: Natalia Makuch, Michael KulkaAbstract:Abstract A hard boride layer was produced on Nimonic 80A-alloy using gas Boriding in N 2 –H 2 –BCl 3 atmosphere. This process was carried out at 920 °C (1193 K) for 2 h. Proposed gas Boriding accelerated the diffusion of boron into the surface of workpiece in comparison with other acceptable methods of diffusion Boriding. The comparable thickness of boride layer was obtained after considerably shorter duration and at lower temperature. The microstructure, microhardness and fracture toughness were in detail studied. The boride layer consisted of a mixture of hard ceramic phases, i.e. nickel and chromium borides. The fracture toughness of borided layer was measured by microindentation technique using a Vickers diamond indenture under loading 100 gf (about 0.981 N). The measurements were carried out through a cross-section of the specimen in order to determine the differences in brittleness distribution. The changeable surface percentage of hard ceramic phases (chromium and nickel borides׳ mixtures) strongly influenced the fracture toughness which obtained the values from 0.609 to 4.436 MPa m 1/2 .
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modelling of paste Boriding process
Surface Engineering, 2015Co-Authors: R Kouba, M Keddam, Michael KulkaAbstract:In this work, a new model was suggested to simulate the paste Boriding process. This model was based on the numerical solving of the diffusion equations in both boride layer and substrate by taking into account the displacement of (Fe2B/substrate) interface. This diffusion problem with moving boundary was solved via a front tracking method. The numerical resolution was achieved by the finite difference method using an implicit scheme. The suggested model was able to predict the boride layer growth kinetics and the boron concentration profiles. The present model was validated by comparing the simulation results with the experimental data available in the literature. The obtained results were also compared to the models previously reported.