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Juan Asensiolozano - One of the best experts on this subject based on the ideXlab platform.
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optimization of thermal processes applied to hypoeutectic white cast iron containing 25 cr aimed at increasing Erosive Wear Resistance
Metals, 2020Co-Authors: Alejandro Gonzalezpocino, Florentino Alvarezantolin, Juan AsensiolozanoAbstract:Hypoeutectic white cast irons containing 25% Cr are used in very demanding environments that require high Resistance to Erosive Wear, for instance, the crushing and processing of minerals or the manufacture of cement. This high percentage in Cr, in turn, favors corrosion Resistance. The application of a Design of Experiments (DoE) allows the analysis of the effects of modifying certain factors related to the heat treatments applied to these alloys. Among these factors, the influence of prior softening treatment to facilitate the machining of these cast irons and the influence of the factors related to the destabilization of austenite, during both quenching and tempering, were analyzed. The precipitated phases were identified by X-ray diffraction (XRD), while the Rietveld structural refinement method was used to determine their percentages by weight. Erosive Wear Resistance was calculated using the ASTM G76 standard test method. It is concluded that the thermal softening treatment, consisting of 2 h at 1000 °C and 24 h at 700 °C, does not result in additional softening of the material compared to its as-cast state. Furthermore, it is observed that not only eutectic carbides influence Wear Resistance, but that the influence of the matrix constituent is also significant. It is also verified that the tempering treatment plays a decisive role in Wear Resistance. Temperatures of 500 °C and tempering times of 6 h increase the Wear Resistance and hardness of the aforementioned matrix constituent. Tempering temperatures of 200 °C lead to an increase in retained austenite content and the presence of M3C carbides versus mixed M7C3 and M23C6 carbides. The quench cooling medium is not found to have a significant influence on the hardness or Wear Resistance.
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influence of thermal parameters related to destabilization treatments on Erosive Wear Resistance and microstructural variation of white cast iron containing 18 cr application of design of experiments and rietveld structural analysis
Materials, 2019Co-Authors: Alejandro Gonzalezpocino, Florentino Alvarezantolin, Juan AsensiolozanoAbstract:High-Cr hypo-eutectic white cast irons are used in very demanding environments that require high Resistance to Erosive Wear. The influence on the microstructural variation and Erosive Wear Resistance of several fundamental factors related to the thermal treatments of these cast irons was analysed by means of a fractional Design of Experiments (DoE). These factors included the ones related to the destabilization of austenite. The precipitated phases were identified by X-ray diffraction (XRD), while the Rietveld structural refinement method was used to determine their percentages by weight. Erosion Wear Resistance was calculated using the test defined by ASTM G76. It was concluded that the quench cooling medium does not significantly influence either Erosive Wear Resistance or the proportion of martensite or retained austenite. The destabilization temperature is a key factor with respect to the percentage of retained austenite. In order to increase the amount of martensite and decrease the amount of retained austenite, temperatures not exceeding 1000 °C are required. An increase of 100 °C in the destabilization temperature can lead to a 25% increase in retained austenite. Moreover, tempering temperatures of around 500 °C favour an additional increase in the percentage of martensite. Erosive Wear commences on the matrix constituent without initially affecting the eutectic carbides. Once the deterioration of the matrix constituent surrounding these carbides occurs, they are released. High tempering times provide an increase in Resistance to Erosive Wear due to a second destabilization of austenite during the said tempering.
Juan Asensio-lozano - One of the best experts on this subject based on the ideXlab platform.
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Optimization of Thermal Processes Applied to Hypoeutectic White Cast Iron containing 25% Cr Aimed at Increasing Erosive Wear Resistance
Metals, 2020Co-Authors: Alejandro González-pociño, Florentino Alvarez-antolin, Juan Asensio-lozanoAbstract:Hypoeutectic white cast irons containing 25% Cr are used in very demanding environments that require high Resistance to Erosive Wear, for instance, the crushing and processing of minerals or the manufacture of cement. This high percentage in Cr, in turn, favors corrosion Resistance. The application of a Design of Experiments (DoE) allows the analysis of the effects of modifying certain factors related to the heat treatments applied to these alloys. Among these factors, the influence of prior softening treatment to facilitate the machining of these cast irons and the influence of the factors related to the destabilization of austenite, during both quenching and tempering, were analyzed. The precipitated phases were identified by X-ray diffraction (XRD), while the Rietveld structural refinement method was used to determine their percentages by weight. Erosive Wear Resistance was calculated using the ASTM G76 standard test method. It is concluded that the thermal softening treatment, consisting of 2 h at 1000 °C and 24 h at 700 °C, does not result in additional softening of the material compared to its as-cast state. Furthermore, it is observed that not only eutectic carbides influence Wear Resistance, but that the influence of the matrix constituent is also significant. It is also verified that the tempering treatment plays a decisive role in Wear Resistance. Temperatures of 500 °C and tempering times of 6 h increase the Wear Resistance and hardness of the aforementioned matrix constituent. Tempering temperatures of 200 °C lead to an increase in retained austenite content and the presence of M3C carbides versus mixed M7C3 and M23C6 carbides. The quench cooling medium is not found to have a significant influence on the hardness or Wear Resistance.
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Erosive Wear Resistance Regarding Different Destabilization Heat Treatments of Austenite in High Chromium White Cast Iron, Alloyed with Mo
Metals, 2019Co-Authors: Alejandro González-pociño, Florentino Alvarez-antolin, Juan Asensio-lozanoAbstract:With the aim of improving Erosive Wear Resistance in hypoeutectic white cast irons with 18% Cr and 2% Mo, several samples of this grade were subjected to different heat treatments at 1000 °C to destabilize the austenite. The dwell times at this temperature varied from 4 to 24 h and the samples were cooled in air or oil. The existing phases were identified and quantified by applying the Rietveld structural refinement method. The results were correlated with the hardness of the material and with the microhardness of the matrix constituent. The greatest Resistance to Erosive Wear was achieved in those samples that had a higher percentage of secondary carbides. The longer the dwell time at the destabilization temperature of austenite, the greater the amount of precipitated secondary carbides. However, the percentage of dissolved eutectic carbides is also higher. These eutectic carbides were formed as a result of non-equilibrium solidification. Low cooling rates (in still air) can offset this solution of eutectic carbides via the additional precipitation of secondary carbides in the 600–400 °C temperature range. A sharp decrease is observed in the percentage of retained austenite in those treatments with dwell times at 1000 °C equal to or greater than 12 h, reaching minimum values of around 2% volume. The percentage of retained austenite was always lower after oil quenching and the hardness of oil quenched samples was observed to be greater than those quenched in air. In these samples, the maximum hardness value obtained was 993 HV after a 12 h dwell, which result from the optimum balance between the percentages of retained austenite and of precipitated carbides.
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A Trade-Off between Mechanical Strength and Erosive Wear Resistance in AlSi12CuMgNi Alloy Used to Manufacture Fan Blades for Underground Mines
Metals, 2019Co-Authors: Florentino Alvarez-antolin, Elvira Segurado-frutos, Alejandro González-pociño, Alberto Cofiño-villar, Juan Asensio-lozanoAbstract:The axial fan blades used in underground mines are usually manufactured in AlSi12CuMgNi alloy (EN AC 48000). They must have a high mechanical strength to withstand the stresses resulting from the rotation speed of the rotor and a high Resistance to Erosive Wear caused by suspended particles from underground mining and transport operations. The aim of this paper is to determine the most suitable thermal treatment to simultaneously improve their mechanical strength and Erosive Wear Resistance. To this end, two solution treatments at 525 °C with cooling in water were analysed, as well as several ageing times at 170 °C. The crystalline phases present in the as-cast state were quantified by X-ray diffraction following quenching and different ageing processes. Furthermore, erosion Wear Resistance was measured by means of compressed air blasting with corundum particles according to ASTM G76 (2004). The highest Wear Resistance was obtained in the as-cast state using gravity die casting, with the presence of Al4Cu2Mg8Si7 and Al3CuNi. This Wear Resistance was higher than that obtained after the ageing treatment. However, a trade-off between mechanical strength and Wear Resistance was observed after 12 h ageing, where the hardness obtained exceeded 160 HV and the Wear Resistance became similar to that obtained in the as-cast state.
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A Trade-Off between Mechanical Strength and Erosive Wear Resistance in AlSi12CuMgNi Alloy Used to Manufacture Fan Blades for Underground Mines
MDPI AG, 2019Co-Authors: Florentino Alvarez-antolin, Elvira Segurado-frutos, Alejandro González-pociño, Alberto Cofiño-villar, Juan Asensio-lozanoAbstract:The axial fan blades used in underground mines are usually manufactured in AlSi12CuMgNi alloy (EN AC 48000). They must have a high mechanical strength to withstand the stresses resulting from the rotation speed of the rotor and a high Resistance to Erosive Wear caused by suspended particles from underground mining and transport operations. The aim of this paper is to determine the most suitable thermal treatment to simultaneously improve their mechanical strength and Erosive Wear Resistance. To this end, two solution treatments at 525 °C with cooling in water were analysed, as well as several ageing times at 170 °C. The crystalline phases present in the as-cast state were quantified by X-ray diffraction following quenching and different ageing processes. Furthermore, erosion Wear Resistance was measured by means of compressed air blasting with corundum particles according to ASTM G76 (2004). The highest Wear Resistance was obtained in the as-cast state using gravity die casting, with the presence of Al4Cu2Mg8Si7 and Al3CuNi. This Wear Resistance was higher than that obtained after the ageing treatment. However, a trade-off between mechanical strength and Wear Resistance was observed after 12 h ageing, where the hardness obtained exceeded 160 HV and the Wear Resistance became similar to that obtained in the as-cast state
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Optimization, by Means of a Design of Experiments, of Heat Processes to Increase the Erosive Wear Resistance of White Hypoeutectic Cast Irons Alloyed with Cr and Mo
MDPI AG, 2019Co-Authors: Alejandro González-pociño, Florentino Alvarez-antolin, Juan Asensio-lozanoAbstract:To identify the design parameters in heat treatments that have a significant effect on the Erosive Wear Resistance of hypoeutectic high chromium white cast irons, a design of experiment was applied to a white cast iron with 18wt.% Cr and 2wt.% Mo. The analyzed factors were the destabilization heat treatment of austenite (1000 or 1100 °C, for 4 or 8 h), different quench cooling media (in air or oil), different tempering treatments (200 or 500 °C, for 3 or 6 h), and the application of an ionic nitriding treatment. Despite what was expected, the nitriding treatment was not found to have a significant effect on said Wear Resistance. However, it is concluded that the highest Wear Resistance is obtained with the shortest dwell time at the destabilization temperature (4 h), quenching in oil, and with the shortest tempering times (3 h). Among the nitrided samples, the highest nitrided layer thicknesses were obtained when the destabilization temperature of the austenite was 1000 °C and the tempering temperature was 200 °C
Carlos Roberto Camello Lima - One of the best experts on this subject based on the ideXlab platform.
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Slurry erosion Resistance of thermally sprayed Nb2O5 and Nb2O5+WC12Co composite coatings deposited on AISI 1020 carbon steel
Ceramics International, 2020Co-Authors: Hipólito Carvajal Fals, Maria Júlia Xavier Belém, Luciano Augusto Lourençato, Mario Sánchez Orozco, Carlos Roberto Camello LimaAbstract:Abstract Niobium pentoxide (Nb2O5) has excellent physicochemical properties regardless of the processing technology. The interest in its application in several fields has increased, especially in corrosive environments. However, when higher Wear Resistance is required, this material shows poorer results when compared to carbide base metals. In this work, the Erosive Wear Resistance of thermally sprayed Nb2O5 coatings with and without carbide addition was evaluated. 500 μm thick coatings of Nb2O5 and Nb2O5 + 25% WC12Co were deposited onto AISI 1020 steel by flame spray. The coatings were characterized in the cross section by SEM/EDS techniques. Microhardness (HV0.05) and fracture toughness (KIC) measurements by the Vickers indentation toughness test (VIT) technique were performed on the cross section of the coatings. Erosive Wear Resistance was determined using a container tribometer with Erosive mixing at a particle velocity of 9.33 m/s and 90° particle incidence angles. A nonparametric Mann-Whitney statistical analysis was performed on the results, considering a p significance level of 0.05. The addition of 25% WC12Co to the Nb2O5 increased the microhardness and fracture toughness of the coating. Nb2O5+ WC12Co composite coatings showed higher Resistance to Erosive Wear, showing 81 ± 9 mg mass loss, 51% lower than the Nb2O5 coating (157 ± 6 mg).
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Evaluation of the Adhesion and Slurry Wear Erosion of Nb_2O_5 Coatings Applied by Flame Spray
Metallurgical and Materials Transactions A, 2019Co-Authors: Maria Júlia Xavier Belém, Hipólito Carvajal Fals, Angel Sánchez Roca, Carlos Roberto Camello LimaAbstract:Niobium pentoxide (Nb_2O_5) has excellent chemical and thermodynamic stabilities, characteristics that have accelerated the applications of this material in the form of coatings to protect against corrosive processes. However, few studies have evaluated its performance in Wear protection applications. In this research, the slurry Wear erosion Resistance of Nb_2O_5 coatings deposited by flame spray was studied. The microstructural characterization of the coatings was performed by optical microscopy and scanning electron microscopy (SEM) assisted by chemical analysis by energy dispersive X-ray spectroscopy (EDS). Adhesion of the coatings was determined by the adhesion test (ASTM C633-13). Image analysis was used for the quantitative study of the adhesion tested areas and porosity of the coatings. Erosive Wear Resistance was determined using a container tribometer with Erosive mixing at a particle velocity of 9.33 m/s and two particle incidence angles. The thinner coatings had fewer microstructural defects, such as pores and microcracks, and greater adhesive strength. The thicker coatings presented a cohesive failure mode. When the impact angle of the erodent particles was 90 deg, the thickness of the Nb_2O_5 coatings should not exceed 350 μ m. Nb_2O_5 coatings applied by flame spray showed good Resistance to slurry Wear erosion, besides inherent low cost and flexibility of the process.
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Evaluation of the Adhesion and Slurry Wear Erosion of Nb2O5 Coatings Applied by Flame Spray
Metallurgical and Materials Transactions A, 2019Co-Authors: Maria Júlia Xavier Belém, Hipólito Carvajal Fals, Angel Sánchez Roca, Carlos Roberto Camello LimaAbstract:Niobium pentoxide (Nb2O5) has excellent chemical and thermodynamic stabilities, characteristics that have accelerated the applications of this material in the form of coatings to protect against corrosive processes. However, few studies have evaluated its performance in Wear protection applications. In this research, the slurry Wear erosion Resistance of Nb2O5 coatings deposited by flame spray was studied. The microstructural characterization of the coatings was performed by optical microscopy and scanning electron microscopy (SEM) assisted by chemical analysis by energy dispersive X-ray spectroscopy (EDS). Adhesion of the coatings was determined by the adhesion test (ASTM C633-13). Image analysis was used for the quantitative study of the adhesion tested areas and porosity of the coatings. Erosive Wear Resistance was determined using a container tribometer with Erosive mixing at a particle velocity of 9.33 m/s and two particle incidence angles. The thinner coatings had fewer microstructural defects, such as pores and microcracks, and greater adhesive strength. The thicker coatings presented a cohesive failure mode. When the impact angle of the erodent particles was 90 deg, the thickness of the Nb2O5 coatings should not exceed 350 μm. Nb2O5 coatings applied by flame spray showed good Resistance to slurry Wear erosion, besides inherent low cost and flexibility of the process.
R. Raman - One of the best experts on this subject based on the ideXlab platform.
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Improving the Wear Behavior of WC-CoCr-based HVOF Coating by Surface Grinding
Journal of Materials Engineering and Performance, 2009Co-Authors: A. K. Maiti, N. Mukhopadhyay, R. RamanAbstract:WC-CoCr-based high velocity oxy fuel (HVOF) coatings are being used for several components which are prone to severe erosion or abrasion. In this study, the HVOF coating was applied by liquid fuel-based equipment. These coated samples were subjected to surface grinding of various depths (100, 200, and 300 μm). Hardness test after surface grinding showed that the coating hardness increased by 33% after grinding to a depth of 200 μm (1472 Hv). The residual stress after different depths of grinding was measured using x-ray diffraction. It showed that the compressive residual stress of coating increased with grinding. Increase in hardness of the coating (after grinding) is believed to be due to the increase in compressive residual stress. The abrasive Wear Resistance increased after grinding to a depth of 100 μm thickness and remained constant during successive grinding. In contrast, the Erosive Wear Resistance increased the most when the grinding thickness was 200 μm. It is concluded that the surface grinding of coatings helps in increasing abrasive and Erosive Wear Resistance. The increase in microhardness of the coating is believed to be the reason for high Wear Resistance. SEM studies of worn out surface show carbide grain pull out due to removal of softer phase, i.e. cobalt and chromium, and is followed by tungsten carbide grain pull out.
J B C Wu - One of the best experts on this subject based on the ideXlab platform.
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Wear corrosion and cracking Resistance of some w or mo containing stellite hardfacing alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: J B C WuAbstract:Abstract Traditional Stellite hardfacing materials are Co–Cr–W–C type of alloys. A series of new Stellite alloys are developed based on Co–Cr–Mo–C system. Immersion–corrosion test is conducted in 10% HNO3 oxidizing acid at boiling temperature, in 10% H2SO4 reducing acid at 66 °C and in 5% HCl reducing acid at 40 °C to evaluate the general corrosion Resistance of the Stellite alloys. The abrasive, adhesive and Erosive Wear Resistance is investigated on these two types of Stellite alloys. Critical plastic shear strain is obtained by conducting scratch test to evaluate the Resistance to cracking. The W-containing Stellite alloys have better corrosion Resistance in oxidizing acid. The Mo-containing Stellite alloys exhibit unusual combination of excellent Wear Resistance and corrosion Resistance in reducing environments. Mo-containing Stellite alloys also have adequate cracking Resistance compared with the W-containing Stellite alloys.