 Subjects -> METALLURGY (Total: 58 journals)
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- Effect of alloying with Ni, Cr and Al on the atmospheric and
electrochemical corrosion resistance of ferritic ductile cast irons
Authors: Andrea Niklas, María Ángeles Arenas, Susana Méndez, Ana Conde, Rodolfo González-Martínez, Juan José de Damborenea, Jon Sertucha
Abstract: The corrosion control of ductile cast irons becomes a technological challenge when supplying castings to customers due to the high reactivity of this alloy in contact with air. An interesting alternative to the protective systems such as coatings or corrosion inhibitors included in packaging processes is the chemical modification of the cast alloys by means of alloying elements addition which are able to improve the corrosion resistance of ductile cast irons. Ni, Cr and Al added to the cast alloys significantly affect their structure and properties, among them their corrosion response, when exposed to air. It has been observed that Ni and Al improve the corrosion behaviour while Cr additionally promoted pearlite and carbides formation. The results from the corrosion tests performed on ductile cast iron alloys which contain these three elements are discussed in the present work.
PubDate: 2022-04-13
DOI: 10.3989/revmetalm.216
Issue No: Vol. 58, No. 1 (2022)
- Effects of cooling media on the formation of Martensite-Austenite
microconstituent in a HSLA steel
Authors: Zayra Moreno-Fabian, Gregorio Solís-Bravo
Abstract: The effect of different cooling conditions on the formation of Martensite-Austenite (MA) in a High - Strength Low - Alloy (HSLA) steel was assessed. The MA constituent is detrimental to impact toughness in pipeline applications, so the purpose of this research was to minimize its presence through the choice of effective cooling media and optimal parameters such as the cooling rate and final cooling temperature. The volume fraction, size and morphology of MA was evaluated by selective etching and corroborated trough SEM and EBSD. Vickers hardness testing agreed with the measured MA volume fractions. The sample cooled with helium gas and salt bath with the lowest final cooling temperature of 460 °C, exhibited a fine mixture of ferritic bainite, granular bainite and the lowest volume fraction of MA, along with MA smaller particle average size. A high cooling rate and a decrease in the final cooling temperature resulted in a decrease in the volume fraction and average particle size of MA.
PubDate: 2022-04-12
DOI: 10.3989/revmetalm.214
Issue No: Vol. 58, No. 1 (2022)
- The evolution of phases in FeNiCoCrCuBx high entropy alloys produced
through microwave sintering and vacuum arc melting
Authors: İrem B. Algan Şimşek, Sükrü Talaş, Adem Kurt
Abstract: Microwave heating and sintering techniques are applied to various production lines and material systems to improved their microstructure and mechanical properties in comparison to conventional means of production. These techniques also consume less power and energy compared to conventional heating methods. In this study, the production of high entropy alloys (HEA) by arc melting was carried out with specimens made from compacted and sintered elemental powders; the sintering process of alloy powders prior to remelting prevents certain problems such as porosity and uneven mixing that may occur during casting. We investigated the effects of conventional and microwave sintering processes prior to remelting and casting on structure and properties of FeNiCoCrCuBx HEA. Our results show that microwave sintering changes the size and shape of phases and microstructure of the alloy by affecting the liquid-phase separation mechanism. Three-point bending strength and ductility of alloys produced by microwave sintering were superior to conventional sintering.
PubDate: 2022-04-12
DOI: 10.3989/revmetalm.215
Issue No: Vol. 58, No. 1 (2022)
- Production and characterization of AA2014-B4C surface-modificated
composite via the squeeze casting technique
Authors: Ahmet Kabil, Çağlar Yüksel, Mustafa Çiğdem
Abstract: Metal matrix composite (MMCs) materials provide superiority to monolithic materials in various mechanical properties such as tensile, yield, abrasion resistance, impact resistance by adding reinforcements such as B4C, SiC, Al2O3. While liquid metal processes offer an important advantage, such as low-cost production in high volumes, the heterogeneous clustering of reinforcements in the matrix and the formation of porosity in the area between the reinforcement and matrix pose a problem for composite production. The squeeze casting method stands out in composite production due to its low cost, suitability for mass production, allowing high reinforcement ratio, and ease of homogeneous distribution of reinforcements. In this study, a composite layer reinforced with B4C was produced with a thickness of 1 and 2 mm on a substrate of aluminum 2014 wrought alloy using the squeeze casting method. The mechanical properties of the composite materials produced were characterized via tensile, wear, impact, and hardness tests, and were examined with the help of Scanning Electron Microscopy (SEM). It has been observed that the composite region contains 50 vol.% of B4C reinforcement and the particles of reinforcement were homogeneously distributed into the matrix. All results of the tests mentioned above are better than those obtained in the monolithic 2014 aluminum alloy.
PubDate: 2022-04-12
DOI: 10.3989/revmetalm.217
Issue No: Vol. 58, No. 1 (2022)
- Industrial scale extrusion performance of cryogenically processed DIN 100
Cr6 and DIN 21NiCrMo2 steels
Authors: Bahadır Karaca, Levent Cenk Kumruoğlu
Abstract: The effects of diferent heat and cryogenic (sub-zero) treatment parameters such as temperature and holding time on the microstructure (amount of retained austenite) and hardness of extrusion molds produced from the 21NiCrMo2 and 100Cr6 steels were investigated. The 21NiCrMo2 grade extrusion die was carburized for 22.5 h in an endogas (25% CO, 35% N2, 40% H2) atmosphere at 920 °C. At the end of the carburization process, the temperature was kept at 850 °C, which is the austenitization temperature, for 2 h, followed by cooling in oil at 80 °C and remaining in oil for 45 minutes. The carburizing process was not performed for the extrusion molds made of 100Cr6 steel grade. Only the austenitizing heat treatment at 850 °C (holding for 2 h) was carried out in this steel. The steel molds which were produced with 21NiCrMo2 and 100Cr6 steels were cryogenically treated at -120 °C for 2 h and subsequently tempered at 150 °C for 1.5 h. As a result of the cryogenic treatment, the hardness of 21NiCrMo2 steel increased to 840 Hv and the wear resistance of the extrusion die surface was improved. The amount of residual austenite decreased from 20% to 6% after the cryogenic treatment. Due to the effect of the cryogenic process, the surface hardness of the 100Cr6 steel sample increased to ~870 Hv, which implies an increase of 4.5%, due to the transformation of residual austenite to martensite. The mass loss, during the wear tests, of the hardened extrusion dies was reduced from 0.1420 mg to 0.0221 mg. The notch impact strength value measured in this condition was 20 J. The 100Cr6 steel after the cryogenic treatment was used to extrude 12 tons of Al alloy in an industrial press. This amount of material is 30% lower than for hot work tool steel. On the other hand, the 100Cr6 steel is more economical and heat treatment is more practical. The extrusion performance of 21NiCrMo2 steel was 50% lower than the hot work tool steel.
PubDate: 2022-04-05
DOI: 10.3989/revmetalm.212
Issue No: Vol. 58, No. 1 (2022)
- Investigation on dry sliding wear behavior of AA5083/nano-Al2O3 metal
matrix composites
Authors: R. Suresh, G. Joshi Ajith, N.G. Siddeshkumar
Abstract: The tribological behavior of aluminum alloy (AA5083)/nano-Al2O3 metal matrix composites with varying reinforcement percentage of 2, 4, 6 and 8 wt.-% nano-Al2O3 particles was studied. The Al/nano-Al2O3 composites were prepared using a stir casting route. The scanning electron microscopy (SEM) images of prepared specimens suggested nearly uniform dispersion of nanoparticles in the Al matrix. Sliding wear behavior was studied using a pin-on-disc test rig. The plan of experiments was in accordance with Taguchi’s L25 orthogonal array using three process parameters at five levels viz. reinforcement weight percentage, applied load and sliding distance. The obtained results reveal that nano-particles reinforced composites exhibited better wear resistance. While the main effects plot suggested that wear increases with an increase in the load, the sliding distance and decreases with an increase in the reinforcement percentage. The analysis of variance (ANOVA) illustrated that the sliding distance was the most significant contributing parameter. The worn surface morphology of the specimen tested under the highest load condition revealed the occurrence of abrasive wear phenomenon.
PubDate: 2022-03-30
DOI: 10.3989/revmetalm.213
Issue No: Vol. 58, No. 1 (2022)
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