CoB Ön Alaşımlarının Alüminotermik Redüksiyon Yöntemiyle Üretilmesi ve Termokimyasal Modellenmesi

Yıl 2020, , 436 - 447, 31.05.2020

Ahmet Turan , Mehmet Buğdaycı

https://doi.org/10.31202/ecjse.652028

Öz

Bu çalışmada CoB ön alaşımlarının metalotermik (alüminotermik) redüksiyon yöntemi ile üretim parametrelerinin belirlenmesi üzerine çalışılmıştır. Çalışmada redüktan olarak aluminyum kullanılmış ve redüktan stokiyometrisindeki değişimin ürünler üzerindeki etkisi incelenmiştir. Redüksiyon sistemi FactSage 7.1 programıyla termokimyasal olarak modellenmiş, deneysel sonuçlar ile tutarlı bulgulara ulaşılmıştır. Deneysel çalışmalar sonunda elde edilen ürünler, X-ışınları difraksiyon spektrometrisi (XRD), optik mikroskobi, taramalı elektron mikroskobisi (SEM-EDS) ve mikro-vickers sertlik ölçüm yöntemleri ile karakterize edilmiştir. Karakterizasyon sonuçları incelendiğinde metal oluşum miktarının artan aluminyum stokiyometrisi ile yükseldiği gözlenirken, hedef alaşıma en yakın kompozisyonun Al stokiyometrisinin en düşük olduğu %100’lük oranda elde edildiği görülmüştür. Ürünlerin sertlik değişimi incelendiğinde, hedef alaşıma en yakın kompozisyonda olan %100 stokiyometrik aluminyum içeren deneyde 950 HV1’lik değer ile en yüksek sertliğe ulaşıldığı belirlenmiş, yapıya giren Co-Al fazının alaşımın sertlik değerini olumsuz etkilediği görülmüştür. Optik mikroskop incelemeleri sonucunda açık ve koyu renkten oluşan iki faz görülmüş, koyu renkli fazın Co-Al bileşiminden oluşan yapı olduğu sonucuna varılmıştır. Artan Al miktarıyla koyu renkli bu fazın miktarının da arttığı görülmüş, gerek kompozisyondaki farklılıkların, gerekse sertlikteki düşüşlerin bu sebeple oluştuğu düşünülmektedir. Termokimyasal incelemeler ve deneysel çalışmalar sonucunda bu alaşımın alüminotermik redüksiyon ile üretilebileceği ve yapılabilecek ilaveler ile istenilen kompozisyonda alaşım üretiminin mümkün olabileceği sonucuna varılmıştır. Gerçekleştirilen literatür taramasında CoB alaşımlarının alüminotermik olarak üretimine ilişkin çalışma bulunmamış ve bu çalışmanın ilgili ön alaşımın metalotermik üretimi üzerine gelecek çalışmalara yön gösterici olacağı kanaati oluşmuştur.

Anahtar Kelimeler

CoB, Metalotermik redüksiyon, Pirometalurji

Production and Thermochemical Modelling of CoB Pre-Alloys through Aluminothermic Reduction Method

Öz

In the present study, experiments were carried out to determine the production parameters of CoB pre-alloys through metallothermic (aluminothermic) reduction method. The aluminium was used as reductant in this study and, effects of Al stoichiometry on product properties were investigated. Reduction system was modelled by using FactSage 7.1 thermochemical simulation program and, results were consistent with experimental results. Experimental products were characterized by means of X-rays diffraction spectrometry (XRD), optical microscopy, scanning electron microscopy (SEM-EDS) and micro-vickers hardness testing methods. When characterization results were investigated, it was understood that the amount of reduced metal increased with the increase in aluminium stoichiometry whilst the closest composition to the target alloy was obtained in the experiment with the lowest Al stoichiometry as 100%. In hardness results, the highest value was measured as 950 HV1 for the sample produced with 100% Al stoichiometry. On the other hand, the increase in Al stoichiometry caused the increase in CoAl formation in microstructures and, therefore hardness values decreased. In optical microscopy micrographs, two phases, dark and bright, were observed in microstructures and, it was anticipated that dark phases were CoAl. The ratio of dark CoAl phase increased with the increase in aluminium stoichiometry and, it was predicted that it was the reason of either composition change and fall in hardness values. As a result of thermochemical investigations and experiments, it was thought that the alloy can be produced by using aluminothermic reduction method and, it is possible to produce almost pure samples with some basic modifications. There are no accounts in the literature on the aluminothermic reduction of CoB pre-alloys and, it was predicted that the present study will help further studies in this area.

Anahtar Kelimeler

CoB, Metallothermic Reduction

Kaynakça

• [1] Yücel O., Addemir O., Tekin A., 1992, ‘‘The Optimization of Parameters for The Carbotermic Production of Ferroboron”, INFACON 6. Cape Town, Vol. 1, 1992, pp. 285-289.
• [2] US 4133681 Allied Chemical Corp. Jan. 1979.
• [3] Hasegawa, R., 1981, “Aplication of Rapidly Solidified Metals in USA and in Japan”, Allied Signal Inc. Metglass Products, 6 Eastmas Road, Rapsippony NJ 0705 Y, USA.
• [4] Jaschinski, W. 1981, “Amorphe Metalle-Entwickking Einer Neuen Werkstoffklasse”, Tech. Mitt. Krupp, Forsch.Ber. Band 39. lt. 1.
• [5] Mitov M., Popov A., Dragieva, I. 1999, Nanoparticles produced by borohydride reduction as precursors for metal hydride electrodes Journal of Applied Electrochemistry 29: 59. https://doi.org/10.1023/A:1003439301820
• [6] Wang Y.D., Ai X.P., Yang H.X. 2004, Electrochemical Hydrogen Storage Behaviors of Ultrafine Amorphous Co−B Alloy Particles Chem. Mater. 16 5194, https://doi.org/10.1021/cm049252f.
• [7] Wang Y.D., Ai X.P., Cao Y.L., Yang H.X. 2004, Exceptional electrochemical activities of amorphous Fe–B and Co–B alloy powders used as high capacity anode materials Electrochem. Commun. 6 780, https://doi.org/10.1016/j.elecom.2004.06.002.
• [8] Tong D.G., Chu W., Zeng X.L., Tian W., Wang D., Synthesis of mesoporous Co–B alloy in room-temperature ionic liquids and its electrochemical properties Mater. Lett. 63 (2009) 1555, https://doi.org/10.1016/j.matlet.2009.04.016.
• [9] Lu D.S., Li W.S., Jiang X., Tan C.L., Zeng R.H., 2009, Magnetic field assisted chemical reduction preparation of Co-B alloys as anode materials for alkaline secondary battery. J Alloys Compd, 485 , pp. 621-626, doi:10.1016/j.jallcom.2009.06.060.
• [10] Patel N., Miotello A., Progress in Co-B related catalyst forhydrogen production by hydrolysis of boron-hydrides: areview and the perspectives to substitute noble metals. Int J Hydrogen Energy 2015;40:1429–64.
• [11] Hernandez A.M., Albores A.M., Duran E.A., Flores J.G., Bueno J.J.P., Meas Y., Trejo G. 2019, Effect of heat treatment on the hardness and wear resistance of electrodeposited Co-B alloy coatings, j mater restechno l.;8(1):960–968, https://doi.org/10.1016/j.jmrt.2018.07.007
• [12] Prado RA, Facchini D, Mahalanobis N, Gonzalez F, Palumbo G. 2009, Electrodeposition of nanocrystalline cobalt alloy coatings asa hard chrome alternative. In: DoD Corrosion Conference.
• [13] Huang YS, Cui FZ. 2007, Effect of complexing agent on themorphology and microstructure of electroless deposited Ni-Palloy. Surf Coat Technol; 201:5416–8.
• [14] Alirezaei S, Monirvaghefi SM, Salehi M, Saatchi A. Wear behavior of Ni-P and Ni-P-Al2O3 electroless coatings. Wear 2007;262:978–85.
• [15] Monteiro OR, Murugesan S, Khabashesku V. 2015, Electroplated Ni-B and Ni-B metal matrix diamond nano composite coatings. Surf Coat Technol 2015;272:291–7.
• [16] Ogihara H, Udagawa K, Saji T. 2012, Effect of boron content and crystalline structure on hardness in electrodeposited Ni-Balloy films. Surf Coat Technol 2012;206:2933–40.
• [17] López JR, Méndez PF, Pérez-Bueno JJ, Trejo G, Stremsdoerfer G, Meas Y. 2016, The effect of boron content, crystal structure,crystal size on the hardness and the corrosion resistance ofelectrodeposited Ni-B coatings. Int J Electrochem Sci 2016;11:4231–44.
• [18] Nava D, Dávalos CE, Martínez-Hernández A, Manríquez F, Meas Y, Ortega-Borges R, et al. 2013, Effects of heat treatment onthe tribological and corrosion properties of electrodeposited Ni-P alloys. Int J Electrochem Sci 2013;8:2670–81.
• [19] Ziyuan S, Deping W, Zhimin D. 2004, Surface strengthening purecopper by Ni-B coating. Appl Surf Sci 2004;221:62–8.
• [20] Oraon B, Majumdar C, Ghosh B. 2008, Improving hardness ofelectroless Ni-B coatings using optimized deposition conditions and annealing. Mater Des 2008;29:1412–8.
• [21] Ogihara H, Wang H, Saji T. 2014, Electrodeposition of Ni-B-SiC composite films with high hardness and wear resistance. Appl Surf Sci 2014;296:108–13.
• [22] Narayanan TSN, Krishnaveni K, Seshadri SK. 2003,Electroless Ni-P/Ni-B dúplex coatings: preparation and evaluation of microhardness, wear and corrosion resistance. Mater Chem Phys 2003;82:771–9.
• [23] Azouani O., Keddam M., Brahimi A., Sehisseh A., Diffusion kinetics of boron in the X200CrMoV12 high-alloy steel, J. Min. Metall. Sect. B-Metall. 51 (1) (2015) 49 (B).
• [24] Stewart K., Boronizing protects metals against wear, Adv. Mater. Process. 155 (1997) 23.
• [25] Kartal G., Kahvecioglu O., Timur S., Investigating the morphology and corrosion behavior of electrochemically borided steel, Coat. Technol. 200 (11) (2006) 3590.
• [26] Dearnley P.A., Bell T., Engineering the surface with boron based Materials, Surf. Eng. 1 (1985) 203.
• [27] Minkevich A.N., Diffusion boride layers in metals, Met. Sci. Heat Treat. 3 (1961) 347.
• [28] Bugdayci M., Alkan M., Turan A., Yücel O., Production of iron based alloys from mill scale through metallothermic reduction, High Temperature Materials and Processes, 37 (9-10) (2018) 889-898. DOI: https://doi.org/10.1515/htmp-2017-0073
• [29] Bugdayci M., Turan A., Alkan M., Yucel O., Effect of reductant type on the metallothermic magnesium production process, High Temperature Materials and Processes, 37 (1) (2018) 1-8. DOI: https://doi.org/10.1515/htmp-2016-0197
• [30] Turan A., Bugdayci M., Yucel O., Self-propagating high temperature synthesis of TiB2, 34 (2) (2015) 185-193. DOI: https://doi.org/10.1515/htmp-2014-0021
• [31] Benzeşik K., Turan A., Yücel O., Volume combustion synthesis of Li4SiO4, XV. International Symposium on Self-propagating High-temperature Synthesis (SHS 2019), 16-20 Eylül 2019, Moskova, Rusya.
• [32] Kaplan S.S., Sonmez M.S., Single step solution combustion synthesis of hexagonal WO3 powders as visible light photocatalysts, 240 (2020) 122152. DOI: https://doi.org/10.1016/j.matchemphys.2019.122152