Investigation of microstructures, mechanical properties, wear behavior and machinability of EN-GJS-500-7 (GGG50) grade ductile cast irons having modified chemical composition

Abstract

Ductile cast irons (DI) are promising candidates for forged steels due to their lower density (10-15 %), lower production cost and good specific strength. The mechanical properties of DIs are heavily influenced by matrix (ferrite, pearlite, or ferrite+pearlite), type and concentration of alloying elements (Si, Cu, Sn, Cr and Ni. etc). The pearlite phase, which is stronger and harder than ferrite phase, depends not only on the chemical composition but also the cooling rate of sections having various section thickness. In this situation non-uniform microstructure and mechanical properties occur between the thick and thin sections of the parts. In this manner solid solution strengthened (with Si) ferritic DIs become prominent with more uniform microstructure and mechanical properties. In the present study, the microstructural properties, mechanical properties (tensile properties, hardness, and impact energy), wear resistance and tool life (turning machining operations) of EN-GJS-500-7 grade ductile cast irons, having modified composition (increased amount of Si, decreased amount of C and pearlite former), are studied in detail. The resultant microstructures and mechanical properties are compared with those for having traditional composition. For modified composition, the ferrite (solid solution strengthened with excess Si) amount considerably increases, and so the cast part exhibits uniform hardness distribution among the surface layer and center regions). In addition, the yield strength and the ultimate tensile strength (UTS) of the modified composition is slightly lower than those for traditional composition. In addition, modified composition exhibits better wear resistance (lower wear loss and friction coefficient) and longer tool life compared to those for traditional composition. As a result, an alloy with improved mechanical properties and good machinability has begun to be applied industrially

Keywords

• Ductile cast iron
• Chemical composition
• Microstructure
• Mechanical Properties
• Wear behavior

Geliştirilmiş kimyasal bileşime sahip EN-GJS-500-7 (GGG50) kalite küresel grafitli dökme demirlerin mikroyapısının, mekanik özelliklerinin aşınma davranışının ve işlenebilirliğinin incelenmesi

Öz

Küresel grafitli dökme demirler (KGDD), düşük yoğunlukları (%10-15), düşük üretim maliyetleri ve iyi özgül mukavemetleri nedeniyle dövme çelikler için aday malzemeler olarak düşünülmektedir. KGDD'lerin mekanik özellikleri matris tipine (ferrit, perlit veya ferrit + perlit), alaşım elementlerinin türü ve konsantrasyonuna (Si, Cu, Sn, Cr ve Ni. vb.) bağlıdır. Ferrit fazına göre daha güçlü ve daha sert olan perlit fazı sadece kimyasal bileşime değil aynı zamanda farklı kesit kalınlığına sahip parçalarda soğuma hızına da bağlıdır. Bu durum parçaların kalın ve ince bölümleri arasında farklı mikroyapıların oluşmasına ve farklı mekanik özelliklerin ortaya çıkmasına sebep olmaktadır. Bu durumda katı çözeltiyle güçlendirilmiş (Si) ferritik KGDD'ler daha homojen mikroyapı ve mekanik özelliklere sahip olarak öne çıkmaktadır. geliştirilmiş bileşime sahip (arttırılmış Si miktarı, azaltılmış C miktarı ve perlit oluşturucu) EN-GJS-500-7 kalite KGDD’lerin mikroyapısal ve mekanik özellikleri (çekme özellikleri, sertlik ve darbe enerjisi), aşınma direnci ve takım ömrü (tornalama sırasında) detaylı biçimde incelenmiştir. Elde edilen mikroyapılar ve mekanik özellikler, geleneksel bileşime sahip KGDD’lerin mikroyapı ve mekanik özellikleri ile karşılaştırılmıştır. Geliştirilmiş bileşim için, ferrit (fazla Si ile güçlendirilmiş katı çözelti) miktarı önemli ölçüde artmakta ve bunun sonucunda döküm parçanın yüzey bölgeleri ile merkez (çekirdek) arasında düzgün bir sertlik dağılımı elde edilmiştir Ek olarak, geliştirilmiş bileşimin akma ve çekme mukavemeti , geleneksel bileşime göre çok az daha düşüktür. Buna ilaveten, geleneksel bileşime kıyasla geliştirilmiş bileşimin daha üstün aşınma direncine (daha düşük aşınma kaybı ve sürtünme katsayısı) sahip olduğu ve talaşlı imalat süreçlerinde uzun takım ömrünü uzattığı tespit edilmiştir. Sonuç olarak, geliştirilmiş mekanik özelliklere ve iyi işlenebilirliğe sahip bir alaşım endüstriyel olarak uygulanmaya başlanmıştır.

Anahtar Kelimeler

• Küresel grafitli dökme demir
• Kimyasal bileşim
• Mikroyapı
• Mekanik Özellikler
• Aşınma Davranışı

Kaynakça

1. [1] Pribulová A, Futaš P, Pokusova M. “Influence of charge composition on EN-GJS-500-7 ductile iron properties in foundry operating conditions”. Materials Science Forum, 998, 42-47, 2020.
2. [2] Veljačić Z, Grilec K. “Increasing the wear resistance of marine diesel engines elements made of ductile iron”. NAŠE MORE: International Journal of Maritime Science and Technıology, 68(3), 150-156, 2021.
3. [3] Pacha-Gołębiowska H, Piekarska W. “Mechanical properties of ductile cast iron relation to the charge elements”. IOP Conference Series: Materials Science and Engineering, 1199(1), 012022, 2021.
4. [4] Gouveia RM, Silva FJ, Paiva OC, Andrade MDF, Pereira LA, Moselli PC, Papis KJ. “Comparing the structure and mechanical properties of welds on ductile cast iron (700 MPa) under different heat treatment conditions”. Metals, 8(1), 72, 2018.
5. [5] Jeshvaghani RA, Shamanian M, Jaberzadeh M. “Enhancement of wear resistance of ductile iron surface alloyed by stellite 6”. Materials & Design, 32(4), 2028-2033, 2011.
6. [6] Iacoviello F, Di Cocco V. “Influence of the graphite elements morphology on the fatigue crack propagation mechanisms in a ferritic ductile cast iron”. Engineering Fracture Mechanics, 167, 248-258, 2016.
7. [7] Sübütay H, Şimşir M, Aydın M, Karaca B. “Effect of chill formation on the mechanical properties and microstructure of grey and nodular cast irons used in automotive industry”. Pamukkale Üniversitesi Mühendislik Bilimleri Dergisi, 22(1), 1-7, 2016.
8. [8] Aşkun Y, Hasirci H, Şeker U. “Evaluation of machinability of ductile irons alloyed with Ni and Cu in terms of cutting forces and surface quality”. Pamukkale Üniversitesi Mühendislik Bilimleri Dergisi, 9(2), 1-7, 2003.

9. [9] Dundar S. “Application of austempered ductile iron to rail wheel sets”. Pamukkale Üniversitesi Mühendislik Bilimleri Dergisi, 9(3), 283-287, 2003.
10. [10] Hütter G, Zybell L, Kuna M. “Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies–A review”. Engineering Fracture Mechanics, 144, 118-141, 2015.
11. [11] Kolukisa S. “The effect of the welding temperature on the weldability in diffusion welding of martensitic (AISI 420) stainless steel with ductile (spheroidal graphite-nodular) cast iron”. Journal of Materials Processing Technology, 186(1-3), 33-36, 2007.
12. [12] Stawarz M. “Comprehensive quality assessment of ductile iron”. Eksploatacja i Niezawodność – Maintenance and Reliability, 2(22), 55-58, 2004.
13. [13] Rojek J, Hyrcza-Michalska M, Bokota A, Piekarska W. “Determination of mechanical properties of the weld zone in tailor-welded blanks”. Archives of Civil and Mechanical Engineering, 12, 156-162, 2012.
14. [14] Collini L, Pirondi A, Bianchi R, Cova M, Milella PP. “Influence of casting defects on fatigue crack initiation and fatigue limit of ductile cast iron”. Procedia Engineering, 10, 2898-2903, 2011.
15. [15] Ferro P, Lazzarin P, Berto F. “Fatigue properties of ductile cast iron containing chunky graphite”. Materials Science and Engineering: A, 554, 122-128, 2012.
16. [16] Collini L, Pirondi A. “Fatigue crack growth analysis in porous ductile cast iron microstructure”. International Journal of Fatigue, 62, 258-265, 2014.
17. [17] Iacoviello F, Di Cocco V. “Degenerated graphite nodules influence on fatigue crack paths in a ferritic ductile cast iron” Frattura ed Integrità Strutturale, 34, 416-414, 2014.
18. [18] Stets W, Löblich H, Gassner G, Schumacher P. “Solution strengthened ferritic ductile cast iron properties, production and application”. International Journal of Metalcasting, 8, 35-40, 2014.
19. [19] DIN Deutsches Institut für Normung. “Founding-Spheroidal Graphite Cast Irons”. Berlin, Germany, DIN EN 1563 Standard, 2012.
20. [20] de La Torre U, Loizaga A, Lacaze J, Sertucha J. “As cast high silicon ductile irons with optimized mechanical properties and remarkable fatigue properties”. Materials Science and Technology, 30(12), 1425-1431, 2014.
21. [21] Yürektürk Y, Baydoğan M. “Effect of aluminizing and austempering processes on structural, mechanical and wear properties of a SSF ductile iron”. Materials Research Express, 6(1), 016550, 2018.
22. [22] Borsato T, Ferro P, Berto F, Carollo C. “Effect of solidification time on microstructural, mechanical and fatigue properties of solution strengthened ferritic ductile iron”. Metals, 9(1), 24, 2018.
23. [23] Hartung C, Logan R, Plowman A, Wilkinson D, Hoel EG, Ott E. “Research on solution strengthened ferritic ductile iron (SSFDI) structure and properties using different treatment and inoculation materials”. International Journal of Metalcasting, 14(4), 1195-1209, 2020.
24. [24] Weiβ P, Brachmann J, Bührig-Polaczek A, Fischer SF. “Influence of nickel and cobalt on microstructure of silicon solution strengthened ductile iron”. Materials Science and Technology, 31(12), 1479-1485, 2015.
25. [25] Erturk SÖ, Ozel A. “Investigation on the production of solution strengthened ductile iron part grade 500-14”. Bayburt Üniversitesi Fen Bilimleri Dergisi, 3(1), 41-45, 2020.
26. [26] Weiß P, Riebisch M, Bührig-Polaczek A. “Mechanical properties and impact toughness of nickel and aluminum alloyed high silicon ductile iron”. Materials Science Forum, 925, 304-310, 2018.
27. [27] Riebisch M, Sönke HG, Pustal B, Bührig-Polaczek A. “Influence of carbide-promoting elements on the pearlite content and the tensile properties of high silicon SSDI ductile iron”. International Journal of Metalcasting, 12, 106-112, 2018.
28. [28] Keleş A, Cengiz R, Yildirim M. “Effect of alloying elements and technological parameters of austempering on the structure and mechanical properties of ductile cast iron (ADI)”. Metal Science and Heat Treatment, 65, 191–199, 2023.
29. [29] Menk W. “A new high strength high ductile nodular iron”. Materials Science Forum, 925, 235-230, 2018.
30. [30] Kandemir AS, Gecu R. “Influence of vanadium content and cooling rate on the characteristics of vanadium-alloyed spheroidal graphite cast irons”. Journal of Alloys and Compounds, 934, 168017, 2023.
31. [31] Aydın E. Mechanical, Machinability, High Temperature Wear, Corrosion and Tribocorrosion Behavior of Alloyed EN-GJS-500-7 Quality Spheroidal Graphite Ductile Iron. PhD Thesis, Bilecik Şeyh Edebali University, Bilecik, Turkey, 2023.
32. [32] Bjsrkegren LE, Hamberg K. “Ductile iron with better machinability compared to conventional grades”. Foundryman, 91, 386-391, 1998.
33. [33] Afseoren M, Ersoz TT, Yildirim M. “Comparison of warm and cold forging with friction welding for inner constant velocity joints (CVJs)”. Transactions of the Indian Institute of Metals, 77(11), 3341-3352, 2024.
34. [34] Yürektürk Y. Effect of Austempering and Aluminizing Processes on Properties of High Silicon Spheroidal Graphite Ductile Irons. PhD Thesis, İstanbul Technical University, İstanbul, Türkiye, 2023.
35. [35] Dawson S, Hollinger I. “The effect of metallurgical variables on the machinability of compacted graphite iron”. Sintercast, 2014, 1-23, 2014.