Östemperlenmiş küresel grafitli dökme demirin abrasiv aşınma davranışına östemperleme işleminde soğutmanın etkisi

Bu çalışmada, geleneksel tek kademeli östemperleme işleminde, küresel grafitli dökme demir (KGDD) numuneler 900oC’de 1 saat östenitlenmiş, müteakiben tuz banyosunda 400oC’de 2 saat östemperlenmiştir. İkikademeli östemperleme prosesinde ise KGDD numuneler 900oC de 1 saat östenitlendikten sonra derhal 400oC’lik tuz banyosuna aktarılmış, 10 dakika bu sıcaklıkta bekletildikten sonra banyonun sıcaklığı 1.88oC/dak hızla 250oC’a soğutulmuştur. Geleneksel tek kademeli östemperleme prosesi ile üretilen üst ösferritik ve ikikademeli prosesle üretilen üst ve alt ösferritik Östemperlenmiş Küresel Grafitli Dökme Demir (ÖKGDD) numunelerin abrasiv aşınma deneyleri, disk üzerinde pim cihazında 10, 20 ve 30 N normal yük altında, 180 mesh (80 µm) boyuta sahip Al2O3 zımpara üzerinde gerçekleştirilmiştir. İki kademeli östemperleme prosesiyle üretilen küresel grafitli dökme demirin sertliği, tek kademeli prosesle üretilen dökme demirinkinden daha yüksek olmasına rağmen, her iki dökme demirin benzer abrasiv aşınma davranışı sergilediği görülmüştür. Ayrıca iki kademeli östemperlenmiş küresel grafitli dökme demirde abrasiv aşınma direnci uygulanan yükün artmasıyla artmıştır.

Effect of the cooling in the austempering process on the abrasive wear behaviour of austempered ductile iron

In this study, ductile iron was austenised at 900 oC for 1 h and austempered at 400 0C for 2 h in single step austempering process, whereas it was austenised at 900 oC for 1 h and immediately quenched in a salt bath at 400 oC for 10 minutes and then the temperature of bath was decreased by 1.88 oC per minutes down to 250 oC in two-step austempering process. The upper ausferritic austempered ductile iron (ADI) specimens produced by conventional single step austempering process and the upper and lower ausferritic specimens produced by twostep austempering process were abraded on the pin on disc apparatus under the normal load of 10, 20, 30 N, by rubbing the specimens on abrasive Al2O3 grains with diameters of 180 Mesh (80 µm). Although the ductile iron austempered in two steps had higher hardness than the ductile iron austempered in single step, they showed similar abrasive wear behavior. In addition, the abrasive wear resistance of two step austempered specimen increased with increasing applied load.

PDF

___

1.Janowak, J.F., Gundlach, R.B., “Development of a Ductile Iron for Commercial Austempering”,AFS Transactions, 83-54,377-388, 1983.
2. Harding, R.A., Gilbert, G.N.J., “Why the Properties of Austempered Ductile Irons Should Interest Engineers”, The British Foundryman, 79, 489-496, 1986.
3. Walton, C.F., “Mechanical Properties of Ductile Iron”, Iron Castings Handbook, Iron Castings Society Inc., 323-376, 1981.
4. Schmidt, I., Schuchert, A.Z., “Unlubricated Sliding Wear of Austempered Ductile Iron”, Metallkunde, 78, 871–875, 1987.
5. Johansson, M., “Austenitic-Bainitic Ductile Iron”, AFS Transactions, 77-73, 117-122, 1977.
6. Lerner, Y.S., “Wear Resistance of Austempered Ductile Iron”, Foundry Management & Technology,74-80, 1999.
7. Bartosiewicz, L., Krause, A.R., Kovacs, B.,Putatunda, S.K., “Fatigue Crack Growth Behavior of Austempered Ductile Cast Iron”, AFS Transactions 92 (135), 135–143, 1992.
8. Bahmani, M., Elliott, R., Varahram, N., “The Relationship between Fatigue Strength and Microstructure in an Austempered Cu–Ni–Mn–Mo alloyed ductile iron”, Journal of Materials Science, 32, 5383-5388, 1997.
9. Greno, G.L. Otegui, J.L., Boeri, R.E., Mechanisms of Fatigue Crack Growth in Austempered Ductile Iron”, International Journal of Fatigue, 21, 35-43, 1999.
10. Dommarco, R.C., Salvande, J.D., “Contact Fatigue Resistance of Austempered and Partially Chilled Ductile Irons”, Wear, 254, 230–236, 2003.
11. Putatunda, S.K., Gadicherla, K., “Influence of Austenitizing Temperature on Fracture Toughness of a Low Manganese Austempered Ductile Iron (ADI) with Ferritic as Cast Structure”, Materials Science and Engineering A 268, 15–31, 1999.
12. Rao,P., Putatunda, S.K., “Investigations on the Fracture Toughness of Austempered Ductile Irons Austenitized at Different Temperatures”, Materials Science and Engineering A 349, 136-149, 2003.
13. Rao, P., Putatunda, S.K., “Investigations on the Fracture Toughness of Austempered Ductile IronAlloyed with Chromium”, Materials Science and Engineering A 346, 254-265, 2003.
14. Jianghuai Yang, J., Putatunda, S.K., “Improvement in Strength and Toughness of Austempered Ductile Cast Iron by a Novel Two-Step Austempering Process”, Materials and Design 25, 219–230, 2004.
15. Putatunda, S.K., “Development of Austempered Ductile Cast Iron (ADI) with Simultaneous High Yield Strength and Fracture Toughness by a Novel Two-Step Austempering Process”, Materials Science and Engineering A 315, 70-80, 2001.
16. Şenel, L., Çetin, M., Gül, F., “Evaluation of Dry Sliding Wear of Ductile Iron with Different Matrix Microstructures”, 3th International Advenced Technologies Symposium, August 18-20, Ankara,154-166, 2003.
17. Zimba, J., Simbi, D.J., Navara, E., “Austempered Ductile Iron: An Alternative Material for Earth Moving Component”, Cement & Concrete Composites, 25, 643-649, 2003.
18. Yescas, M.A.,. Bhadeshia, H.K.D.H., “Model for the Maximum Fraction of Retained Austenite in Austempered Ductile Cast Iron”, Materials Science and Engineering A 333 60–66, 2002.
19. Bosnjak, B., Verlinden, B., and Radulovic, B.,“Dry Sliding Wear of Low Alloyed Austempered Ductile Iron”, Materials Science and Technology, 19, 650-656, 2003.
20. Hamid Ali A.S. and Elliot, R., “Influence of Austenitising Temperature on Austempering of an Mn-Mo-Cu Alloyed Ductile Iron, Part 1- Austempering Kinetics and the Processing Window”, Materials Science and Technology,12, 1021-1031, 1996.
21. Prado, J.M., Oujol, A., Cullell, J., and Tartera, J.,“Dry Sliding Wear of Austempered Ductile Iron”,Materials Science and Technology, 11, 294-298, 1995.
22. Owhadi, A., Hedjazi, J.,Davami, P., “Wear Behavior of 1.5Mn Austempered Ductile Iron”,Journal of Materials Science, 14, 245-250, 1998.
23. Jeng, M.C., “Abrasive Wear Study of Bainitic Nodular Cast Iron”, Journal of Materials Science,28, 6555-6561, 1993.
24. Shepperson, S., and Allen, C., “The Abrasive Wear Behavior of Austempered Spheroidal Cast Irons”,Wear, 121, 271-287, 1988.
25. Velez, J. M., Tanaka, D.K., Sinatora, A., Tschiptschin, A.P., “Evaluation of Abrasive Wearof Ductile Cast Iron in a Single Pass Pendulum Device”, Wear , 251, 1315–1319, 2001.
26. Çetin, M., Gül, F., “Effect of Mg on Abrasive and Adhesive Wear Behavior of Al-Cu Casting Alloy”,3th International Advanced Technologies Symposium, August 18-20, Ankara, 134-145,2003.