FATIGUE BEHAVIOR OF TOUGHENED AUSTEMPERED DUCTILE IRON
Keywords:
Toughened, Fatigue, Retained Austenite, Bainite, MicrohardnessAbstract
Austempered ductile iron is a new engineering material which has a combination of good strength, toughness and wear resistance. The toughness can be further enhanced by employing special heat treatment to the ductile iron samples generally termed as QB1 process. The resulting toughened austempered ductile iron samples have been found to possess superior toughness and wear resistance.The Fatigue behavior of toughened austempered ductile iron (TADI) samples have been studied and reported. The austempering temperature has been held constant at 3500C and the austempering time has been varied from 15-210 minutes in steps of 15 minutes. The austempered samples were also tested for microhardness and the results analyzed. The results indicate that the fatigue strength increases as the holding time increases from 15 to 150 minutes. Samples austempered beyond 150 minutes shows a decrease in fatigue strength. The maximum hardness value reported with micro hardness test was at an austempering time of 150 minutes. Further, the retained austenite content and distribution of bainite in the matrix play a vital role on the fatigue properties of Toughened austempered ductile iron.
Downloads
References
Dorazil E (1986), “Mechanical Properties of Austempered Ductile Iron”, Foundry Management and Technology, 36-45.
Shepperson S and Allen C (1988), “The Abrasive Wear Behavior of Austempered Spheroidal Cast Irons”, Wear, Vol. 121, 271-287.
Rundman K B (1991), “Austempered Ductile Iron: Striving for Continuous Improvement”, World Conference on Austempered Ductile Iron, Bloomingdale, IL, 1-21.
Toshiro Kobayashi and Shinya Yamada (1996), “Effect of Holding Time in the (α+γ) Temperature Range on Toughness of Specially Austempered Ductile Iron”, Metallurgical and Materials Transactions A, Vol. 27, 1961-1971
Narasimha Murthy K, Uma T R and Simh J B (2009), “Abrasive Wear Behavior of Permanent Molded Toughened Austempered Ductile Iron”, Proceedings of the ASME/STLE International Joint Tribology Conference (IJTC), 103-105.
Tayanc M, Aztekin K, Bayram A (2007), “The Effect of Matrix Structure on the Fatigue Behavior of Austempered Ductile Iron”, Materials and Design, Vol. 28, 797-803.
Jianghuai Yang and Susil K Putatunda (2004), “Near Threshold Fatigue Crack Growth Behavior of Austempered Ductile Cast Iron (ADI) Processed by a Novel Two-step Austempering Process”, Materials Science and Engineering A, Vol. 393, 254-268.
Mohamed H Alaalam (2008), “Fatigue Properties of an Alloyed Austempered Ductile Iron of Initially Ferritic Matrix Structure Using Thermography as NDT”, The 2nd International conference on Technical Inspection and NDT (TINDT), Tehran, Iran.
Gülcan Toktaş, Alaaddin Toktaş and Mustafa Tayanç (2008), “Influence of Matrix Structure on the Fatigue Properties of an Alloyed Ductile Iron”, Materials and Design, Vol. 29(8), 1600-1608.
Jen K P, Wu J and Kim S (1992), “Study of Fracture and Fatigue Behavior of Austempered Ductile Iron.” AFS Transactions, Vol. 100, 833-846.
Krishnaraj D, Rao K V and Seshan S (1989), “Influence of Matrix Structure on the Fatigue Behavior of Ductile Iron.” AFS Transactions, Vol. 97, 315–20.
Shanmugham P, Prasad Rao P, Rajendra Udupa K and Venkataraman N (1994), “ Effect of Microstructure on the Fatigue Strength on Austempered Ductile Iron”, Journal of Materials Science, Vol.29, 4933-4940.
Stanislav Vechet, Jan kohout, Lenka klakurkova (2008), “Fatigue Properties of Austempered Ductile Iron in Dependence on transformation Temperature”, Materials Science, Vol. 14, 324-327
Salman S, Findik F and Topuz P (20067),”Effects of Various Austempering Temperatures on Fatigue Properties in Ductile Iron”, Materials and Design ,Vol.28, 2210-2214.
