Sementasyon yapılan SAE 8620 çeliğinde meydana gelen kalıntı gerilmelerin incelenmesi

Bu çalışmada, dişli çark ve mil gibi makine parçalarının yapımında yaygın olarak kullanılan SAE 8620 (21NiCrMo2) sementasyon çeliğinde, sementasyon işlemleri sonucunda meydana gelen kalıntı gerilmeler incelenmiştir. Gaz atmosferinde 940 C 'de sementasyon işlemleri yapılan numunelerin kalıntı gerilme değerleri ve kalıntı östenit miktarları X-ışını difraksiyonu metoduyla tespit edilmiştir. Sementasyon yapılan tüm numunelerin yüzey ve yüzey altı bölgelerinde basma kalıntı gerilmeleri meydana gelmiştir. Sementasyon derinliğinin artması basma kalıntı gerilmelerinin düşmesine neden olmuştur.

An investigation of residual stresses developed in carburized SAE 8620 steel

In this study, the residual stresses developed in carburized SAE 8620 (21NiCrMo2) steel were investigated. Carburizing programs were carried out in gas atmosphere at 940 C. X-ray diffraction was used to determine residual stresses and retained austenite levels in the case-hardened microstructures of the carburized specimens. Test results indicated that residual stresses are all compressive at the carburized cases of specimens. The thicker case depth exhibited the lower compressive residual stress at the surfaces and/or very near the surfaces of carburized specimens.

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1.Krauss, G., "Steels: heat treatment and processing principles", ASM International, 291-305(1989).
2.Hyde, R.S., Krauss, G. and Matlock, D.K., "Phosphorus and carbon segregation: effects on fatigue and fracture of gas-carburized modified 4320 steel", Metallurgical and Materials Transactions A, 25(A): 1229-1239(1994).
3.Parrish, G., "Carburizing: microstructures and properties", ASM International (1999).
4.TSE 1719, Çelikler sementasyon (karbürleme) ve sertleştirmede elde edilen etkili derinliğin tayini ve kontrolü, Türk Standartları Enstitüsü, Ankara (1974).
5.Genel, K. and Demirkol, M., "Effect of case depth on fatigue performance of AISI 8620 carbunzed steel",International Journal of Fatigue, 21 (1999): 207-212 (1999).
6.Krauss, G., "Microstructures and properties of carburized steels", ASM International, Metals Handbook,4 (Heat Treating): 363-375 (1991).
7.Zürn, J., Razim, C. and Grosch, J., "The effect of residual stress in case hardening", o International Congress on Heat Treatment of Materials, September, Chicago, 28-30: 279-283(1988).
8.Kim, H.J. and Kweon, Y.G., "High cycle fatigue behavior of gas-carburized medium carbon Cr-Mo steel",Metallurgical and Materials Transactions A, 27(A): 2557-2564 (1996).
9.Preston, S., "Fatigue crack initiation and growth from a gas carburized surface", Materials Transactions,JIM, 34(1): 27-32 (1993).
10.Evanson, K., Krauss, G. and Medlin, D., "Bending fatigue behaviour of vacuum carburized AISI 8620 steel", Proceedings of the Second International Conference on Carburizing and Nitriding with Atmospheres, 6-8 December 1995, Cleveland, Ohio, ASM, 61-69 (1995).
11.Almer, J.D., Cohen, J.B. and Moran, B., "The effect of residual macrostresses and microstresses on fatigue crack initiation", Materials Science & Engineering, A284 (2000): 268-279 (2000).
12.Wise, J. P., Matlock, D. K., Krauss, G., "Bending fatigue of carburized steels", ASM Heat Treating Progress, August/September 2001:33- 41 (2001).