Microstructure and cavitation behaviour of alloyed austempered ductile irons

ABSTRACT

In this paper, the study of cavitation behaviour of austempered ductile iron (ADI) alloyed with copper, as well as copper and nickel with a fully ausferritic microstructure, is presented. The ADI materials used were austenitized at 900 °C and austempered at 350 °C having an ausferrite microstructure with 16 and 19% of austenite, respectively. The experimental investigations were conducted using the ultrasonically induced cavitation test method. The results show that the cavitation damage was initiated at graphite nodules, as well as in the interface between a graphite nodule and an ausferrite matrix. The cavitation rate revealed that the ADI material alloyed with Cu + Ni austempered at 350 °C/3 h has a higher cavitation resistance in water than ADI alloyed with Cu. An increased cavitation resistance of the ADI material alloyed with Cu and Ni is due to the matrix hardening by stress assisted phase transformation of austenite into the martensite (SATRAM) phenomenon.

KEYWORDS:

• Cavitation
• austempered ductile iron
• cast iron
• austenite-to-martensite phase transformation

Acknowledgements

The authors gratefully acknowledge research funding from The Ministry of Education, Science and Technological Development of The Republic of Serbia under grant number TR34015. The authors are also very grateful to Mr. Michael A. Maier for technical support.