Table of Contents
ISRN Materials Science
Volume 2011, Article ID 923241, 5 pages
http://dx.doi.org/10.5402/2011/923241
Research Article

The Effect of Cooling Rate on Bainite Phase Formation in Austempered Nickel-Molybdenum Gray Cast Iron

Department of Metallurgical and Materials Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, P.O. Box 91775-1111, Mashhad, Iran

Received 24 August 2011; Accepted 26 September 2011

Academic Editor: E. J. Nassar

Copyright © 2011 A. R. Kiani-Rashid et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Taking into account the importance of the amount of bainite phase on the microstructure of cast irons and its influence on the improvement of mechanical properties, this research selected an alloy of gray cast iron containing Nickel-Molybdenum and conducted the austenitising and austempering processes at 900°C and 400°C for 60 minutes, respectively. The way of bainite phase formation and the effect of sample thickness, that is, cooling rate, were examined by selecting a standard staircase sample. The results indicated that, by increasing the cross sections of samples, the martensite percentage decreases and the phase proportion of bainitic ferrite increases.