TITLE:
Effect of Cu-Ni and Cu-Ni-Mn on the Microstructural and Mechanical Behaviour of As-Cast Non-Inoculated Hypereutectic Grey Iron
AUTHORS:
Seidu Ojo, Adama Sumaila, Onigbajumo Adetunji
KEYWORDS:
Hypereutectic Grey Iron, Microstructure, Hardness, Tensile Strength, Inoculation, Graphitization, Cast Iron, Alloying
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.8 No.2,
March
20,
2020
ABSTRACT: The
hypereutectic region of grey cast iron has received very little attention
especially for designing cast products by researchers. Due to its high carbon
equivalence, hypereutectic grey iron poses some challenges especially its
tendency for grey to white transition (GWT) at this level of carbon content.
However, hypereutectic grey iron possesses inherent properties that could be
easily utilized for improved performance in automobile engines and brake pad
system. Significantly, they could be modified for superior hardness, strength
and toughness. This study presents the effect of microalloying on the
mechanical behaviour of hypereutectic grey cast iron with carbon equivalence
above 4.5. The first part of this work presented in this paper considers the
addition of Cu-Ni and Cu-Ni-Mn to series of as-cast hypereutectic grey cast
iron and their hardness and tensile strength were studied and compared. A total
of 33 cast samples were obtained with the control sample. The examination of
the micrographs revealed that graphite eutectics cells of Type A and A + D were
obtained in the resulting microstructure. Results analyses showed that the
ferrite forming tendency of silicon was suppressed due to the high carbon
content of the as-cast hypereutectic grey iron coupled with the absence of
inoculation which plays a great role in the graphite flake type, network, size
and distribution. Cu-Ni microalloying was also confirmed to promote hardness
with the hardening effect limit of nickel observed at 1.3% composition. For
Cu-Mi-Mn addition, excess and free sulphur in the hyper- eutectic grey iron
results in reverse effect of manganese on strength, hardness, reduced graphite
flake size and shape.