SPECIAL IRONS FOR
WEAR, HEAT AND CORROSION RESISTANCE
In addition to the conventional Meehanite flake and nodular
graphite irons for general engineering applications, certain
ranges of material have been specially developed to suit environmental
conditions involving wear, heat and corrosion. These are essentially
types of flake and nodular graphite iron where, by suitable
changes in composition, such as by alloy additions or by heat
treatment, the irons have been modified to meet specific difficult
conditions.
Wear Resistance
Wear is essentially a surface phenomenon. It involves many
properties such as hardness, impact, fatigue under compression,
friction, corrosion, thermal shock, grain structure, solidity
and lubrication. If follows, therefore, that every wear problem
must be carefully considered and selection of material must
be made according to the service conditions.
Heat Resistance
Normal flake and nodular graphite irons show different reactions
to changes in temperature. For example, up to 500² C, all
irons show a rapid drop in tensile strength and hardness. Above
500² C, structural breakdown and the effect of atmospheric
conditions affect service life.
No single type of iron can successfully withstand all possible
thermal environments. Special types of iron are therefore required.
Selection of these must be based on various conditions, such
as type of service, temperature cycle and rate of heating, condition
of stress, both mechanical and thermal, resistance of the material
to oxidation and thermal cycling, and machinability requirements
