The mechanical properties of ductile iron with mixed structures

Abstract

The scope of the present investigation is: 1) to develop an austempering heat treatment process that yields maximum bulk ductility in an unalloyed cast iron and 2) to improving the wear resistance of the surface by laser surface remelting treatment thus obtaining an optimum combination of ductility, toughness and tribological characteristics The study showed that, the ductile iron with ferritic or pearlitic matrix structures have generally poor wear resistance particularly at higher loads. This was attributed to the softness and low strength of these structures. On the other hand, the austempering heat treatment increased the wear resistance remarkably. This was attributed to a number of factors including: the relatively high hardness of the ausferritic structure, the effect of graphite nodules and oxides in reducing friction coefficient and the tendency of the ausferritic structure to work harden.

We can conclude that an austempered structure may be ideal for applications involving moderate loads and relatively mildly corro8ivc environments whilst a laser treated surface may proof to be advantageous in case of high loads or possibly conditions involving simultaneous wear and corrosion. The selection of the treatment depends therefore on the application.