Modification of the Surface Layer of Grey Cast Iron by Laser Heat Treatment

This paper presents possible modifications to the properties of grey cast iron by laser heat treatment. These modifications are analyzed especially with regard to wear properties as a result of graphite content, which is a well-known solid lubricant. Examples of applications of grey cast iron in cases where good wear resistance is required are presented. Laser hardening from the solid state, laser remelting, and laser alloying are characterized. In this study, changes in the surface layer caused by these treatments were analyzed (especially the influence on the microstructure—including graphite content—and wear properties). It was shown that all of these treatments enable the wear resistance of the surface layer to be enhanced, mostly due to the increase in the hardness and microstructure homogeneity. It was also proven that it is possible to retain the graphite phase (at least partially) in the modified surface layer, which is crucial in the case of friction wear resistance. In particular, laser hardening from the solid state does not eliminate graphite. Laser remelting and alloying cause the dilution of carbon from the graphite phase to the melted metal matrix, but, in the case of nodular cast iron, it is possible that not all of the valuable graphite in the surface layer is lost.