Electron beam surface melting of as cast and austempered ductile irons

In this study surface melting of ductile iron before and after austempering was studied. Surface melting resulted in the formation of ledeburite (white iron) in the melted zone and a martensitic structure in the heat affected zone (HAZ) and the hardness in these areas was considerably higher than the hardness of base metal. The results also indicated that austempering before surface melting had no effect on the hardness of the surface melted region and HAZ. A number of these materials were also tempered after surface melting. The tempering had little effect on the hardness of melted region, but resulted in the reduction of the hardness of the HAZ.