Influence of Heat Treatment in the Microstructure of a Joint of Nodular Graphite Cast Iron when Using the Tungsten Inert Gas Welding Process with Perlitic Grey Cast Iron Rods as Filler Material

The present article analyses the influence of preheating and a postweld heat treatment in the microstructure, mechanical properties and wear behaviour of a joint of nodular graphite cast iron when using the tungsten inert gas (TIG) welding process with perlitic grey cast iron rods as filler material. Data obtained from the tests and the microstructural study of the samples show that the absence of a postweld heat treatment and of preheating leads to the apparition of hard structures and a notable reduction in elongation. Preheating or annealing the weld avoid the presence of these hard structures and increase the ductile behaviour of the joint although at the cost of a further loss of mechanical strength. Wear rate was found to be higher at the weld bead than at the base metal, even when the hardness of both areas is the same.