Heat Treatment of Heat-Resistant Ferrous Cast Alloys

Heat-resistant ferrous cast alloys are generally divided into four groups: ferritic cast iron, austenitic ductile iron, ferritic stainless steel, and austenitic stainless steel. There is an active debate about whether or not heat treatment should be imposed on these ferrous castings prior to placing them in service. In this investigation, a series of experiments were conducted to evaluate the effect of heat treatment on the microstructure, tensile properties, hardness, linear growth, and thermal fatigue life for alloys of each of the four groups. In general, heat treatment appeared to cause similar microstructural changes in these alloys such as the formation of precipitated particles adjacent to the cell boundary regions, but it also affected each material’s properties in a different fashion. In spite of a slight increase in tensile elongation at room temperature, annealing had no impact on the ductility minima at medium temperatures for ferritic cast iron. Heat treatment did not appreciably alter the tensile properties of austenitic ductile iron. The Brinell hardness of ferritic stainless steel samples was reduced, but the hardness was increased for austenitic stainless steel samples after heat treatment.