Effect of specimen preparation on evaluation of cast iron microstructures

Examples of the use of different etchants for revealing unalloyed cast iron microstructures, such as: pearlite, ferrite and cementite, are presented. The phosphorous eutectic (Steadite) in gray iron can be observed after etching with 4% nital, but selective color etching helps to differentiate the revealing constituents. This method is also helpful in phase differentiation of the ADI matrix as well as revealing silicon segregation in ductile iron and microsegregation in the austenitic matrix of mottled iron. Color etching of chromium carbides in alloyed white irons facilitates the use of the color image analyzer for measurements of the amount and morphology of this phase.