Development of an Oxidation Contrast Method for Pearlite Colony Revelation in Eutectoid Steels

Several studies available in technical literature highlight that small variations in pearlite interlamellar spacing and colony average size promote significant changes in the mechanical properties of eutectoid steels. Therefore, the quantitative characterization of these parameters aiming to establish, or to predict, microstructure-property relationships is of great importance. However, the characterization techniques currently available for revealing pearlite colonies are complex, laborious and often require the use of high-cost resources. In this context, this work presents results about the development of an oxidation contrast method capable to reveal pearlite colonies for direct observation by optical microscopy. The developed method was applied to three different eutectoid steels and the average sizes of pearlite colonies were measured. The results obtained using the proposed technique were compared with those determined applying a usual method described in the literature. It was concluded that the proposed contrast method is effective and, once standardized among users, it can be a representative way for determining the average size of pearlite colonies.