Investigation of Microstructure of Cast Iron by Color Etching

Abstract

A lot of phases can be present in the structure of cast iron depending on the quality and the heat treatment processes. By using the color etching, the different phases – e.g. the carbides – can exactly be identified and their quantity can be measured. The carbide of iron (cementite) or other types of carbides existing in the structure have a significant influence on the properties of cast product therefore strict prescriptions regulate their quantity mainly in case of making cast products for the motor-car industry. In the course of our experiments performed by using the color etching, we proved that carbides can be detected and their quantity can be determined by using the digital image processing method by means of the different reagents. Other different characteristics of the structure can become visible by means of the reagents used during the color etching. During the investigations, it was experienced that some of the ferrite grains are etched in different color. This is probably connected to the orientation of grains as the thickness of interference-film is different on the anode phases having different orientation and therefore they color in different tones.