Effects of austenitizing process on microstructures and properties of carbidic austempered ductile iron

The effect of austenitizing process of carbidic austempered ductile iron (CADI) on the microstructure, mechanical properties and abrasion resistance was studied. The results indicate that with the increase of austenitizing temperature acicular ferrite and high carbon austenite become thicker and bigger gradually, and the amount of high carbon austenite and its carbon content increase. CADI contains a large amount of proeutectoid ferrite when 850 C austenitizing temperature, which greatly reduces the hardness and abrasion resistance. With the rise of austenitizing temperature, the proeutectoid ferrite disappears and carbides partially dissolve into the matrix gradually. The hardness first increases and then reduces, while the effect of austenitizing time is very little. During the wear test, specimens with low hardness exhibit a huge plastic deformation but little wear debris, besides, feathery ausferrite can protect graphite from being pulled out. More carbon amount makes austenite stable enough to avoid brittle damage due to the appearance of martensite.