The effect of chills thickness to microstructure and surface hardness layer on specimen ductile cast iron.

One of the methods used to surface hardening of ductile iron is chilled cast iron. Chill as the fast cooling rate in the mold during solidification and chill thickness greatly affects the thickness of the hardness layer. The main material used is ductile iron, and the chill material is SS 304. Casting uses the sand casting method. Before pouring, the chill plate has been inserted onto the surface of the pattern that has been formed in the mold, then the chill plate is preheated at 700°C. Pouring was carried out at a melting temperature of 1400°C, and then cooled with argon and O₂ sprays into the mold in solidification conditions at exactly 700°C. The results analyzed were the microstructure, hardness value, and the hardness of the thickness layer. This chill coolant will absorb heat very quickly and the Cr and Ni alloy will diffuse to the specimen surface to stabilize the ferrite and austenite phases in the final solidification. The particles on the hard surface are has ferro carbide M₇C₃, which is in the form of cementite and martensitic phases so that to categorized as white cast iron structure formed on the surface with the area around 1.5-3mm has a hardness of 61-65HRC. But in the center area is 31-49HRC. [ABSTRACT FROM AUTHOR]