One of the surface hardening processes is chill casting. Chill casting is used for surface hardening of nodular cast iron materials. The problem that often occurs in the chill casting method is porosity which is influenced by the fast-cooling rate between the casting object and the mold wall. This study aims to analyze the microstructure, hardness, and porosity that will form on the surface of the Y-shaped specimen after chilled casting. The material used for casting the Y-Shape specimen is nodular cast iron and the chill material is stainless steel plate. The chill is varied with a thickness of 0.2mm and 0.4mm and will be coated on the surface of the sand mold wall then the chill is preheated at a temperature of 700oC and 900oC, then pouring is done at a temperature of 1400oC. The average hardness value on the surface of the specimen is 500HV-900HV, but in the middle area the hardness only reaches 200HV while the microstructure results in the surface layer are cementite and ledeburite phases, but in the middle area ferrite, and perlite are seen surrounding the nodule graphite structure. In the chill-coated area, although the hardness is high, there are micro-porosities and macro-porosities formed randomly.