The purpose of this work is to propose a model for evaluating the fracture toughness along the SAE 5115 steel carburized layer. Due to the small thickness of those layers, it is impossible to machine specimens from those layer in accordance with standards. For simulating the microstructures of the carburized layer in order to get samples for tensile and the fracture toughness testing, specimens of SAE 5115, 5140, 5160, and 52100 steels have been machined, assuming the local influence just the variation of the content of carbon and considering that the contents of the other alloy elements are essentially constant. The specimens after electroplated copper layer were heat treated in an industrial load of carburizing, quenching, and tempering for they be submitted to the thermal effects without absorption of carbon. The results of the microstructure analysis and microhardness, tension, and fracture toughness tests were placed in a single graph and compared with the profile of the carburizing of the steel SAE 5115 heat treated in the same conditions. It was confirmed that the fracture toughness varies inversely proportional to the microhardness (HV1) and that the forecast of the behavior of a crack in a carburized layer can be made through equation or it designs that relate the microhardness (HV1) with the fracture toughness (K IC or CTOD C).
Fracture toughness; carburizing; steel SAE 5115
