Evaluation of Chromium Effect on the Fracture Toughness of Hadfield Steel By Using Charpy Impact Test

In this study, effect of chromium addition on the fracture toughness of Hadfield steel was investigated by using charpy impact test. For this purpose, 3 casting blocks were prepared from Hadfield steel (without Cr addition, and containing 1.5% Cr and 3% Cr) by using coreless induction furnace. After casting, all blocks austenitized in 1100°C for 2 hours and immediately quenched in the pure water. In the next step, uniaxial tensile test, hardness test and charpy impact test were applied on specimens. Evaluation of the microstructures was conducted by optical microscope and the fractured surfaces were observed by scanning electron microscope. The results of charpy impact test and fracture toughness empirical relationships were used for determination of fracture toughness values of specimens. As a result, it was found that sample without Cr had lowest hardness – highest fracture toughness value – highest critical crack length and the sample containing 3% Cr had the highest hardness – lowest fracture toughness value – lowest critical crack length. Also, scanning electron microscope images indicated increasing crack growth in the charpy impact test specimens by addition of Cr to chemical composition of Hadfield manganese steel.