Influence of the Tempering Cooling Rate on the Temper Embrittlement (TE) of a Low Alloyed Martensitic Mn-Cr-Ni Steel

Low alloyed martensitic resistant steels could become a solution for material saving and components lightweighting in the industrial activity due to the combination of high strength and good weldability and toughness characteristics. However, it is known that martensitic resistant steels are susceptible to temper embrittlement (TE), which can cause undesirable brittle fracture during service of components. In this investigation the influence of the cooling rate after a high temperature tempering (650 ºC) on TE of a low alloyed martensitic Mn-Cr-Ni steel was studied. Charpy impact tests and metallurgical analysis using emission Scanning Electron and Transmission Electron Microscopy were carried out on specimens cooled in different cooling media after the tempering to stablish a relation between the microstructures and the TE. Obtained results shown a considerable influence of the tempering-carbides location at grain boundaries at low post-tempering cooling rates on the TE of the selected steel.