Hydrogen embrittlement in AISI 4340 steel (AMS 6415S) quenched and tempered
Ícaro Zanetti de Carvalho1; Célia Marina de Alvarenga Freire1; Itamar Ferreira1; Margarita Ballester Cardona1; Leonardo Taborda Sandor2
1 School of Mechanical Engineering - UNICAMP; 2 Villares Metals - Sumaré
doi:10.20906/CPS/COB-2015-0362
Resumo
The phenomenon of hydrogen embrittlement in AISI 4340 steel was investigated due to the fact that it is a high strength low alloy steel quite susceptible to this phenomenon. The analysis was done through the fracture toughness test by bending based on ASTM E 399-09. Specimens were machined with crack plane L-C, quenched at 845 °C and tempered at three different temperatures (350 °C, 400 °C and 500 °C). The hydrogen loading was made by means of an electrochemical cell where the specimens were immersed in a solution of 0.01 M sulfuric acid by applying a current density of 10 mA/cm² and three different hydrogenation times, in order to obtain three levels of contamination. After the tests were performed fractographies of the specimen fracture surfaces for each condition of temper and contamination by hydrogen, with observed changes in the micromechanisms of fracture for the different conditions. The test results of fracture toughness by bending were correlated with the micromechanisms of fracture, the microstructure and hydrogen contamination. Under conditions of tempering of 400 °C and 350 °C, AISI 4340 steel proved to be very susceptible to hydrogen embrittlement, with reductions of 10% and 20%, respectively, on the values of fracture toughness of contaminated specimens. The same was not observed in AISI 4340 quenched and tempered at 500 °C, which did not presented embrittlement.
Palavras-chave: Hydrogen Embrittlement; Fracture Toughness; AISI 4340 Steel