Influencia del tiempo de revenido en la tenacidad a fractura de un acero 42CrMo4 precargado con hidrogeno

Laburpena

This work aims to find the most suitable 42CrMo4 steel grade for working in energetic applications dealing with high pressure hydrogen gas. On this context, the influence of the tempering time on hydrogen sensitivity of 42CrMo4 steel quenched and tempered at 600ºC was investigated. Fracture toughness compact tensile (CT) specimens were thus precharged with gaseous hydrogen in a pressurized reactor at 19.5 MPa and 450ºC for 21 hours and tested afterwards in air. The fracture micromechanisms were subsequently identified using scanning electron microscopy. In addition, in order to have a better knowledge of hydrogen trapping phenomena in these grades, thermal desorption analysis and electrochemical hydrogen permeation techniques were also employed. It was demonstrated that all the studied steel grades have suffered a significant hydrogen embrittlement, being the fracture toughness drop, at best, around 50%. In addition, brittle fracture micromechanisms, associated to hydrogen decohesion phenomena were present to a lesser or greater degree in all the range of studied tempering times. This behaviour seems to be closely correlated to the hydrogen trapping capability of the steel, as those steels with lower diffusion coefficient and higher hydrogen absorption capacity were the most susceptible to hydrogen embrittlement.