Effect of structure on fracture resistance of hydrogenated structural steels of different strengths

The resistance to delayed hydrogen fracture of low-alloy steels 35KhGM and 33KhMF (Russian names) with troostite and troostomartensitic structure of high strength (yield strength 940-1440 MPa) was studied. Samples deformed to σ = 0.8σ0.2 by four-point bending were locally galvanically hydrogenated for 10 h with simultaneous recording of acoustic emission signals. It is shown that a 1.5-fold increase in the strength of 35KhGM steel with a troostomartensitic structure as compared to steel with a troostite structure increases the volume of absorbed hydrogen by 30 times, reduces the time of hydrogen crack initiation by 2.7 times, increases the rate of its stable growth by 3.6 times and reduces the crack resistance parameter KIH by 1.3 times. A 1.5-fold increase in the strength of 33KhMF steel with a troostite structure due to an increase in the density of carbides as compared to 35KhGM steel increases the volume of absorbed hydrogen by 20 times, reduces the crack initiation time by 2 times and increases the rate of its growth by 2.5 times with unchanged KIH values.