Hydrogen Effect on Cumulation of Failure, Mechanical Properties, and Fracture Toughness of Ni-Cr Alloys

Influence of hydrogen pressure and internal hydrogen contents on short-term strength, plasticity, and plane-stress fracture toughness of 05Cr19Ni55 alloys at pressure up to 30 MPa was investigated. It was established that the crack resistance parameters K-c of alloys decrease with displacement rates decreasing similar to elongation (delta) and reduction of area (psi) of smooth specimens. The maximum hydrogen influence is achieved at strain rate speeds less than 0.1 mm/min and hydrogen pressures above 15 MPa when delta and K-c of prehydrogenated samples are reduced by 3 times. The plane-strain conditions required for the evaluation of K-Ic were fulfilled on compact tension 05Cr19Ni55 alloy specimens with thickness above 20 mm under hydrogen pressure 30 MPa and preliminary dissolved hydrogen concentration above 20 wppm. Regardless of the test conditions, the value of the characteristics of plasticity (delta, psi) and fracture toughness (K-c) of alloy (TO1) specimens oriented in the transverse direction (orientation TV) is significantly lower than that of specimens oriented in the longitudinal direction (LT). Alloy cleaning by vacuum arc remelting and optimization of heat treatment regime increase their hydrogen resistance.