13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- 30 MPa and to 68 MPa·m1/2 in hydrogen under the pressure 30 MPa after preliminary high-temperature hydrogenation (with hydrogen concentration 19 ppm). The plane-strain conditions were not fulfilled at these two cases. 400 600 800 0.0 0.3 0.6 0.9 1000 2000 3000 6 β N, N, cycles T, K 1 2 3 4 5 Figure 6. Temperature dependences of number cycles to failure N (1-4) (ε = 1,6%) and coefficients of hydrogen influence βN = NH/NHe (5, 6) on 04Cr16Ni56 (1, 2, 6) and 05Cr19Ni55 (3, 4, 5) alloys: 1, 3 – helium, 2, 4 – hydrogen under the pressure 30 MPa. 300 400 500 600 700 0.4 0.6 80 120 160 8 7 6 5 4 β K Kc,MPa√m T,K 3 2 1 Figure 7. Temperature dependences of plane-stress fracture toughness Kc (1-5) and coefficients of hydrogen influence βK = Kc H/Kc He (6-8) on 04Cr16Ni56Nb5Mo5TiAl (1, 5, 8) and 05Cr19Ni55Nb2Mo9Al (2-4, 6, 7) alloys: 1, 2 – helium, 2, 3, 6 – hydrogen under the pressure 30 MPa, 4, 7 – hydrogen under the pressure 30 MPa after preliminary hydrogenation (623 K, 35 MPa H2, 10 h). Conclusions. The parameters of loading and the modes of hydrogen action for which the mechanical characteristics of the investigated alloys are minimum at room temperature can be formulated as follows: – strain rate Vdef ≤ 6.7·10 -5 s-1 for tensile test and the strain amplitude ε = 1.6 % under the conditions of low-cycle fatigue at hydrogen pressures above 10 MPa for the alloy 04Cr16Ni56 and hydrogen pressures above 15 MPa at concentration of preabsorbed hydrogen 19 wppm for the alloy 05Cr19Ni55; – for static crack propagation at hydrogen pressure above 10 MPa for the alloy 04Cr16Ni56 and hydrogen pressure above 15 MPa at concentration of absorbed hydrogen 19 wppm for the alloy 05Cr19Ni55. The plane-strain conditions required for the evaluation of KІс were fulfilled on compact tension specimens made of alloy 04Cr16Ni56 with thickness of 20 mm at hydrogen pressure above 10 MPa in the temperature range 293…473 K. For all loading modes, the degree and temperature interval of hydrogen degradation for 04Cr16Ni56 alloy is much larger than for 05Cr19Ni55 alloy. References [1] Chandler W.I. and Walter R.I. Testing to determine the effect of high pressure hydrogen environment on the mechanical properties of metals, in: Hydrogen Emrittlement Testing,
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