Markov A. Evaluation of degradation of thermal stable steels welding joints in high-temperature hydrogenating environments

The high-temperature hydrogen degradation of welding-joint metal of heat resistant steels under service and modeling laboratory conditions. To establish the weld joint metal state from the position of workability in great welded constructions. Optical metallography; optospectral analysis of chemical composition; SEM fractography; Metal degradation under laboratory conditions; chromatographic analysis; mechanical tests. As a result of high temperature service of steam pipelines welding joints the weld metal become degraded most intensively. New peculiarities of weld metal degradation appearance were revealed. They become apparent of atypical simultaneous decreasing of brittle and ductile fracture resistant of metal and also correlation absence of plasticity parameters. The high sensitivity of many mechanical parameters, including hardness, fracture toughness, static and cyclic crack resistance to the weld metal degradation has been shown, whereas to the base metal degradation are sensitive crack resistance parameters. The highest sensitivity of tensile mechanical parameters to the weld metal degradation was revealed on the radial directed specimens. The critical state of exploited weld metal was established, using inversion of hydrogen effect on the effective threshold of crack resistance of the metal, degarded under laboratory conditions. Sphere of use is the energy and petroleum industry of Ukraine.