The Effect of Electrolytic Hydrogenation on Mechanical Properties of T92 Steel Weldments under Different PWHT Conditions

Abstract

In the present work, the effects of electrolytic hydrogen charging of T92 steel weldments on their room-temperature tensile properties were investigated. Two circumferential weldments between the T92 grade tubes were produced by gas tungsten arc welding using the matching Thermanit MTS 616 filler material. The produced weldments were individually subjected to considerably differing post-welding heat treatment (PWHT) procedures. The first-produced weldment was conventionally tempered (i.e., short-term annealed below the Ac1 critical transformation temperature of the T92 steel), whereas the second one was subjected to its full renormalization (i.e., appropriate reaustenitization well above the T92 steel Ac3 critical transformation temperature and subsequent air cooling), followed by its conventional subcritical tempering. From both weldments, cylindrical tensile specimens of cross-weld configuration were machined. The room-temperature tensile tests were performed for the individual welds’ PWHT states in both hydrogen-free and electrolytically hydrogen-charged conditions. The results indicated higher hydrogen embrittlement susceptibility for the renormalized-and-tempered weldments, compared to the conventionally tempered ones. The obtained findings were correlated with performed microstructural and fractographic observations.

Analysis of Mechanical Properties of Welded Joint Metal from TPP Steam Piping after Its Operational Degradation and Hydrogenation

“…A significant part of the hydrogen absorbed by the WM during welding and operation on the steam piping or on the hydrogenation reactor could migrate to the zones of the volumetric stress state and, thereby, affect the mechanical properties of the WM during tensile testing of specimens [52,53]. After all, it is known that hydrogen can contribute both to the strengthening of metals (at the macro level) [54] and their plastification (at the micro level) [55].…”

The Effects of Electrochemical Hydrogen Charging on Charpy Impact Toughness and Dry Sliding Tribological Behavior of AISI 316H Stainless Steel

“…In our previously published works [19][20][21][22][23][24], we investigated the effects of various conditions of heat treatment, including long-term isothermal expositions and the electrolytic hydrogen charging of welded joints of advanced creep-resistant steels on their mechanical and brittle-fracture properties. In these complex material systems, certain small improvements in HE resistance were observed after laboratory high-temperature aging experiments, which could be explained by internal stress relieving as well as by the additional precipitation of fine carbide particles leading to irreversible hydrogen trapping at carbide/matrix interfaces [19][20][21][22][23][24]. However, at the same time, the gradual development of thermal embrittlement was clearly observed due to the precipitate coarsening of several secondary phases (e.g., special alloy carbides and intermetallic phases) with the increasing duration of thermal exposure.…”

History, Developments and Trends in the Heat Treatment of Steel

“…In the fifth paper [11], the effects of the electrolytic hydrogen charging of T92 steel weldments on their room-temperature tensile properties were investigated and discussed. The weldments were differently heat treated after the welding procedure-either tempered below the transformation A 1 temperature or normalized (i.e., austenitized above the Ac 3 critical transformation temperature and subsequently air cooled) and tempered.…”