Gaseous hydrogen embrittlement of PH 13-8 Mo steel

Metallurgical and Hydrogen Effects on the Small Punch Tested Mechanical Properties of PH-13-8Mo Stainless Steel

“… The Vickers hardness variation over time for PH-13-8Mo stainless steel as was previously reported for aging at 590–600 °C (blue points 1–4 [ 18 ]; 5: an average value from References [ 1 , 6 , 10 , 13 , 18 , 19 , 20 , 21 , 22 ] and curve) and 550–575 °C (black points 6–10 [ 24 ]; 11: an average value from References [ 1 , 6 , 10 , 13 , 18 , 19 , 20 , 21 , 22 ] and curve) as well as the variation following solution and quenching treatment (red point 12 [ 1 , 6 ]). The currently measured points under the investigated thermal treatment conditions are shown as the star points 11 (550 °C), 15 (600 °C), and 13 (following solution and quenching).…”

“…These treatments usually create different amounts of strengthening precipitates, intermetallic or metallic phases and some amounts of reverted austenite γ-FCC phase [ 1 , 2 , 3 , 4 , 5 , 6 ]. Another common characteristic of PHMSS is their extremely high sensitivity to hydrogen induced cracking at their peak-aged condition which was extensively shown [ 2 , 3 , 4 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Yet, like other steel alloys, the effects of hydrogen on the mechanical properties, e.g., yield strength, tensile strength, under different testing conditions and metallurgical conditions are still non-conclusive [ 15 , 16 , 17 ].…”

“…Reverted austenite in this alloy is mainly formed through a combination of diffusional processes at lath boundaries in the alloy yielding a local (nanometer sized) Ni enrichment stabilizing the austenite phase. Its presence contributes to a higher fracture toughness and it is also claimed to improve the resistance to hydrogen embrittlement [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”

“…PH-13-8Mo was extensively studied in recent years in terms of its metallurgical and mechanical behavior, including the precipitation sequence as manifested by hardness tests, and the formation and stability (mechanical and thermal) of reverted austenite (γ-FCC) [ 23 , 24 , 25 ]. As can be seen in Figure 1 , hardness values following aging durations of this steel have been published [ 1 , 6 , 10 , 13 , 18 , 19 , 20 , 21 , 22 , 24 ]. As can be seen in this figure, previously reported hardness variation values with the aging time at the two temperature ranges of 590–600 °C (blue points and curve) and 550–575 °C (black points and curve), had shown that the maximal aging conditions for the former were ~0.2–0.7 h, and ~1–6 h for the latter.…”

“…A longer aging duration results in over-aging and decreased hardness values. Based on these observations, a 4 h aging duration was established as an accepted standard aging condition for both of these temperature ranges [ 1 , 6 , 10 , 13 , 18 , 19 , 20 , 21 , 22 ], while considering that this period of time is equivalent for maximal aging for a temperature range of 550–575 °C, while over-aging conditions will occur at temperatures of around 600 °C. Due to this standardization, most of the practically applied PH-13-8Mo stainless steel components are being aged at these temperatures for 4 h, prior to being subjected to practical environmental conditions, including hydrogen exposure.…”