Improving Hydrogen Embrittlement Resistance of Hot-Stamped 1500 MPa Steel Parts That Have Undergone a Q&P Treatment by the Design of Retained Austenite and Martensite Matrix

Abstract

Hydrogen embrittlement is one of the largest obstacles against the commercialisation of ultra-high strength quenching and partitioning (Q&P) steels with ultimate tensile strength over 1500 MPa, including the hot stamped steel parts that have undergone a Q&P treatment. In this work, the influence of partitioning temperature on hydrogen embrittlement of ultra-high strength Q&P steels is studied by pre-charged tensile tests with both dog-bone and notched samples. It is found that hydrogen embrittlement resistance is enhanced by the higher partitioning temperature. Then, the hydrogen embrittlement mechanism is analysed in terms of hydrogen, retained austenite, and martensite matrix. Thermal desorption analysis (TDA) shows that the hydrogen trapping properties are similar in the Q&P steels, which cannot explain the enhancement of hydrogen embrittlement resistance. On the contrary, it is found that the relatively low retained austenite stability after the higher temperature partitioning ensures more sufficient TRIP effect before hydrogen-induced fracture. Additionally, dislocation recovery and solute carbon depletion at the higher partitioning temperature can reduce the flow stress of the martensite matrix, improving its intrinsic toughness and reducing its hydrogen sensitivity, both of which result in the higher hydrogen embrittlement resistance.

Advanced High-Strength Steels by Quenching and Partitioning

“…Wang and Huang [10] showed that the hydrogen embrittlement resistance of an ultrahigh-strength Fe-0.3C-1-57Si-2.94Mn Q&P steel can be improved by applying a higher partitioning temperature (450 • C). Partitioning temperature did not affect the hydrogen trapping properties of the Q&P-treated steel.…”

Investigation of Hydrogen Embrittlement of Haynes 617 and Hastelloy X Alloys Using Electrochemical Hydrogen Charging

“…in fact, using hydrogen as fuel in gas turbines can deteriorate the mechanical properties of ni-based superalloys [11][12][13][14]. Because hydrogen permeates to the surface of a specimen by electrochemical hydrogen charging [15,16], the geometry of a specimen may affect the sensitivity to hydrogen embrittlement. in ni-based alloys, various studies on test conditions such as test temperature, strain rate, and heat treat conditions have been conducted [13,14], but studies on hydrogen embrittlement according to the specimen geometry have not been conducted.…”