A fast fracture approach to assess hydrogen embrittlement (HE) susceptibility and mechanism(s) of high strength martensitic steels

Low alloy TRIP steel is expected to be applied to automobile bodies because of its high strength, high ductility, and excellent impact properties and press formability. It has been reported that the low alloy TRIP steel of hydrogen embrittlement resistance is improved by utilizing the hydrogen storage characteristics of highly stable retained austenite. Therefore, for the purpose of increasing the volume fraction of retained austenite, it was produced at various cooling rates below the martensite transformation start temperature. As a result, the volume fraction of retained austenite increased, and then the effect of hydrogen embrittlement decreased. The matrix phase and retained austenite is refined with decrees of the cooling rate. It is considered that the size and surface area of the retained austenite also affected the improvement of hydrogen embrittlement resistance.

Download Full-text

Heuristic Design of Advanced Martensitic Steels That Are Highly Resistant to Hydrogen Embrittlement by ε-Carbide

Metals ◽

10.3390/met11020370 ◽

2021 ◽

Vol 11 (2) ◽

pp. 370

Author(s):

Michio Shimotomai

Keyword(s):

Hydrogen Embrittlement ◽

Hydrogen Absorption ◽

Martensitic Steel ◽

High Strength ◽

Literature Survey ◽

Martensitic Steels ◽

Tempered Martensite ◽

Grain Structures ◽

Controlled Nucleation ◽

Experimental Survey

Many advanced steels are based on tempered martensitic microstructures. Their mechanical strength is characterized by fine sub-grain structures with a high density of free dislocations and metallic carbides and/or nitrides. However, the strength for practical use has been limited mostly to below 1400 MPa, owing to delayed fractures that are caused by hydrogen. A literature survey suggests that ε-carbide in the tempered martensite is effective for strengthening. A preliminary experimental survey of the hydrogen absorption and hydrogen embrittlement of a tempered martensitic steel with ε-carbide precipitates suggested that the proper use of carbides in steels can promote a high resistance to hydrogen embrittlement. Based on the surveys, martensitic steels that are highly resistant to hydrogen embrittlement and that have high strength and toughness are proposed. The heuristic design of the steels includes alloying elements necessary to stabilize the ε-carbide and procedures to introduce inoculants for the controlled nucleation of ε-carbide.

Download Full-text

Prediction of diffusion assisted hydrogen embrittlement failure in high strength martensitic steels

Journal of the Mechanics and Physics of Solids ◽

10.1016/j.jmps.2015.08.010 ◽

2015 ◽

Vol 85 ◽

pp. 143-159 ◽

Cited By ~ 12

Author(s):

Q. Wu ◽

M.A. Zikry

Keyword(s):

Hydrogen Embrittlement ◽

High Strength ◽

Martensitic Steels

Download Full-text

Effects of Alloying Elements Addition on Delayed Fracture Properties of Ultra High-Strength TRIP-Aided Martensitic Steels

Metals ◽

10.3390/met10010006 ◽

2019 ◽

Vol 10 (1) ◽

pp. 6 ◽

Cited By ~ 4

Author(s):

Tomohiko Hojo ◽

Junya Kobayashi ◽

Koh-ichi Sugimoto ◽

Akihiko Nagasaka ◽

Eiji Akiyama

Keyword(s):

Hydrogen Embrittlement ◽

Retained Austenite ◽

Hydrogen Diffusion ◽

High Strength ◽

Alloying Elements ◽

Bending Test ◽

Hydrogen Trapping ◽

Martensitic Steels ◽

Diffusible Hydrogen ◽

Martensite Matrix

To develop ultra high-strength cold stamping steels for automobile frame parts, the effects of alloying elements on hydrogen embrittlement properties of ultra high-strength low alloy transformation induced plasticity (TRIP)-aided steels with a martensite matrix (TM steels) were investigated using the four-point bending test and conventional strain rate tensile test (CSRT). Hydrogen embrittlement properties of the TM steels were improved by the alloying addition. Particularly, 1.0 mass% chromium added TM steel indicated excellent hydrogen embrittlement resistance. This effect was attributed to (1) the decrease in the diffusible hydrogen concentration at the uniform and fine prior austenite grain and packet, block, and lath boundaries; (2) the suppression of hydrogen trapping at martensite matrix/cementite interfaces owing to the suppression of precipitation of cementite at the coarse martensite lath matrix; and (3) the suppression of the hydrogen diffusion to the crack initiation sites owing to the high stability of retained austenite because of the existence of retained austenite in a large amount of the martensite–austenite constituent (M–A) phase in the TM steels containing 1.0 mass% chromium.

Download Full-text