Hydrogen Embrittlement and Microstructure Characterization of 1500 MPa Martensitic Steel

Abstract

The application of ultrahigh‐strength martensitic steel in automotive key parts can achieve automotive lightweight. However, the hydrogen embrittlement sensitivity of ultrahigh‐strength martensitic steel is widely concerned by the industry. This article compares the microstructure and the hydrogen brittleness resistance of two 1500 MPa martensitic steels. The grain boundary, the grain size, the martensitic lath, and the precipitate phase in martensitic steel are analyzed by electron backscatter diffraction and transmission electron microscope. The hydrogen desorption curves of the two steels are measured by thermal desorption analysis, and the phenomenon of hydrogen trapping in the materials is analyzed. A U‐bend test is used to compare the hydrogen embrittlement of these two samples. The results demonstrate that the thickness of the martensitic lath and the dislocation are directly related to the diffuse hydrogen concentration in the material. In addition, the Cu‐rich nanoparticles show a better hydrogen trapping effect, which is beneficial in improving the hydrogen embrittlement resistance of the material.

Effect of Controlled Rolling on the Strength and Toughness of Low‐Alloy Martensitic Steel

“…[25,26] The modified W-H method was used to calculate the dislocation density of the test steel. [27] ρ ¼ 14.4…”

“…The modified W–H method was used to calculate the dislocation density of the test steel. [ 27 ] where e is the effective microstrain, and b is Burger's vector having a value of 2.48 Å. [ 28 ]…”

Characterization of Retained Austenite in Advanced High-Strength Steel

“…Several studies indicated that the RA as island type is the main microstructural constituent controlling this toughness, which highlights the need for a precise identification of these constituents in the studies dealing with the microstructure-toughness relation [ 22 , 23 ]. In the temperature of ferrite nucleation, the carbons will diffuse in the austenite.…”

Hydrogen Impact: A Review on Diffusibility, Embrittlement Mechanisms, and Characterization

“…In both steels, the DFS decreased with increasing HD; however, the V-added steel showed higher resistance to HE than the SCM435 steel at the same level of HD. Si et al [184] applied a U-bend test to compare the HE resistance of two 1500 MPa martensitic steels, in which a hydraulic press was used to impose constant pressure downward to form a 180° bend on the samples that were fixed by bolts. The deformed samples were then immersed in 0.5 mol•L −1 HCL solution and time to fracture was recorded to compare the HE resistance of the two samples (Figure 28a-c).…”