ASTM F1624 Hydrogen embrittlement of high-strength metallic materials
The ASTM F1624 standard describes an accelerated test method for determining the susceptibility of high-strength metallic materials to time-delayed failure due to hydrogen embrittlement.
Objective & applications Test principle Specimen types Suitable testing systems Interesting customer projects
An overview of the ASTM F1624 standard
ASTM F1624 describes an accelerated test method (tensile or flexural loading) for determination of the susceptibility of steels to time-delayed failure such as that caused by hydrogen. This is done by determining the time for the onset of subcritical crack growth (SCG). The test duration is normally shorter than that according to ASTM F519. The test is performed either on air to measure whether there is residual hydrogen in the steel due to processing (internal hydrogen embrittlement, IHE) or in a controlled environment to measure the effect of hydrogen from external hydrogen sources (environmental hydrogen embrittlement, EHE).
- Quantitatively measures stress parameters used in a design or error analysis, taking into account the effects of environmental influences, including those that occur during processing (e.g., plating).
- For plating processes, δth-IHE is used to specify the maximum operating stress.
- For fasteners, δth-IHE is used to specify the maximum loading during installation and operation to avoid premature failure.
Test principle to ASTM F1624
At least three specimens are required to determine the threshold stress for the onset of subcritical crack growth.
The first specimen is subjected to a tensile test according to ASTM E8 to determine the fast fracture strength (FFS).
This is followed by at least two further tests with incremental step loading including holding times (=load increase test) - the load profile depends on the specimen hardness. The load is increased after defined time intervals until the specimen breaks. The loading rate between the load steps is 10-5 s-1 to 10-8 s-1.
The type of hold at the respective steps is position-controlled. In addition to the specific load profiles, the subsequent Pmax for each load profile is set to 1.1 times the threshold load (Pth-n) of the previous test. The level of the load steps is based on the failure load in the tensile test (according to ASTM E8) or the failure load of the previously respective determined threshold. The threshold load Pth-n is the load that occurs in the last load step before the crack growth starts. The test is completed when the difference between two successive threshold loads is ≤ 5% of PFFS.
Specimen types according to ASTM F1624
ASTM F1624 provides the following specimen types for evaluation of hydrogen embrittlement:
- Notched specimens such as those in ASTM F519
- CT-specimens such as those to ASTM E399
notched specimens
Notched specimens of specimen type 1 are used for tests performed according to ASTM F1624, as also described in ASTM F519:
- Type 1a: Notched, round, tensile load
- Type 1a.1: Standard size
- Type 1a. 2: oversized
- Type 1b: notched, round, tension, self loading fixture
