Delayed fracture and H embrittlement
Mechanical tests
Slow Strain Rate Test (SSRT)
Uniaxial tensile slow strain rate tests on notched and/or unnotched specimens based on the guidelines of ASTM F-519/ ASTM G-129 standards.
Samples are charged with different diffusible hydrogen contents before testing, and relative average diffusible hydrogen concentration is measured at the end of the test by hot extraction method.
Critical diffusible hydrogen concentration is determined with reference to ASTM STP 962 in correspondence of a reduction of the 30% of a significant material’s property in comparison with hydrogen free sample.
Four Point Bending Test (FPBT)
Incremental step loading four-point bending test is performed as per ASTM F-1624 fully in the elastic range of the material on notched sheet metal specimens. Test is useful to evaluate the critical diffusible hydrogen concentration with reference to ASTM STP 962 in correspondence of a reduction of the 30% of a significant property in comparison with hydrogen free sample.
Samples are charged with different diffusible hydrogen contents before testing, and relative average diffusible hydrogen concentration is measured at the end of the test by hot extraction method.
Stress corrosion cracking evaluation using the constant load test
The constant load test is a method that estimates the hydrogen content threshold at which a steel does not fail due to hydrogen embrittlement under a constant load. The steel is considered not susceptible to hydrogen embrittlement if the failure doesn’t appear at 150h or 240h.
Step load test
This test method is based on standard ASTM F1624 and establishes a procedure to measure the susceptibility of steel to a time-delayed failure due to hydrogen embrittlement. The test consists on increase incrementally the load applied to the sample until its failure.
Diffusion tests
H diffusion testing
Hydrogen permeation test performed by using HELIOS 2 PERMEATION equipment with reference to the electrochemical technique described in ASTM G-148.
Tests can be performed on bare or coated sheet metal, at a controlled temperature from room temperature up to 50°C.
The test is useful to evaluate the effective hydrogen diffusivity and other hydrogen diffusion-related parameters.
H measurement by Hot Gas Extraction
Measurement of diffusible hydrogen content in metal samples by hot extraction methodology, that consists in heating the sample in order to enhance hydrogen diffusion out of the metal for a quick measurement.
Tests will be executed with HELIOS 3 equipment.
