Hydrogen test

Hydrogen Embrittlement Testing

Hydrogen Embrittlement testing aims to detect the presence of hydrogen in a material, which can cause embrittlement, decreased ductility, and cracking due to high stresses. It is usually used to examine metals that are subject to hydrogen attack, such as high strength steels, aluminum alloys and raw titanium.

Hydrogen embrittlement is caused by the diffusion of hydrogen atoms through a material and the formation of cracks through the interaction of molecular stresses. These molecular stresses increase with increasing temperature and pressure. This causes the formation of brittle flakes in the material which are visible under a microscope.

Hydrogen embrittlement testing methods involve the use of pressurised hydrogen gas. The gas is injected in carefully calibrated concentrations into the specimen at different temperatures and pressures. The hydrogen penetrates into the specimen and causes a reduction in ductility, which manifests itself in cracking.

Hydrogen embrittlement testing consists of four steps: sample preparation, mechanics testing, analysis, and characterization. Preparation of the sample involves the application of an extractant on the specimen surface. This extractant helps to delineate the boundaries of that undergoing mechanical testing. During the mechanics testing, the specimen is subjected to static tests, such as a tensile test, and/or dynamic tests, such as fatigue. During all of these tests, the hydrogen levels in the test atmospheres are monitored and recorded using gas analyzers.

In order to analyse whether hydrogen embrittlement has occurred, researchers look for the presence of microstructural defects and surface defects on the specimen. These defects are usually the result of hydrogen bonding to the material during hydrogen fracturing. Characterization of the defects involves the use of microscopy techniques that measure surface pore size, surface crack widths, and chemical composition.

The most common type of hydrogen embrittlement test is the Charpy impact test. In this test, the material specimens are subjected to increasingly high amounts of hydrogen gas and examined for changes. The results from the Charpy impact test help to provide a better understanding of the hydrogen embrittlement behavior of a material in a certain environment.

The results of hydrogen embrittlement testing help to determine if a material is prone to brittle fracture due to hydrogen attack. Combined with other knowledge, such as structures and loading conditions, these tests help in designing structures that are not susceptible to hydrogen embrittlement. With proper testing techniques and analysis, hydrogen embrittlement testing can be an important way of ensuring that specimens are safe and reliable.

Hydrogen testing is a technique used to test the integrity of welding joints. It is done in part to detect hydrogen-induced cold cracking, also known as HICC, as it poses a danger to safety of the weldment. The test is usually performed after the completion of welding and pre-heat treatments, both of which can introduce hydrogen into the weldment.

Hydrogen testing generally involves exposing the weldment to a neutral salt solution, such as Dilute Hydrochloric Acid or Magnesium Nitrate, and measuring the electrode potential of the solution in relation to the material. This is done using a regular electrical multimeter.

If the electrode potential is lower than the maximum permissible level, the weldment is deemed to be safe and the test is concluded. A higher than acceptable level of hydrogen may be indicative of hydrogen-induced cold cracking and may necessitate further examination of the weldment.

In order to ensure accuracy and validity of the hydrogen test, it is important to pay attention to the details of the test procedure. This includes cleaning the weldment surface before testing and ensuring the correct test solution is used.

The test should be repeated to obtain a representative sample of the weldment’s integrity. Moreover, using welding fume extraction equipment may help to reduce the amount of hydrogen in the weldment, thereby reducing the possibility of cold cracking.

Overall, hydrogen testing is an important technique for ensuring the safety and quality of welding joints. It provides valuable insight into the integrity of the weldment, allowing for fast and effective determination of whether or not the weldment is safe, or if further measures must be taken to repair any hydrogen-induced cold cracking.