How does hydrogen embrittlement of metal fasteners occur, and how can it be prevented and detected?
Publish Time: 2024-08-01
Metal fasteners play a key role in many engineering applications, but hydrogen embrittlement may cause their performance to deteriorate or even fail.
The occurrence of hydrogen embrittlement is usually related to the following factors. First, during manufacturing, processing or use, metal fasteners may be exposed to hydrogen-containing environments, such as pickling, electroplating, cathodic protection and other processes. Hydrogen atoms will penetrate into the metal and diffuse and aggregate in the lattice. When the concentration of hydrogen atoms reaches a certain level, it will weaken the bonding force between metal atoms, resulting in reduced plasticity and toughness of the material, thereby inducing hydrogen embrittlement.
Secondly, materials such as high-strength steel are more likely to absorb and accommodate hydrogen due to the characteristics of their microstructure and chemical composition, thereby increasing the risk of hydrogen embrittlement.
In order to prevent hydrogen embrittlement of metal fasteners, there are a variety of measures that can be taken. During the manufacturing process, optimizing the heat treatment process can improve the microstructure of the metal and reduce the sensitivity to hydrogen embrittlement. It is also important to choose a suitable surface treatment method, such as using a hydrogen-free electroplating process or controlling hydrogen absorption during pickling. In terms of the use environment, metal fasteners should be avoided from being exposed to hydrogen-containing corrosive media as much as possible. For fasteners that have been treated, dehydrogenation treatment can be carried out to expel the infiltrated hydrogen by heating.
Methods for detecting hydrogen embrittlement include hardness testing, tensile testing, and metallographic analysis. Hardness testing can detect abnormal increases in material hardness, which may be a sign of hydrogen embrittlement. Tensile testing can directly evaluate the plasticity and toughness loss of materials. Metallographic analysis can observe damage and cracks caused by hydrogen in the microstructure. For example, in automobile manufacturing, high-strength bolts may cause serious safety hazards if hydrogen embrittlement occurs. Therefore, the electroplating process is strictly controlled during the production process to ensure that the amount of hydrogen absorption is within a safe range. At the same time, key fasteners are regularly sampled and tested, and potential hydrogen embrittlement problems are promptly discovered through methods such as tensile testing.
In short, understanding the causes of hydrogen embrittlement in metal fasteners, taking effective preventive measures, and using appropriate detection methods for monitoring are of great significance for ensuring the safe and reliable operation of engineering structures.
