The phenomenon of brittle fracture in metallic materials caused by the combined action of hydrogen and stress is referred to as hydrogen embrittlement fracture. Stress corrosion and hydrogen embrittlement often occur simultaneously. Therefore, it is difficult to clearly distinguish between stress corrosion and hydrogen embrittlement from a mechanistic perspective. However, from a prevention standpoint, distinguishing them is highly necessary.

Hydrogen embrittlement typically manifests as delayed fracture under stress. There have been instances where zinc-plated components such as screws, washers, springs, and leaf springs fractured successively within hours after assembly, with a fracture rate reaching 40% to 50%. Hydrogen does not cause significant corrosion to steel under normal temperature and pressure, but when the temperature exceeds 300°C and the pressure is above 30MPa, hydrogen embrittlement—a type of corrosion defect—can occur, especially under high-temperature conditions.

The electronic slow strain rate high-temperature high-pressure hydrogen embrittlement stress corrosion testing machine, developed by Xi'an Lichuang Material Testing Technology Co., Ltd., is primarily used to accurately determine the sensitivity of metals to sulfide-induced stress corrosion cracking under H2S exposure. It can also be employed for testing and researching the mechanical properties of metallic materials, such as static persistent tensile strength, creep, and stress corrosion. It is suitable for determining the stress corrosion failure characteristics of metals in environments containing NaOH, NO3-, H2S, CL- solutions, methanol, N2O4, NH3, humid air, water, and other media.

Main technical specifications and parameters:

1. Maximum test force: 50kN

2. Test force range: 1--100% full range without grading

3. Accuracy class: Grade 1; indication accuracy better than ±1%

4. Equipped with threaded connection fixtures (two types) and pin-type connection fixtures with automatic centering devices;

5. Speed accuracy better than ±1%, indication accuracy better than ±1%, deformation and displacement accuracy better than ±0.5%.

6. The tensile speed for slow strain rate tests can be continuously adjusted between 10-6 and 1mm/min.

7. Test tensile space: 0-400mm, adjustable test space

8. Test control methods: force, time, loading rate, step (multi-stage) loading

9. Test environment control temperature: room temperature to 300°C

10. Reactor withstand pressure: 10MPa

Since hydrogen embrittlement is related to the diffusion of hydrogen atoms, and diffusion requires time—with its speed depending on concentration gradient, temperature, and material type—hydrogen embrittlement typically manifests as delayed fracture. Currently, fractures in elastic fasteners caused by delayed hydrogen embrittlement naturally represent a serious product quality issue. Various techniques can be adopted to reduce and prevent hydrogen embrittlement in elastic fasteners.