Experimental Study of Thermal Ageing and Hydrogen Embrittlement Effect on the Equipments of a Rocket Engine

In the present study employed disc pressure tests to assess the effects of hydrogen embrittlement and thermal ageing on the fatigue life of a thin-wall circular part within a rocket engine. The technique compared the pressure resistance of membranes tested under helium and hydrogen, offering a simple, sensitive, and reliable method. Disc tests were selected to mimic natural operating conditions, as they align with those of a thin-wall circular part within a rocket engine. The originality of these tests appears to lie in their enhanced performance in terms of sensitivity and reproducibility. To achieve this, tests were conducted across various conditions, including sample thicknesses of ۰.۷۵ mm, a broad range of strain rates from ۱۰-۶ s-۱ to ۱۰۰ s-۱, temperatures spanning from ۲۰°C to ۹۰۰°C, and pressure rates from ۱۰-۲ to ۲.۱۰۴ MPa/min. Furthermore, a variety of materials were investigated, including copper, nickel alloy, and stainless steel. The results demonstrated that thermal aging leads to precipitation, particularly intergranular precipitation. These precipitates diminish the material's ductility, particularly when they are nearly continuous. Additionally, the material's sensitivity to hydrogen becomes significant when hydrogen, supersaturated due to rapid cooling, becomes trapped on precipitates formed at high temperatures. Furthermore, the results indicated that thermal and hydrogen-induced damage mutually reinforces each other, resulting in reduced fatigue life under high deformation.

Keywords:

Disc pressure tests , Thermal embrittlement , Hydrogen Embrittlement , rocket engine , fatigue cycle