When Should You Worry about Hydrogen Embrittlement?
Hydrogen embrittlement is not a new problem, but the ins and outs of hydrogen embrittlement can still be difficult to grasp for those new to dealing with hydrogen. That's why we put together a four-part Ask Swagelok video series detailing what it is, how components can be affected, and can be done to counter embrittlement issues. In the second video, Senior Scientist Buddy Damm discusses what three factors, when acting together, can be a concern when dealing with hydrogen embrittlement.
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CRAIG GIFFORD:
Welcome to Ask Swagelok. I'm Craig Gifford, here today with Buddy Damm, who is a senior scientist of metallurgy here at Swagelok. We've been talking about hydrogen embrittlement. And today, we're going to talk about: “When should you worry about hydrogen embrittlement?”
BUDDY DAMM:
Right, okay. Hydrogen embrittlement occurs when three things happen together. The first thing is a tensile stress. Second, you need the availability of atomic hydrogen. And third, you need a susceptible material.
CRAIG GIFFORD:
Okay, makes sense. Let's unpack that a little bit.
BUDDY DAMM:
From a tensile stress perspective, our components are containing high-pressure hydrogen. That pressure puts our components into a tensile stress. That’s the primary source. The secondary sources could be external — things that put a bending load on the material. These loads could be static, meaning they're just sitting there under constant pressure, or dynamic, like cyclic pressure going on and off. It's important to understand both.
Second, availability of atomic hydrogen. In gaseous hydrogen systems, hydrogen is H₂ — a diatomic molecule, much like oxygen (O₂) or nitrogen (N₂). But when that H₂ molecule touches the surface of an engineering alloy, it can dissociate into two atoms. And the hydrogen atom, being among the smallest of atoms, can diffuse into the metal lattice. From there, it can migrate to critical areas and cause hydrogen embrittlement.
And the third part is a little more complex: the susceptibility of the material. As a rule of thumb, all alloys are susceptible to hydrogen embrittlement in some way. Very high-strength alloys with lower ductility are at greater risk of failing. On the other hand, lower-strength or moderate-strength alloys with higher ductility — such as many stainless steels — perform much better in hydrogen environments.
CRAIG GIFFORD:
Right. Yeah. Well, thank you, Buddy. And thank you for joining us at Ask Swagelok.